sound travel in straight line

Does Sound Travel Upstairs or Downstairs? (Explained for Beginners)

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If you live in an apartment, the common question is how much you can hear from someone living downstairs or upstairs.

A typical apartment building has a shared wall, which means that the sound from the other doors can reach your ears once they make a noise. It is easy to hear the loud stereo or people shouting living next door.

Some apartments have a drop ceiling that also works as an acoustic underlayment.

But how about the sound from upstairs, or downstairs, if you are on the second floor? Does sound traveling work the same way wherever you are in a room? How does noise travel?

What do we know about sound waves and vibrations?

While sound does not travel in one direction or a straight line, we have to dig deeper into the concept of sound.

Pro tip: Do you know that the reason why megaphones are cone-shaped is for sound to travel in a particular and directional area? Because the megaphone physically directs where the sound will go.

How Sound Travels

Before we can understand how far sound can travel or its direction, we need to know the simple facts about sound waves.

Next Read: How to Reduce Noise Through Walls? (Explained for Beginners)

What are Sound Waves?

Sound waves are best represented by moving particles in matter. For example, on a solid matter, like a pole, intact with atoms or particles.

When you poke the pole, thus creating sound for the first time, you are pressing the atoms or applying force (creating vibration) for them to move. When particles are pushed, they bounce. Thus, the bouncing particles represent sound waves.

However, the speed of movement of the atoms depends on the type of material.

Materials like solids, with particles intact, will make the sound speed faster than the particles on wood and air.

Sound transmitted from the impact of an object is called structure-borne noise. On the opposite, airborne noise or airborne sound is a sound directed to the air, such as speech and music.

In simple perspective:

• Vibrations produce sound.
• Sound waves are particles that are called bouncing atoms of vibrating particles.
• The speed of sound is dependent on the type of surface it pokes.

How far Does Sound Travel?

The answer to this question is complicated because there are many variables at play. To understand this better, let’s say that sound travels depending on the phase of matter it will pass through.

• Sound waves travel at a speed of approximately 332 m/sec in air.
• But it travels faster through liquid and fastest in solid.
• If objects hit one another, you are generating an impact sound or impact noise.

Do all Sounds Travel the Same Distance?

Perhaps, the better question would be, “do all sounds travel at the same speed?” The answer is no because it depends on the type of medium they travel .

As explained above, it is more difficult for sound waves to pass through gas or air, and liquids than solid materials. Ironic, right? Because solids, as we know them, are non-permeable materials.

However, since sound vibrations are flowing, they are more effective in passing through and bouncing back if the medium is harder or has more intact atoms.

To illustrate this, imagine throwing a ball into the air or the water and then comparing which medium the ball came back to faster. The ball, representing the sound wave, travels most quickly in solids.

Meaning sounds pass slower in liquids and slowest in air. That’s why when you are in an open space and you shout, the listener will hardly hear you more than when you are in a closed room. The walls in that space absorb the sound coming from you and reflect it to the listener.

How does Sound Travel Through Floors?

If your apartment has levels, it is divided by drywall and wood floors. Also, you will be wondering how sound travels through floors and if they do.

We will take a similar concept about sound traveling on solids. However, this is quite a complex matter because there are many situations at play.

Let us learn from them, and then we can infer the manner of sound travel.

Next Read: STC Ratings: Understanding STC Ratings for Wall and Stud Framed Walls

Sound travels in any direction, meaning it is omnidirectional. But different factors affect their speed.

• Though sounds can be primarily heard through solids , this doesn’t mean you can listen to the noise from a different floor, whether upstairs or downstairs.
• Since floors are partitioned by a solid matter in the form of wood or hardwood floor , they will block the sound from within a room traveling to the downstairs apartment.
• The sound is reduced when the source is closed, and you are not in that space . This explains that the sound made in that room is absorbed by the closed door, leaving less or no space for sound waves to travel. That’s why you hear a little when people are having a conversation in a closed room.
• But if a sound is produced directly hitting the floor or dropping something on it, the sound source travels now to the floor and then through the listener .
• Sound travels through floors , but its speed and level vary depending on the medium used.

PRO TIP : Does sound travel upwards? No, because sound waves are omnidirectional. They travel in all directions.

Does Sound Travel Through Walls?

With the same concept of sound traveling through the floors, yes, sound also travels through walls.

So when your child is playing loud music in the other room, you can hear it unless that room is soundproof or insulated to enclose the sound for better quality. Soundproofing is a way to reduce the impact of unwanted noise.

Sound can travel through depending on how much the room is insulated. Sound insulation is an effective way to enhance or lessen sound.

Sound Reflection and Absorption

Reflection and absorption are two elements or acoustical tools that absorb and reduce the strength of sound.

Photo Credit: Acousticsciences

We use sound absorbers to reduce or eliminate sound.

• Sound absorbers are like when your wall has a hole in it. And when you throw the sound, it will dissipate in a vacuum.
• A sound absorber will completely destroy the noise so it won’t reach its listener in a crisp sound.
• Objects with curved and uneven shapes can serve as sound reducers. They are called curved surface diffusers. Why?
• The curves on the surface reduce the vibration. It lessens the strength of sound rather than eliminating it.

So in a room where you desire to eliminate noise, you use a combination of diffusers and absorbers. And this is explained in the sound-deadening articl e we previously discussed.

Now you know how the room next door is set up if you hear a loud noise.

Why does Sound Travel Faster in Warm Water?

In basic science, water molecules in warm or hot water move faster than in cold water because they have more energy to transmit vibration within particles quickly.

So, if the water becomes ice, it is now in solid form. And from that, we can say that the molecules hardly move and cause vibration.

Relevant Questions on Sound That Require Answers

Do higher-pitched sounds travel faster.

No. Higher-pitched sounds equate to high-frequency sound waves . Low-frequency or low-pitched sounds like bass will travel faster and downward due to gravity.

Practically speaking, it is like comparing a heavy stone, and a tin can simultaneously drop. You know which drops faster.

If you have a family member, who gets annoyed with the loud bass sound from your subwoofer, install bass traps in your room.

Why are you more likely to hear noise from an upstairs apartment than from downstairs?

Because the people upstairs can direct the foot traffic, causing the sound and noise downwards. Unless the floor has carpet padding, so, your lower-floor apartment dweller will hear your footsteps and furniture moving.

Apartment living is different from single-attached home living when it comes to hearing sounds and background noise.

Why does sound only travel from upstairs neighbor to downstairs and not vice versa?

Sound will not travel up or down. It travels in all directions unless something redirects it. As mentioned, the speed and direction of sound will depend on the medium it is applied to.

How much noise travels upwards to a second-floor apartment from the first floor?

This would be explained by understanding the concept in number 2.

It is actually the reverse of the idea that those on the second floor can create more sound as the floor joist (the ceiling on the first floor) receives the sound directly from foot traffic, while no sound stimulant will directly hit the joists of those on the first floor.

This will also answer that a top apartment won’t be less noisy than the bottom. Indeed you will have noisy upstairs neighbors. The same with the downstairs neighbor.

If you can hear your downstairs neighbor talking, can you also hear me talking?

This depends on where you are.

If you are in the same room, of course, you will be heard. But if you are on the upper floor, it still depends on how loud you talk, how much furniture you have, and how rich the volume you have in your speakers.

Floor underlayment also adds sound insulation, especially if it serves as acoustic insulation or acoustic underlayment.

PRO TIP: Frequency is measured in Hertz (Hz) units. It measures sound speed in radios, giving amplitude modulation (AM) and frequency modulation (FM).

Now you know the answer to sound travel upstairs or downstairs.

Generally, the discussion about sound and sound speed is a broad topic. But there are ways we can improve the transfer of sound in a particular area if that is our aim.

Yet, to understand the technicality of sound direction, adapting to the nature of your room and the objects in that room that will receive the sound will help you achieve a quieter room and get rid of noises in the neighborhood.

Next time, you’ll know why there is a noisy neighbor on the lower or upper floor.

Robert Castelao

Robert is an electronic engineer with more than five years of experience with a solid affinity for helping people reduce noise. He writes about these silent home appliances and easy soundproofing measures to help everyone avoid the negative effect of extended exposure to high noise levels.

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How Far Does Sound Travel: The Science of Acoustics

Do you ever stop to think about how sound travels? It’s an interesting phenomenon that occurs everyday and yet we often take it for granted. In this blog post, we will explore the science of acoustics and how sound travels. We will answer the question of how far sound can travel and how it is affected by different factors. Stay tuned for an in-depth look at this fascinating topic!

Nature Of Sound

Sound is a mechanical wave that is an oscillation of pressure transmitted through some medium, such as air or water. Sound can propagate through solids and liquids better than gases because the density and stiffness are greater. So how far does sound travel? In this article we will answer how sound travels and how to calculate how far it travels in different scenarios.

Sound Transmits Conception

A common misconception with regard to how sound transmits itself between two points (for example from speaker to ear) is that the source creates waves of compression in the surrounding gas which then proceed on their way at a constant speed until they strike something else; either another solid object or our ears . This analogy might be okay for describing what goes on at low frequencies but once we go beyond around 1000 Hz, the propagation of sound becomes far more complex.

At low frequencies (below around 1000 Hz), sound waves tend to travel in all directions more or less equally and bounce off objects like a rubber ball would. As frequency increases however, the directivity of sound increases as well. So high-frequency sounds are more likely to travel in a straight line between two points than low frequencies. This is why we can often hear someone calling from some distance away when there is loud music playing – because the higher frequencies carry further than the lower ones.

How Far Can Sound Travel

There are three ways that sound can be transmitted: through air, through water, or through solids. The speed of sound through each medium is different and depends on the density and stiffness of the material.

The speed of sound through air is about 343 m/s (or 760 mph), and it travels faster in warmer air than colder air. The speed of sound through water is about 1500 m/s, and it travels faster in salt water than fresh water. The speed of sound through solids is much faster than through either gases or liquids – about 5000-15000 m/s. This is why we can often hear someone coming before we see them – the sound waves are travelling through the solid ground to our ears!

Now that we know how sound propagates and how its speed depends on the medium, let’s take a look at how to calculate how far it will travel between two points. We can use the equation

distance = speed x time

For example, if we want to know how far a sound will travel in one second, we have:

distance = 343 m/s x 0.001 s = 343 m

So sound travels 1 kilometer in roughly 3 seconds and 1 mile in roughly 5 seconds.

Does Вecibel Level affect the Sound Distance?

The surface area around a sound source’s location grows with the square of the distance from the source. This implies that the same amount of sound energy is dispersed over a larger surface, and that the energy intensity decreases as the square of the distance from the source (Inverse Square Law).

Experts of Acoustical control says, that

For every doubling of distance, the sound level reduces by 6  decibels  (dB), (e.g. moving from 10 to 20 metres away from a sound source). But the next 6dB reduction means moving from 20 to 40 metres, then from 40 to 80 metres for a further 6dB reduction.

How Far Can Sound Travel In Real World

In real world, there are many factors that can affect how far a sound travels. Factors such as air density, temperature and humidity have an impact on its propagation; obstacles like buildings or mountains could also block some frequencies from going through while letting others pass (this happens because at high frequencies they behave more like waves).

Sounds can propagate through solids better than they can propagate through air because their density/stiffness are greater (this means that sound travels faster). In addition to this, we also know that it takes less time for a high frequency wave to reach us from its source compared with low frequencies. For example if there’s some kind of obstacle blocking our path then it might take longer for waves at higher frequencies than those below 1000 Hz to past them.

Can Sound Waves Travel Infinitely?

No. The higher the frequency of a sound wave, the shorter its wavelength becomes. As wavelength decreases, the amount of energy in a sound wave also decreases and eventually it dissipates completely. This is why we often can’t hear someone calling from very far away when there’s loud music playing – because the high frequencies are being blocked out by all the noise!

Can Sound Travel 20 Miles?

The air may be permeable to these lower-frequency, sub-audible sound waves generated by elephants. Some whale species’ frequencies might travel through seawater for 1500 kilometers or 900 miles.

How Far Can a Human Scream Travel?

The normal intelligible outdoor range of the male human voice in still air is 180 m (590 ft 6.6 in).

The Guiness World Record of the Farthest distance travelled by a human voice belongs the Spanish-speaking inhabitants of the Canary Island of La Gomera, is intelligible under ideal conditions at 8 km (5 miles).

In Conclusion

At the end of this blog post, you should have a better understanding of how sound travel and what factors affect it. If you want to learn more about acoustics and sounds, you can check out our resources here.

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Understanding Sound Waves and How They Work

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Sound. When a drum is struck, the drumhead vibrates and the vibrations are transmitted through the air in the form of sound waves . When they strike the ear, these waves produce the sensation of sound.

Technically, sound is defined as a mechanical disturbance traveling through an elastic medium — a material that tends to return to its original condition after being deformed. The medium doesn't have to be air. Metal, wood, stone, glass, water, and many other substances conduct sound — many of them even better than air.

The Basics of Sound

Sound waves, speed of sound, the behavior of a sound wave, sound quality, history of sound.

There are many sources of sound. Familiar kinds include the vibration of a person's vocal cords, vibrating strings (piano, violin), a vibrating column of air (trumpet, flute), and vibrating solids (a door when someone knocks). It's impossible to list them all because anything that imparts a disturbance to an elastic medium is a source of sound.

Sound can be described in terms of pitch — from the low rumble of distant thunder to the high-pitched buzzing of a mosquito — and loudness. Pitch and loudness , however, are subjective qualities; they depend in part on the hearer's sense of hearing. Objective, measurable qualities of sound include frequency and intensity, which are related to pitch and loudness. These terms, as well as others used in discussing sound, are best understood through an examination of sound waves and their behavior.

Speed of sound in various mediums

Air, like all matter, consists of molecules. Even a tiny region of air contains vast numbers of air molecules. The molecules are in constant motion, traveling randomly and at great speed. They constantly collide with and rebound from one another and strike and rebound from objects that are in contact with the air.

When an object vibrates it produces sound waves in the air. For example, when the head of a drum is hit with a mallet, the drumhead vibrates and produces sound waves. The vibrating drumhead produces sound waves because it moves alternately outward and inward, pushing against, then moving away from, the air next to it. The air particles that strike the drumhead while it is moving outward rebound from it with more than their normal energy and speed, having received a push from the drumhead.

These faster-moving molecules move into the surrounding air. For a moment, the region next to the drumhead has a greater-than-normal concentration of air molecules — it becomes a region of compression. As the faster-moving molecules overtake the air molecules in the surrounding air, they collide with them and pass on their extra energy. The region of compression moves outward as the energy from the vibrating drumhead is transferred to groups of molecules farther and farther away.

Air molecules that strike the drumhead while it's moving inward rebound from it with less than their normal energy and speed. For a moment, the region next to the drumhead has fewer air molecules than normal — it becomes a region of rarefaction. Molecules colliding with these slower-moving molecules also rebound with less speed than normal, and the region of rarefaction travels outward.

The nature of sound is captured through its fundamental characteristics : wavelength (the distance between wave peaks), amplitude (the height of the wave, corresponding to loudness), frequency (the number of waves passing a point per second, related to pitch), time period (the time it takes for one complete wave cycle to occur), and velocity (the speed at which the wave travels through a medium). These properties intertwine to craft the unique signature of every sound we hear.

The wave nature of sound becomes apparent when a graph is drawn to show the changes in the concentration of air molecules at some point as the alternating pulses of compression and rarefaction pass that point. The graph for a single pure tone, such as that produced by a vibrating tuning fork, would show a sine wave (illustrated here ). The curve shows the changes in concentration. It begins, arbitrarily, at some time when the concentration is normal and a compression pulse is just arriving. The distance of each point on the curve from the horizontal axis indicates how much the concentration varies from normal.

Each compression and the following rarefaction make up one cycle. (A cycle can also be measured from any point on the curve to the next corresponding point.) The frequency of a sound is measured in cycles per second or hertz (abbreviated Hz). The amplitude is the greatest amount by which the concentration of air molecules varies from the normal.

The wavelength of a sound is the distance the disturbance travels during one cycle. It's related to the sound's speed and frequency by the formula speed/frequency = wavelength. This means that high-frequency sounds have short wavelengths and low-frequency sounds have long wavelengths. The human ear can detect sounds with frequencies as low as 20 Hz and as high as 20,000 Hz. In still air at room temperature, sounds with these frequencies have wavelengths of 75 feet (23 m) and 0.68 inch (1.7 cm) respectively.

Intensity refers to the amount of energy transmitted by the disturbance. It's proportional to the square of the amplitude. Intensity is measured in watts per square centimeter or in decibels (db). The decibel scale is defined as follows: An intensity of 10-16 watts per square centimeter equals 0 db. (Written out in decimal form, 10-16 appears as 0.0000000000000001.) Each tenfold increase in watts per square centimeter means an increase of 10 db. Thus, an intensity of 10-15 watts per square centimeter can also be expressed as 10 db and an intensity of 10-4 (or 0.0001) watts per square centimeter as 120 db.

The intensity of sound drops rapidly with increasing distance from the source. For a small sound source radiating energy uniformly in all directions, intensity varies inversely with the square of the distance from the source. That is, at a distance of two feet from the source the intensity is one-fourth as great as it is at a distance of one foot; at three feet it is only one-ninth as great as at one foot, etc.

Pitch depends on the frequency ; in general, a rise in frequency causes a sensation of rising pitch. The ability to distinguish between two sounds that are close in frequency, however, decreases in the upper and lower parts of the audible frequency range. There is also variation from person to person in the ability to distinguish between two sounds of very nearly the same frequency. Some trained musicians can detect differences in frequency as small as 1 or 2 Hz.

Because of how the hearing mechanism functions, the perception of pitch is also affected by intensity. Thus, when a tuning fork vibrating at 440 Hz (the frequency of A above middle C on the piano) is brought closer to the ear, a slightly lower tone, as though the fork were vibrating more slowly, is heard.

When the source of a sound is moving at a relatively high speed, a stationary listener hears a sound higher in pitch when the source is moving toward him or her and a sound lower in pitch when the source is moving away. This phenomenon, known as the Doppler effect , is due to the wave nature of sound.

In general, an increase in intensity will cause a sensation of increased loudness. But loudness does not increase in direct proportion to intensity. A sound of 50 dB has ten times the intensity of a sound of 40 dB but is only twice as loud. Loudness doubles with each increase of 10 dB in intensity.

Loudness is also affected by frequency because the human ear is more sensitive to some frequencies than to others. The threshold of hearing — the lowest sound intensity that will produce the sensation of hearing for most people — is about 0 dB in the 2,000 to 5,000 Hz frequency range. For frequencies below and above this range, sounds must have greater intensity to be heard. Thus, for example, a sound of 100 Hz is barely audible at 30 dB; a sound of 10,000 Hz is barely audible at 20 dB. At 120 to 140 dB, most people experience physical discomfort or actual pain, and this level of intensity is referred to as the threshold of pain .

When we visualize waves, we often think of transverse waves — like the rolling waves on a beach — where the motion of the wave is perpendicular to the direction of energy transfer. However, sound waves are a different type altogether — a longitudinal wave. In longitudinal sound waves, such as sound waves produced by a vibrating drumhead or our vocal cords, the particles of the medium move parallel to the wave's direction of travel. This movement creates areas of compression and rarefaction in the medium — be it air, water, or a solid — which our ears interpret as sound. Understanding the difference between longitudinal and transverse waves is central to understanding sound.

The speed of sound depends on the elasticity and density of the medium through which it is traveling. In general, sound travels faster in liquids than in gases and faster in solids than in liquids. The greater the elasticity and the lower the density, the faster sound moves in a medium. The mathematical relationship is speed = (elasticity/density).

The effect of elasticity and density on the speed of sound can be seen by comparing the speed of sound in air, hydrogen, and iron. Air and hydrogen have nearly the same elastic properties, but the density of hydrogen is less than that of air. Sound travels faster (about 4 times as fast) in hydrogen than in air. Although the density of air is much less than that of iron, the elasticity of iron is very much greater than that of air. Sound travels faster (about 14 times as fast) in iron than in air.

The speed of sound in a material, particularly in a gas or liquid, varies with temperature because a change in temperature affects the material's density. In air, for example, the speed of sound increases with an increase in temperature . At 32 °F. (0 °C.), the speed of sound in air is 1,087 feet per second (331 m/s); at 68 °F. (20 °C.), it is 1,127 feet per second (343 m/s).

The terms subsonic and supersonic refer to the speed of an object, such as an airplane, in relation to the speed of sound in the surrounding air. A subsonic speed is below the speed of sound; a supersonic speed is above the speed of sound. An object traveling at supersonic speed produces shock waves rather than ordinary sound waves. A shock wave is a compression wave that, when produced in air, can usually be heard as a sonic boom .

The speeds of supersonic objects are often expressed in terms of Mach number — the ratio of the object's speed to the speed of sound in the surrounding air. Thus, an object traveling at Mach 1 is traveling at the speed of sound; at Mach 2, it is traveling at twice the speed of sound.

Like light waves and other waves, sound waves are reflected, refracted, and diffracted, and exhibit interference.

Sound is constantly being reflected off many different surfaces. Most of the time the reflected sound is not noticed, because two identical sounds that reach the human ear less than 1/15 of a second apart cannot be distinguished as separate sounds. When the reflected sound is heard separately, it's called an echo .

Sound is reflected from a surface at the same angle at which it strikes the surface. This fact makes it possible to focus sound by means of curved reflecting surfaces in the same way that curved mirrors can be used to focus light. It also accounts for the effects of so-called whispering galleries, rooms in which a word whispered at one point can be heard distinctly at some other point fairly far away, though it cannot be heard anywhere else in the room. (The National Statuary Hall of the United States Capitol is an example.) Reflection is also used to focus sound in a megaphone and when calling through cupped hands.

The reflection of sound can pose a serious problem in concert halls and auditoriums. In a poorly designed hall, a speaker's first word may reverberate (echo repeatedly) for several seconds, so that the listeners may hear all the words of a sentence echoing at the same time. Music can be similarly distorted. Such problems can usually be corrected by covering reflecting surfaces with sound-absorbing materials such as draperies or acoustical tiles. Clothing also absorbs sound; for this reason, reverberation is greater in an empty hall than in one filled with people. All these sound-absorbing materials are porous; sound waves entering the tiny air-filled spaces bounce around in them until their energy is spent. They are, in effect, trapped.

The reflection of sound is used by some animals, notably bats , for echolocation — locating, and in some cases identifying, objects through the sense of hearing rather than the sense of sight. Bats emit bursts of sound of frequencies far beyond the upper limits of human hearing. Sounds with short wavelengths are reflected even from very small objects. A bat can unerringly locate and catch even a mosquito in total darkness. Sonar is an artificial form of echolocation .

When a wave passes from one material to another at an angle, it usually changes speed, causing the wave front to bend. The refraction of sound can be demonstrated in a physics laboratory by using a lens-shaped balloon filled with carbon dioxide to bring sound waves to a focus.

Diffraction

When sound waves pass around an obstacle or through an opening in an obstacle, the edge of the obstacle or the opening acts as a secondary sound source, sending out waves of the same frequency and wavelength (but of lower intensity) as the original source. The spreading out of sound waves from the secondary source is called diffraction . Because of this phenomenon, sound can be heard around corners despite the fact that sound waves generally travel in a straight line.

Interference

Whenever waves interact, interference occurs. For sound waves, the phenomenon is perhaps best understood by thinking in terms of the compressions and rarefactions of the two waves as they arrive at some point. When the waves are in phase so that their compressions and rarefactions coincide, they reinforce each other ( constructive interference ). When they are out of phase, so that the compressions of one coincide with the rarefactions of the other, they tend to weaken or even cancel each other ( destructive interference ). The interaction between the two waves produces a resultant wave.

In auditoriums, destructive interference between sound from the stage and sound reflected from other parts of the hall can create dead spots in which both the volume and clarity of sound are poor. Such interference can be reduced by the use of sound-absorbing materials on reflecting surfaces. On the other hand, interference can improve an auditorium's acoustical qualities. This is done by arranging the reflecting surfaces in such a way that the level of sound is actually increased in the area in which the audience sits.

Interference between two waves of nearly but not quite equal frequencies produces a tone of alternately increasing and decreasing intensity because the two waves continually fall in and out of phase. The pulsations heard are called beats. Piano tuners make use of this effect, adjusting the tone of a string against that of a standard tuning fork until beats can no longer be heard.

Sound waves are fundamentally pressure waves, traveling through the compression and rarefaction of particles within a medium. Sound waves consist of areas where particles are bunched together, followed by areas where they're spread apart. These high-pressure and low-pressure regions propagate through environments such as air, water or solids, as the energy of the sound wave moves from particle to particle. It's the rapid variation in pressure that an ear drum detects and the brain decodes into the sounds we hear.

Sounds of a single pure frequency are produced only by tuning forks and electronic devices called oscillators ; most sounds are a mixture of tones of different frequencies and amplitudes. The tones produced by musical instruments have one important characteristic in common: they are periodic, that is, the vibrations occur in a repeating pattern. The oscilloscope trace of a trumpet's sound shows such a pattern. For most non-musical sounds, such as those of a bursting balloon or a person coughing, an oscilloscope trace would show a jagged, irregular pattern, indicating a jumble of frequencies and amplitudes.

A column of air, as that in a trumpet, and a piano string both have a fundamental frequency — the frequency at which they vibrate most readily when set in motion. For a vibrating column of air, that frequency is determined principally by the length of the column. (The trumpet's valves are used to change the effective length of the column.) For a vibrating string, the fundamental frequency depends on the string's length, its tension, and its mass per unit length.

In addition to its fundamental frequency, a string or vibrating column of air also produces overtones with frequencies that are whole-number multiples of the fundamental frequency. It is the number of overtones produced and their relative strength that gives a musical tone from a given source its distinctive quality or timbre . The addition of further overtones would produce a complicated pattern, such as that of the oscilloscope trace of the trumpet's sound.

How the fundamental frequency of a vibrating string depends on the string's length, tension, and mass per unit length is described by three laws:

1. The fundamental frequency of a vibrating string is inversely proportional to its length.

Reducing the length of a vibrating string by one-half will double its frequency, raising the pitch by one octave, if the tension remains the same.

2. The fundamental frequency of a vibrating string is directly proportional to the square root of the tension.

Increasing the tension of a vibrating string raises the frequency; if the tension is made four times as great, the frequency is doubled, and the pitch is raised by one octave.

3. The fundamental frequency of a vibrating string is inversely proportional to the square root of the mass per unit length.

This means that of two strings of the same material and with the same length and tension, the thicker string has the lower fundamental frequency. If the mass per unit length of one string is four times that of the other, the thicker string has a fundamental frequency one-half that of the thinner string and produces a tone one octave lower.

One of the first discoveries regarding sound was made in the sixth century B.C. by the Greek mathematician and philosopher Pythagoras . He noted the relationship between the length of a vibrating string and the tone it produces — what is now known as the first law of strings. Pythagoras may also have understood that the sensation of sound is caused by vibrations. Not long after his time it was recognized that this sensation depends on vibrations traveling through the air and striking the eardrum.

About 1640 the French mathematician Marin Mersenne conducted the first experiments to determine the speed of sound in air. Mersenne is also credited with discovering the second and third laws of strings. In 1660 the British scientist Robert Boyle demonstrated that the transmission of sound required a medium — by showing that the ringing of a bell in a jar from which the air had been pumped could not be heard.

Ernst Chladni , a German physicist, made extensive analyses of sound vibrations during the late 1700s and early 1800s. In the early 1800s, the French mathematician Fourier discovered that such complex waves as those produced by a vibrating string with all its overtones consist of a series of simple periodic waves.

An important contribution to the understanding of acoustics was made by Wallace Clement Sabine , a physicist at Harvard University, in the late 1890s. Sabine was asked to improve the acoustics of the main lecture hall in Harvard's Fogg Art Museum. He was first to measure reverberation time — which he found to be 5 1/2 seconds in the lecture hall. Experimenting first with seat cushions from a nearby theater, and later with other sound-absorbing materials and other methods, Sabine laid the foundation for architectural acoustics. He designed Boston Symphony Hall (opened in 1900), the first building with scientifically formulated acoustics.

In the second half of the 20th century, the rising level of noise in the modern world — particularly in urban areas — prompted a whole new series of investigations, dealing in large part with the physiological and psychological effects of noise on humans.

This article was updated in conjunction with AI technology, then fact-checked and edited by a HowStuffWorks editor.

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by Chris Woodford . Last updated: July 23, 2023.

Photo: Sound is energy we hear made by things that vibrate. Photo by William R. Goodwin courtesy of US Navy and Wikimedia Commons .

What is sound?

Photo: Sensing with sound: Light doesn't travel well through ocean water: over half the light falling on the sea surface is absorbed within the first meter of water; 100m down and only 1 percent of the surface light remains. That's largely why mighty creatures of the deep rely on sound for communication and navigation. Whales, famously, "talk" to one another across entire ocean basins, while dolphins use sound, like bats, for echolocation. Photo by Bill Thompson courtesy of US Fish and Wildlife Service .

Robert Boyle's classic experiment

Artwork: Robert Boyle's famous experiment with an alarm clock.

How sound travels

Artwork: Sound waves and ocean waves compared. Top: Sound waves are longitudinal waves: the air moves back and forth along the same line as the wave travels, making alternate patterns of compressions and rarefactions. Bottom: Ocean waves are transverse waves: the water moves back and forth at right angles to the line in which the wave travels.

The science of sound waves

Picture: Reflected sound is extremely useful for "seeing" underwater where light doesn't really travel—that's the basic idea behind sonar. Here's a side-scan sonar (reflected sound) image of a World War II boat wrecked on the seabed. Photo courtesy of U.S. National Oceanographic and Atmospheric Administration, US Navy, and Wikimedia Commons .

Whispering galleries and amphitheaters

Photos by Carol M. Highsmith: 1) The Capitol in Washington, DC has a whispering gallery inside its dome. Photo credit: The George F. Landegger Collection of District of Columbia Photographs in Carol M. Highsmith's America, Library of Congress , Prints and Photographs Division. 2) It's easy to hear people talking in the curved memorial amphitheater building at Arlington National Cemetery, Arlington, Virginia. Photo credit: Photographs in the Carol M. Highsmith Archive, Library of Congress , Prints and Photographs Division.

Measuring waves

Understanding amplitude and frequency, why instruments sound different, the speed of sound.

Photo: Breaking through the sound barrier creates a sonic boom. The mist you can see, which is called a condensation cloud, isn't necessarily caused by an aircraft flying supersonic: it can occur at lower speeds too. It happens because moist air condenses due to the shock waves created by the plane. You might expect the plane to compress the air as it slices through. But the shock waves it generates alternately expand and contract the air, producing both compressions and rarefactions. The rarefactions cause very low pressure and it's these that make moisture in the air condense, producing the cloud you see here. Photo by John Gay courtesy of US Navy and Wikimedia Commons .

Why does sound go faster in some things than in others?

Chart: Generally, sound travels faster in solids (right) than in liquids (middle) or gases (left)... but there are exceptions!

How to measure the speed of sound

Sound in practice, if you liked this article..., find out more, on this website.

• Electric guitars
• Speech synthesis
• Synthesizers

On other sites

• Explore Sound : A comprehensive educational site from the Acoustical Society of America, with activities for students of all ages.
• Sound Waves : A great collection of interactive science lessons from the University of Salford, which explains what sound waves are and the different ways in which they behave.

Educational books for younger readers

• Sound (Science in a Flash) by Georgia Amson-Bradshaw. Franklin Watts/Hachette, 2020. Simple facts, experiments, and quizzes fill this book; the visually exciting design will appeal to reluctant readers. Also for ages 7–9.
• Sound by Angela Royston. Raintree, 2017. A basic introduction to sound and musical sounds, including simple activities. Ages 7–9.
• Experimenting with Sound Science Projects by Robert Gardner. Enslow Publishers, 2013. A comprehensive 120-page introduction, running through the science of sound in some detail, with plenty of hands-on projects and activities (including welcome coverage of how to run controlled experiments using the scientific method). Ages 9–12.
• Cool Science: Experiments with Sound and Hearing by Chris Woodford. Gareth Stevens Inc, 2010. One of my own books, this is a short introduction to sound through practical activities, for ages 9–12.
• Adventures in Sound with Max Axiom, Super Scientist by Emily Sohn. Capstone, 2007. The original, graphic novel (comic book) format should appeal to reluctant readers. Ages 8–10.

Popular science

• The Sound Book: The Science of the Sonic Wonders of the World by Trevor Cox. W. W. Norton, 2014. An entertaining tour through everyday sound science.

Academic books

• Master Handbook of Acoustics by F. Alton Everest and Ken Pohlmann. McGraw-Hill Education, 2015. A comprehensive reference for undergraduates and sound-design professionals.
• The Science of Sound by Thomas D. Rossing, Paul A. Wheeler, and F. Richard Moore. Pearson, 2013. One of the most popular general undergraduate texts.

Text copyright © Chris Woodford 2009, 2021. All rights reserved. Full copyright notice and terms of use .

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Middle school physics - NGSS

Course: middle school physics - ngss   >   unit 4.

• Wave transmission
• Refraction and frequency
• Refraction in a glass of water

Transmission and refraction

• Understand: transmission and refraction

Key points:

• Transmission happens when a wave travels through a medium or into a new medium .
• Transmission depends on the type of wave, type of material and even the frequency of the wave.
• For example, if you knock on a door the vibration you create will transmit through the door and be heard as sound. However, light does not transmit through a door so you cannot be seen through it.
• Usually, waves travel in a straight line until they interact with a boundary. Refraction happens when a wave’s path bends at a boundary as it transmits into a new medium.
• The amount a wave refracts depends on the type of wave, the frequency of the wave, and the material it is moving into.

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Does Sound Travel in a Straight Line? | The Science of Sound

Does Sound Travel in a Straight Line?

Have you ever wondered why you can hear a car coming from around a corner? Or why you can hear someone calling your name from down the street? It’s because sound waves travel in straight lines.

In this article, we’ll explore the science of sound waves and how they travel through the air. We’ll also look at some of the factors that can affect the way sound waves travel, such as obstacles and the shape of the environment.

By the end of this article, you’ll have a better understanding of how sound waves work and why they travel the way they do.

Does Sound Travel In A Straight Line?

| Column 1 | Column 2 | Column 3 | |—|—|—| | Question | Does sound travel in a straight line? | Yes, sound travels in a straight line in a homogeneous medium. | | Explanation | Sound waves are longitudinal waves, which means that they travel through a medium by causing the particles of the medium to vibrate back and forth in the same direction that the wave is moving. In a homogeneous medium, the particles of the medium are all evenly spaced, so the sound waves can travel in a straight line. | | Examples | If you clap your hands in a quiet room, you will hear a sound that travels in a straight line from your hands to your ears. |

What is Sound?

Sound is a vibration that travels through a medium, such as air or water. When an object vibrates, it creates a disturbance in the surrounding medium. This disturbance is what we perceive as sound. The pitch of a sound is determined by the frequency of the vibration, while the loudness of a sound is determined by the amplitude of the vibration.

Sound waves are longitudinal waves, which means that they move in the same direction as the vibration. The speed of sound in a given medium is determined by the elasticity and density of the medium. In air, the speed of sound is about 343 meters per second (767 miles per hour).

How Does Sound Travel?

Sound travels through a medium in a series of compressions and rarefactions. A compression is a region of increased pressure, while a rarefaction is a region of decreased pressure. As the sound wave travels, the compressions and rarefactions alternate.

When a sound wave strikes an object, the object vibrates. The vibrations of the object then create a new sound wave, which travels through the medium. This process can continue for many reflections, until the sound wave eventually dies out.

The speed at which a sound wave travels through a medium is determined by the following factors:

• The elasticity of the medium. Elasticity is the ability of a material to return to its original shape after being deformed.
• The density of the medium. Density is the mass of a substance per unit volume.

The speed of sound is greater in more elastic and less dense media. For example, the speed of sound in air is about 343 meters per second (767 miles per hour), while the speed of sound in water is about 1,484 meters per second (2,776 miles per hour).

No, sound does not travel in a straight line. Sound waves are reflected, refracted, and diffracted by objects in their path. This means that the direction of a sound wave can change as it travels through a medium.

The amount of reflection, refraction, and diffraction that a sound wave undergoes depends on the properties of the object that it encounters. For example, a sound wave will be reflected more strongly by a hard surface than by a soft surface. A sound wave will also be refracted more strongly when it travels from a denser medium to a less dense medium.

The effect of reflection, refraction, and diffraction on the path of a sound wave can be seen in a number of everyday phenomena. For example, when you talk to someone in a noisy room, you can hear their voice more clearly if you turn your head so that your ear is facing them. This is because the sound waves from their voice are reflected off your head and into your ear.

Another example of the effect of reflection, refraction, and diffraction on sound waves can be seen when you listen to a radio. The radio waves from a broadcasting station are reflected off of the ionosphere, which is a layer of charged particles in the upper atmosphere. This reflection allows the radio waves to travel around the Earth, so that you can receive them even if you are not located directly in the path of the radio waves.

Sound is a vibration that travels through a medium. The speed at which a sound wave travels through a medium is determined by the elasticity and density of the medium. Sound waves can be reflected, refracted, and diffracted by objects in their path. This means that the direction of a sound wave can change as it travels through a medium.

Sound waves are a type of mechanical wave, which means that they require a medium to travel through. In the case of sound waves, the medium is air. Sound waves are created when an object vibrates, and these vibrations cause the air molecules around the object to move. As the air molecules move, they bump into other air molecules, and this creates a chain reaction that carries the sound wave away from the object that created it.

So, does sound travel in a straight line? The answer is: it depends. In a perfect vacuum, sound waves would travel in a straight line. However, in the real world, there are always obstacles in the way of sound waves, such as objects, walls, and even the air itself. These obstacles can cause sound waves to bend, reflect, and refract.

Examples of Sound Waves that Do Not Travel in a Straight Line

There are many examples of sound waves that do not travel in a straight line. Here are a few of the most common:

• Reflection: When sound waves hit a hard surface, they bounce off of it and travel in a different direction. This is why you can hear someone talking in another room even if you can’t see them.
• Refraction: When sound waves travel through a medium that changes density, they bend. This is why you can hear a car horn sound different when it’s coming towards you than when it’s going away from you.
• Diffraction: When sound waves encounter an obstacle, they spread out and travel around the obstacle. This is why you can hear someone talking even if they’re behind a wall.
• Absorption: When sound waves hit a surface, some of the energy is absorbed by the surface. This is why you can’t hear someone talking if they’re in a soundproof room.

These are just a few of the ways that sound waves can travel in the real world. The next time you hear a sound, take a moment to think about how it’s traveling through the air. You might be surprised at how complex it can be!

Sound waves are a fascinating phenomenon that can be found all around us. They play an important role in our lives, allowing us to communicate with each other and enjoy music and other forms of entertainment. By understanding how sound waves travel, we can better appreciate the world around us.

Does sound travel in a straight line?

No, sound waves travel in a three-dimensional wavefront. However, in many cases, the sound waves are emitted from a point source and travel in a relatively straight line until they encounter an obstacle.

Why doesn’t sound travel in a straight line?

Sound waves are caused by the vibration of objects. When an object vibrates, it creates a disturbance in the air molecules around it. This disturbance is what we perceive as sound. The disturbance in the air molecules travels in a wave-like pattern, and this is what we refer to as a sound wave.

The shape of the sound wave depends on the source of the vibration. If the source is a point source, the sound waves will be spherical. If the source is a line source, the sound waves will be cylindrical.

In most cases, the sound waves will travel in a relatively straight line until they encounter an obstacle. When the sound waves encounter an obstacle, they can be reflected, refracted, or absorbed.

** What factors affect the way sound travels?

The way sound travels is affected by a number of factors, including:

• The medium through which the sound is traveling
• The temperature of the medium
• The presence of obstacles
• The shape of the obstacle

** How does the medium affect the way sound travels?

The speed of sound is different in different media. The speed of sound in air is about 343 meters per second (767 miles per hour). The speed of sound in water is about 1,480 meters per second (3,290 miles per hour). The speed of sound in steel is about 5,120 meters per second (11,300 miles per hour).

The different speeds of sound in different media are due to the different densities of the media. The denser the medium, the faster the speed of sound.

** How does the temperature affect the way sound travels?

The speed of sound increases with temperature. This is because the molecules in a warmer medium are moving faster than the molecules in a cooler medium. The faster the molecules are moving, the more easily they can transmit sound waves.

** How does the presence of obstacles affect the way sound travels?

When sound waves encounter an obstacle, they can be reflected, refracted, or absorbed.

• Reflection occurs when the sound waves bounce off the obstacle and travel in a different direction.
• Refraction occurs when the sound waves bend as they pass through the obstacle.
• Absorption occurs when the sound waves are converted into heat energy.

The way sound waves are affected by an obstacle depends on the size, shape, and material of the obstacle.

** How does the shape of the obstacle affect the way sound travels?

The shape of the obstacle can affect the way sound waves are reflected, refracted, or absorbed.

• Sharp corners can cause sound waves to be reflected in a more focused way.
• Curved surfaces can cause sound waves to be refracted in a more diffuse way.
• Porous materials can absorb sound waves more effectively than solid materials.

The shape of the obstacle can also affect the way sound waves are heard. For example, a sound wave that is reflected off a sharp corner will be louder than a sound wave that is reflected off a curved surface.

Sound waves do not travel in a straight line. However, in many cases, the sound waves are emitted from a point source and travel in a relatively straight line until they encounter an obstacle. The way sound travels is affected by a number of factors, including the medium through which the sound is traveling, the temperature of the medium, the presence of obstacles, and the shape of the obstacle.

In this article, we have discussed the question of whether or not sound travels in a straight line. We have seen that the answer is not always straightforward, as sound waves can be reflected, refracted, and diffracted. However, in general, sound waves do travel in a straight line through a homogeneous medium. This is because sound waves are a form of energy, and energy travels in a straight line unless it is acted upon by some force.

The implications of this are that sound can be used to communicate over long distances, as long as there is a clear path between the source and the listener. This is why we can hear people talking to us from across a room, or why we can hear a car coming down the street.

However, it is also important to note that sound waves can be blocked by obstacles. This is why we cannot hear people talking to us from behind a wall, or why we cannot hear a car coming down the street if there is a building in the way.

Overall, the answer to the question of whether or not sound travels in a straight line is a complex one. However, it is important to understand the basic principles of sound wave propagation in order to understand how sound works and how it can be used.

Key Takeaways:

• Sound waves are a form of energy that travels in a straight line through a homogeneous medium.
• Sound waves can be reflected, refracted, and diffracted.
• Sound can be used to communicate over long distances, as long as there is a clear path between the source and the listener.
• Sound waves can be blocked by obstacles.

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DK Science: Acoustics

The science of how sound behaves, especially when it travels through our everyday world, is called acoustics. Sound waves normally travel in straight lines directly outwards from their source, but they do not always travel in that way. An object standing in the path of a sound wave can affect its movement. When a sound wave hits a hard object, the sound reflects back towards the source in the form of an ECHO . When soft objects get in the way, they can ABSORB the sound and stop it from travelling any further. Scientists use sound reflection and absorption to investigate places that they cannot visit, such as the depths of oceans and the interior of the Earth.

HOLLYWOOD BOWL

The Hollywood Bowl is a famous, open-air amphitheatre in California, USA. An amphitheatre is a bowl-shaped place that reflects sound naturally and evenly into the landscape around it. The Hollywood Bowl was carved into the side of a mountain at Bolton Canyon in the 1920s and can seat 20,000 people.

CONCERT HALL

Music must sound clear in an auditorium, no matter where people are sitting in the audience. It should sound the same whether the hall is full or nearly empty. The curved shapes in modern concert halls are designed to help distribute the sound evenly to every seat in the auditorium.

If you shout at a distant wall, you can hear your voice return as a reflected sound wave, or echo. When the reflected sound wave has to travel some distance, it takes time to return and you hear it separately from the original sound. Sound waves that reflect off nearer objects return almost instantly. Our brains blend these waves with the original sound and we hear no echo.

ECHOLOCATION

Like many other sea creatures, dolphins use sound to find their way around, locate their companions, and discover sources of food. The clicking sounds they make are reflected back from the seabed and objects around them and are picked up by the dolphins’ long, bony heads. Using echoes to find things is known as echolocation.

EXPLORING WITH SONAR

The depth of the ocean can be measured using SONAR (SOund Navigation And Ranging). A loudspeaker under the ship sends down a beam of high-frequency ultrasound. Echoes of the sound waves are detected by hydrophone (underwater microphone) as they bounce back up.

Hard objects reflect sounds, but soft materials absorb sounds and silence them. When sound waves reach a soft material, their energy is soaked up and they travel no further. Things that absorb sound can be useful for reducing noise. Trees are sometimes planted by motorways so that their leaves will reduce the sound of traffic. Walls can be padded with soft materials to stop sound from travelling through them.

ANECHOIC CHAMBER

Engineers test loudspeakers and audio equipment in specially designed laboratories called anechoic chambers. The walls and ceiling are covered by spikes of soft foam that absorb sound and stop any echoes and reverberations (very fast echoes). Sounds made inside an anechoic chamber sound very dull or “dead”, which is why the chambers are also called “dead rooms”.

FIND OUT MORE

Refraction of Sound

After reading this section you will be able to do the following:.

• Define sound refraction and why it occurs.
• Describe what occurs when a sound wave reaches the critical angle.

Set Materials 1 and 2 to different values. Set the angle of Material 1 to 90 degrees. Try this with multiple material pairs and observe what happens.

Sound traveling between materials

Remember that sound travels faster in some materials than others. Sound waves travel outward in straight lines from their source until something interferes with their path. When sound changes mediums (enters a different material) at an angle other that 90 degrees, it is bent from its original direction. This change in angle of direction is called refraction . Because of the angle, part of the wave enters the new medium first and changes speed. The difference in speeds causes the wave to bend. The velocity of sound in each material is determined by the material properties (elastic modulus and density) for that material.

In the animation below, a series of plane waves are shown traveling in one material and entering a second material that has a higher acoustic velocity. Therefore, when the wave encounters the interface between these two materials, the portion of the wave in the second material is moving faster than the portion of the wave in the first material. It can be seen that this causes the wave to bend.

The angle of refraction depends on the angle that the waves has when it enters the new medium and the velocities of the waves in the two materials. Snell's Law describes the relationship between the angles and the velocities of the waves.  Snell's law equates the ratio of material velocities V 1 and V 2 to the ratio of the sine's of incident (Q 1 ) and refracted (Q 2 ) angles, as shown in the applet above and in the following equation.

It should be noted that only a portion of the sound enters the second medium.  A portion of the sound is also reflected back into the first medium. The angle which the incident wave makes with a line normal to the interface is equal to the angle which the reflected wave makes to the same normal line.  It should also be noted that when the angle of the incident wave reaches a large enough angle, the sound wave no longer enters the second material but instead the wave runs along the interface between the two materials. The angle where this occurs is called the critical angle.

• Sound travels faster in some materials than others.
• The angle of refraction depends on the angle that the waves has when it enters the new medium and the velocities of the waves in the two materials.

Reflecting on the Journey

Does sound travel up or down noise guide.

Let’s address the main question: Does sound travel up or down? In reality, sound doesn’t have a fixed direction of travel like light, which travels in straight lines. Sound waves radiate out in all directions from their source.

• September 25, 2023

Home » Blog » Does sound travel up or down? Noise Guide

Sound is like an exquisite tapestry that winds its way through our lives. We can’t see it, but it’s always with us.

There are sound waves all around us all the time, from the birds singing in the morning to the soothing music we listen to.

In the middle of this sound symphony, though, an interesting question comes up: does sound have a set path that it follows, going up or down?

In this blog, we’ll start a trip to figure out the mysteries of sound waves by looking into how they travel and breaking down the puzzle of their direction.

Explore the fascinating world of sound with us. This is where science meets magic, and sometimes the answers aren’t as simple as they seem.

The Nature of Sound Waves

To understand how sound moves, you need to know the basics of sound waves . Sound is a type of mechanical wave that moves through a medium, like air but also things and liquids. 

The vibrations of things, like voice cords, musical instruments, or even the sound of thunder during a storm, make these waves.

Compressions and rarefactions make up sound waves. Compressions are places where the medium’s particles are close to each other, while rarefactions are places where the particles are far apart. 

Since these changes in pressure travel through the medium, they make sound when they reach our ears.

Does sound travel up or down?

Sound doesn’t have a fixed direction of travel like a projectile or a ray of light. Instead, sound waves propagate outward spherically from their source in all directions, creating a three-dimensional sphere of expanding waves. 

This means sound moves in every direction at the same time, including up, down, sideways, and all other directions you can think of. 

If you throw a stone into a still pond, the waves will move outward in a circle, not just up and down. In the same way, sound waves spread out from their source and fill the space around them. 

The way our ears pick up a sound, on the other hand, gives us an idea of its direction. Our brains use the small difference in time between when a sound hits each ear and the difference in sound intensity to figure out where the sound is coming from. 

This lets us know if it’s above, below, or somewhere else in our environment. In other words, sound travels in all directions, but our hearing and the surroundings affect where we think it came from.

Types of Sound & How Each Sound Types Works

Sound is a complex and diverse phenomenon, and it can be categorized into various types based on several characteristics and properties. Here, we’ll explore the primary types of sound:

Audible Sound:

Audible sound is any sound that falls in the 20 Hz to 20,000 Hz frequency band that humans can hear. In a medium, like air, pressure waves move through it and make it work. 

When an item vibrates, it causes the molecules of air around it to compress and expand. 

These changes in air pressure move through the air like waves, hitting our ears and making our eardrums tremble. 

Next, our inner ear turns these movements into electrical signals. These signals are sent to the brain to be interpreted as sound.

Infrasound:

Infrasound is made up of sound waves with frequencies below 20 Hz, which is the lowest frequency that humans can hear. Infrasound is often made by natural events like meteorites hitting Earth, earthquakes, and volcanic fires.

It can also come from things that people make, like industry machinery. Even though we can’t hear infrasound, it can have an effect on our bodies because it can make different structures vibrate and resonate.

Ultrasound:

Ultrasound uses sound waves with levels above 20,000 Hz, which are higher than what the human ear can pick up. Ultrasound sounds are sent into the body by a transducer, which is used in medical imaging. 

These waves hit organs and other parts of the body inside the body and then go back to the transducer to be turned into pictures. In medicine, ultrasound is used for non-invasive screening and diagnosis. In industry, ultrasound is used to find flaws and measure them.

White Noise:

White noise is a random signal that is the same strength at all levels that humans can hear. 

It makes a constant sound that sounds like static or “shushing” by mixing sound waves with different frequencies and amplitudes. 

White noise is often used to block out other sounds that aren’t needed, to help people relax, or to help them concentrate.

Pink Noise:

While pink noise is like white noise, it has more energy in the lower levels. As the frequency goes up, the loudness of the higher-frequency parts goes down, making it. 

Pink noise is used to test and calibrate audio because it has a more even sound range.

Brownian Noise (Brown Noise):

Compared to pink noise, brownian noise has even more energy in the low levels. It is made by making the lower-frequency parts louder as the frequency goes down. 

The sound of brownian noise is often heavy and rumbling, and it is sometimes used to help people relax and sleep.

Musical Sound:

The structured vibrations of musical instruments, such as strings, air columns, or membranes, produce sound. Based on its physical properties, an instrument produces particular frequencies or harmonics when it is played. 

Melodies and harmonies can be produced by combining the musical notes that are produced by these vibrations. The way these frequencies are arranged and interact is a major factor in how we perceive music.

Speech is a type of sound that people make to communicate. It requires exact synchronization of the respiratory system, tongue, lips, and vocal cords. 

Vocal cord vibrations and airflow are adjusted to create various speech sounds, or phonemes, which are then articulated into words and sentences. 

The physiology of speech generation and the language processing abilities of our brains work together to produce the tremendously complex speech that is human.

Environmental Sounds:

Environmental noises are a wide range of sounds that are produced by nature around us. These noises come from a variety of sources, including machines, weather, animals, and more. 

The features of these entities are contingent upon the particular source and the propagation channel.

In addition to giving us information about our surroundings and affecting our mood and emotions, ambient sounds are essential to our sensory experience.

Electronic Sounds:

Synthesizers and other electronic equipment are used to artificially create electronic sounds. These gadgets generate electrical impulses, which speakers or headphones then translate into sound waves. 

Electronic sounds are adaptable and can be used in a variety of media and entertainment, including music, movies, video games, and other forms of entertainment because their frequencies, amplitudes, and waveforms can be precisely adjusted.

How We Perceive Sound Direction

Our ears are amazing devices that are made to pick up sound coming from a variety of sources. Because our two ears are on different sides of our head, we can distinguish between variances in the sound’s loudness and arrival time to establish the direction of a sound source.

Time Difference: Sound travels significantly faster to the closest ear when it comes from a source that is closer to that ear than the other. The direction of the sound source is established by our brain using this time difference.

Difference in Intensity: An ear that is nearer the source of the sound will pick up a louder sound wave than an ear that is farther away. This variation in intensity is used by our brain to enhance our understanding of sound direction.

To put it simply, our ears triangulate the direction of a sound source in order to tell us if it is coming from above, below, in front of us, or behind us.

Why does sound seem to travel upward more easily than it does horizontally?

Sound perception often gives the impression that it travels upward more easily than horizontally due to a combination of factors related to the environment, human anatomy, and the physics of sound propagation.

Acoustic Reflection and Refraction

The way that sound waves interact with their environment is one of the main reasons that sound seems to move upward more readily than horizontally. 

Sound waves have a tendency to reflect and bounce off of flat surfaces like floors, walls, and ceilings in different directions. 

Sound waves, for example, frequently bounce off of ceilings and can be deflected downward, giving the impression that sound is coming from above. 

Particularly in small areas, this sound reflection and refraction can give the impression that noises are coming from above.

Human Ear Anatomy

The idea that sound travels upward can also be attributed to the structure of the human ear . Owing to their slightly elevated position on the sides of the head, our ears are inherently more perceptive to noises coming from above than from below. 

We can find sound sources thanks to this anatomical arrangement, which enables us to notice minute differences in sound arrival timings and intensities between our ears. 

Because our ears are sensitive to upward-oriented sound signals, even when sound waves are moving horizontally, they may appear to be coming from above.

Atmospheric Conditions

The path that sound takes can be affected by atmospheric conditions. At different elevations, variations in temperature and wind speed can cause sound waves to refract, or bend. 

It may be believed that sound moves more readily upward in specific weather situations because of this refraction, which can lead sound to travel in unexpected ways, including upward.

Unlike a laser beam of light, sound is a fascinating phenomenon that is not limited to one direction of propagation. Rather, sound waves travel in all directions at once, enveloping us in a complex auditory landscape. Our ears assist us in determining the direction of sound sources because of their remarkable capacity to distinguish variations in sound arrival timings and intensities.

Thus, keep in mind that sound is all around you and that your ears are cooperating to help you identify the source of those sounds the next time you hear a bird singing in a tree, a car horn honking, or your favorite song playing on your headphones.

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Light basics.

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Light is a form of energy produced by a light source. Light is made of photons that travel very fast. Photons of light behave like both waves and particles.

Light sources

Something that produces light is called a light source. There are two main kinds of light sources:

Fireworks show how light travels faster than sound. We see the light almost instantly, but the sound arrives later. To work out how many kilometres away the fireworks are, count the seconds until you hear the bang and divide by 3.

Incandescent sources use heat to produce light. Nearly all solids, liquids and gases will start to glow with a dull red colour once they reach a temperature of about 525 °C. At about 2300 °C, the filament in a light bulb will start to produce all of the colours of the visible spectrum, so it will look white. The Sun, stars, a flame and molten metal are all incandescent.

Luminescent sources are normally cooler and can be produced by chemical reactions, such as in a glowstick or a glow-worm. Other luminescent sources include a computer screen, fluorescent lights and LEDs.

Light travels much faster than sound

Light travels at a speed of 299,792,458 m/s (that’s nearly 300,000 km/s!). The distance around the Earth is 40,000 km, so in 1 second, light could travel seven and a half times around the world.

Sound only travels at about 330 m/s through the air, so light is nearly a million times faster than sound.

If lightning flashes 1 kilometre away from you, the light reaches you in 3 millionths of a second, which is almost instantly. The sound of the thunder takes 3 seconds to travel 1 kilometre – to work out many kilometres away lightning is, count the seconds for the thunder to arrive and divide by 3.

Lightning storms are important for converting nitrogen gas in the atmosphere through to forms that are biologically available.

Light takes about 8 minutes and 20 seconds to reach the Earth from the Sun. When we see the Sun, we are seeing what it looked like over 8 minutes ago.

Light can travel through empty space

Unlike sound, which needs a medium (like air or water) to travel through, light can travel in the vacuum of space.

Light travels in straight lines

Once light has been produced, it will keep travelling in a straight line until it hits something else.

Shadows are evidence of light travelling in straight lines. An object blocks light so that it can’t reach the surface where we see the shadow. Light fills up all of the space before it hits the object, but the whole region between the object and the surface is in shadow. Shadows don’t appear totally dark because there is still some light reaching the surface that has been reflected off other objects.

Once light has hit another surface or particles, it is then absorbed, reflected (bounces off), scattered (bounces off in all directions), refracted (direction and speed changes) or transmitted (passes straight through).

Models for light

Wave length, height and frequency

A wave can be described by its length, height (amplitude) and frequency.

Light as waves

Rainbows and prisms can split white light up into different colours. Experiments can be used to show that each of these colours has a different wavelength.

When white light shines through a prism, each colour refracts at a slightly different angle. Violet light refracts slightly more than red light. A prism can be used to show the seven colours of the spectrum that make up white light.

At the beach, the wavelength of water waves might be measured in metres, but the wavelength of light is measured in nanometres – 10 -9 (0.000,000,001) of a metre. Red light has a wavelength of nearly 700 nm (that’s 7 ten-thousandths of a millimetre) while violet light is only 400 nm (4 ten-thousandths of a millimetre).

Visible light is only a very small part of the electromagnetic spectrum – it’s just that this is the range of wavelengths our eyes can detect.

Light as particles

In 1905, Albert Einstein proposed that light is made of billions of small packets of energy that we now call photons. These photons have no mass, but each photon has a specific amount of energy that depends on its frequency (number of vibrations per second). Each photon still has a wavelength. Shorter wavelength photons have more energy.

The photoelectric effect

University of Waikato science researcher Dr Adrian Dorrington explains the photoelectric effect. He then describes how camera sensors can be designed on the basis of this effect to enable light energy to be converted into electric potential energy.

The photoelectric effect is when light can cause electrons to jump out of a metal. These experiments confirm that light is made of these massless particles called photons.

Simple explanations of some of these concepts can be found in the article Building Science Concepts: Shadows .

Nature of science

In order to understand the world we live in, scientists often use models. Sometimes, several models are needed to explain the properties and behaviours of a phenomenon. For example, to understand the behaviour of light, two models are needed. Light needs to be thought of as both waves and particles.

Useful links

Even though light doesn’t have mass, learn how it still has a tiny amount of momentum. Find out about NASA’s solar sails to power spacecraft.

Read about the LightSail project, a crowdfunded project from The Planetary Society, aiming to demonstrate that solar sailing is a viable means of propulsion for CubeSats (miniature satellites intended for low Earth orbit).

Explore solar sails more in your classroom, with this activity Solar Sails: The Future of Space Travel from the TeachEngineering website.

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How to Prove That Light Travels in a Straight Path

Last Updated: April 24, 2024 Fact Checked

This article was co-authored by Chris Hasegawa, PhD . Dr. Chris Hasegawa was a Science Professor and the Dean at California State University Monterey Bay. Dr. Hasegawa specializes in teaching complex scientific concepts to students. He holds a BS in Biochemistry, a Master’s in Education, and his teaching credential from The University of California, Davis. He earned his PhD in Curriculum and Instruction from The University of Oregon. Before becoming a professor, Dr. Hasegawa conducted biochemical research in Neuropharmacology at the National Institute of Health. He also taught physical and life sciences and served as a teacher and administrator at public schools in California, Oregon, and Arizona. This article has been fact-checked, ensuring the accuracy of any cited facts and confirming the authority of its sources. This article has been viewed 211,678 times.

Light is an essential part of your day. It allows you to see objects, shapes, and colors. In fact, the pupils in your eyes filter in light to help you see everything around you. As part of a school assignment, you may be asked to prove that light travels in a straight line. You can do this using basic household items in three easy experiments.

Making a Light Pinhole

• Three index cards.
• A piece of modeling clay or sticky tack. You can also use double sided tape.

• A hole puncher.

• Take the hole puncher and punch a hole at the center of the card where the two lines intersect. Do this for the other two cards.

• Form a stand for the cards using the clay so the cards are straight and upright. Use the ruler to ensure the cards are two to five inches from each other.
• You can also use double sided tape to attach the cards to a surface in a vertical position. Do not cover or obstruct the hole in the center of the cards with modeling clay or tape.

• Note that the light can be seen through all the holes. You should be able to see the light go through all the holes and land on a wall or surface beyond the last index card.

Using a Mirror and a Flashlight

• Two to three sheets of black paper.
• Small objects like buttons, bottle caps, or dimes.

• The other person will use the small mirror to reflect the flashlight so it hits the objects. Move close to the light, at an angle, to catch the light so it hits the objects.
• You may need to position more than one mirror to create a light path that shines on the objects. Play around with reflecting the light on the mirrors until the light hits the objects. You can also move the objects around the room to create a more complicated light path, using the flashlight as the light source.
• This experiment shows that light travels in a straight line in the air. But it also bounces off of a reflective surface, like a mirror. The angle of the light as it bounces off the mirror will be the same as the angle of the light as it hits the mirror. The mirror reflects the light and changes its path from a straight line to an angled straight line.

Using Water and Oil

• A large glass jar.
• Access to water.
• One cup of oil.

• Make sure the jar is large enough to fit the ruler.

• Note that the numbers appear stretched or magnified as the light rays bend in the oil and the water. Move the ruler from side to side to note the different appearances of the ruler numbers in the oil and in the water.
• This will show that light travels at different speeds in different mediums, such as air, oil, and water. It will travel in a straight line in the air, but it will bend when it changes speed due to contact with a certain medium, like oil or water.

Expert Q&A

Things You'll Need

• A piece of modeling clay or sticky tack. You can also use tape.
• A flashlight or a laser pointer.
• A flashlight.
• A small mirror.

You Might Also Like

• ↑ http://www.ducksters.com/science/experiment_light_travel.php
• ↑ Chris Hasegawa, PhD. Retired Science Professor & Dean. Expert Interview. 29 July 2021.
• ↑ https://www.science-sparks.com/science-fair-projects-light-maze/
• ↑ https://www.scientificamerican.com/article/now-you-see-it-testing-out-light-refraction/

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Does Light Travel in a Straight Line? Can It Be Bent?

Last Updated on Jan 27 2023

A basic principle of physics states that light travels in a straight line. It’s easy to prove, too. Simply shine a light through a parallel series of openings and it will pass through each one successively. You can also see it in real-time when looking at shadows. The division between the lighted area in the background and the object obstructing the light follows the perimeter. 

Keep reading to learn more about how light travels and more pertinent information regarding the subject.

• Light vs. Sound

We can learn more about the properties of light by comparing it to another intangible force: sound. Sound is variable, depending on what it’s traveling through it and its temperature. At 59℉ at sea level, it will go 761.2 miles per h our (mph) . That may sound fast until you start delving into Albert Einstein’s Theory of Special Relativity . Essentially, nothing can exceed the speed of light.

While sound is moving around at 761.2 mph, light is zipping along at a blazing 983,571,056 feet or 186,282 miles per second. It’s worth noting that this measurement is in a vacuum. Light sound, the medium—in this case, air—can affect its speed.

We can put the two properties in perspective with lightning and thunder. Remember that that bolt is moving 186,282 miles per second. The thunder is lagging behind at 1,100 feet per second . Both are moving at a constant speed, making it easy to calculate the distance between the lightning and the clap of thunder. Count the seconds between the two and divide by five to get the number of miles away.

If you’ve seen lightning strike, you’ll notice it’s following a straight path, although it may come at an angle. However, does that mean that light never deviates from this course? The answer is no.

• Scattering the Light

If you’ve seen light shine through a cloud of dust, you may notice that it’s traveling in different directions. That’s the variations in the air medium changing with the suspended particles. Another classic example involves putting an object like a spoon in a glass of water. It will look like it’s bent. What you’re seeing is the difference between traveling through air and water.

Air is composed primarily of nitrogen, oxygen, water, and carbon dioxide. Of course, water is hydrogen and oxygen. However, there’s also the glass, which adds another factor to the mix. A prism will have a similar effect by refracting light into its various colors. However, we still have to dig a bit deeper. All things being equal, can light ever bend on its own?

• Bending Light

Scientists thought that they had solved these riddles until they discovered the Airy waveform in the late 1970s. Researchers found that light could bend ever so slightly. Next, fast forward to 2012. The reason behind the discovery is based on heavy-duty mathematics and physics . Suffice to say that self-bending light is possible, opening up opportunities to use it for various purposes, such as redirecting lasers.

It might not be something that you would ever need to do. However, it does answer some questions. So, yes, light can travel in a straight line and also bend.

• Final Thoughts

Understanding how light and sound travel tells us a lot about physics, mathematics, and science. It also shows us how much we have yet to learn about our planet and its place in the Solar System . While light does travel in a straight line, there are also times when it can bend.

• https://www.livescience.com/37022-speed-of-sound-mach-1.html
• https://www.space.com/36273-theory-special-relativity.html
• https://www.space.com/15830-light-speed.html
• https://www.grc.nasa.gov/www/k-12/airplane/sound2.html
• http://tornado.sfsu.edu/geosciences/classes/m201/Atmosphere/AtmosphericComposition.html
• https://www.britannica.com/technology/prism-optics
• https://www.science.org/content/article/light-bends-itself
• https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.108.163901

Featured Image Credit: donatas1205, Shutterstock

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About the Author Chris Dinesen Rogers

Chris has been writing since 2009 on a variety of topics. Her motto with all of her writing is “science-based writing nurtured by education and critical thinking.” Chris specializes in science topics and has a special love for health and environmental topics, and animals of all shapes and sizes.

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Characteristics of Light: Light travels in a straight line

In this lab experience, the students will be asked questions about characteristics of light and sound and whether these energy sources travel in straight lines. The teacher briefly demonstrates light and sound travel. Students will discover that light travels in a straight line. Within small groups, students explore how to prove that light travels in a straight line using 3 cards, with a hole punched in each one, and a flashlight.

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Next stop: Sound Transit East Line now links Bellevue to Redmond

Despite delays connecting the 2 Line to Seattle, hundreds rode the rails this weekend as the eight stations opened after years of construction.

• Jadenne Radoc Cabahug &

Venice Buhain

People hold up their phones as the first trains arrive to pick up the first passengers at the Bellevue Downtown Station during the opening of Sound Transit’s 2 Line light-rail service in Bellevue on Saturday, April 27, 2024. (Jason Redmond for Cascade PBS)

Sound Transit’s long-anticipated East Link debuted over the weekend, connecting Bellevue with Redmond via light rail.

The train, which will eventually travel across Lake Washington, has been a long time in the works. The extension project, formally approved by voters in 2008, was expected to cost about $3.68 billion for the line. By next year, Sound Transit expects to connect Bellevue to Seattle – where Link Light Rail opened in 2009.

Passengers take in the view of the Bellevue skyline during an innagural ride on Sound Transit’s 2 Line. (Jason Redmond for Cascade PBS)

The current configuration of what’s called the 2 Line is expected to move about 6,000 riders between Bellevue and Redmond daily on trains with two cars each, according to the agency. That number is expected to rise once the connection to Seattle is completed. Currently, Eastside riders can connect between South Bellevue and Downtown Seattle via bus.

More expansions are coming in the next few years. Light rail connecting Shoreline, Mountlake Terrace and Lynnwood to the existing 1 Line in Seattle is scheduled to open in the fall. Two more Eastside stations – Marymoor Village, next to the popular Marymoor Park, and Downtown Redmond – are anticipated to open next year.

Trains arrive at the Bellevue Downtown Station on opening day of Sound Transit’s 2 Line light-rail service in Bellevue on Saturday. (Jason Redmond for Cascade PBS)

The original plan for East Link was for a mid-2023 opening, but construction delays pushed the opening date back one year . Then, plans to open this year all the way from Seattle to Redmond over the Interstate 90 bridge were derailed when the agency announced last year that the rail line’s I-90 supports had to be redone due to faulty concrete . That connection, which will include stations at Judkins Park and Mercer Island, is expected to open in 2025 at the same time as the Redmond stations.

King County Councilmember and Sound Transit board member Claudia Balducci said the agency opted to get use out of the completed stations, and perhaps give people who had never taken light rail the chance to experience it.

“Option 1 was to mothball the stations and pay for security for a year. Option 2 was to open it to the public and get some use out of it,” said Balducci, who pushed for the East Link partial opening.

Sound Transit Interim CEO Goran Sparrman speaks at the opening of Sound Transit’s 2 Line light-rail service. (Jason Redmond for Cascade PBS)

The crowd listens to speakers at the opening of Sound Transit’s 2 Line light-rail service. (Jason Redmond for Cascade PBS)

King County Executive Dow Constantine, second from right, and U.S. Sen. Maria Cantwell applaud remarks at the opening of Sound Transit’s 2 Line. (Jason Redmond for Cascade PBS)

From left, former Sound Transit CEO Joni Earl (seated); Bellevue Mayor Lynne Robinson; U.S. Sen. Maria Cantwell; Microsoft Vice Chair and President Brad Smith; U.S. Sen. Patty Murray; King County Executive Dow Constantine; King County Councilmember Claudia Balducci (holding scissors); Gov. Jay Inslee; Redmond Mayor Angela Birney; and Lynnwood Mayor Christine Frizzell at the ribbon-cutting ceremony for the opening of Sound Transit’s 2 Line light-rail service. (Jason Redmond for Cascade PBS)

Balducci also pointed out that the 1 Line between Tukwila and Seattle originally opened only between Tukwila International Boulevard and Westlake Station, with extensions to the south and north following in the decade afterward.

Balducci, who has been working on the East Link extension since she was a Bellevue City Councilmember in the late 2000s, said she was delighted to see the trains start moving.

“I’ve been working on this for almost two decades. All this work is finally turning into service,” she told Cascade PBS a few days before the official opening of the line.

Redmond Mayor Angela Birney said ever since the locations of the stations were identified, the city has approved multifamily housing and other amenities nearby to capitalize on the transit option.

“We put a lot of housing right around our stations and many of those families … would rather not use their cars. That’s intentionally that they moved to those areas. So I’m really excited for them to actually be able to get on the train and leave their cars behind,” Birney said.

The city also added two bike/pedestrian bridges for the Redmond stations.

“And so we’re really making another option for people to ride, bike, get on the train and get through the Eastside,” Birney said.

Passengers exit as others wait to board Sound Transit’s 2 Line. (Jason Redmond for Cascade PBS)

Hundreds of people attended the ribbon-cutting Saturday at the Downtown Bellevue station, despite the gray skies and cold rain, although many more boarded at other stations just to ride the rails. Royal-blue balloons and booths lined the station adjacent to the Bellevue Transit Center on Northeast Sixth Street near Meydenbauer Center, with local booths lined up as well as food trucks from local businesses.

Redmond resident Gary Fujioka boarded the train with his electric bike at the Redmond Technology Station on opening day and rode it south to celebrate. 

“It’s busier than I thought it would be, but that’s a good thing. I’m surprised by the turnout; I hope all these people return and use it regularly,” Fujioka said. “Everybody should be open-minded to our public transportation in the region and I invite them to come out and try it, it’s much nicer than you think it is.” 

Sound Transit says the trip between Redmond Technology Center near Microsoft and Bellevue Downtown should take about 10 minutes. The trains come by each station every 10 minutes seven days a week, from 5:30 a.m. to 9:30 p.m.

Passengers take in the view from above State Route 520. (Jason Redmond for Cascade PBS)

On Saturday public officials from Bellevue, Redmond and King County were in attendance alongside Gov. Jay Inslee and both U.S. Senators Maria Cantwell and Patty Murray. Representatives from Microsoft and Amazon, which have built up their workforces on the Eastside over the past decades, also attended.

Attendees of all ages – from small children wearing Thomas the Tank Engine train conductor hats to groups of the elderly – came to the Bellevue downtown station to celebrate. Many took photos and videos to commemorate the opening of the line that took two decades to complete. Although it’s not yet connected to other regions around Puget Sound, people traveled from Mercer Island or Seattle and even as far as Vancouver, B.C., to experience the moment. 

People crowded each station entrance to watch the ribbon-cutting and cheered all the way down the tracks as two trains pulled in. Riders were excited as they filled cars, many with no specific destination in mind.

Most riders were taking the train to enjoy the journey, or to stop at each station and look at the artwork, only to hop on the next train and repeat the process across the eight stations.

People explore the Redmond Technology Station. (Jason Redmond for Cascade PBS)

Jenny Pai and her family drove down from Bothell for the event. Her family wanted to take the line for an adventure. Pai said that if more lines open, she’d be open to taking the train to work.

Like Pai, retiree Sand Stron from Mercer Island came for the opening day just to travel south to north and vice versa to his parking spot in the South Bellevue parking garage. 

“I think this is an important thing for our region and we’re looking forward to it coming from Mercer Island. We’ll probably use the transit a lot.” 

University of Washington student Yoshi Takano came with a group of 25 from the university chapter of the Institute of Transportation Engineers, a group passionate about improving transportation in the state. Takano said attendees from the University of Oregon also came for the opening day. The groups were going up and down the line, stopping at each station to explore. 

“There’s been construction delays and I think that’s frustrating, but I’m glad they were able to open this segment. I think they wanted to be able to show voters that their tax dollars are going to something that’s positive and show the benefits of the light rail,” Takano said. 

He hopes that people will continue to use it regularly, but worries that they’ll still opt to drive instead due to the abundance of parking in Bellevue. 

“But that doesn’t necessarily mean it’s a failure, it’s a product of past policies and it’ll require additional new development and as they finish the line to Seattle; I think ridership can increase,” Takano said. 

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Jadenne Radoc Cabahug is Crosscut's emerging journalist news fellow for 2024.

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How PNW trans swimmers are finding comfort in and out of water

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• Traffic Lab

Your how-to guide for the new Eastside light rail line

The East Link Starter Line, also called the 2 Line, begins service 11 a.m. Saturday with eight stops in Bellevue and Redmond. If you’re a newcomer to Sound Transit light rail, here’s what to know.

Hours: Eastside trains are scheduled to arrive every 10 minutes, seven days a week from 5:30 a.m. to 9:30 p.m.

Travel time: A ride on the 6-mile line, end to end, lasts 20 minutes.

Capacity: Two-car trains are intended to carry 300 people, when half are seated and half standing.

Locations: At the south end is South Bellevue Station. From there, trains head northeast to East Main, Bellevue Downtown, Wilburton, Spring District, BelRed, Overlake Village and the last stop, Redmond Technology Station. Free park-and-ride space is available at South Bellevue (1,500 stalls), BelRed (300), Overlake Village (203 stalls, four blocks away) and Redmond Technology (300). The other four stations include passenger drop-off sites and connecting bus stops.

Fares: Standard adult fares are $2.25 to $2.50 depending on distance. Link light rail charges $1 for 65+, disabled and low-income passengers holding a discounted ORCA fare card. People 18 and younger ride transit free throughout Washington state. Fares will be collected opening weekend.

How to pay: Fares are paid before entering trains. Most people use a regional ORCA fare card, tapping it on a yellow detector near the station entrance. Tap again when leaving a station to avoid overcharges. See orcacard.com to order fare cards online or find in-person sites . ORCA cards are available at many QFC and Fred Meyer stores. Paper single-trip and all-day tickets are sold in station vending machines, which accept cash or credit/debit cards. If you’re taking more than a couple of rides, it’s simpler to buy an ORCA fare card directly from the ticket machine. You pay $3 for the card, then load it with funds. Or download the Transit Go app .

Station entry: There are no turnstiles. “Fare ambassadors” canvass some trains to check for proof of payment and help people navigate. They issue advice or warnings and can cite repeat evaders for $50 or more. Pedestrians should look all ways for trains next to station platforms and at grade crossings around BelRed Station.

Bicycles: Bikes are allowed onboard light rail, hanging from a hook in a nook that doubles as luggage space.

Restrooms: There are no public restrooms in the eight stations.

Buses: The primary train-bus connections are I-90 routes that swing by South Bellevue Station; Highway 520 routes next to Redmond Technology Station; and I-405 buses that converge at Bellevue Downtown Station. Metro’s B Line bus links the Crossroads neighborhood to multiple train stops including Wilburton.

Traffic Lab | Eastside Light Rail

• Here’s how many people celebrated Eastside light rail opening
• Video: Ride Eastside’s new light rail train with us
• Eastside’s biggest employer has been getting ready for this day for years
• Eastside light rail line opens as huge crowds try out the ride
• The highs and lows of Eastside’s 8 new light rail stations, from parking to traffic hazards
• New to light rail? Here’s your starter kit for riding
• Eastside’s light rail wait is almost over with ‘Starter Line’
• Map: Eastside’s first light rail stations open April 27
• Timeline: Eastside light rail has been a long time coming

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The opinions expressed in reader comments are those of the author only and do not reflect the opinions of The Seattle Times.

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The trains and stations of the Moscow Metro

2 Comments · Posted by Alex Smirnov in Cities , Travel , Video

The Moscow Metro is the third most intensive subway system in the world after Tokyo and Seoul subways. The first line was opened on May 15, 1935. Since 1955, the metro has the name of V.I. Lenin.

The system consists of 12 lines with a total length of 305.7 km. Forty four stations are recognized cultural heritage. The largest passenger traffic is in rush hours from 8:00 to 9:00 and from 18:00 to 19:00.

Cellular communication is available on most of the stations of the Moscow Metro. In March 2012, a free Wi-Fi appeared in the Circle Line train. The Moscow Metro is open to passengers from 5:20 to 01:00. The average interval between trains is 2.5 minutes.

The fare is paid by using contactless tickets and contactless smart cards, the passes to the stations are controlled by automatic turnstiles. Ticket offices and ticket vending machines can be found in station vestibules.

Tags:  Moscow city

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Tomás · August 27, 2012 at 11:34 pm

The Moscow metro stations are the best That I know, cars do not.

Alberto Calvo · September 25, 2016 at 8:57 pm

Great videos! Moscow Metro is just spectacular. I actually visited Moscow myself quite recently and wrote a post about my top 7 stations, please check it out and let me know what you think! :)

http://www.arwtravels.com/blog/moscow-metro-top-7-stations-you-cant-miss

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Delta recovers emergency slide that separated from Boeing plane

An emergency slide that fell from a Delta flight just a few minutes after takeoff has been recovered from the Atlantic Ocean in New York City.

The New York City Department of Parks and Recreation said that the airline recovered the slide on Sunday in a jetty near Beach 131st Street in Queens, about 10 miles from where the flight took off Friday at John F. Kennedy International Airport.

"As nothing is more important than the safety of our customers and people, Delta flight crews enacted their extensive training and followed procedures to return to JFK," Delta said in a statement about the diverted plane issued Friday.

The company said that the plane landed safely and "it was observed that the emergency slide had separated from the aircraft," after returning to a gate.

The company confirmed the recovery of the slide Monday and referred to its earlier statement.

Flight returned due to alert crew

Flight 520 to Los Angeles returned to JFK after the flight crew saw an indicator light related to the right overwing exit and heard a "non-routine" sound near the right wing.

The crew also reported a vibration , according to the Federal Aviation Administration.

The flight was operated by a 33-year-old Boeing 767 , according to data from  Airfleets.net , and passengers were accommodated on a different flight later in the morning. There were 183 people aboard the flight.

The FAA said it is investigating the incident and Delta said it would cooperate with that investigation.

Contributing: Sara Al-Arshani, Eve Chen, Kathleen Wong

• Articles   >

The Moscow Metro Museum of Art: 10 Must-See Stations

There are few times one can claim having been on the subway all afternoon and loving it, but the Moscow Metro provides just that opportunity.  While many cities boast famous public transport systems—New York’s subway, London’s underground, San Salvador’s chicken buses—few warrant hours of exploration.  Moscow is different: Take one ride on the Metro, and you’ll find out that this network of railways can be so much more than point A to B drudgery.

The Metro began operating in 1935 with just thirteen stations, covering less than seven miles, but it has since grown into the world’s third busiest transit system ( Tokyo is first ), spanning about 200 miles and offering over 180 stops along the way.  The construction of the Metro began under Joseph Stalin’s command, and being one of the USSR’s most ambitious building projects, the iron-fisted leader instructed designers to create a place full of svet (radiance) and svetloe budushchee (a radiant future), a palace for the people and a tribute to the Mother nation.

Consequently, the Metro is among the most memorable attractions in Moscow.  The stations provide a unique collection of public art, comparable to anything the city’s galleries have to offer and providing a sense of the Soviet era, which is absent from the State National History Museum.  Even better, touring the Metro delivers palpable, experiential moments, which many of us don’t get standing in front of painting or a case of coins.

Though tours are available , discovering the Moscow Metro on your own provides a much more comprehensive, truer experience, something much less sterile than following a guide.  What better place is there to see the “real” Moscow than on mass transit: A few hours will expose you to characters and caricatures you’ll be hard-pressed to find dining near the Bolshoi Theater.  You become part of the attraction, hear it in the screech of the train, feel it as hurried commuters brush by: The Metro sucks you beneath the city and churns you into the mix.

With the recommendations of our born-and-bred Muscovite students, my wife Emma and I have just taken a self-guided tour of what some locals consider the top ten stations of the Moscow Metro. What most satisfied me about our Metro tour was the sense of adventure .  I loved following our route on the maps of the wagon walls as we circled the city, plotting out the course to the subsequent stops; having the weird sensation of being underground for nearly four hours; and discovering the next cavern of treasures, playing Indiana Jones for the afternoon, piecing together fragments of Russia’s mysterious history.  It’s the ultimate interactive museum.

Top Ten Stations (In order of appearance)

Kievskaya station.

Kievskaya Station went public in March of 1937, the rails between it and Park Kultury Station being the first to cross the Moscow River.  Kievskaya is full of mosaics depicting aristocratic scenes of Russian life, with great cameo appearances by Lenin, Trotsky, and Stalin.  Each work has a Cyrillic title/explanation etched in the marble beneath it; however, if your Russian is rusty, you can just appreciate seeing familiar revolutionary dates like 1905 ( the Russian Revolution ) and 1917 ( the October Revolution ).

Mayakovskaya Station

Mayakovskaya Station ranks in my top three most notable Metro stations. Mayakovskaya just feels right, done Art Deco but no sense of gaudiness or pretention.  The arches are adorned with rounded chrome piping and create feeling of being in a jukebox, but the roof’s expansive mosaics of the sky are the real showstopper.  Subjects cleverly range from looking up at a high jumper, workers atop a building, spires of Orthodox cathedrals, to nimble aircraft humming by, a fleet of prop planes spelling out CCCP in the bluest of skies.

Novoslobodskaya Station

Novoslobodskaya is the Metro’s unique stained glass station.  Each column has its own distinctive panels of colorful glass, most of them with a floral theme, some of them capturing the odd sailor, musician, artist, gardener, or stenographer in action.  The glass is framed in Art Deco metalwork, and there is the lovely aspect of discovering panels in the less frequented haunches of the hall (on the trackside, between the incoming staircases).  Novosblod is, I’ve been told, the favorite amongst out-of-town visitors.

Komsomolskaya Station

Komsomolskaya Station is one of palatial grandeur.  It seems both magnificent and obligatory, like the presidential palace of a colonial city.  The yellow ceiling has leafy, white concrete garland and a series of golden military mosaics accenting the tile mosaics of glorified Russian life.  Switching lines here, the hallway has an Alice-in-Wonderland feel, impossibly long with decorative tile walls, culminating in a very old station left in a remarkable state of disrepair, offering a really tangible glimpse behind the palace walls.

Dostoevskaya Station

Dostoevskaya is a tribute to the late, great hero of Russian literature .  The station at first glance seems bare and unimpressive, a stark marble platform without a whiff of reassembled chips of tile.  However, two columns have eerie stone inlay collages of scenes from Dostoevsky’s work, including The Idiot , The Brothers Karamazov , and Crime and Punishment.   Then, standing at the center of the platform, the marble creates a kaleidoscope of reflections.  At the entrance, there is a large, inlay portrait of the author.

Chkalovskaya Station

Chkalovskaya does space Art Deco style (yet again).  Chrome borders all.  Passageways with curvy overhangs create the illusion of walking through the belly of a chic, new-age spacecraft.  There are two (kos)mosaics, one at each end, with planetary subjects.  Transferring here brings you above ground, where some rather elaborate metalwork is on display.  By name similarity only, I’d expected Komsolskaya Station to deliver some kosmonaut décor; instead, it was Chkalovskaya that took us up to the space station.

Elektrozavodskaya Station

Elektrozavodskaya is full of marble reliefs of workers, men and women, laboring through the different stages of industry.  The superhuman figures are round with muscles, Hollywood fit, and seemingly undeterred by each Herculean task they respectively perform.  The station is chocked with brass, from hammer and sickle light fixtures to beautiful, angular framework up the innards of the columns.  The station’s art pieces are less clever or extravagant than others, but identifying the different stages of industry is entertaining.

Baumanskaya Statio

Baumanskaya Station is the only stop that wasn’t suggested by the students.  Pulling in, the network of statues was just too enticing: Out of half-circle depressions in the platform’s columns, the USSR’s proud and powerful labor force again flaunts its success.  Pilots, blacksmiths, politicians, and artists have all congregated, posing amongst more Art Deco framing.  At the far end, a massive Soviet flag dons the face of Lenin and banners for ’05, ’17, and ‘45.  Standing in front of the flag, you can play with the echoing roof.

Ploshchad Revolutsii Station

Novokuznetskaya Station

Novokuznetskaya Station finishes off this tour, more or less, where it started: beautiful mosaics.  This station recalls the skyward-facing pieces from Mayakovskaya (Station #2), only with a little larger pictures in a more cramped, very trafficked area.  Due to a line of street lamps in the center of the platform, it has the atmosphere of a bustling market.  The more inventive sky scenes include a man on a ladder, women picking fruit, and a tank-dozer being craned in.  The station’s also has a handsome black-and-white stone mural.

Here is a map and a brief description of our route:

Start at (1)Kievskaya on the “ring line” (look for the squares at the bottom of the platform signs to help you navigate—the ring line is #5, brown line) and go north to Belorusskaya, make a quick switch to the Dark Green/#2 line, and go south one stop to (2)Mayakovskaya.  Backtrack to the ring line—Brown/#5—and continue north, getting off at (3)Novosblodskaya and (4)Komsolskaya.  At Komsolskaya Station, transfer to the Red/#1 line, go south for two stops to Chistye Prudy, and get on the Light Green/#10 line going north.  Take a look at (5)Dostoevskaya Station on the northern segment of Light Green/#10 line then change directions and head south to (6)Chkalovskaya, which offers a transfer to the Dark Blue/#3 line, going west, away from the city center.  Have a look (7)Elektroskaya Station before backtracking into the center of Moscow, stopping off at (8)Baumskaya, getting off the Dark Blue/#3 line at (9)Ploschad Revolyutsii.  Change to the Dark Green/#2 line and go south one stop to see (10)Novokuznetskaya Station.

Check out our new Moscow Indie Travel Guide , book a flight to Moscow and read 10 Bars with Views Worth Blowing the Budget For

Jonathon Engels, formerly a patron saint of misadventure, has been stumbling his way across cultural borders since 2005 and is currently volunteering in the mountains outside of Antigua, Guatemala.  For more of his work, visit his website and blog .

Photo credits:   SergeyRod , all others courtesy of the author and may not be used without permission

2 Zamoskvoretskaya Line map - Moscow metro

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