does sound travel in space

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Is there any sound in space? An astronomer explains

How far can sound travel through space, since it’s so empty? Is there an echo in space? – Jasmine, age 14, Everson, Washington

In space, no one can hear you scream.

You may have heard this saying. It’s the tagline from the famous 1979 science fiction movie “ Alien .” It’s a scary thought, but is it true? The simple answer is yes, no one can hear you scream in space because there is no sound or echo in space.

I’m a  professor of astronomy , which means I study space and how it works. Space is silent – for the most part.

How sound works

To understand why there’s no sound in space, first consider how sound works.  Sound is a wave  of energy that moves through a solid, a liquid or a gas.

Sound is  a compression wave . The energy created when your vocal cords vibrate slightly compresses the air in your throat, and the compressed energy travels outward.

A good analogy for sound is a  Slinky toy . If you stretch out a Slinky and push hard on one end, a  compression wave travels  down the Slinky.

When you talk, your vocal cords vibrate. They jostle air molecules in your throat above your vocal cords, which in turn jostle or bump into their neighbors, causing a sound to come out of your mouth.

Sound moves through air the same way it moves through your throat. Air molecules near your mouth bump into their neighbors, which in turn bump into their neighbors, and the sound moves through the air. The  sound wave travels quickly , about 760 miles per hour (1,223 kilometers per hour), which is faster than a commercial jet.

Space is a vacuum

So what about in space?

Space is a vacuum, which means it contains almost no matter. The word vacuum  comes from the Latin word for empty .

Sound is carried by atoms and molecules. In space, with no atoms or molecules to carry a sound wave, there’s no sound. There’s nothing to get in sound’s way out in space, but there’s nothing to carry it, so it doesn’t travel at all. No sound also means no echo.  An echo  happens when a sound wave hits a hard, flat surface and bounces back in the direction it came from.

By the way, if you were caught in space outside your spacecraft with no spacesuit, the fact that no one could hear your cry for help is the least of your problems. Any air you still had in your lungs would expand because it was at higher pressure than the vacuum outside. Your lungs would rupture. In a mere  10 to 15 seconds , you’d be unconscious due to a lack of oxygen.

Sound in the solar system

Scientists have wondered how human voices would sound on our nearest neighboring planets, Venus and Mars. This experiment is hypothetical because  Mars is usually below freezing , and its atmosphere is  thin, unbreathable carbon dioxide .  Venus is even worse  – its air is hot enough to melt lead, with a thick carbon dioxide atmosphere.

On Mars, your voice would sound tinny and hollow, like the  sound of a piccolo .  On Venus , the pitch of your voice would be much deeper, like the sound of a booming bass guitar. The reason is the thickness of the atmosphere. On Mars the thin air creates a high-pitched sound, and on Venus the thick air creates a low-pitched sound. The team that worked this out  simulated other solar system sounds , like a waterfall on Saturn’s moon Titan.

Deep space sounds

While space is a good enough vacuum that normal sound can’t travel through it, it’s actually not a perfect vacuum, and it does have some particles floating through it.

Beyond the Earth  and its atmosphere, there are five particles in a typical cubic centimeter – the volume of a sugar cube – that are mostly hydrogen atoms. By contrast, the air you are breathing is 10 billion billion (10 19)  times more dense. The density goes down with distance from the Sun, and in  the space between stars  there are 0.1 particles per cubic centimeter. In vast  voids between galaxies , it is a million times lower still – fantastically empty.

The voids of space are kept very hot by radiation from stars. The very spread-out matter found there is in a physical state  called a plasma .

A plasma is a gas in which electrons are separated from protons. In a plasma, the  physics of sound waves get complicated . Waves travel much faster in this low-density medium, and their wavelength is much longer.

In 2022, NASA released a  spectacular example of sound in space . It used X-ray data to make an audible recording that represents the way a massive black hole stirs up plasma in the Perseus galaxy cluster, 250 million light years from Earth. The black hole itself emits no sound, but the diffuse plasma around it carries very long wavelength sound waves.

The natural sound is far too low a frequency for the human ear to hear, 57 octaves below middle C, which is the middle note on a piano and in the middle of the range of sound people can hear. But after raising the frequency to the audible range, the result is chilling – it’s the sound of a black hole growling in deep space.

This article was first published on The Conversation .

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Why isn’t there any sound in space? An astronomer explains why in space no one can hear you scream

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Chris Impey receives funding from the National Science Foundation.

University of Arizona provides funding as a member of The Conversation US.

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How far can sound travel through space, since it’s so empty? Is there an echo in space? – Jasmine, age 14, Everson, Washington

In space, no one can hear you scream.

You may have heard this saying. It’s the tagline from the famous 1979 science fiction movie “ Alien .” It’s a scary thought, but is it true? The simple answer is yes, no one can hear you scream in space because there is no sound or echo in space.

I’m a professor of astronomy , which means I study space and how it works. Space is silent – for the most part.

How sound works

To understand why there’s no sound in space, first consider how sound works. Sound is a wave of energy that moves through a solid, a liquid or a gas.

Sound is a compression wave . The energy created when your vocal cords vibrate slightly compresses the air in your throat, and the compressed energy travels outward.

A good analogy for sound is a Slinky toy . If you stretch out a Slinky and push hard on one end, a compression wave travels down the Slinky.

When you talk, your vocal cords vibrate. They jostle air molecules in your throat above your vocal cords, which in turn jostle or bump into their neighbors, causing a sound to come out of your mouth.

Sound moves through air the same way it moves through your throat. Air molecules near your mouth bump into their neighbors, which in turn bump into their neighbors, and the sound moves through the air. The sound wave travels quickly , about 760 miles per hour (1,223 kilometers per hour), which is faster than a commercial jet.

Space is a vacuum

So what about in space?

Space is a vacuum, which means it contains almost no matter. The word vacuum comes from the Latin word for empty .

Sound is carried by atoms and molecules. In space, with no atoms or molecules to carry a sound wave, there’s no sound. There’s nothing to get in sound’s way out in space, but there’s nothing to carry it, so it doesn’t travel at all. No sound also means no echo. An echo happens when a sound wave hits a hard, flat surface and bounces back in the direction it came from.

By the way, if you were caught in space outside your spacecraft with no spacesuit, the fact that no one could hear your cry for help is the least of your problems. Any air you still had in your lungs would expand because it was at higher pressure than the vacuum outside. Your lungs would rupture. In a mere 10 to 15 seconds , you’d be unconscious due to a lack of oxygen.

Sound in the solar system

Scientists have wondered how human voices would sound on our nearest neighboring planets, Venus and Mars. This experiment is hypothetical because Mars is usually below freezing , and its atmosphere is thin, unbreathable carbon dioxide . Venus is even worse – its air is hot enough to melt lead, with a thick carbon dioxide atmosphere.

On Mars, your voice would sound tinny and hollow, like the sound of a piccolo . On Venus , the pitch of your voice would be much deeper, like the sound of a booming bass guitar. The reason is the thickness of the atmosphere. On Mars the thin air creates a high-pitched sound, and on Venus the thick air creates a low-pitched sound. The team that worked this out simulated other solar system sounds , like a waterfall on Saturn’s moon Titan.

Deep space sounds

While space is a good enough vacuum that normal sound can’t travel through it, it’s actually not a perfect vacuum, and it does have some particles floating through it.

Beyond the Earth and its atmosphere, there are five particles in a typical cubic centimeter – the volume of a sugar cube – that are mostly hydrogen atoms. By contrast, the air you are breathing is 10 billion billion (10 19) times more dense. The density goes down with distance from the Sun, and in the space between stars there are 0.1 particles per cubic centimeter. In vast voids between galaxies , it is a million times lower still – fantastically empty.

The voids of space are kept very hot by radiation from stars. The very spread-out matter found there is in a physical state called a plasma .

A plasma is a gas in which electrons are separated from protons. In a plasma, the physics of sound waves get complicated . Waves travel much faster in this low-density medium, and their wavelength is much longer.

In 2022, NASA released a spectacular example of sound in space . It used X-ray data to make an audible recording that represents the way a massive black hole stirs up plasma in the Perseus galaxy cluster, 250 million light years from Earth. The black hole itself emits no sound, but the diffuse plasma around it carries very long wavelength sound waves.

The natural sound is far too low a frequency for the human ear to hear, 57 octaves below middle C, which is the middle note on a piano and in the middle of the range of sound people can hear. But after raising the frequency to the audible range, the result is chilling – it’s the sound of a black hole growling in deep space.

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Can Humans Hear Sound in Space?

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Is it possible to hear sounds in space? The short answer is "No." Yet, misconceptions about sound in space continue to exist, mostly due to the sound effects used in sci-fi movies and TV shows. How many times have we "heard" the starship Enterprise or the Millennium Falcon whoosh through space? It's so ingrained our ideas about space that people are often surprised to find out that it doesn't work that way. The laws of physics explain that it can't happen, but often enough producers don't really think about them. They're going for "effect."

Plus, it's not just a problem in TV or movies. There are mistaken ideas out there that planets make sounds , for example. What's really happening is that specific processes in their atmospheres (or rings) are sending out emissions that can be picked up by sensitive instruments. In order to understand them, scientists take the emissions and "heterodyne" them (that is, process them) to create something we can "hear" so they can try to analyze what they are. But, the planets themselves aren't making sounds.

The Physics of Sound

It is helpful to understand the physics of sound. Sound travels through the air as waves. When we speak, for example, the vibration of our vocal cords compresses the air around them. The compressed air moves the air around it, which carries the sound waves. Eventually, these compressions reach the ears of a listener, whose brain interprets that activity as sound. If the compressions are high frequency and moving fast, the signal received by the ears is interpreted by the brain as a whistle or a shriek. If they're lower frequency and moving more slowly, the brain interprets it as a drum or a boom or a low voice.

Here's the important thing to remember: without anything to compress, sound waves can't be transmitted. And, guess what? There's no "medium" in the vacuum of space itself that transmits sound waves. There is a chance that sound waves can move through and compress clouds of gas and dust, but we wouldn't be able to hear that sound. It would be too low or too high for our ears to perceive. Of course, if someone were in space without any protection against the vacuum, hearing any sound waves would be the least of their problems. 

Light waves (that aren't radio waves) are different. They do not require the existence of a medium in order to propagate. So light can travel through the vacuum of space unimpeded. This is why we can see distant objects like planets , stars , and galaxies . But, we can't hear any sounds they might make. Our ears are what pick up sound waves, and for a variety of reasons, our unprotected ears aren't going to be in space.

Haven't Probes Picked Up Sounds From the Planets?

This is a bit of a tricky one. NASA, back in the early 90s, released a five-volume set of space sounds. Unfortunately, they were not too specific about how the sounds were made exactly. It turns out the recordings weren't actually of sound coming from those planets. What was picked up were interactions of charged particles in the magnetospheres of the planets; trapped radio waves and other electromagnetic disturbances. Astronomers then took these measurements and converted them into sounds. It is similar to the way that a radio captures the radio waves (which are long-wavelength light waves) from radio stations and converts those signals into sound.

Why Apollo Astronauts Report Sounds Near the Moon

This one is truly strange. According to NASA transcripts of the Apollo moon missions, several of the astronauts reported hearing "music" when orbiting the Moon . It turns out that what they heard was entirely predictable radio frequency interference between the lunar module and the command modules.

The most prominent example of this sound was when the Apollo 15 astronauts were on the far side of the Moon. However, once the orbiting craft was over the near side of the Moon, the warbling stopped. Anyone who has ever played with a radio or done HAM radio or other experiments with radio frequencies would recognize the sounds at once. They were nothing abnormal and they certainly didn't propagate through the vacuum of space. 

Why Movies Have Spacecrafts Making Sounds

Since we know that no one can physically hear sounds in the vacuum of space, the best explanation for sound effects in TV and movies is this: if producers didn't make the rockets roar and the spacecraft go "whoosh", the soundtrack would be boring. And, that's true. It doesn't mean there's sound in space. All it means is that sounds are added to give the scenes a little drama. That's perfectly fine as long as people understand it doesn't happen in reality. 

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How Sound Travels in Space – Echoes of the Cosmos

When we consider the vast expanses of space, many of us imagine a silent, infinite void. However, the science behind how sound travels—or, more accurately, does not travel—in space is a fascinating subject that bridges fundamental physics and our understanding of the universe.

The vacuum of space

Space is a near-perfect vacuum , meaning it has extremely low density and pressure. It contains so few particles that the concept of sound as we experience it on Earth doesn’t apply. Since sound waves need a medium to travel, the vacuum of space presents a unique challenge:  there are simply not enough particles to transmit sound .

This silence underscores the isolation of space environments, fundamentally altering our sensory experience outside of Earth’s atmosphere. The understanding of this concept is crucial for designing spacecraft and equipment that operate effectively in such conditions.

Common misconceptions

Popular culture and science fiction often depict sounds in space, which leads to a common misconception that space can carry sound.  Films show spacecrafts roaring as they travel and star explosions making loud noises, but in reality, space’s vacuum would render these sounds inaudible.

This creative liberty taken by filmmakers creates dramatic but scientifically inaccurate scenes.  Educating the public about the reality of sound in space helps in understanding the true nature of space travel and the environment beyond Earth’s atmosphere.

This knowledge is essential for aspiring astronomers and engineers who are building the future of space exploration.

Propagation through space dust and cosmic gas

For instance, within nebulae —clouds of gas and dust—sound might theoretically propagate, but this would be vastly different from how sound travels on Earth. In these denser regions of space, such as within nebulae or gas giants, the sparse particles could facilitate a form of sound transmission, though this would be more akin to vibrations than the sound waves we are familiar with.

The role of planetary atmospheres

Planetary bodies with atmospheres, such as Earth, Venus, or  Titan (a moon of Saturn) , can carry sound because they have gases that serve as a medium.  For example, if you were standing on the surface of Titan, wearing a suit that could withstand its harsh conditions, you might hear sounds carried by its thick atmosphere.

Experiments and theoretical physics

Researchers and scientists use theoretical models and space probes to study how sound might behave in different celestial environments. While we cannot yet simulate the exact conditions of space in a laboratory, advanced technology allows scientists to make educated guesses and simulations.

These theoretical explorations and practical experiments help refine our understanding of the universe and guide the development of technology for future missions. They also foster a better understanding of the fundamental laws of physics, which in turn inform other areas of scientific inquiry, including cosmology and quantum mechanics.

Vibrations in spacecrafts

One practical aspect of sound in space involves astronauts inside spacecrafts. Here, sound can indeed travel because the air inside the spacecraft acts as a medium.  This phenomenon is crucial for communication among astronauts and for the monitoring of spacecraft integrity through sound.

The ability to hear and diagnose potential issues through auditory cues is vital for maintaining the safety and functionality of spacecraft. It also illustrates the adaptability of human senses and technologies to different environments, ensuring that astronauts can operate effectively in the confines of spaceborne habitats.

Why is this important?

Understanding how sound or similar vibrations travel through different environments in space has practical applications. For example:

• Monitoring seismic activities on other planets  through vibrations can tell us about their internal structures. This is crucial for assessing the geological activity and potential habitability of other celestial bodies. Such monitoring could also aid in the search for extraterrestrial life by identifying planets with active geological processes.
• Communication technology could be adapted  based on how sound-like vibrations propagate through planetary atmospheres or the surface of moons. This adaptation is vital for developing communication systems that are effective across the varied environments of the solar system. It could lead to breakthroughs in how we transmit information across vast distances in space.

While the silence of space might seem empty, it tells us a great deal about the fundamental laws of physics and the nature of the cosmos. Each probe we send and every planet we study adds to our understanding, bringing us one step closer to uncovering the mysteries of the universe.

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Is There Sound in Space?

No, there is no sound in space. At least, not in the way we traditionally understand sound on Earth. The misconception exists largely due to popular culture. Movies and TV shows often depict space battles with roaring rockets and booming exploding stars, but in reality, space is eerily silent.

The reason for this silence lies in the nature of sound itself. Sound is a vibration that travels through a medium, like air or water. For sound waves to propagate, they need particles. Space is a near- perfect vacuum , meaning it has very few particles. Without a medium for these sound waves, there is no sound.

NASA’s “Space Sounds”: Understanding Sonification

Despite the silence of space, there are videos and recordings labeled as “sounds from space” released by NASA. These are not sounds in the traditional sense. Instead, they are products of a process called sonification.

Sonification is the conversion of data into sound. In the context of space, instruments on spacecraft record electromagnetic vibrations or particle interactions. These signals, which are not audible, get converted into sound waves that we can hear. When scientists represent data in an auditory format, it makes certain patterns and anomalies easier to detect.

For instance, the eerie “whistles” and “howls” from recordings of Jupiter or Saturn aren’t sounds that an astronaut could hear. Instead, they are sonifications of radio waves or other electromagnetic phenomena detected by spacecraft.

Gravitational Waves: A Type of Sound in Space

The groundbreaking discovery of gravitational waves adds a new layer to our understanding of “sounds” in space. Detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO), these are ripples in spacetime caused by cataclysmic events, like the merging of two black holes.

Now, gravitational waves aren’t sounds in the traditional sense. They don’t propagate through air or water; they literally stretch and compress the fabric of the universe. However, much like the sonifications mentioned earlier, scientists often convert gravitational wave data into sound.

When scientists at LIGO do this, the results are astounding. The final moments of two black holes spiraling into one another can be “heard” as a chirp. In this context, these gravitational waves are akin to the universe’s symphony, a testament to the colossal events unfolding in the cosmos.

Sound in Space: Can You Hear Sound on the Moon?

Similar to the vastness of space, the Moon is also an environment where sound doesn’t propagate in the traditional manner. The Moon has an extremely thin atmosphere or exosphere, which consists of very few particles. Because of this near- vacuum condition, there’s no medium for sound waves to travel through on the Moon’s surface. So, if an astronaut shouts on the Moon without any equipment, the sound doesn’t travel. Another astronaut standing a distance can’t hear it.

How Astronauts Talk on the Moon

Given the lack of an effective medium for sound transmission on the Moon, you might wonder how astronauts communicate with each other. Astronauts wear helmets that are part of a sealed system, connected to their spacesuits. Inside these helmets, there’s an atmosphere – usually a mix of oxygen and other gases – which transmits sound. When an astronaut speaks, the sound waves travel through the air inside the helmet, reaching a microphone. This microphone then converts the sound into an electrical signal, which transmits the signal to the communication systems of other astronauts or to mission control on Earth.

Any vibrations caused by an astronaut’s activities on the Moon are felt through their spacesuit. If an astronaut taps on another’s helmet, the latter “hears” it through the vibrations conducted by their spacesuit and helmet.

The Mysterious Music of Apollo

During the Apollo 10 mission, astronauts reported hearing a strange “whistling” sound, which some described as “outer-space-type music,” while they were orbiting the dark side of the Moon. This event remained classified until 2008 and spurred numerous speculations and theories.

However, the source of this “music” wasn’t extraterrestrial. The sounds were likely radio interference between the lunar module and the command module of the spacecraft. When two radios are close to each other and set to similar frequencies, they produce a whistling sound due to interference. This phenomenon, while eerie in the context of space exploration, is quite common and has a straightforward scientific explanation.

Sound on Mars

Mars has a very thin atmosphere composed mainly of carbon dioxide, with traces of nitrogen and argon. This atmosphere is about 100 times less dense than Earth’s. The atmospheric pressure at the Martian surface averages 0.6% of Earth’s sea level pressure. Such a tenuous atmosphere significantly affects the way sound travels on Mars compared to Earth.

Sound travels through the movement of particles in a medium, be it solid, liquid, or gas. The speed and character of sound waves are influenced by the properties of this medium. Given Mars’ thin atmosphere, sound travels slower than it does on Earth. Additionally, the composition of the Martian atmosphere means that certain frequencies, especially higher ones, get absorbed more quickly and do not travel as far.

In practical terms, this means that sounds on Mars are quieter and muffled than we’re used to. High-pitched noises are particularly hard to hear. If you were to have a conversation on Mars without the aid of communication equipment, voices would sound different, and you’d need to be much closer to the source of a sound to hear it clearly.

Are Wind and Dust Storms Silent?

Mars has frequent wind events and massive dust storms. But would a human standing on the Martian surface hear these?

Wind on Mars, even during a strong gust, sounds very faint. Given the thin atmosphere, there simply aren’t enough particles colliding with one another to produce a sound as loud as on Earth.

The massive dust storms that engulf the entire planet are visually impressive, but are surprisingly quiet. The movement of the fine dust and the thin atmosphere does not generate the roaring sounds we associate with storms on Earth. Instead, you might hear a soft hiss or a very low rumble, but it would be much subtler than one might expect.

• Abbott, R.; et al. (29 June 2021). “Observation of Gravitational Waves from Two Neutron Star–Black Hole Coalescences”. The Astrophysical Journal Letters . 915 (1): L5. doi: 10.3847/2041-8213/ac082e
• Everest, F. (2001).  The Master Handbook of Acoustics . New York: McGraw-Hill. ISBN 978-0-07-136097-5.
• Kinsler, L.E.; Frey, A.R.; Coppens, A.B.; Sanders, J.V. (2000).  Fundamentals of Acoustics  (4th ed.). New York: John Wiley & Sons. ISBN 0-471-84789-5.
• Maurice, S.; et al. (2022). “In situ recording of Mars soundscape:. Nature. 605: 653-658. doi: 10.1038/s41586-022-04679-0

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Explainer: Is there sound in space?

Imma Perfetto

Imma Perfetto is a science journalist at Cosmos. She has a Bachelor of Science with Honours in Science Communication from the University of Adelaide.

If you’ve seen the famous promotional poster for the 1979 cult science fiction horror film Alien , then you might be under the impression that we can’t hear any sounds in space – let alone screams of abject terror.

So how could the 2018 SCINEMA International Science Film Festival Best Experimental Film, Astroturf , use the strange sounds of recordings from satellites in space?

No, there isn’t sound in space.

Sound doesn’t exist in space, at least not the way we experience it on Earth. This is because sound travels through the vibration of particles, and space is a vacuum . On Earth, sound mainly travels to your ears by way of vibrating air molecules, but in near-empty regions of space there are no (or very, very few) particles to vibrate – so no sound.

We’re lucky that’s the case, because otherwise the sound of the Sun would roar at an impressive 100 decibels to us on Earth – like hearing a rock concert all day every day. 

Sound travels in what’s known as a longitudinal wave, which causes back-and-forth vibration of the particles in the medium through which it is moving. It propagates through a medium at the speed of sound which varies from substance to substance – generally more slowly through gases, faster in liquids, and fastest in solids.

This back and forth causes regions of high pressure where particles are compressed together (compressions) and regions of low pressure where they are more spread apart (rarefactions). The distance it takes to complete one wave cycle – for instance, the distance between each repeating compression – is what’s known as its wavelength.

The frequency of the wave is measured in hertz (Hz), which is a measure of the number of waves that pass through a fixed point in a second. So, the longer the wavelength the lower the frequency, and vice versa.

Human beings can usually hear sounds within a narrow range of frequencies, usually between 20Hz and 20,000Hz.

So, what are we hearing in Astroturf ?

This short film is just one part of a greater anthology , where independent filmmakers were challenged by the Space Sound Effects (SSFX) project to create short films which incorporated sounds recorded in space by satellites.

Now, although we just reminded ourselves that space is a vacuum, it should be clarified that it isn’t completely empty. For instance, it contains solar wind which streams off the Sun – a constant flow of charged particles ( plasma ) which Earth’s magnetic field protects us from.

The magnetosphere shields us from this ionising radiation and from erosion of the atmosphere by solar wind, but the interactions occurring here are complex and dynamic, and can result in phenomena which disrupt the technology we rely upon, such as electrical grids, global positioning systems (GPS), and weather forecasts.

It’s these plasma waves, electromagnetic vibrations, which can be measured. But the waves fall within the ultra low frequency (ULF) range – with frequencies from fractions of a millihertz to 1Hz – that are undetectable to human hearing. For scale, that’s wavelengths of around 300,000km, and pressure variations so small you’d need an eardrum comparable to the size of Earth to hear them.

In space no one can hear you scream – or can they?

But satellites can still observe them. Scientists took a year’s worth of these recordings, dramatically sped up their playback, and condensed them down to just six minutes of audio at frequencies within the human auditory range. This is a process called sonification – like visualisation but instead with sound – where non-speech audio is used to convey information or data, the most famous application of which is the Geiger counter.

This audio was also used in a citizen science project in which high-school students identified an interesting sound-stamp that, when further explored by the scientists, turned out to be a coronal mass ejection – or solar storm – arriving at Earth. By making the data audible they were able to pinpoint an interesting event which the researchers wouldn’t have otherwise spotted.

Detecting the pitch and frequency of electromagnetic waves has also been used to tell us about the density of gas surrounding the Voyager 1 spacecraft – the space probe launched by NASA in 1977 to study the outer solar system and interstellar space.

From this they were able to determine when Voyager 1 had left the heliosphere – the vast bubble of magnetism surrounding the Sun and planets in the solar system – and moved into the denser gas in the interstellar medium between planetary systems.

Are there other instances of the sonification of space data?

There are a lot of these “ sounds of space ” collected by instruments on various spacecraft, from Juno spacecraft observing the plasma wave signals emanating from Jupiter’s ionosphere, to Cassini’s detection of radio emissions from Saturn (which are well above the audio frequency range and are shifted downward so we can hear them).

Another example is gravitational waves. These stretch and shrink space and can be detected through the distortion, or vibration, of space between masses – but needs to be amplified a billion times to be audible .

Going another route, X-ray, optical and infrared light can be translated into sounds in an ensemble musical piece to represent the position and brightness of light sources in a region of space in the Milky Way.

So, while we can’t hear sound in space as we can on Earth, it’s still possible for us to convert the emissions of space into something the human ear can perceive – and isn’t that much nicer to listen to than a scream, anyway?

Originally published by Cosmos as Explainer: Is there sound in space?

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• 09 November 2022

Sounds of the stars: how scientists are listening in on space

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The Perseus cluster contains thousands of galaxies in a cloud of super-heated gas. A tweet from NASA about the sound of the black hole at its centre has been played millions of times. Credit: NASA/CXC/SAO/E. Bulbul et al.

For astronomers who are sighted, the Universe is full of visual wonders. From shimmering planets to sparkling galaxies, the cosmos is spectacularly beautiful. But those who are blind or visually impaired cannot share that experience. So astronomers have been developing alternative ways to convey scientific information, such as using 3D printing to represent exploding stars, and sound to describe the collision of neutron stars.

On Friday, the journal Nature Astronomy will publish the latest in a series of articles on the use of sonification in astronomy 1 – 3 . Sonification describes the conversion of data (including research data) into digital audio files, which allows them to be heard, as well as read and seen. The researchers featured in Nature Astronomy show that sound representations can help scientists to better identify patterns or signals in large astronomical data sets 1 .

The work demonstrates that efforts to boost inclusivity and accessibility can have wider benefits. This is true not only in astronomy; sonification has also yielded discoveries in other fields that might otherwise not have been made. Research funders and publishers need to take note, and support interdisciplinary efforts that are simultaneously more innovative and inclusive.

Sonification and sound design for astronomy research, education and public engagement

For decades, astronomers have been making fundamental discoveries by listening to data, as well as looking at it. In the early 1930s, Karl Jansky, a physicist at Bell Telephone Laboratories in New Jersey, traced static in radio communications to the centre of the Milky Way — a finding that led to the discovery of the Galaxy’s supermassive black hole and the birth of radio astronomy. More recently, Wanda Díaz-Merced, an astronomer at the European Gravitational Observatory in Cascina, Italy, who is blind, has used sonification in many pioneering projects, including the study of plasma patterns in Earth’s uppermost atmosphere 4 .

The number of sonification projects picked up around a decade ago, drawing in researchers from a range of backgrounds. Take Kimberly Arcand, a data-visualization expert and science communicator at the Center for Astrophysics, Harvard & Smithsonian in Cambridge, Massachusetts. Arcand began by writing and speaking about astronomy, particularly discoveries coming from NASA’s orbiting Chandra X-Ray Observatory. She then moved on to work that centred on the sense of touch; this included making 3D printed models of the ‘leftovers’ of exploded stars that conveyed details of the physics of these stellar explosions. When, in early 2020, the pandemic meant she was unable to get to a 3D printer, she shifted to working on sonification.

In August, NASA tweeted about the sound of the black hole at the centre of the Perseus galaxy cluster; the attached file has since been played more than 17 million times. In the same month, Arcand and others converted some of the first images from the James Webb Space Telescope into sound. They worked under the guidance of people who are blind and visually impaired to map the intensity and colours of light in the headline-grabbing pictures into audio.

Wanda Díaz-Merced has used sonification in many projects. Credit: NG Images/Alamy

These maps are grounded in technical accuracy. The sonification of an image of gas and dust in a distant nebula, for instance, uses loud high-frequency sounds to represent bright light near the top of the image, but lower-frequency loud sounds to represent bright light near the image’s centre. The black hole sonification translates data on sound waves travelling through space — created by the black hole’s impact on the hot gas that surrounds it — into the range of human hearing.

Scientists in other fields have also experimented with data sonification. Biophysicists have used it to help students understand protein folding 5 . Aspects of proteins are matched to sound parameters such as loudness and pitch, which are then combined into an audio representation of the complex folding process. Neuroscientists have explored whether it can help with the diagnosis of Alzheimer’s disease from brain scans 6 . Sound has even been used to describe ecological shifts caused by climate change in an Alaskan forest, with researchers assigning various musical instruments to different tree species 7 .

How one astronomer hears the Universe

In the long run, such approaches need to be rigorously evaluated to determine what they can offer that other techniques cannot. For all the technical accuracy displayed in individual projects, the Nature Astronomy series points out that there are no universally accepted standards for sonifying scientific data, and little published work that evaluates its effectiveness.

More funding would help. Many scientists who work on alternative data representations cobble together support from various sources, often in collaboration with musicians or sound engineers, and the interdisciplinary nature of such work makes it challenging to find sustained funding.

On 17 November, the United Nations Office for Outer Space Affairs will highlight the use of sonification in the space sciences in a panel discussion that includes Díaz-Merced and Arcand. This aims to raise awareness of sonification both as a research tool and as a way to reduce barriers to participation in astronomy. It’s time to wholeheartedly support these efforts in every possible way.

Nature 611 , 204 (2022)

doi: https://doi.org/10.1038/d41586-022-03597-5

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Misdariis, N. et al. Nature Astron . https://doi.org/10.1038/10.1038/s41550-022-01821-w (2022).

Díaz-Merced, W. L. Sound for the Exploration of Space Physics Data . PhD thesis, Univ. Glasgow (2013).

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How Sound Travels

Sound travels in mechanical waves . A mechanical wave is a disturbance that moves and transports energy from one place to another through a medium . In sound, the disturbance is a vibrating object. And the medium can be any series of interconnected and interactive particles. This means that sound can travel through gases, liquids and solids.

Let's take a look at an example. Imagine a church bell. When a bell rings, it vibrates, which means the bell itself flexes inward and outward very rapidly. As the bell moves outward, it pushes against particles of air. Those air particles then push against other adjacent air particles, and so on. As the bell flexes inward, it pulls against the adjacent air particles, and they, in turn, pull against other air particles. This push and pull pattern is a sound wave. The vibrating bell is the original disturbance, and the air particles are the medium.

The bell's vibrations push and pull against adjacent air

Molecules, creating a sound wave..

Sound isn't restricted to moving through the air. Press your ear against a solid surface like a table and close your eyes. Tell someone else to tap his or her finger on the other end of the table. The tapping becomes the initial disturbance. Each tap sends vibrations through the table. The particles in the table collide with each other and become the medium for the sound. The particles in the table collide with air particles between the table and your eardrum . When a wave moves from one medium to another like this, it's called transmission .

The air particles collide with your ear's tympanic membrane , also known as the eardrum. This sets off a series of vibrations in several structures inside the ear. The brain interprets these vibrations as sounds. The whole process is pretty complex. You can learn more in How Hearing Works .

So, sound needs a physical medium in order to travel anywhere. Is there enough physical material in space to act as a medium for sound waves? Find out in the next section.

The speed of a sound wave depends upon the medium through which it travels. In general, sound travels faster through solids than through liquids or gases. Also, the denser the medium, the slower sound will travel through it. The same sound will travel at a different speed on a cold day than it would on a warm day.

Please copy/paste the following text to properly cite this HowStuffWorks.com article:

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Rethinking Sound in Space: Physicists Demonstrate How Sound Can Cross the Vacuum

By University of Jyväskylä August 12, 2023

Sound waves tunneling across a vacuum gap. Credit: Zhuoran Geng and Ilari Maasilta

The iconic movie Alien once claimed: “In space, no one can hear you scream.” However, physicists Zhuoran Geng and Ilari Maasilta from the Nanoscience Center at the University of Jyväskylä, Finland, beg to differ. Their recent research suggests that under specific conditions, sound can indeed be transmitted powerfully across a vacuum.

Their findings, published recently in the journal Communications Physics , reveal that in certain scenarios, sound waves can “tunnel” through a vacuum gap between two solid objects, provided those objects are piezoelectric. These particular materials generate an electrical response when subjected to sound waves or vibrations. Given that an electric field can be present in a vacuum, it can effectively carry these sound waves across.

The requirement is that the size of the gap is smaller than the wavelength of the sound wave. This effect works not only in the audio range of frequencies (Hz-kHz), but also in ultrasound (MHz) and hypersound (GHz) frequencies, as long as the vacuum gap is made smaller as the frequencies increase.

“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 % efficiency, without any reflections. As such, the phenomenon could find applications in microelectromechanical components (MEMS, smartphone technology) and in the control of heat,” says Professor Ilari Maasilta from the Nanoscience Center at the University of Jyväskylä.

Reference: “Complete tunneling of acoustic waves between piezoelectric crystals” by Zhuoran Geng and Ilari J. Maasilta, 14 July 2023, Communications Physics . DOI: 10.1038/s42005-023-01293-y

The study was funded by the Academy of Finland and the European Union’s Horizon 2020 program.

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10 comments on "rethinking sound in space: physicists demonstrate how sound can cross the vacuum".

This is BS. The sound is not propogating through a vaccuum, an electric field is.

According to the topological vortex gravitational field theory, sound waves are similar to light waves that the formation and propagation are inseparable from the interaction of vortex gravitational fields, and produce different physical effects in different vortex environments. Vortex gravity is the source of all things and the most essential force that maintains and connects the world. From the accretion disk of the universe to quantum spin, there is no exception.

Ho hum. We’ve been transmitting sound through vacuum for decades…by converting it to radio waves. Essentially similar to what they described. Nothing new here.

Oh please, that’s not sound through vacuum. You can just as easily modulate light to carry sound to the edge of the universe.

The blog you posted is beautiful and it has been very beneficial. Start shopping for school must-have items for less. Back-to-school uniforms under $10 can be gotten at Amazon. Moreover, these wears are well designed and you will love them.  Please don't hesitate to check my content on this same topic.

On the cusp of long range space communication a gapless time delay. I have a question can sound waves halt the combustion process of fire disrupting the reaction stage.

Sound waves dislike halting combustion, and will only do so if given proper recognition for their work, and are taken out for ice cream afterwards.

Wayall… I’ll tell ya what. If this is true then there is gonnuh be a bunch of sound already existing maybe it will have some intelligible content. Record it. Let the world hear it.

“Scientists prove the sound can pass over vacuum provided at the source is a microphone and at the receiver end is a speaker. Coupled together”

In the beginning was the word!

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What is a standing wave, what makes the air move in the first place, graphing sound waves, consider the following.

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Does Sound Travel Faster or Slower in Space?

By quora .com | oct 22, 2018.

Viktor T. Toth :

It is often said that sound doesn’t travel in space. And it is true … in empty space. Sound is pressure waves, that is, propagating changes in pressure. In the absence of pressure, there can be no pressure waves, so there is no sound.

But space is is not completely empty and not completely devoid of pressure. Hence, it carries sound. But not in a manner that would match our everyday experience.

For instance, if you were to put a speaker in interstellar space, its membrane may be moving back and forth, but it would be exceedingly rare for it to hit even a single atom or molecule. Hence, it would fail to transfer any noticeable sound energy to the thin interstellar medium. Even the somewhat denser interplanetary medium is too rarefied for sound to transfer efficiently from human scale objects; this is why astronauts cannot yell to each other during spacewalks. And just as it is impossible to transfer normal sound energy to this medium, it will also not transmit it efficiently, since its atoms and molecules are too far apart, and they just don’t bounce into each other that often. Any “normal” sound is attenuated to nothingness.

However, if you were to make your speaker a million times bigger, and let its membrane move a million times more slowly, it would be able to transfer sound energy more efficiently even to that thin medium. And that energy would propagate in the form of (tiny) changes in the (already very tiny) pressure of the interstellar medium, i.e., it would be sound.

So yes, sound can travel in the intergalactic, interstellar, interplanetary medium, and very, very low frequency sound (many octaves below anything you could possibly hear) plays an important role in the formation of structures (galaxies, solar systems). In fact, this is the mechanism through which a contracting cloud of gas can shed its excess kinetic energy and turn into something compact, such as a star.

How fast do such sounds travel, you ask? Why, there is no set speed. The general rule is that for a so-called perfect fluid (a medium that is characterized by its density and pressure, but has no viscosity or stresses) the square of the speed of sound is the ratio of the medium’s pressure to its energy density. The speed of sound, therefore, can be anything between 0 (for a pressureless medium, which does not carry sound) to the speed of light divided by the square root of three (for a very hot, so-called ultrarelativistic gas).

This post originally appeared on Quora. Click here to view.

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NASA says there is a misconception that there is no sound in space

NASA released a sound from the black hole at the center of the Perseus galaxy cluster. What you'll hear is pressure waves emitted from the black hole causing ripples in the star cluster's hot gas.

Copyright © 2022 NPR. All rights reserved. Visit our website terms of use and permissions pages at www.npr.org for further information.

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Ask an Explainer

What is the speed of sound in space.

Sound can’t actually travel in space. Sound is created when particles vibrate in a pattern, creating waves. Since space is a vacuum, there are almost zero particles in space. This means that since there are no particles to vibrate against, sound cannot travel through space. It is like trying to create water waves in an empty pool, there is no water to create a wave from.

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Is there sound in space?

How astronomers listen to the pulsating roar of objects across the Universe.

Dave Hawksett

Astronomy is all about light. Of course, when we say ‘light’, we mean the complete span of the electromagnetic spectrum, of which only a tiny proportion is visible to the naked eye.

But astronomy can also be about sound. As we all know, sound waves are different to light waves.

Light waves can pass through many media, depending on their wavelength and the medium’s properties.

Light waves don’t actually require a material to travel through, and so the light from stars is unhindered by the vacuum of space.

For more on astronomical audio, read our guide on how astronomers listen to the sound of stars .

Sound waves, however, involve the compression and rarefaction of matter.

The vibration of the surface of a drum, for example, also makes the air molecules vibrate.

These in turn cause adjacent air molecules to vibrate and so a sound wave travels outward from the drum.

In a vacuum, there are no molecules in contact with the surface of a struck drum, so a microphone next to it will pick up absolutely nothing, no matter how hard the drum is banged.

So how do astronomers hear any sound at all in space ?

They do it using a technique called sonification, where data is converted into sound to allow it to be interpreted.

The humble Geiger counter is an excellent example of this, measuring radiation levels and portraying the results as audio.

Just as X-ray data from space is often turned into coloured images, various astronomical data can be usefully ‘sonified’.

Can sounds travel through space?

Are there actually sounds in space? If so, how can they be heard, and how do astronomers know they're there?

Space is not a perfect vacuum: the stream of charged particles flowing from the Sun – the solar wind – pervades the Solar System with an extremely thin gas in which various ethereal phenomena occur.

Unlike the gas in our atmosphere, which is bound together by the mutual collisions of air molecules, this plasma is bound together by the magnetic field surrounding it.

The turbulent nature of the Sun’s surface means that pressure and density disturbances travel outwards at the speed of sound in the solar wind.

Due to the temperature and density of the plasma, this is around a few hundred kilometres per second.

These pressure disturbances are effectively sound waves in interplanetary space.

The thin plasma of the solar wind, along with the solar magnetic field that binds it, becomes weaker and even more sparse as you travel outwards into the depths of the Solar System.

Eventually it becomes so weak that it is overwhelmed by the combined magnetic fields and particles from all the other stars in the Galaxy.

This zone, known as the ‘heliopause’, marks the end of the Sun’s dominion and is the true edge of the Solar System .

Below we've taken a look at some bodies of the Universe capable of making sound, and how astronomers are able to hear them.

Probably the most widespread use of sonification is by amateur astronomers and radio enthusiasts, who regularly tune in to Jupiter using short-wave receivers and antennae connected to speakers.

First discovered in 1955, the radio sounds from Jupiter are diverse.

They have been described variously as sounding like waves crashing on a beach, woodpeckers and whale song.

The broadcasts from ‘Radio Jove’ come from natural radio lasers, caused by electrically conducting gas spewed into Jupiter’s magnetic field by volcanoes on its satellite Io .

This gas collects in a doughnut-shaped torus around Jupiter and, as Io ploughs through it, creates magnetic ‘Alfven’ waves.

These waves move along the lines of magnetic force in Jupiter’s field and transmit a staggering 40 trillion watts of power to its polar regions, powering the radio lasers that periodically sweep across the Earth.

The Galileo mission at Jupiter

However, it is not only amateurs who use sonification in astronomy. The epic Galileo mission , which operated for nearly 8 years in Jupiter orbit, used sonification to present some of its results.

In June 1996, Galileo passed close to the planet-sized moon Ganymede, and the onboard Plasma Wave Experiment discovered the presence of a magnetic field surrounding the moon – the first discovered in the Solar System.

The flyby lasted a couple of hours, and when the magnetic data is compressed so that 45 minutes of spacecraft time becomes a sound file just one minute long, you can hear the loud burst of noise when Galileo enters the moon’s magnetosphere.

As the spacecraft closes on Ganymede you hear a gradually rising tone that goes on to decline.

This provides a direct measure of the density of charged particles in the space around Ganymede.

Closer to home, we can listen in to the Sun using the techniques of helioseismology.

In the 1960s it was discovered that the surface of the Sun rises and falls with a period of five minutes.

This was discovered using spectroscopy and the Doppler Effect.

If a sound-emitting object moves away from your ear, you hear the pitch of the sound drop; if it moves toward you, the pitch rises.

A similar effect occurs with light waves: a receding object appears redder (known as redshift ) and an approaching one, bluer (known as blueshift).

At the end of the 1970s the Sun was observed from the Earth’s south pole during the Antarctic summer for a continuous 4.5 days, when scientists were able to measure its pulsation to a precision of 2cm per second.

Since then, international networks of telescopes and space-based instruments have monitored the movement of our nearest star.

The Sun’s oscillations are caused by sound waves trapped inside the solar interior, which are in turn produced by the convective turbulence in the outer 30% of the Sun.

We see the effects of this turbulence as granulation on the surface of the photosphere.

The sound waves caused by pressure fluctuations in this turbulence reflect inwards once they hit the Sun’s surface.

The inward-moving waves are refracted (their direction is bent) by the increase of the speed of sound – due to the rising temperature within the Sun – before eventually returning to the surface.

The combination of all these internal sound waves makes the Sun vibrate in millions of different ways.

It is at this point that the mathematics becomes complicated, but it is enough to say that helioseismologists can use these patterns to infer the internal structure of the Sun in similar ways that seismologists use earthquake patterns to understand Earth’s interior.

Helioseismology can be thought of as a branch of asteroseismology.

As the Sun is much closer than other stars, it has been easier to study how it vibrates.

And what helioseismologists have learned about the Sun’s interior can be transferred to other stars of different types, with a view to probing their interiors using sound waves.

The variability of some stars has been known for more than 400 years, since David Fabricus recorded the changing brightness of the most famous variable star , Mira, in 1596.

Mira still pulsates today, which means that its variability is being sustained by something – if it wasn’t, the bulk of the star itself would damp out the motions.

This sustaining mechanism can be thought of as a layer within the star, opaque to certain wavelengths of radiation, that is trying to escape into space.

This layer is forced to absorb the radiation, heating and expanding it, making the star swell up beyond its normal size.

As the opaque layer heats up it becomes ionized, which makes it less opaque and allows the radiation to get through.

As it is no longer absorbing radiation, the now transparent layer cools back down and is forced to contract by the weight of the gas above it, becoming opaque and starting the entire process once again.

Another class of vibrating stars was discovered by Donald Kurtz at the University of Central Lancashire some 25 years ago.

He was studying Przybylski’s star – an unusual, near-main sequence star whose spectrum revealed it to contain 100,000 times more metals than the Sun, the type of abundances you would expect from a much older and more evolved star.

Conventional wisdom dictated that such a star should not pulsate, as its very strong magnetic field would stabilise it.

Kurtz discovered that Przybylski’s star vibrated with a frequency of 12 minutes – energetic indeed for a star heavier than the Sun.

Since then, more than 30 of these ‘rapidly oscillating peculiar A stars’ have been discovered, with pulsation periods ranging from five to 20 minutes, most of them by Kurtz and his team.

They are amongst the strangest stars yet discovered by astronomers.

Asteroseismology is far from being a mature field of study, but advances in instrumentation are accelerating its evolution.

For Alpha Centauri A, for example (the nearest star visible to the naked eye), astronomers can now measure the speed of the surface oscillations to an accuracy of 2cm per second.

4 stars that make sounds

This star is 160 lightyears away, and measures around 10 times the diameter of the Sun, with about 60 times its luminosity. It oscillates with several periods of around three hours, like a ‘sub ultra bass’ instrument. It is the most massive star in which solar-type oscillations have been discovered.

Alpha Centauri A

The nearest star to the Sun pulsates every seven minutes – very similar to the Sun. With a frequency of around 35cm per second, these pulsations make the star’s surface rise and fall by around 40m. This is an amazing observation on a star that measures some 1.75 million km across.

BPM 37093 is a white dwarf – the core of a dead star – that is located 50 lightyears away. It pulses as its brightness changes by around one per cent every five to 10 minutes, allowing astronomers to deduce that this star has partially crystallised into a gigantic diamond.

Vela Pulsar

One of the youngest pulsars yet found, this supernova remnant rotates every 89 milliseconds. More than a dozen ‘glitches’ have been observed where it spins slightly faster by a matter of nanoseconds. This is caused by starquakes: huge stresses being released in a solid crust over a ‘superfluid’ interior.

Black holes

It is not just the stars that produce sounds; other, more exotic phenomena have recently been shown to be ‘noisy’.

In September 2003 a media fanfare accompanied the announcement of the discovery of sound waves emanating from a supermassive black hole in the Perseus cluster of galaxies about 250 million lightyears away.

The observations were made by NASA’s Earth-orbiting Chandra X-Ray Observatory, which collected 53 hours of data on the phenomenon.

Black holes themselves are invisible, but they create a riotous, chaotic and energetic environment in their immediate vicinity, as in-falling matter is accelerated to close to the speed of light.

All types of radiation have been detected from these regions, from radio waves right through the electromagnetic spectrum to high-energy X-rays.

Many black holes have also been discovered to emit powerful jets of matter along their axes of rotation.

Perseus cluster

In the Perseus cluster, these jets are thought to be slamming into the thin intergalactic gas surrounding the cluster.

The results of this ongoing collision were revealed by the observations from Chandra to be immense circular ripples, spreading out in all directions, like those created by an object dropped into water.

These ripples, or pressure waves, obey the same laws as sound waves and, even though no one can hear them, they are true sound waves travelling through very thin gas in space.

Just as on Earth, where the pitch of a musical note created in air depends on either the sound’s wavelength, or the distance between each ripple of compression, the same is true of the Perseus black hole.

The ripples seen by Chandra are 35,000 lightyears apart. Dubbed ‘the deepest note in the Universe’, this is what you would get if you could make a musical note 57 octaves below middle C.

The sounds made by black holes have not been directly heard – they have not travelled through space to the Earth as sound waves.

Rather we can see the effect they have on the gas surrounding them using X-rays, like using visible light to witness the waves when a stone is dropped into a pond.

A normal piano covers seven octaves of musical notes, but the Perseus black hole sings some 57 octaves below middle C – or more than a million billion times deeper than the range of human hearing.

These sound waves are more than a curiosity, and may help explain how galactic clusters grow.

It has been a long-standing puzzle to astronomers as to why there should be so much hot gas in clusters of galaxies.

It would normally be expected to cool and fall towards the centre of the galaxies, forming lots of new stars as it clumps together.

Heat from a large central black hole could be the answer. The jets of material streaming from the Perseus black hole form cavities in the thin cluster gas as they collide with it.

Sound waves then travel outwards as huge ripples.

The sheer amount of energy required to create these cavities is equivalent to around 100 million supernovae, a lot of which is carried away in sound waves.

These then warm the cluster gas as they dissipate – preventing it from cooling and forming stars.

The Big Bang

Precise measurements of the Cosmic Microwave Background give a view of the Universe around 400,000 years after the Big Bang, just as it had cooled enough to allow the first atoms to form from the primordial plasma.

Detailed studies of the minute variations in this background radiation suggest that, at this stage of the early Universe, titanic acoustic waves propagated through this plasma.

Stars and galaxies had yet to form and all matter existed as a kind of hot fog in the rapidly expanding Universe.

It is this foggy, thin gas that allowed sound waves to form and propagate.

Tiny differences in the data from the Wilkinson Microwave Anisotropy Probe (WMAP) show peaks and troughs in these sound waves.

So did the Big Bang actually bang? Analysis of the WMAP data by US astronomer Mark Whittle suggests that the Big Bang was initially silent, but the noise quickly grew into a "descending scream", followed by a "deep roar" and ending in a "deafening hiss", with a peak volume of around 110 decibels – equivalent to the noise of a rock concert.

These sound waves had wavelengths of around 20,000 lightyears, around 50 octaves below the range of human hearing.

Their discovery and measurement marks the beginning of a new era in precision cosmology.

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No, you cannot hear any sounds in near-empty regions of space. Sound travels through the vibration of atoms and molecules in a medium (such as air or water). In space, where there is no air, sound has no way to travel.

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

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

What is sound?

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

Robert Boyle's classic experiment

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

How sound travels

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

The science of sound waves

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

Whispering galleries and amphitheaters

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

Measuring waves

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

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

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

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

How to measure the speed of sound

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

• Electric guitars
• Speech synthesis
• Synthesizers

On other sites

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

Educational books for younger readers

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

Popular science

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

Academic books

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

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

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