When you imagine inquiring in the universe, your first idea is probably someone looking at something – an image.

But there are other ways of sensing and studying the world, too. Last week’s detection of gravitational waves, confirming the presence of what had been predicted by Einstein, is special in that it heralds a new significance to sound in physics.


Now, we’re biased as musicians, of course. But that makes it doubly inspiring when you hear the scientists talk this way.

“Finally, astronomy grew ears,” says team member Szabolcs Marka in The New York Times. “We never had ears before,” he says.

Here’s a video by the legendary Brian Greene, explaining more:

In antiquity, the division between music and cosmos was blurred – sound, mathematics, and philosophy not yet having evolved into today’s specializations. So this notion of a music of the spheres, a resonance between the universe and musical output, was a natural one.

But we don’t think quite like the Ancients. So let’s consider what we mean by sound.

First, even in this enlightened scientific age, we’re all most of the day limited by our senses. So we think of “light” as what we can see, and “sound” as what we can hear.

In the case of the Laser Interferometer Gravitational-Wave Observatory (LIGO), the gravitational wave detectors are really nothing like our ears, let alone a typical sound transducer. They have mirrors and lasers inside, so your first impression might be of something resembling a (really weird) telescope or optical device rather than something to do with sound.

There are antenna arms running 4 km (2.5 mi) long, each containing a long vacuum chamber. Suspended mirrors calibrated with lasers are able to register impossibly minute vibrations – on a subatomic scale (smaller than a proton).

So why do we describe these as sound at all? Well, we are talking vibrations. If the LIGO detectors are built to detect the cosmic equivalent of ripples on a pond, we’re talking very big events (the collision of two black holes) very long ago (a billion years) making a tiny but now measurable impact here on Earth.

But once we get to that level, the principle actually is the same as what happens in your inner ear. Vibrations in the outside world – even these very low frequency, very brief ones – are what we think of as sound. And detecting variation in those vibrations is how we now a sound has happened (that’s the “if a tree fell in a forest and someone is actually there to hear it” idea).

Now, I’m not a physicist. (Seriously – ask my high school physics teacher.) But what we can offer as people in music and sound is a chance to start to talk again with our scientific counterparts. Because from the point LIGO turns its detections into sound, you’ll find yourself in surprisingly familiar territory.

The New York Times had an especially poetic video and article on the announcement:
Gravitational Waves Detected, Confirming Einstein’s Theory [Science Thursday]

And they also posted the “chirp” associated with the announcement:

There are images associated with major discoveries in space exploration and science, but sometimes, you get sounds, too.

As Dennis Overbye writes for The New York Times, “If replicated by future experiments, that simple chirp, which rose to the note of middle C before abruptly stopping, seems destined to take its place among the great sound bites of science, ranking with Alexander Graham Bell’s “Mr. Watson — come here” and Sputnik’s first beeps from orbit.”

It didn’t take long for people to become intrigued by messing around with these sounds. And why not? Pictures of the universe routinely tickle our imaginations and inspire art, so why not sounds of the universe, too?

For instance, here’s an early example of a stretched-out rendition of the chirp from LIGO. It’s actually a bit easier to hear this way:

Sonifications aren’t necessarily used by scientists in this sort of work, but they can be – sometimes, it’s just as easy or easier to hear a signal as to see it. (And it’s also possible to do both.)

There’s reason to expect more of this sort of sonic activity, too. Now that LIGO has been proven, you can expect more experiments in this range. And the sources are likely to be juicy ones – cosmologist Michael Turner notes in that NYT story that “the loudest things in the gravity-wave sky are the most exotic things in the universe: black holes, neutron stars and the early universe.”

And there are more detectors coming to do just that job – including a forthcoming orbiting gravitational wave observatory. Just as having more senses as humans allows us to be more aware, combining senses and instruments can help verify results. As PBS reports, other groups are “trying to spot a transitory light source that coincides with the gravitational wave signal. They want to see what LIGO hears.”

Kate Becker, writing for PBS’ program NOVA, explains how the process works:
How LIGO Detected Gravitational Waves [NOVA NEXT]

And while we have had sonifications of electro-magnetic signatures of our sky, it’s a new thing to actually be listening to vibrations directly as a principle means of investigation (hence the “growing ears” references).

Calla Cofield in a story for The Christian Science Monitor explains that significance. Now, interestingly, that author stumbles over the metaphors a bit, explaining sound as a new way to “see” – even as the scientists interviewed very carefully use hearing as the way of putting this in perspective:

No longer blind: Why that gravitational wave discovery is so heavy [Christian Science Monitor / SPACE.com]

So get ready to listen to the music of the cosmos across billions of years.

And what’s next – is there more that can be done with the sonification of this experiment? Remixes? Other ways of listening to the universe? Discuss.

  • Eric Beam

    I was inspired by last weeks finding, & assembled a sample set from the available LIGO files. I’m sure these will find their way into my future works. I have them freely available here http://ericbeam.com/?p=6091

    • newmodernscience

      oh hey, awesome!

    • Thanks Eric! 🙂

  • Eric Beam

    I was inspired by last weeks finding, & assembled a sample set from the available LIGO files. I’m sure these will find their way into my future works. I have them freely available here http://ericbeam.com/?p=6091

  • newmodernscience

    I guess the obvious question is, can we use that sample in something?

  • David Geissbühler

    Thanks Peter! I’m happy to find someone that shares my enthusiasm about that very point: One of the biggest discovery in fundamental physics of the last decades comes as an audio signal! Now, i’m doubly biased, first as electronic music producer and second as a theoretical physicist that has been working five years on gravitation and quantum variations thereof… We’re typically used from our experimental colleagues to very cryptic indications of the physics beneath but there, for once, you get a superbly clean signal in the audio range! And what a signal: a sublime sweepy techno sub-bass (plus pad-like detector noise) that, once reversed, gives you a superbe punchy kick drum… These two guy in their last dance, 1.3 billion light-years afar, had delicious taste… Nature’s really well done me thinks. Yea remixes on their way.

    If of interest to someone, you can point to the original data (open as i understand): https://losc.ligo.org/events/GW150914/ where there’s the processed data in wav format as well as the python scripts to generate them from the raw dataset (good resources for folks that want to jump into spectral processing with python btw…). There also the excellent http://www.black-holes.org where one can find explanations, pretty videos and simulated sound samples for different types of merger (looks like Einstein’s good at percussion…)…

  • Jesse Engel

    “So why do we describe these as sound at all?” Just wanted to give a little perspective from physics / neuroscience on the cool difference between sound and light. It’s all just waves, true, but frequency matters. The first level of our eye works as an array of band pass filters because light oscillates so fast, we either detect it’s presence or not, but have no idea about it’s phase. Sound waves in the ear, however, are much slower, on the ms timescales that it takes for a neuron to fire, so they phase lock to the incoming signal. Firing in bursts at a rate depending on the magnitude, and a phase locked to the wave itself (much like a Fourier transform actually). We don’t really know how this phase is used yet, but interestingly the highest range in which phase locking occurs (~4kHz) also happens to be the highest note on the piano and about the highest frequency that we hear sound as tones as opposed to texture and timbre. So it’s all just waves, but when we listen to waves in the audio range our neurons respond differently very much based on the biological timescales of how fast neurons spike.

  • misksound

    this article, peter, is and example of why cdm continues to kick ass.

  • Nate Carter

    A couple of years ago I found a rare set of CDs that were each nearly an hour of soundbytes captured by Voyager as it passed by some of the planets. They are quite incredible and each disk is totally unique. They are inspiring, and eerie and were captured by a sophisticated device designed to detect sound in space. The sounds themselves are awe inspiring; deep droning, whistling, massively bassy earth rattling sounds. I created a handful of tracks and integrate them into my improv live performance. I am also a scientist and amateur astronomer and use the wonders of science often as an inspiration for my music and feel like the two worlds, though often treated as separate entities are truly one. The pursuit of science is an art; only achieved through rigorous practice, dedication and passion. And to think that modern electronic music was born of the pursuit of science and furthering technology. Modular synthesizers were born of analog computers used to calculate things like the gravitation of our solar system. This article is fantastic as it captures that blending that needs to occur between science and music.

  • Robin Parmar

    I was as excited as you to learn of the discovery of gravity waves. And also happy to hear the audible chirp as two massive black holes collided over a billion light years away. But does this discovery mean that we can now “listen” to the universe? Are the claims for this as some sort of a revolutionary sensory phenomenology valid?


    tl;dr No. 😉

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