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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.

Does sound travel up or down

  • 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 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 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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About author.

Muhaiminul is the insightful article’s author on Quiethall.com and a fervent DIY living enthusiast. Muhaiminul has spent countless hours learning about and exploring the world of soundproofing techniques and products because he has a deep fascination with creating peaceful and noise-free spaces. Muhaiminul shares helpful advice, detailed how-to guides, and product reviews on Quiethall.com out of a desire to help others cultivate peace in their lives.

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Muhaiminul Anik

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does sound travel up or down

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does sound travel up or down

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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does sound travel up or down

Does Sound Travel Up or Down? Noise Explained

Children playing, music, laughter, waves crashing, birds chirping, the pitter patter of little feet, raindrops falling; there are so many beautiful sounds.

However, there are times when even the most beautiful sounds can be distracting. For example, when you’re trying to get some work done in your home office and the sounds of your kiddos playing in their upstairs bedrooms are pouring through the ceiling, or when the music your downstairs neighbors are playing travels through the floor of your bedroom while you’re trying to sleep.

When you want to block out unwanted sounds, you need to figure out where it’s coming from in order to apply the right soundproofing methods. Pinpointing the source involves determining whether sound travels up or down.

Sound Explained

model of sound wave

Sound is a form of energy, and that energy is created when objects move forward and backward in a fast motion, causing a vibration.

For instance, if you were to knock on a door, the hard surface of the door would vibrate at a very high speed; so high, in fact, that you probably can’t even see it.

The vibration on the surface of the door then creates a vibration in the air that surrounds it. When the air moves, the energy that’s created when you knock on the door is carried out in all directions.

Eventually, the energy in the air travels into your ear, creating a vibration against your ear drum, and hence, you can hear the sound of a knock on the door.

To summarize, the creation of sound is comprised of two separate processes:

  • The physical process, which creates sound energy (or soundwaves). Once soundwaves are created, they travel through a medium. In the example listed above, that medium is the air; however, sound can also travel through structures.
  • The physiological process, which is what happens when your ears pick up soundwaves and your brain then processes the energy to differentiate what type of sound you’re hearing.

While both fascinating, for the purposes of soundproofing, we’re going to focus on the physical process of sound.

How does Sound Travel?

In order for soundwaves to be transmitted, they need to have a medium to travel on; in other words, the energy created by an object that makes a noise needs to be picked up by something.

The mediums that soundwaves travel on include air, solids, and water. As long as there are particles for soundwaves to bounce off of, they can travel through these mediums; but, if there aren’t any particles for the waves to bounce off of, they can’t move, and thus sound can’t move.

It is for this reason that sound cannot be heard within the vacuum of space; there’s nothing for soundwaves to vibrate off of.

Does Sound Travel Up or Down?

omnidirectional sound

In short, sound is omnidirectional, meaning that it can travel in all directions, including up and down. However, with that said, there are factors that can influence sound’s direction.

For example, the way in which sound wave travel can change in different types of settings. Another factor that can influence the travel of sound is the medium that sound travels on; for instance, the type of materials that are used to create a floor and a ceiling can influence the way sound travels and the types of sounds you hear.

The position of the source of the sound will impact where the soundwaves that the source creates are heard. To illustrate, the closer you are to the source of the sound, the higher the sound is going to be.

So, as you can see, while sound travels in all directions, the amount of noise you hear depends on several different factors. As such, in order to effectively soundproof a space, these factors need to be taken into consideration.

Types of Sound

Another important factor that needs to be taken into consideration when you’re soundproofing is the type of noise you’re attempting to eliminate. Believe it or not, not all sound is the same; there are actually two different types of sound.

Airborne Sound

airborne noise transmission

The first type is known as airborne sound; this is the type of sound that you’re probably the most familiar with.

Examples include people speaking, dogs barking, laughter, and music. As mentioned, in order for soundwave to travel, they need to have a medium that they can travel on, and in the case of airborne sound, that medium is air. The energy is picked up by and travels through the air until it collides with a solid object and passes into the space beyond it.

Impact Sound

impact noise

The second type of sound is referred to as structure-born or impact sound.

With this type of noise, a structure serves as the medium that soundwaves travel on; in other words, the sound is traveling directly through a solid structure, such as a floor, a wall, a door, or a ceiling. Structure-borne sound occurs when two objects collide.

The impact of that collision creates a vibration, and that vibration passes through the structure into the adjoining space. Examples of structure-borne noise include a washing machine thumping a floor, a ball being thrown into a ceiling, or someone knocking on a door.

Determining the type of noise you’re dealing with involves a simple test: When you hear a sound, place your hand against the surface that you hear it traveling through. If you can feel a vibration in your hand, then it’s impact or structure-borne noise, if you don’t feel a vibration yet you hear a sound, then it’s airborne noise.

The science of sound really is quite fascinating, and in order to effectively soundproof a space, you do need to have at least a basic understanding of this science.

Once you are familiar with how sound is made, travels, and the different types, you can then apply the proper techniques to eliminate or at least minimize the passage of soundwaves, thereby effectively soundproofing a space.

does sound travel up or down

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Does Sound Travel Up or Down? What way does sound travel?

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Does sound travel up or down? That’s one of the popular questions I encounter from apartment dwellers on various online forums.

So, I decided to compile an article based on authoritative sources (mentioned in the course of the article) to help you understand how sound travels and in what directions.

Sound does travel in both directions, up and down- it can travel in any direction to be precise. However, some factors influence the direction of the sound.

How sound travel can vary and will change depending on a variety of factors such as environment and the material that gets in the way of how the sound is traveling.

For instance, assuming you live in an apartment, the intensity of the noise from neighbors upstairs and that downstairs will vary depending on the material used for ceiling and floor construction.

How Sound Travel- Does It Travel Up and Down Only?

Sound travels through mechanical waves. A mechanical wave is defined as a disturbance that moves and transfers energy from one place to another through a given medium. ( Source )

The disturbance, in this case, is a vibrating object, while the medium is any series of interconnected and interactive particles.

For this reason, sound can travel through solids, liquids, and gases.

A good example is when using an acoustic drum. When you hit the drum head with a drum stick, the drum head vibrates and flexes inward and outward very fast.

As the drum head moves outward, it pushes against air particles. The air particles vibrate and push the adjacent air particles, and so on.

As the drum head flexes inward, the adjacent air particles are pulled inward, and they, in turn, pull against other air particles.

The action of pushing and pulling patterns is referred to as a sound wave. The drum head is the disturbance, and the air particles are the medium. Check out this guide on quiet drum sets for apartment practice.

Does Sound Travel Up or Down

Impact and Airborne Noise and How they Travel

In your entire soundproofing journey, you will find yourself dealing with either of the two types of noises.

There are different methods on how to deal with the two noises . These methods will require the use of varying soundproofing materials.

Impact Sound/ Structure- Borne Sound

Impact sound is as a result of an actual impact of an object on a building element such as floor, wall, or ceiling.

Here’s a good example:

Assuming you live below someone else in your apartment or you live in a two-story house.  The footsteps you hear from above or objects falling on the floor is as a result of impact/structure-borne noise.

Impact sound occurs because the impact makes both sides of the building element to vibrate creating sound waves. Impact noises are the hardest to isolate.

Airborne Sound

Airborne noise is transmitted through the air. An example is barking dogs, television, radio, or people having conversations.

When airborne sound waves traveling through the air reach a building element such as walls, doors, or windows, they cause vibrations.

The vibrations are transmitted through the structure and radiated on the other side. If your neighbors hosted a party across the streets, you may have felt the music they played reverberating loudly within your house.

This is mainly caused by airborne noise, which are a major source of noise leakage. Use green glue sealant to deal with cracks on these building elements.

Does Sound Travel Up or Down

Some Solutions for Minimizing Airborne And Impact Sound/Noise

Now that you are familiar with the different types of sound and how they travel: let’s have a look at the different methods on how you can minimize the impacts of noise.

  • Seal all the holes and cracks – the small cracks and gaps on your windows, doors, walls, ceiling, and floor can significantly make a bit different when it comes to the amount of noise that leaks in your house.
  • Use floor underlayment, carpet, or soundproofing layers- these are great in preventing impact noise. They also can minimize sounds frequency levels depending on the material used.
  • Be mindful of your neighbors- be a good neighbor and care about other people’s neighbors, especially during the late hours of the day, and expect your neighbors will do the same for you.

Final Thoughts on Does Sound Travel Up or Down

The answer to the question does sound travel up or down is- YES.  Sound travels in all directions from its source.

Various factors affect how sound travels. And for this reason, the two types of sound will require different approaches when soundproofing .

Mike O'Connor

Meet Mike O’Connor, (a DIY enthusiast), living in Cincinnati, a city ranked as the noisiest in the USA.

As a work from home dad, I have a first hand experience of how noise can truly affect your well being.

Soundproofing isn’t something that should be taken as a hobby, it should be a skill that every homeowner should be equipped with.

Most of the work documented on this blog comes from purely first hand experience, and the products recommended work as indicated.

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How do sound waves work?

By Brian S. Hawkins

Updated on Jun 1, 2023 2:00 PM EDT

7 minute read

We live our entire lives surrounded by them. They slam into us constantly at more than 700 miles per hour, sometimes hurting, sometimes soothing . They have the power to communicate ideas, evoke fond memories, start fights, entertain an audience, scare the heck out of us, or help us fall in love. They can trigger a range of emotions and they even cause physical damage. This reads like something out of science fiction , but what we’re talking about is very much real and already part of our day-to-day lives. They’re sound waves. So, what are sound waves and how do they work?

If you’re not in the industry of audio, you probably don’t think too much about the mechanics of sound. Sure, most people care about how sounds make them feel, but they aren’t as concerned with how the sound actually affects them. Understanding how sound works does have a number of practical applications , however, and you don’t have to be a physicist or engineer to explore this fascinating subject. Here’s a primer on the science of sound to help get you started.

What’s in a wave

When energy moves through a substance such as water or air, it makes a wave. There are two kinds of waves: longitudinal ones and transverse ones. Transverse waves, as NASA notes , are probably what most people think of when they picture waves—like the up-down ripples of a battle rope used to work out. Longitudinal waves are also known as compression waves, and that’s what sound waves are. There’s no perpendicular motion to these, rather, the wave moves in the same direction as the disturbance.

How sound waves work

Sound waves are a type of energy that’s released when an object vibrates. Those acoustic waves travel from their source through air or another medium, and when they come into contact with our eardrums, our brains translate the pressure waves into words, music, or signals we can understand. These pulses help you place where things are in your environment.

We can experience sound waves in ways that are more physical, not just physiological, too. If sound waves reach  a microphone —whether it’s a plug-n-play  USB livestream mic  or a studio-quality  microphone for vocals —it transforms them into electronic impulses that are turned back into sound by vibrating speakers . Whether listening at home or at a concert, we can feel the deep bass in our chest. Opera singers can use them to shatter glass. It’s even possible to see sound waves sent through a medium like sand, which leaves behind a kind of sonic footprint. 

That shape is rolling peaks and valleys, the signature of a sine (aka sinusoid) wave. If the wave travels faster, those peaks and valleys form closer together. If it moves slower, they spread out. It’s not a poor analogy to think of them somewhat like waves in the ocean. It’s this movement that allows sound waves to do so many other things. 

It’s all about frequency

When we talk about a sound wave’s speed, we’re referring to how fast these longitudinal waves move from peak to trough and back to peak. Up … and then down … and then up … and then down. The technical term is frequency , but many of us know it as pitch. We measure sound frequency in hertz (Hz), which represents cycles-per-second, with faster frequencies creating higher-pitched sounds. For instance, the A note right above Middle C on a piano is measured at 440 Hz—it travels up and down at 440 cycles per second. Middle C itself is 261.63 Hz—a lower pitch, vibrating at a slower frequency.

Understanding frequencies can be useful in many ways. You can precisely tune an instrument by analyzing the frequencies of its strings. Recording engineers use their understanding of frequency ranges to dial in equalization settings that help sculpt the sound of the music they’re mixing . Car designers work with frequencies—and materials that can block them—to help make engines quieter. And  active noise cancellation  uses artificial intelligence and algorithms to measure external frequencies and generate inverse waves to cancel environmental rumble and hum, allowing top-tier ANC headphones and earphones to isolate the wearer from the noise around them. The average frequency range of human hearing is 20 to 20,000 Hz.

What’s in a name? 

The hertz measurement is named for the German physicist Heinrich Rudolf Hertz , who proved the existence of electromagnetic waves. 

Getting amped

Amplitude equates to sound’s volume or intensity. Using our ocean analogy—because, hey, it works—amplitude describes the height of the waves.

We measure amplitude in decibels (dB). The dB scale is logarithmic, which means there’s a fixed ratio between measurement units. And what does that mean? Let’s say you have a dial on your guitar amp with evenly spaced steps on it numbered one through five. If the knob is following a logarithmic scale, the volume won’t increase evenly as you turn the dial from marker to marker. If the ratio is 4, let’s say, then turning the dial from the first to the second marker increases the sound by 4 dB. But going from the second to the third marker increases it by 16 dB. Turn the dial again and your amp becomes 64 dB louder. Turn it once more, and you’ll blast out a blistering 256 dB—more than loud enough to rupture your eardrums. But if you’re somehow still standing, you can turn that knob one more time to increase your volume to a brain-walloping 1,024 decibels. That’s almost 10 times louder than any rock concert you’ll ever encounter, and it will definitely get you kicked out of your rehearsal space. All of which is why real amps aren’t designed that way.

Twice as nice

We interpret a 10 dB increase in amplitude as a doubling of volume. 

Parts of a sound wave

Timbre and envelope are two characteristics of sound waves that help determine why, say, two instruments can play the same chords but sound nothing alike. 

Timbre is determined by the unique harmonics formed by the combination of notes in a chord. The A in an A chord is only its fundamental note—you also have overtones and undertones. The way these sound together helps keep a piano from sounding like a guitar, or an angry grizzly bear from sounding like a rumbling tractor engine. 

[Related: Even plants pick up on good vibes ]

But we also rely on envelopes, which determine how a sound’s amplitude changes over time. A cello’s note might swell slowly to its maximum volume, then hold for a bit before gently fading out again. On the other hand, a slamming door delivers a quick, sharp, loud sound that cuts off almost instantly. Envelopes comprise four parts: Attack, Decay, Sustain, and Release. In fact, they’re more formally known as ADSR Envelopes. 

  • Attack: This is how quickly the sound achieves its maximum volume. A barking dog has a very short attack; a rising orchestra has a slower one. 
  • Decay: This describes how fast the sound settles into its sustained volume. When a guitar player plucks a string , the note starts off loudly but quickly settles into something quieter before fading out completely. The time it takes to hit that sustained volume is decay. 
  • Sustain: Sustain isn’t a measure of time; it’s a measure of amplitude, or volume. It’s how loud the plucked guitar note is after the initial attack but before it fades out. 
  • Release: This is the time it takes for the note to drift off to silence. 

Speed of sound

Science fiction movies like it when spaceships explode with giant, rumbling, surround-sound booms . However, sound needs to travel through a medium so, despite Hollywood saying otherwise, you’d never hear an explosion in the vacuum of space. 

Sound’s velocity , or the speed it travels at , differs depending on the density (and even temperature) of the medium it’s moving through—it’s faster in the air than water, for instance. Generally, sound moves at 1,127 feet per second, or 767.54 miles per hour. When jets break the sound barrier , they’re traveling faster than that. And knowing these numbers lets you estimate the distance of a lightning strike by counting the time between the flash and thunder’s boom—if you count to 10, it’s approximately 11,270 feet away, or about a quarter-mile. (Very roughly, of course.) 

A stimulating experience

Anyone can benefit from understanding the fundamentals of sound and what sound waves are. Musicians and content creators with home recording set-ups and studio monitors obviously need a working knowledge of frequencies and amplitude. If you host a podcast, you’ll want as many tools as possible to ensure your voice sounds clear and rich, and this can include understanding the frequencies of your voice, what microphones are best suited to them , and how to set up your room to reflect or dampen the sounds you do or do not want. Having some foundational information is also useful when doing home-improvement projects— when treating a recording workstation , for instance, or just soundproofing a new enclosed deck. And who knows, maybe one day you’ll want to shatter glass. Having a better understanding of the physics of sound opens up wonderful new ways to explore and experience the world around us. Now, go out there and make some noise!

This post has been updated. It was originally published on July 27, 2021.

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Traveling waves

17 How sound moves

Speed of sound.

There’s a delay between when a sound is created and when it is heard. In everyday life, the delay is usually too short to notice. However, the delay can be noticeable if the distance between source and detector is large enough. You see lightning before you hear the thunder. If you’ve sat in the outfield seats in a baseball stadium, you’ve experienced the delay between seeing the player hit the ball and the sound of the “whack.” Life experiences tell us that sound travels fast, but not nearly as fast as light does. Careful experiments confirm this idea.

The speed of sound in air is roughly 340 m/s. The actual value depends somewhat on the temperature and humidity. In everyday terms, sound travels about the length of three and a half foot ball fields every second- about 50% faster than a Boeing 747 (roughly 250 m/s). This may seem fast, but it’s tiny compared to light, which travels roughly a million times faster than sound (roughly 300,000,000 m/s).

Sound requires some material in which to propagate (i.e. travel). This material sound travels through is called the medium . You can show that sound requires a medium by putting a cell phone inside a glass jar connected to a vacuum pump. As the air is removed from the jar, the cell phone’s ringer gets quieter and quieter. A youTube video (2:05 min) produced by the UNSW PhysClips project shows the demo with a drumming toy monkey [1] instead of a cell phone.

What affects the speed of sound?

Sound travels at different speeds though different materials. The physical properties of the medium are the only factors that affect the speed of sound- nothing else matters.

The speed of sound in a material is determined mainly by two properties- the stiffness of the material and the density of the material. Sound travels fastest through materials that are stiff and light. In general, sound travels fastest through solids, slower through liquids and slowest through gasses. (See the table on this page). This may seem backwards- after all, metals are quite dense. However, the high density of metals is more than offset by far greater stiffness (compared to liquids and solids).

The speed of sound in air depends mainly on temperature. The speed of sound is 331 m/s in dry air at 0 o Celsius and increases slightly with temperature- about 0.6 m/s for every 1 o Celsius for temperatures commonly found on Earth. Though speed of sound in air also depends on humidity, the effect is tiny- sound travels only about 1 m/s faster in air with 100% humidity air at 20 o C than it does in completely dry air at the same temperature.

Nothing else matters

The properties of the medium are the only factors that affect the speed of sound- nothing else matters.

Frequency of the sound does not matter- high frequency sounds travel at the same speed as low frequency sounds. If you’ve ever listened to music, you’ve witnessed this-  the low notes and the high notes that were made simultaneously reach you simultaneously, even if you are far from the stage. If you’ve heard someone shout from across a field, you’ve noticed that the entire shout sound (which contains many different frequencies at once) reaches you at the same time. If different frequencies traveled at different rates, some frequencies would arrive before others.

The amplitude of the sound does not matter- loud sounds and quiet ones travel at the same speed. Whisper or yell- it doesn’t matter. The sound still takes the same amount of time to reach the listener.  You’ve probably heard that you can figure out how far away the lightning by counting the seconds between when you see lightning and hear thunder. If the speed of sound depended on loudness, this rule of thumb would have to account for loudness- yet there is nothing in the rule about loud vs. quiet thunder. The rule of thumb works the same for all thunder- regardless of loudness . That’s because the speed of sound doesn’t depend on amplitude.

Stop to thinks

  • Which takes longer to cross a football field: the sound of a high pitched chirp emitted by a fruit bat or the (relatively) low pitched sound emitted by a trumpet?
  • Which sound takes longer to travel 100 meters: the sound of a snapping twig in the forest or the sound of a gunshot?
  • Which takes longer to travel the distance of a football field: the low pitched sound of a whale or the somewhat higher pitched sound of a human being?

Constant speed

Sound travels at a constant speed. Sound does not speed up or slow down as it travels (unless the properties of the material the sound is going through changes). I know what you’re thinking- how is that possible? Sounds die out as they travel, right? True. That means sounds must slow down and come to a stop, right? Wrong. As sound travels, its amplitude decreases- but that’s not the same thing as slowing down. Sound (in air) covers roughly 340 meters each and every second, even as its amplitude shrinks. Eventually, the amplitude gets small enough that the sound is undetectable. A sound’s amplitude shrinks as it travels, but its speed remains constant.

The basic equation for constant speed motion (shown below) applies to sound.


In this equation, [latex]d[/latex] represents the distance traveled by the sound, [latex]t[/latex] represents the amount of time it took to go that distance and [latex]v[/latex] represents the speed.

Rule of thumb for lightning example

Example: thunder and lightning.

The rule of thumb for figuring out how far away a lightning strike is from you is this:

Count the number of seconds between when you see the lightning and hear the thunder. Divide the number of seconds by five to find out how many miles away the lightning hit.

According to this rule, what is the speed of sound in air? How does the speed of sound implied by this rule compare to 340 m/s?

Identify important physics concept :   This question is about speed of sound.

List known and unknown quantities (with letter names and units):

At first glance, it doesn’t look like there’s enough information to solve the problem. We were asked to find speed, but not given either a time or a distance. However, the problem does allow us to figure out a distance if we know the time- “Divide the number of seconds by five to find out how many miles away the lightning hit.” So, let’s make up a time and see what happens; if the time is 10 seconds, the rule of thumb says that the distance should be 2 miles.

[latex]v= \: ?[/latex]

[latex]d=2 \: miles[/latex]

[latex]t=10 \: seconds[/latex]

You might ask “Is making stuff up OK here?” The answer is YES! If the rule of thumb is right, it should work no matter what time we choose. (To check if the rule is OK, we should probably test it with more than just one distance-time combination, but we’ll assume the rule is OK for now).

Do the algebra:  The equation is already solved for speed. Move on to the next step.

Do unit conversions (if needed) then plug in numbers:  If you just plug in the numbers, the speed comes out in miles per second:

[latex]v = \frac{2 \: miles} {10 \: seconds}=0.2 \: \frac{miles} {second}[/latex]

We are asked to compare this speed to 340 m/s, so a unit conversion is in order; since there are 1609 meters in a mile:

[latex]v =0.2 \: \frac{miles} {second}*\frac{1609 \: meters} {1 \:mile}=320 \frac{m}{s}[/latex]

Reflect on the answer:

  • The answer for speed from the rule of thumb is less than 10% off the actual value of roughly 340 m/s- surprisingly close!
  • At the beginning, we assumed a time of 10 seconds. Does the result hold up for other choices? A quick check shows that it does! For instance, if we use a time of 5 seconds, the rule of thumb gives a distance of 1 mile, and the math still gives a speed of 0.2 miles/second. The speed will be the same no matter what time we pick. The reason is this:  The more time it takes the thunder to arrive, the farther away the lightning strike is, but the speed remains the same. In the equation for speed, both time and distance change by the same factor and the overall fraction remains unchanged.

Stop to think answers

  • Both sounds take the same amount of time. (High and low pitched sounds travel at the same speed).
  • Both sounds take the same amount of time. (Quiet sounds and loud sounds travel at the same speed).
  • The sound of the whale travels the distance in less time- assuming sound from the whale travels in water and sound from the human travels in air. Sound travels faster in water than in air. (The info about frequency was given just to throw you off- frequency doesn’t matter).
  • Wolfe, J. (2014, February 20). Properties of Sound. Retrieved from https://www.youtube.com/watch?v=P8-govgAffY ↵

Understanding Sound Copyright © by dsa2gamba and abbottds is licensed under a Creative Commons Attribution 4.0 International License , except where otherwise noted.

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