how does sound travel through air experiment

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Sound is a pressure wave, but this wave behaves slightly differently through air as compared to water. Water is denser than air, so it takes more energy to generate a wave, but once a wave has started, it will travel faster than it would do in air.

A relay race

Sound travels by particles bumping into each other as they vibrate. It is a little like a relay race – each runner holds a little bit of information (the baton), and when they make contact with the next runner, they pass the information on.

In the case of sound, the runners are particles and the information (baton) they are passing along is energy of vibration. In a sound wave, a particle picks up some energy and keeps it until it bumps into a neighbouring particle. The next particle will then pick up the energy and transfer it to the next one in the chain. This happens extremely fast and is detected as a wave of pressure.

Sound won’t travel in a vacuum because there are no particles to bump together to transmit the vibration.

Sound in air

In a gas like air, the particles are generally far apart so they travel further before they bump into one another. There is not much resistance to movement so it doesn’t take much to start a wave, but it won’t travel as fast.

Sound in water

In water, the particles are much closer together, and they can quickly transmit vibration energy from one particle to the next. This means that the sound wave travels over four times faster than it would in air, but it takes a lot of energy to start the vibration. A faint sound in air wouldn’t be transmitted in water as the wave wouldn’t have enough energy to force the water particles to move.

Sound in solids

In a solid, the particles are even closer together and linked by chemical bonds so the wave travels even faster than it does in either liquid or air, but you need quite a lot of energy to start the wave at the beginning.

Sound and temperature

Temperature has a marked influence on the speed of sound. This is not due to a change in how closely together the particles are to each other but relates to the amount of energy that each particle has. Hot particles have more energy and transmit sound better than cold particles. Water in Antarctica will transmit sound slower than water in the tropics.

Some comparisons for the speed of sound in different materials

Related content

Explore the science concept related to sound further with these articles:

• Hearing sound – the basics of sound waves
• Measuring sound – the different parts of a sound wave, how we talk about and measure sound
• Sound – visualising sound waves – helps students to 'see’ sound waves with videos and diagrams

In our recorded PLD session Sounds of Aotearoa a group of primary science educators introduce some fun ways you can learn and teach about sound.

Activity ideas

Use these activities to explore some essential physics ideas relating to sound, but in a whole new way.

• Modelling waves with slinkies – stay indoors and model how sound travels.
• Catching worms using ground sounds – go outdoors and investigate whether there is any evidence that earthworms respond to vibrations in the ground.
• Sound detectives – can you locate sounds while blindfolded?
• Make and use a hydrophone – and listen to underwater sounds.
• Sound on an oscilloscope – use oscilloscope software and your computer to make and watch a visual sound display.
• Investigating sound – simple exploratory activities and questions to experience and build an understanding of sound.
• Hearing sounds – using whispers and vibrations to hear and experience how sound moves.
• Hearing sounds under water – go underwater yourselves to listen to sounds
• Measuring the speed of sound – use a timing app to measure the speed of sound.

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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..., don't want to read our articles try listening instead, 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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Physics archive

Course: physics archive   >   unit 8.

• Production of sound
• Sound properties: amplitude, period, frequency, wavelength
• Speed of sound

Relative speed of sound in solids, liquids, and gases

• Decibel Scale
• Why do sounds get softer?
• Ultrasound medical imaging

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Video transcript

What does sound travel through?

My kids are fascinated by sound. Maybe it’s because they are very good at making lots of it! But what causes sound?

Let’s get started:

You will need:.

• 2 empty plastic cups
• Science With Me! lab partner
• Lab notebook & pencil
• 2 paper clips

Instructions:

• Using a pencil poke a hole in the center of the bottom of each of the plastic cups.
• Using the scissors cut a piece of string that is about 15 feet long.
• Thread the end of the string through the hole in the cup.
• Have your child pull the string a few inches through the cup then help them tie the end of the string in a knot so that the string can’t pull back through the cup. You can also attach a paper clip to the knot to stop the string from slipping back through the cup.
• Repeat steps 3 and 4 with the other end of the string and the other cup.
• Have your child walk away until the string is tight. Get them to hold the cup up to their ear while you whisper loudly into your cup.

Can your child hear what you are saying? Now it’s your child’s turn to talk. Can you hear what they are saying?

Questions to ask your child:

• What happens if we pinch the string between the two cups? Can we hear each others voice as well?
• What happens if the string between the cups isn’t pulled tight? Will the telephone work as well?

Have your child write or draw their observations in their Science With Me! Lab notebook. Recording you observations is a very important part of being a scientist.

Hypothesis:

All sounds are vibrations. Your voice is no different! When your child talks into their cup, this causes the air inside their cup to start vibrating. The vibrations then travel through the cup, into the string and into the other cup. The 2nd cup channels the vibrating air molecules into your ear so you can hear what they are saying loud and clear.

Conclusions:

For the cup telephone to work, the string between the two cups must be able to vibrate freely. That’s why if the string is pinched the vibrations are disrupted and your child can’t hear your voice as well. This also explains why the string between the cups must be pulled tight for the telephone to work. If the string is loose, the sound vibrations will die out before they reach the other cup. This is similar to the way sound travels in real telephones with wires. Want to learn more about sound? Be sure to check out the f ree previews from our Sound Activity Set. Your thoughts?

Interesting Sound Facts:

Sound waves travel more slowly than light waves. That explains why during a thunderstorm you see the lightning first and then hear the thunder several seconds later, even though they happened at the same time.

• How fast sound travels (i.e. the speed of sound) depends on what medium it is traveling through. The speed of sound is 340 meters per second in air while as the speed of sound is 1450 meters per second in water.

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Sound as a Longitudinal Wave

• Sound is a Mechanical Wave
• Sound is a Longitudinal Wave
• Sound is a Pressure Wave

Sound waves in air (and any fluid medium) are longitudinal waves because particles of the medium through which the sound is transported vibrate parallel to the direction that the sound wave moves. A vibrating string can create longitudinal waves as depicted in the animation below. As the vibrating string moves in the forward direction, it begins to push upon surrounding air molecules, moving them to the right towards their nearest neighbor. This causes the air molecules to the right of the string to be compressed into a small region of space. As the vibrating string moves in the reverse direction (leftward), it lowers the pressure of the air immediately to its right, thus causing air molecules to move back leftward. The lower pressure to the right of the string causes air molecules in that region immediately to the right of the string to expand into a large region of space. The back and forth vibration of the string causes individual air molecules (or a layer of air molecules) in the region immediately to the right of the string to continually vibrate back and forth horizontally. The molecules move rightward as the string moves rightward and then leftward as the string moves leftward. These back and forth vibrations are imparted to adjacent neighbors by particle-to-particle interaction. Other surrounding particles begin to move rightward and leftward, thus sending a wave to the right. Since air molecules (the particles of the medium) are moving in a direction that is parallel to the direction that the wave moves, the sound wave is referred to as a longitudinal wave. The result of such longitudinal vibrations is the creation of compressions and rarefactions within the air.

Regardless of the source of the sound wave - whether it is a vibrating string or the vibrating tines of a tuning fork - sound waves traveling through air are longitudinal waves. And the essential characteristic of a longitudinal wave that distinguishes it from other types of waves is that the particles of the medium move in a direction parallel to the direction of energy transport.

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How to Measure Sound Travel in the Air

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Key Takeaways

• Sound can travel through air, water and solids but not through a vacuum, as it requires a medium to propagate.
• The speed of sound in air is approximately 1,130 feet (344 meters) per second at room temperature, though this speed can vary with changes in temperature and humidity.
• You can perform a simple experiment involving two blocks of wood, a stopwatch and a tape measure to measure the speed of sound in air by calculating the time it takes for the sound to travel a known distance.

Sound can travel through most materials -- the most commonly known being air (gas), water (liquid) and steel (solid). However, it does not travel at all in a vacuum, because the sound waves need some kind of medium in which to travel. In addition, some materials absorb, rather than reflect or pass, sound waves. This is the basis of soundproofing [source: Kurtus ].

The average speed of sound through air is about 1130 feet per second (344 meters per second) at room temperature. However, changes in temperature and humidity will affect this speed [source: Kurtus ].

Here is a simple way to measure the speed at which sound travels through air. You'll need the following items:

• Two blocks of wood, or other items that make a loud, sharp sound when struck together
• A stopwatch
• A friend to help with the experiment
• A tape measure

Instructions:

• Find a large empty area, such as a field or large court.
• Choose two spots on opposite ends of the area where each person will stand.
• Measure the distance between the two spots using a tape measure. Alternatively, you can count off measured steps between the two spots.
• Have your friend take the blocks and stand at one spot, holding them up high.
• Take the stopwatch and stand at the other spot. Make sure you have a clear view of the blocks.
• Signal your friend to bang the two blocks together hard.
• Start the stopwatch as soon as you see the blocks hit each other.
• Press stop as soon as you hear the sound from the blocks.
• Calculate the speed of the sound by dividing the distance between you and your friend by the elapsed time. To get a more accurate measurement, repeat the above steps a few times and then take an average of the results [source: Green Planet Solar Energy ]. //]]]]> ]]>

Frequently Asked Questions

How does the humidity level affect the speed of sound in air, can the speed of sound vary at different altitudes.

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May 6, 2011

Talk through a String Telephone

Bring Science Home: Activity 5

By Katherine Harmon

Key concepts Sound Waves Hearing

From National Science Education Standards : Transfer of energy

Introduction Have you ever tried to have a conversation with someone so far away that you couldn't really hear each other? Without yelling, it's hard to have a conversation over long distances. So these days it's nice to be able to use telephones to talk with someone—whether he or she is 100 yards or 100 miles away.

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Back before there were cell phones or even cordless phones, all telephones were hooked up to wires that helped to carry the sound of a person's voice (via an electric signal). And you can use the same concept to build your own telephone using just cups and some string. What message are you going to share over the string?

Background When we talk, our vocal cords make molecules in the air vibrate. (You can feel the vibrations by holding your hand against your throat while you talk.) Those vibrating air molecules make other air molecules around them vibrate, and so on, which is how sound travels through the air. (Different pitches of sound move in waves that have different spacing between them—or "frequency.") Other sources of sound, such as guitar, violin or piano strings are good examples of how vibrations can generate sound.

Inside our ears are tiny sensitive hairs. They pick up the vibrations and transmit that information to our brains, which interpret it as sound. The brain interprets sounds as having different pitches, or tones, based on the frequency, or spacing, of the waves.

But the particles in air are spread out from one another more than particles in a liquid or solid. So sound vibrations tend to peter out before they travel very far. Having a soft connective material, such as cotton string—which has a higher density, or number of molecules in a given amount of space, than air—can help the sound waves move over a greater distance.

Materials •   Two large paper cups (disposable plastic cups will also work) •   Two paperclips or toothpicks •   Length of cotton string or fishing line approximately 10 to 30 feet long •   Quiet area

Preparation •   Punch a small hole in center of the bottom of each cup (for plastic cups, you might need a nail or other sharp tool, so use caution when completing this step). •   Thread one end of string through the bottom of each cup. •   Place a paperclip or toothpick in the bottom of each cup and tie the loose end of the string around it (the clip or pick is just here to keep the string from slipping through the bottom of the cup).

Procedure •   Give one cup to your conversation partner and hold one yourself. •   Walk slowly apart until the string connecting the cups is straight and tight. •   Put your cup over your ear and have your partner talk into his or her cup (keep the conversation relatively quiet if you are standing close to one another, but be sure to talk louder than a whisper). •    Can you hear your partner talking? •   Now you try talking into your cup and have your partner listen into his or her cup. Can he or she hear you? •   Try letting the string go slack. Is the cup-and-string telephone still effective? •   Now, keeping your voice at the same level and remaining the same distance apart, try talking to each other without using the cups. Can you hear as well? •    Extra: If you have plenty of space, see how far apart you can get the cup-and-string telephone to work. •    Extra: If you have a third person around, ask them to hold on to the center of the string with their hand. Will the sound still carry through? Why or why not? •    Extra: If you have other materials (such as yarn, fishing line, nylon string, etc.) on hand, try them out. How do different materials change the quality of sound or how far the sound will travel?

Read on for observations, results and more resources.

Observations and results Could you hear your partner better using the cups and tight string than if you were speaking to each other in the same volume over the air?

In this activity, your voice vibrated the air inside of the cup, which in turn made the bottom of the cup vibrate. These vibrations were transferred to the string and then into the bottom of your partner's cup, which made the air inside of his or her cup vibrate and become detectable sound. When the string goes slack, the vibrations dissipate more easily and get lost along the way. (Landline phones work on the same idea but they transfer the sound waves into an electrical signal, which can travel even farther over wires—and the landlines don't have to be kept taut.)

Sound, such as human speech, travels in incredibly small waves—incredibly fast (about 1,126 feet per second), which is why you couldn't see it or detect a delay while it traveled across the cups and string.

Have you ever noticed how things sound different underwater? Because water's molecules are packed together more closely than those in air, sound waves move more easily—faster and farther—under water. Whales and other marine animals that use sound to communicate under water take advantage of this fact. Scientists think whales can hear each other from hundreds (and maybe even thousands) of miles away—without even a string telephone!

Share your string telephone observations and results! Leave a comment below or share your photos and feedback on Scientific American 's Facebook page .

Cleanup Untie or cut the string from the paperclips or toothpicks. Recycle or reuse what materials you can.

More to explore "Ear Cells Actively Amplify Sound" from Scientific American "(Don't) Pump Up the Volume: Sound Waves Silence Whales' Song" from Scientific American "Sound" Activities from The NASA Sci Files "Frequency, Wavelength and Pitch" overview from Connexions Sounds All Around by Wendy Pfeffer, ages 4-8 Janice VanCleave's Physics for Every Kid: 101 easy experiments in motion, heat, light, machines and sound by Janice VanCleave, ages 9-12

Up next… Yeast Alive! Watch Yeast Live and Breathe

What you'll need •   Fresh packet of baker's yeast (check the expiration date) •   Tablespoon of sugar •   Clear plastic bottle with a small opening (such as a water bottle) •    Funnel •   Small balloon •   Warm water

Sound Really Can Travel in a Vacuum, And We Can Finally Explain How

Given the right circumstances, it is possible for sound to travel through a perfect vacuum. Now two physicists have worked out what those conditions need to be.

Zhuoran Geng and Ilari Maasilta of the University of Jyväskylä in Finland say their findings represent the first rigorous proof of complete acoustic tunneling in a vacuum.

To achieve it, you'll need two piezoelectric materials, which are capable of turning movements into voltages (and vice versa). The objects need to be separated by a gap that's smaller than the wavelength of the sound you want to send, which will then completely jump – or 'tunnel' – across that space.

We've known about acoustic wave tunneling since the 1960s , but scientists have only begun to investigate the phenomenon relatively recently, which means we don't yet have a very good understanding of how it works.

Geng and Maasilta have been working on fixing that, first by describing a formalism for the study of acoustic tunneling, and now by applying it.

In order to propagate, sound requires a medium to travel through. Sound is generated by vibrations, which causes atoms and molecules in the medium to vibrate; that vibration is passed on to adjacent particles . We sense these vibrations via a sensitive membrane in our ears.

A perfect vacuum is a complete absence of a medium. Since there are no particles to vibrate, sound shouldn't be able to propagate.

But there are loopholes. What qualifies as a vacuum can still buzz with electrical fields, which makes piezoelectric crystals an intriguing material for the study of sound across otherwise empty spaces.

These are materials that convert mechanical energy into electrical energy , and vice versa. In other words, if you place a mechanical stress on the crystal, it will produce an electric field. And if you expose the crystal to an electrical field, the crystal will deform. That's known as the inverse piezoelectric effect .

OK this is where it gets fun. A sound vibration exerts mechanical stress. Using zinc oxide as their piezoelectric crystals, Geng and Maasilta found that a crystal can convert this stress into an electrical field if certain conditions are met.

If there is a second crystal within range of the first, it can convert the electrical energy back into mechanical energy – et voila, the sound wave has traversed the vacuum. In order to do this, the two crystals have to be separated by a gap no wider than the length of the initial acoustic wave.

And the effect scales with frequency. As long as the vacuum gap is scaled accordingly, even ultrasound and hypersound frequencies can tunnel through the vacuum between the two crystals.

Because the phenomenon is analogous to the quantum mechanical effect of tunneling , the results of the research could help scientists study quantum information science, as well as other areas of physics.

"In most cases the effect is small, but we also found situations where the full energy of the wave jumps across the vacuum with 100 percent efficiency, without any reflections," Maasilta says .

"As such, the phenomenon could find applications in microelectromechanical components (MEMS, smartphone technology) and in the control of heat."

The research has been published in Communications Physics .

How Does Sound Travel Through Air? Complete Explanation

It’s hard to imagine the world without any sound since we rely on it so much. It’s the first thing we hear in the morning, whether it’s the birds or your alarm clock. The sound is everything around us – when people talk, when we watch TV or listen to music, etc. It might also be the last thing you hear before you fall asleep if your neighbor is loud or the dogs are barking.

How does sound travel?

It’s an impressive thing, and though the question seems simple, the answer to it is quite complicated. In the simplest words, the sound is an energy created by vibrations.

However, there’s much more to it so make sure to continue reading. We’ll talk about what the sound is, how it travels, what does it go through the best and much more.

It’s an impressive thing, and though the question seems simple, the answer to it is quite complicated. In the simplest words, the sound is an energy created by vibrations. However, there’s much more to it so make sure to continue reading. We’ll talk about what the sound is, how it travels, what does it go through the best and much more.

Interference

What exactly is sound.

We’re talking about energy produced by vibration. Think about what happens when you hit a drum. Its skin vibrates so quickly forcing the air to vibrate. The air then moves and carries the energy everywhere around the drum.

The physical process of sound is what produces and sends it through the air. The psychological process is what happens in our brain and ears. It converts the energy into what we then call noise, music, speech, etc.

The sound, much like light, comes from its source. The difference is that sound can’t travel through a vacuum. It has to move through something like glass, air, water, metal, etc.

The science behind sound

Interestingly, sound, light, and water behave similarly. Have you ever noticed how beach waves are never the same? Some are larger while others have more power. This is because the energy that carries them is often at different levels.

The same thing happens with sound and light as well. Have you ever tried reflecting light off a mirror? In a similar way, you can also reflect vibration which is something we know as an echo. Echo is the energy that travels to the wall before it bounces back and to your ears. We all know echo doesn’t happen right after the sound as it takes time for the energy to travel.

One thing you have to remember is that these waves lose their energy. This is why you can only hear so far and on calm weather days. If the winds are too strong, you probably won’t hear the noisy club in the other street although you hear it well when the weather is calm. This is because the wind dissipates the energy.

Sound characteristics

Its speed mostly depends on the ambient conditions and the density of the medium. The medium can be thin or thick which will then determines how fast the energy will travel through it. The frequency is the total number of vibrations produced by the source.

Sound waves that have long wavelengths are those we know as low-pitch. Those with short wavelengths are what we know as high-pitch.

How is sound created?

Every physical object causes vibrations when it moves in the air. This leads to creation of waves in the air that then continue to travel as a form of sound.

Much like the drum example we’ve mentioned above, our vocal cords also vibrate when we talk. This vibration happens in air, solid mediums and liquid. These vibrations can travel long distance which is what happens with trains on steel railroad. You know how you can hear the train approaching even when it’s still far away? It’s the vibration.

How do sound waves travel?

Vibrations travel through air at a speed of 343 m/s at room temperature. This goes up to 1482 m/s through water and 5960 m/s through steel. If it’s gaseous medium, the sound will go slowly because the molecules are loosely bound.

They have to travel a long distance in which case they often collide with other molecules. When it’s a solid medium, the atoms are much tightly packed, so the they travel fast. If the medium is liquid, the fragments won’t be as strongly linked, so the waves won’t move as quickly as they do through solid mediums.

The speed of sound

Have you ever heard of someone saying that an airplane broke through the sound barrier? Do you know what that means?

It means that the plane went so fast that it overtook these high-intensity waves it produces. The airplane then makes a sound called a sonic boom. This is why its sound comes to you before you ever see a plane up in the sky.

There’s no one way to tell how quickly it travels. It all depends on the medium since it moves at different speed trough liquid, solid, and gas medium. Its speed depends on how dense is the medium.

The noise travels through steel about 15 times faster than through air and about 4 times faster through water than through air. This is precisely why submarines use SONAR and why it’s nearly impossible to tell where the noise is coming from if you’re swimming in the sea.

Sound also travels differently through different gases. If the air is warm, it will travel much faster than in cold air. It also moves 3x faster in helium than in ordinary air. You know the funny voices you talk in when you breathe in helium? This happens because the waves travel faster and in higher frequency.

How do we hear sound?

We hear with our ears in a seemingly simple process that’s actually quite complex. The impressive organ allows us to hear all kinds of sounds at different frequencies and distances.

The waves travel from the outer ear and through the auditory canal. This causes the eardrum to vibrate which then causes the ossicles to move. The vibrations move with the oval window through the fluid in the inner ear which then stimulates many tiny hair cells. As a result, the vibrations transform into an electrical impulse that our brain perceives as sound.

How does sound travel through a liquid?

Sound always travels in waves regardless of whether it goes through a gas, liquid or a solid medium. They move by particles that collide with one another. It’s a domino effect as one particle hits another much in the same way that the heat travels as well.

The waves don’t go at a rigid pattern in space when it comes to traveling through a liquid. The bond between molecules is usually much weaker, and it keeps breaking and re-forming. Once the pressure is raised at least a little bit, the liquid causes the particles to move to areas with lower pressure. These molecules then push those that are already there causing the pressure to grow in the area.

Molecules have inertia, so they usually go farther than it takes to even out the pressure. The process repeats until the waves carry the energy away. The best example of this are the multiple waves that spread out from where you drop a rock in the water.

How does sound travel through gas?

Gases react much like the liquids. Since they are less dense, gases are more compressible. Sound travels faster when the materials are less dense and more compressed. The compressibility change has a more significant effect on the wave than when the density changes.

In conclusion, the sound travels much slower through gas than through liquids even when it’s the same substance.

Why do different instruments produce different sounds?

If you ever thought about what sound is and how it travels, you probably also thought about music instruments. They are all essentially the same thing, producing sound waves with the same frequency and amplitude. So how they sound different?

Most people think how waves are identical, but the instruments vibrate differently from one another. However, the truth is that the waves aren’t identical. Every instrument produces lots and lots of different waves at the same time. The fundamental wave is the basic one and the one that has a specific amplitude and pitch. Higher-pitched sounds are harmonics also known as overtones. Every overtone has a frequency that’s higher than the fundamental.

This means that every instrument makes a pattern of fundamental frequencies and overtones called timbre. The combination of these waves gives a shape to produce a unique sound of each instrument. That’s precisely why each instrument is different.

There’s another reason and is that the amplitude of each wave changes uniquely every second. A flute produces quick sounds that die soon, while piano vibrations die slowly as they also take longer to build up.

The sound is always reflected from a particular surface at the same angle it strikes it. This allows us to focus sound with curved reflections the same way we use curved mirrors to focus light.

You must’ve heard of whispering galleries, the rooms where you can whisper a word at one point that can then be heard at another point quite far away. We use reflection to focus sound when talking through cupped hands and a megaphone.

However, reflection can be a severe problem in auditoriums and concert halls. If a hall isn’t designed the right way, the first word someone says in the microphone can echo for seconds. If they continue to talk, each word would then echo creating a whole mess. This happens with music just as well.

The issue is usually solved with sound-absorbing materials used to cover the reflecting surfaces. Acoustical tile, draperies, cloths, and many other materials can help. They are all porous allowing waves to enter through the small air-filled spaces and bounce in them until the energy is spent.

Interestingly, some animals also use sound reflection for echolocation. They rely on hearing instead of the sense of sight. Animals such as toothed whales and bats can emit sounds that are beyond our hearing limits and high as 200,000 Hz. Bats can even hear and locate a mosquito even if it’s in total darkness.

When a wave goes from one material to another at a certain angle, it always changes speed. This causes the wavefront to bend and is called refraction.

The best way to understand it is in a physics lab where they use a lens-shaped balloon, fill it with carbon dioxide and focus the sound wave.

Diffraction

When waves go through or around a barrier, the edge of it then becomes a secondary sound source that sends waves of the equally wavelength and frequency.

These waves then spread around, and we call that diffraction. This is a fun phenomenon because it allows us to hear sounds around corners even though sound waves actually travel in a straight line.

Interference occurs each time waves interact. In auditoriums, the interference between the sounds can create dead spots in which clarity and volume are poor. However, it can improve an auditorium’s acoustics if you arrange the reflecting surfaces, so the sound level is increased where the audience sits.

When the two waves that interfere have different frequencies, they create a tone of alternately decreasing and increasing intensity. The pulsations we then hear are called beats. This can be used to your advantage and is something piano turners do all the time. They adjust the tone of a string against a standard tuning fork until you can no longer hear the beat.

How do we use sound?

The sound has a huge part in our lives and is something we rely on every day. Animals probably depend on it even more as they use it for survival. They exchange sounds to communicate or scare off possible threats and different predators.

People have developed a bit more, so we use language. However, every language and every word is essentially a sound we use to communicate.

There are many different sound technologies and musical instruments that produce many different sounds. We’ve also developed technologies that allow us to record sounds on MP3, compact discs, memory sticks, etc.

People also use high frequency sounds otherwise known as ultrasound for so many things from cleaning teeth to checking the baby inside a womb.

Why Does Closing A Door Help In Blocking Out Noise?

What is sound, how does sound travel through a medium, why does a closed door block out noise.

When a door is closed, it helps to block out noise because sound waves travel faster through solids and the door absorbs some of the energy of the waves. Additionally, the sound waves that do make it through the door into the room will lose more energy as they travel through the air, making them less noticeable.

You may recall from your high school science classes that of the three states of matter, i.e., solid, liquid and gas, sound waves travel the fastest through solids. The second best is liquid, meaning that sound travels the slowest through gases. What this means is that if you want sound to travel from one place to another, you should try to make it pass through a solid.

However, if that’s the case, why do we close doors to a room when we want to prevent noise from entering it? Since sound travels best through solids (and the worst through air), why do doors, walls and other solid ‘obstructions’ inhibit the detection of sound?

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A sound is actually a pressure wave created by a vibrating object. In other words, you could say that when something vibrates, it creates sound. Originating from a source, these sound waves travel outwards in all directions at the same rate. As the waves travel, they bounce off and/or are absorbed by objects that lie in their path.

These waves are then picked up by our ears, which send the waves to the brain, where they are processed so we can make some ‘sense’ out of them.

Now, unlike light (which is an electromagnetic wave), sound is a mechanical wave, meaning that it needs a medium in order to travel. It cannot move through a vacuum (whereas light can). That’s the reason why  space is silent , because sound cannot travel with an absence of any air.

Also Read: How Has NASA Recorded Sound If Sound Cannot Travel In Space?

We are constantly surrounded by air, so it’s natural that the sound we hear reaches our ears after traveling through air. For starters, sound travels in dry air at a speed of around 343 m/s (767 mph). I should also remind you that sound travels the slowest in air; it travels much faster through solids.

The reason it travels so fast through solids is that sound is actually a local disturbance whose propagation is accomplished through collisions between constituent particles in a medium. In the case of solids, the constituent particles are packed closely together. As a result of this, the vibrations that these particles experience (due to incoming sound waves) are quickly passed on to their neighboring particles, which then pass it on even further.

That’s why sound travels so quickly and effectively through solids!

But if that’s the case, then….

Also Read: Does The Speed Of Wind Affect How Fast Sound Waves Travel Through It?

It’s true that sound travels fastest through solids, but solid objects actually block sound waves from reaching a given space. The reason behind this is very simple: you see, when sound originates from a point, travels through a medium, and then encounters a solid object, it loses some of its energy. In other words, a change in the medium triggers a reduction in the energy being carried by the sound wave. That’s essentially why sounds lose their ‘loudness’ when they run into a different medium.

The same thing happens when a closed door or wall reduces outside noise. Noises (sound waves) that originate outside a room (let’s call it the ‘target room’) travel through air before they hit the door. Now, the door absorbs some of the energy of those waves and reflects some of those waves back. Thus, the original sound waves lose a considerable amount of their total energy.

Then, the remaining sound waves travel through the solid door and enter another medium, i.e., the air of the target room, and consequently lose even more energy. The upshot? The noise is either completely blocked out or is too low-intensity to be noticed by anyone within the target room.

That’s why closed doors and walls are so good at blocking outside noise, despite the skill of solid objects to pass sound waves so effectively.

• Sound Waves: The Symphony of Physics - The Open University. Open University
• What Is Sound?. cs.toronto.edu
• The Propagation of sound. Johns Hopkins University

Ashish is a Science graduate (Bachelor of Science) from Punjabi University (India). He spearheads the content and editorial wing of ScienceABC and manages its official Youtube channel . He’s a Harry Potter fan and tries, in vain, to use spells and charms ( Accio! [insert object name]) in real life to get things done. He totally gets why JRR Tolkien would create, from scratch, a language spoken by elves, and tries to bring the same passion in everything he does. A big admirer of Richard Feynman and Nikola Tesla, he obsesses over how thoroughly science dictates every aspect of life… in this universe, at least.

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Breaking The Sound Barrier: Can Pilots Hear Sonic Booms?

What If Something Travels Faster Than The Speed Of Light?

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Underwater Sound Experiment for Kids

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Science project, how well does sound travel through a gas a liquid a solid.

Grade Level: Preschool to 2nd grade; Type: Physics

Chidren will experience sounds travelling through things in different states: a bag of air, a bag of water, a wooden block.

Research Questions:

Will a pencil tap heard through a bag of air sound different than a pencil tap heard through a bag of water? Will these taps sound different than a tap heard through a wooden block?

• Zippered sandwich bag
• Wooden block

Experimental Procedure:

• Blow into the sandwich bag and quickly seal it to create a puffed up bag of air (a gas).
• Cover one ear with your hand and the other ear with the bag of air.
• Have an assisstant tap the bag with a pencil. How does it sound?
• Now fill the bag with water (a liquid) and seal it.
• Hold this water-filled bag against one ear while covering the other ear with your hand.
• Have your assistant tap this bag with a pencil. How does it sound?
• Finally hold a wooden block (a solid) over one ear while covering the other ear with your hand. Have your friend tap the block with the pencil. How does it sound?
• Compare and discuss your observations.

Terms/Concepts: Things exist in different states: gas, liquid. solid; Sound travels.

References: "How to Demonstrate Sound Waves to Kids," eHow Family

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Bookmark this to easily find it later. Then send your curated collection to your children, or put together your own custom lesson plan.

Sound Science Experiment: Can sound travel through water? Build a hydrophone

Make your own hydrophone to listen for sounds underwater.

 Monster Sciences Sound Experiment:  Can you hear underwater?

What you will need:.

• A large bowl half full of water
• An empty plastic soft drink bottle with no lid
• 2 hard things, e.g. pebbles, marbles, metal spoons

What you will do:

• Gently click the hard things (pebbles, spoons etc) together.  How do they sound?
• Place your bowl of water on a table or the ground so it is no higher off the ground than your waist.
• VERY CAREFULLY cut the bottom off your plastic container, about level with the bottom of the label.
• Put the bottle, cut side down, into the bowl of water and put your ear up against the hole at the other end.
• Ask your partner to gently tap the spoons or other hard things together under the water.  What can you hear?
• Swap and let your partner listen.

  What is going on?

You are listening to the sound waves from the clicking traveling through the water.  Sound travels in waves caused by vibrations, bumping the molecules around them together.  Does the sound travel through the air better than the water, or the water better than the air?  Compare it to a solid by tapping the hard object gently on the table while you put your ear against it.  What did you discover?

  Monster Challenges: 

• The bottle you have cut off catches sound waves – how else could you use it for this?  Could you make a phone?  How?
• The bottle can also be used to magnify sound waves.  Can you figure out how?
• Try this next time you’re swimming!

Teaching Notes:

Key concepts:.

Sound travels in waves.

• Investigation Record IR01– one copy per student
• Experiment Description Sound S04– one copy per student
• Large bowl with water, empty soft drink bottle, scissors, hard objects

Lesson Notes:

When doing this experiment with younger students I usually cut down the bottles myself prior to the lesson.

The hard objects can be anything water proof.  Remind students not to tap them too hard – it can be too loud!

As a class discuss the experiment prior to undertaking it, and students should complete the sections of their Investigation Report IR01 from ”Title to “Hypothesis”.

What should happen in this experiment, and why?

The students should be able to clearly hear the clicking underwater, in fact is should be easier to hear and clearer than in the air.  This is because the molecules in a liquid like water are closer together so bounce off each other more effectively than the molecules of air.  The solid table should transfer the sound even better than the water because its molecules are closer together again.

The children should note that the clicking rocks vibrate the water, the vibration creates sound waves which vibrate the bottle and then the air inside it to carry the sound to their ear.  If their ear was in the water the sound is even better.

Follow up discussion questions:

• How do whales and dolphins use sound in the water?
• What about submarines?
• Can you think of a way to use water to improve a string phone?  (If you wet the string between the cups closely packed water molecules replace the loosely packed air molecules within the fibers of the string).

Get this experiment here or as part of a bundle of Sound Experiments here .

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