sound cannot travel through space because

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

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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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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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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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Why Can't Sound Travel in Space?

The vast expanse of space has always fascinated humanity, prompting us to explore and unravel its mysteries. Yet, amidst the awe-inspiring wonders of the cosmos, one peculiar absence stands out – the absence of sound.

In the silence of space, where no air molecules exist to carry sound waves, the deafening silence remains unbroken. But why is this the case? Why can't sound, a fundamental aspect of our daily lives, travel through the vacuum of space?

The answer lies in the very nature of sound waves and the unique conditions of the interstellar void.

The Nature of Sound Waves

Sound waves are a fundamental component of the nature of sound, playing a crucial role in its propagation and perception. Sound is created by the vibration of an object, which generates compressions and rarefactions in the surrounding medium. These compressions and rarefactions then travel through the medium as waves, carrying the energy of the sound.

Sound waves are characterized by several properties, including frequency, amplitude, and wavelength. Frequency refers to the number of cycles or vibrations per second, and it determines the pitch of the sound. Amplitude, on the other hand, corresponds to the intensity or loudness of the sound. Lastly, wavelength represents the distance between two consecutive compressions or rarefactions.

Understanding the nature of sound waves is essential to comprehend how sound travels and how it is perceived by our ears.

The Vacuum of Space

In the absence of a medium to propagate through, such as in the vacuum of space, sound waves are unable to travel and therefore cannot be perceived.

Sound waves are mechanical waves that require a medium, such as air, water, or solid objects, to travel. These waves are created by the vibration of particles in the medium, which then transmit the energy from one particle to the next.

However, in space, there is an almost complete absence of matter, resulting in an extremely low density. This lack of particles means that there is no medium for sound waves to travel through.

As a result, sound cannot be transmitted in the vacuum of space, leaving it devoid of the characteristic auditory experience found on Earth or in other environments that contain a medium for sound propagation.

Absence of Air as a Medium

The absence of air in space creates a significant barrier for sound propagation. Sound waves require a medium, such as air or water, to travel through. In the absence of air, like in the vacuum of space, sound waves cannot propagate because there are no particles to vibrate and transmit the sound energy.

In air, sound waves travel by causing particles to compress and expand, creating a wave-like motion. However, in space, the lack of air molecules means that there is nothing for the sound waves to interact with, resulting in silence. This absence of air as a medium in space is one of the main reasons why sound cannot travel there.

Sound Transmission and Particle Interaction

One crucial aspect to consider when discussing sound transmission in space is the interaction between sound waves and particles. Unlike on Earth, where sound waves propagate through the medium of air, space is a vacuum devoid of air or any other form of matter.

In the absence of particles, sound waves cannot travel as they require a medium to propagate. Sound waves are mechanical vibrations that travel through particles by causing them to oscillate. These oscillations then transmit the sound energy from one particle to another, allowing the sound wave to propagate.

Without particles to interact with, sound waves cannot be transmitted in space. Therefore, the absence of particles in space is a significant factor in the inability of sound to travel in this vast expanse.

Implications for Astronauts and Space Exploration

Astronauts and the field of space exploration face significant implications due to the inability of sound to travel in the vacuum of space. This absence of sound propagation has several consequences that affect both the safety and communication of astronauts during space missions.

One of the primary implications is the need for alternate methods of communication. Without sound, astronauts rely on visual signals, radio transmissions, and written messages to convey information. This requires precise coordination and can lead to delays and misunderstandings.

Additionally, the absence of sound can affect the mental well-being of astronauts. Sound plays a crucial role in creating a sense of familiarity and comfort. In the isolated and silent environment of space, astronauts may experience feelings of loneliness and disorientation.

The table below summarizes the implications faced by astronauts in the absence of sound during space exploration:

These implications highlight the importance of developing effective communication systems and strategies to ensure the success and well-being of astronauts during space missions.

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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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As discussed in the previous unit of The Physics Classroom Tutorial, a wave can be described as a disturbance that travels through a medium, transporting energy from one location to another location. The medium is simply the material through which the disturbance is moving; it can be thought of as a series of interacting particles. The example of a slinky wave is often used to illustrate the nature of a wave. A disturbance is typically created within the slinky by the back and forth movement of the first coil of the slinky. The first coil becomes disturbed and begins to push or pull on the second coil. This push or pull on the second coil will displace the second coil from its equilibrium position . As the second coil becomes displaced, it begins to push or pull on the third coil; the push or pull on the third coil displaces it from its equilibrium position. As the third coil becomes displaced, it begins to push or pull on the fourth coil. This process continues in consecutive fashion, with each individual particle acting to displace the adjacent particle. Subsequently the disturbance travels through the slinky. As the disturbance moves from coil to coil, the energy that was originally introduced into the first coil is transported along the medium from one location to another.

A sound wave is similar in nature to a slinky wave for a variety of reasons. First, there is a medium that carries the disturbance from one location to another. Typically, this medium is air, though it could be any material such as water or steel. The medium is simply a series of interconnected and interacting particles. Second, there is an original source of the wave, some vibrating object capable of disturbing the first particle of the medium. The disturbance could be created by the vibrating vocal cords of a person, the vibrating string and soundboard of a guitar or violin, the vibrating tines of a tuning fork, or the vibrating diaphragm of a radio speaker. Third, the sound wave is transported from one location to another by means of particle-to-particle interaction. If the sound wave is moving through air, then as one air particle is displaced from its equilibrium position, it exerts a push or pull on its nearest neighbors, causing them to be displaced from their equilibrium position. This particle interaction continues throughout the entire medium, with each particle interacting and causing a disturbance of its nearest neighbors. Since a sound wave is a disturbance that is transported through a medium via the mechanism of particle-to-particle interaction, a sound wave is characterized as a mechanical wave .

Production and Propagation of Sound Waves

The creation and propagation of sound waves are often demonstrated in class through the use of a tuning fork. A tuning fork is a metal object consisting of two tines capable of vibrating if struck by a rubber hammer or mallet. As the tines of the tuning forks vibrate back and forth, they begin to disturb surrounding air molecules. These disturbances are passed on to adjacent air molecules by the mechanism of particle interaction. The motion of the disturbance, originating at the tines of the tuning fork and traveling through the medium (in this case, air) is what is referred to as a sound wave. The generation and propagation of a sound wave is demonstrated in the animation below.

Check Your Understanding

1. A sound wave is different than a light wave in that a sound wave is

a. produced by an oscillating object and a light wave is not. b. not capable of traveling through a vacuum. c. not capable of diffracting and a light wave is. d. capable of existing with a variety of frequencies and a light wave has a single frequency.

Sound is a mechanical wave and cannot travel through a vacuum. Light is an electromagnetic wave and can travel through the vacuum of outer space.

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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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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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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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Can you hear sound in space?

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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.

Turns out you can transmit sound in a vacuum, just not very far

For the first time, researchers were able to transmit, or "tunnel," sound waves across extremely small distances between two crystals in a vacuum.

For the first time, scientists have shown that sound can travel through the emptiness of a vacuum. However, the rule-breaking trick requires specific circumstances and can only be carried out over extremely small distances.

The iconic tagline of the 1979 sci-fi film "Alien" tells us that "in space no one can hear you scream." This was based on the fact that space is a vacuum, a region devoid of any particles. Sound waves travel by vibrating through the particles of a medium, such as air or water, from a source to a receiver. So in a vacuum, there is no travel medium. (Outer space is not actually a total vacuum because it does contain small amounts of gas, plasma and other particles. But this matter is surrounded by vast swathes of emptiness.)

But in a new study, published July 14 in the journal Communications Physics , researchers showed that sound can move through a vacuum. Unfortunately for space explorers being hunted by aliens, this does not extend to human screams.

In the new experiment, researchers transmitted, or "tunneled," sound waves across a vacuum between two zinc oxide crystals by transforming the vibrating waves into ripples within an electric field between the objects.

Related: Eerie sounds triggered by plasma waves hitting Earth's magnetic field captured in new NASA sound clip

A zinc oxide crystal is a piezoelectric material, which means that when force or heat is applied to it, the material produces an electrical charge. Therefore, when sound is applied to one of these crystals, it creates an electrical charge that disrupts nearby electric fields. If the crystal shares an electric field with another crystal, then the magnetic disruption can travel from one to the other across a vacuum. The disruptions mirror the frequency of the sound waves, so the receiving crystal can turn the disruption back into a sound on the other side of the vacuum.

However, the disruptions cannot travel a distance greater than the wavelength of a single sound wave. In theory, this works with any sound no matter how small the wavelength of that sound is, as long as the gap between the crystals is small enough. 

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The method is not always reliable. In a large percentage of the experiments, the sound was not perfectly transmitted between the two crystals: parts of the wave were warped, or reflected, as it passed through the electric field, the researchers found. However, occasionally the piezoelectric crystals perfectly transmitted the entire sound wave.

— Why is space a vacuum?

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"In most cases the effect [sound transmitted] is small, but we also found situations, where the full energy of the wave jumps across the vacuum with 100 % efficiency, without any reflections," study co-author Ilari Maasilta , a material physicist at the University of Jyväskylä in Finland, said in a statement .

The finding could one day help develop microelectromechanical components, like those found in smartphones and other technology, the researchers said. 

Harry is a U.K.-based senior staff writer at Live Science. He studied marine biology at the University of Exeter before training to become a journalist. He covers a wide range of topics including space exploration, planetary science, space weather, climate change, animal behavior, evolution and paleontology. His feature on the upcoming solar maximum was shortlisted in the "top scoop" category at the National Council for the Training of Journalists (NCTJ) Awards for Excellence in 2023. 

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• Sound Waves
• Sound Vibration Propagation Of Sound

What Is Sound? Vibration and the Propagation of Sound

Have you ever used a musical instrument like a guitar, drum or violin? When we strike the strings of a guitar, we hear a sound. Same with the drum, when we hit a drum we hear a ‘thump’ sound. Also, how is one instrument able to create a wide variety of sounds? How does this happen? What is sound? How do we make a sound? How is the sound produced and about the propagation of sound?

What Is Sound?

A sound is a form of energy, just like electricity, heat or light. Sound is one of the important senses of the human body. Some sounds are pleasant, and some are annoying. We are subjected to various types of sound all time. Sound waves are the result of the vibration of objects. Let’s examine some sources of sounds like a bell. When you strike a bell, it makes a loud ringing noise. Now, instead of just listening to the bell, put your finger on the bell after you have struck it. Can you feel it vibrating? This is the key to sound. It is even more evident in guitars and drums. You can see the wires vibrating every time you pluck it. When the bell or the guitar stops vibrating, the sound also stops.

The to and fro motion of the body is termed vibration. You can see examples of vibrations everywhere. Vibrating objects produce sound. Some vibrations are visible; some aren’t. If you pull and then release a stretched rubber band, the band moves to and fro about the central axis and while doing, so it also produces a sound. The sound moves through a medium by alternately contracting and expanding parts of the medium it is travelling through.

In physics, the sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid.

Read More: Forms of Energy

Watch the video and learn about the fundamentals of sound

Sound Wave Characteristics

After understanding what is sound, let us study the characteristics of the sound wave. The distance between two consecutive peaks or troughs is termed as the wavelength of the wave or the period . The number of cycles per unit time is termed as the frequency of the sound . Frequency is measured in cycles per second or Hertz.

The faster an object vibrates, i.e. the higher the frequency, the higher the pitch of the sound. The difference between the voices of a man and a woman must be clearly evident to you. The voice of a man has a lower frequency which contributes to the deepness of the bass in the voice. Women, in contrast, have a voice with higher frequency resulting in a higher shrillness or pitch.

Closing Our Ears When We Hear Loud Noise

If you hear a very loud sound, what do you do? You cover your ears. How do you think that helps? When you cover your ears, you shut off the air inside your ears from the rest of the atmosphere. The sound waves travelling around you are now unable to get through to your ear or the intensity of the sound you hear is greatly reduced. Blocking your ears creates a discontinuity in the medium due to which the flow of sound energy is disturbed. Through this, we can make a very important observation; Sound waves rely on the medium for propagation. The propagation of the sound wave is not possible through the vacuum. The medium here can be gas, liquid or solid. The speed of sound when it is travelling through a medium depends on the type of medium. The speed of sound when travelling through air is 343 m/s or 1,235 km/h.

Speed of Sound

The speed of a sound wave is affected by the type of medium through which it travels. Sound waves travel the fastest in solids due to the proximity of molecules. Likewise, sound waves travel slowest in gases because gases are spread far apart from one another. The state of the medium through which sound travels is not the only factor that affects a sound’s speed. The speed of a sound wave can also be affected by the density, temperature, and elasticity of the medium through which the sound waves travel. Below is a table, we have listed the speed of sound in various materials.

Can Sound Travel in Space?

A medium is essential for the propagation of sound. Sound cannot travel through a vacuum because there are no molecules that can be compressed and expanded in space. Our voice is produced by the vibration of strings known as the vocal cords which are inside Adam’s apple. When you make a sound, its vibration travels through the air, and when it reaches your brain through your ears, it is interpreted as sound. In this case propagation of sound takes place through the air medium. How your brain and ear decode pressure variation in sound waves into sound is fascinating!

Human Hearing and Speech

Humans can hear sounds ranging from 20 Hz to 20 kHz. Sounds with frequencies above the range of human hearing are called ultrasound. Sounds with frequencies below the range of human hearing are called infrasound. The typical sound produced by human speech has frequencies in the order of 100 to 1,000 Hz.

Characteristics of Sound Waves

Reflection of Sound

Frequently Asked Questions – FAQs

List physical factors that affect sound propagation.

• 1. Atmospheric Turbulence: If the atmosphere in which the sound wave is travelling is turbulent, sound waves would scatter due to velocity fluctuations of the medium.
• 2. Wind Gradient: Sound propagating along the wind would bend downwards while sound propagating against the wind would bend upwards.
• 3. Temperature Gradient: Sound waves travel faster in a warm atmosphere near the surface of the earth. Here, there is upward refraction of sound waves. In case of a decrease in temperature at higher altitudes, the refraction would be downwards.

Which property of sound is affected by the change in temperature?

What waves are used in sonography, what do you mean by an echo, the below video helps to completely revise the chapter sound class 9.

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

August 16, 2023 by admin 0 Comments

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

The research has been published in Communications Physics .

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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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June 5, 2024

This article has been reviewed according to Science X's editorial process and policies . Editors have highlighted the following attributes while ensuring the content's credibility:

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A strange intermittent radio signal from space has astronomers puzzled

by Manisha Caleb and Emil Lenc, The Conversation

When astronomers turn our radio telescopes out towards space, we sometimes detect sporadic bursts of radio waves originating from across the vast expanse of the universe. We call them "radio transients": some erupt only once, never to be seen again, and others flicker on and off in predictable patterns.

We think most radio transients come from rotating neutron stars known as pulsars, which emit regular flashes of radio waves, like cosmic lighthouses. Typically, these neutron stars spin at incredible speeds, taking mere seconds or even a fraction of a second to complete each rotation.

Recently, we discovered a radio transient that isn't like anything astronomers have seen before. Not only does it have a cycle almost an hour long (the longest ever seen), but over several observations we saw it sometimes emitting long, bright flashes, sometimes fast, weak pulses—and sometimes nothing at all.

We can't quite explain what's going on here. It's most likely a very unusual neutron star, but we can't rule out other possibilities. Our research is published in Nature Astronomy .

A lucky find

Meet ASKAP J1935+2148 (the numbers in the name point to its location in the sky). This periodic radio transient was discovered using CSIRO's ASKAP radio telescope on Wajarri Yamaji Country in outback Western Australia.

The telescope has a very wide field of view, which means it can survey large volumes of the universe very quickly. This makes it very well suited for detecting new and exotic phenomena.

Using ASKAP, we were simultaneously monitoring a source of gamma rays and searching for pulses from a fast radio burst, when we spotted ASKAP J1935+2148 slowly flashing in the data. The signal leapt out because it was made up of "circularly polarized" radio waves, which means the direction of the waves corkscrews around as the signal travels through space.

Our eyes cannot differentiate between circularly polarized light and ordinary unpolarized light. However, ASKAP functions like a pair of polaroid sunglasses, filtering out the glare from thousands of ordinary sources.

After the initial detection, we conducted further observations over several months using ASKAP and also the more sensitive MeerKAT radio telescope in South Africa.

The slowest radio transient ever found

ASKAP J1935+2148 belongs to the relatively new class of long-period radio transients. Only two others have ever been found, and ASKAP J1935+2148's 53.8 minute period is by far the longest.

However, the exceptionally long period is just the beginning. We have seen ASKAP J1935+2148 in three distinct states or modes.

In the first state, we see bright, linearly (rather than circularly) polarized pulses lasting from 10 to 50 seconds. In the second state, there are much weaker, circularly polarized pulses lasting only about 370 milliseconds. The third state is a quiet or quenched state, with no pulses at all.

These different modes, and the switching between them, could result from an interplay of complex magnetic fields and plasma flows from the source itself with strong magnetic fields in the surrounding space.

Similar patterns have been seen in neutron stars, but our current understanding of neutron stars suggests they should not be able to have such a long period.

Neutron stars and white dwarfs

The origin of a signal with such a long period remains a profound mystery, with a slow-spinning neutron star the prime suspect. However, we cannot rule out the possibility the object is a white dwarf—the Earth-sized cinder of a burnt-out star that has exhausted its fuel.

White dwarfs often have slow rotation periods, but we don't know of any way one could produce the radio signals we are seeing here. What's more, there are no other highly magnetic white dwarfs nearby, which makes the neutron star explanation more plausible.

One explanation might be that the object is part of a binary system in which a neutron star or white dwarf orbits another unseen star.

This object might prompt us to reconsider our decades-old understanding of neutron stars or white dwarfs, particularly in how they emit radio waves and what their populations are like within our galaxy. Further research is needed to confirm what the object is, but either scenario would provide valuable insights into the physics of these extreme objects.

The search continues

We don't know how long ASKAP J1935+2148 has been emitting radio signals, as radio astronomy surveys don't usually search for objects with periods this long. Moreover, radio emissions from this source are only detected for a mere 0.01% to 1.5% of its rotation period, depending on its emission state.

So we were quite fortunate we happened to catch sight of ASKAP J1935+2148. It's quite likely there are many other objects like it elsewhere in our galaxy, waiting to be discovered.

Journal information: Nature Astronomy

Provided by The Conversation

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Is It a Sound of Music…or of Speech? Scientists Uncover How Our Brains Try to Tell the Difference

Music and speech are among the most frequent types of sounds we hear. But how do we identify what we think are differences between the two?

An international team of researchers mapped out this process through a series of experiments—yielding insights that offer a potential means to optimize therapeutic programs that use music to regain the ability to speak in addressing aphasia. This language disorder afflicts more than 1 in 300 Americans each year, including Wendy Williams and Bruce Willis.

“Although music and speech are different in many ways, ranging from pitch to timbre to sound texture, our results show that the auditory system uses strikingly simple acoustic parameters to distinguish music and speech,” explains Andrew Chang, a postdoctoral fellow in New York University’s Department of Psychology and the lead author of the paper , which appears in the journal PLOS Biology . “Overall, slower and steady sound clips of mere noise sound more like music while the faster and irregular clips sound more like speech.”

Scientists gauge the rate of signals by precise units of measurement: Hertz (Hz). A larger number of Hz means a greater number of occurrences (or cycles) per second than a lower number. For instance, people typically walk at a pace of 1.5 to 2 steps per second, which is 1.5-2 Hz. The beat of Stevie Wonder’s 1972 hit “ Superstition ” is approximately 1.6 Hz, while Anna Karina’s 1967 smash “ Roller Girl ” clocks in at 2 Hz. Speech, in contrast, is typically two to three times faster than that at 4-5 Hz.

Anna Karina, circa 1967. Photo credit: Dino De Laurentiis Cinematografica, public domain, via Wikimedia Commons.

It has been well  documented  that a song’s volume, or loudness, over time—what’s known as “amplitude modulation”—is relatively steady at 1-2 Hz. By contrast, the amplitude modulation of speech is typically 4-5 Hz, meaning its volume changes frequently.

Despite the ubiquity and familiarity of music and speech, scientists previously lacked clear understanding of how we effortlessly and automatically identify a sound as music or speech.

To better understand this process in their  PLOS Biology  study, Chang and colleagues conducted a series of four experiments in which more than 300 participants listened to a series of audio segments of synthesized music- and speech-like noise of various amplitude modulation speeds and regularity.

The audio noise clips allowed only the detection of volume and speed. The participants were asked to judge whether these ambiguous noise clips, which they were told were noise-masked music or speech, sounded like music or speech. Observing the pattern of  participants sorting hundreds of noise clips as either music or speech revealed how much each speed and/or regularity feature affected their judgment between music and speech. It is the auditory version of “seeing faces in the cloud,” the scientists conclude: If there’s a certain feature in the soundwave that matches listeners’ idea of how music or speech should be, even a white noise clip can sound like music or speech. Examples of both music and speech may be downloaded from the  research page .

Knowing how the human brain differentiates between music and speech can potentially benefit people with auditory or language disorders such as aphasia—melodic intonation therapy is a promising approach to train people with aphasia to sing what they want to say, using their intact “musical mechanisms” to bypass damaged speech mechanisms.

The results showed that our auditory system uses surprisingly simple and basic acoustic parameters to distinguish music and speech: to participants, clips with slower rates (<2Hz) and more regular amplitude modulation sounded more like music, while clips with higher rates (~4Hz) and more irregular amplitude modulation sounded more like speech.

Knowing how the human brain differentiates between music and speech can potentially benefit people with auditory or language disorders such as aphasia, the authors note. Melodic intonation therapy, for instance, is a promising approach to train people with aphasia to sing what they want to say, using their intact “musical mechanisms” to bypass damaged speech mechanisms. Therefore, knowing what makes music and speech similar or distinct in the brain can help design more effective rehabilitation programs.

The paper’s other authors were Xiangbin Teng of Chinese University of Hong Kong, M. Florencia Assaneo of National Autonomous University of Mexico (UNAM), and David Poeppel, a professor in NYU’s Department of Psychology and managing director of the Ernst Strüngmann Institute for Neuroscience in Frankfurt, Germany.

The research was supported by a grant from the National Institute on Deafness and Other Communication Disorders, part of the National Institutes of Health (F32DC018205), and Leon Levy Scholarships in Neuroscience.

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