The world’s spaceflight programs generate astounding piles of images. But sight is just sense through which we can understand and imagine space exploration. And the medium of sound has been comparatively under-used.

That’s starting to change. Recently, both NASA and the European Space Agency announced new archives of sounds were being made public and Creative Commons licensing. The licensing on these sounds means that you can not only listen, but also remix, sample, and share those sounds.

This could be just the beginning. In November, I visited ESA’s European Space Research and Technology Centre (ESTEC) in Noordwijk, Netherlands as part of a collaboration with them. The continuing mission: learn the significance of sound in the space program, record new sounds, and then demonstrate why these sounds could be powerful in a talk and performance.

Now, from a simulated launch to the sounds of a prototype Mars rover, we can share those sounds for you to download.

Making music from sounds at ESA's research facility. Photo: ESA/TEDxESA.

Making music from sounds at ESA’s research facility. Photo: ESA/TEDxESA.

Why sounds matter in space exploration

I was suspicious that sound was significant, if I happen to be a bit biased about the role of sound and music. But I was frankly surprised just how important I learned sound could be, through the collaboration with ESA.

I talked about that – and then performed a bit – in my talk/performance/demo wrapping up a day of TEDx programming at ESA.

Space Science Sound System | Peter Kirn | TEDxESA

“There’s no sound in space,” is, of course, the first reaction you’ll hear (even from some scientists and engineers). That’s true to the extent that you need a medium (like air or water) to convey sound waves. But we can look at the role of sound more broadly – just as we do imagery.

In our conversations, we found a number of distinct roles for sound in documenting space. Obviously, any sound recording can serve as documentation (voice recordings, field recordings, and so on). But there are ways that sound is more directly involved in in the space programs, too:

Sound is a technically sensitive part of every launch. This one may seem obvious – rockets are freakin’ loud – but it has a practical implication. Satellites and spacecraft have to withstand powerful sound pressure levels. One of the largest test facilities at ESTEC is exclusively dedicated to testing this.

Discovery News has a great video that explains just how loud rockets can be, and why that matters to engineering:

Sound is part of how engineers do their job on Earth. Microphones can be part of how instruments are calibrated and detect vibrations. This doesn’t always mean an engineer will listen to sounds directly – they may only display it visually, for instance. But in some industries, listening to sound directly may be part of a test or evaluation process.

Listening to sounds generated by the LEAF facility. Photo: Marco Trovatello, ESA.

Listening to sounds generated by the LEAF facility. Photo: Marco Trovatello, ESA.

Sound can be used to evaluate equipment on the ISS – and the ISS is really loud. I had the pleasure in Noordwijk of sitting at dinner next to Frank De Winne, an experienced Belgian pilot and astronaut who now heads the European Astronaut Centre. Frank told me that making recordings is one way the space station can communicate with engineers on the ground. Now, you may have had the experience of a car mechanic saying, “what does it sound like” when trying to solve a problem. (Our American readers may have listened to the “Car Talk” radio show.) This evidently happens quite literally on the ISS. For instance, Frank said that the astronauts made a recording of a malfunctioning treadmill and then uploaded that recording to mission controllers.

The acoustic environment on ISS is also much louder than you might imagine. Commander Chris Hadfield made a recording of the US lab module to illustrate this. (I hope we can get a better recording at some point. I also hear the Russian module is even louder, though I have to verify that.) It’s not really CDM material, per se, but if you’re interested in life on the ISS, I really recommend the amazing talk given at our event by Samantha CristoforettiFUTURA mission: 200 days in space | Samantha Cristoforetti | TEDxESA.)

Beyond human hearing

Vibrations and sonifications from space can be heard. Human exploration of space was heard before it was seen, starting with the iconic sound of Sputnik’s radio transmission. Sonification is now going beyond just playback of radio signals, however.

The Philae lander had onboard an experiment involving what is essentially a contact mic. Remember that you can detect acoustic vibrations without requiring a medium like air or water, as vibrations travel through a physical body. That’s what the Cometary Acoustic Surface Sounding Experiment (CASSE) sensors did – even without any air, this is literally the acoustic sound (traveling through the body of the spacecraft) as it makes contact with Comet 67P/Churyumov-Gerasimenko:

Imagery from space relies heavily on the use of false colors, simulation, and other enhancements that allow us to see beyond what our eyes normally would. So it makes sense that other signals would be enhanced, too. When we say the same comet “sings,” we don’t mean literally in terms of sound waves. The oscillation is in the magnetic field. On the other hand, you could think of the comet as a kind of synthesizer. Whereas an analog synthesizer oscillator works with voltage, this one – flying through our cosmos – is producing oscillations in electro-magnetic radiation.

The next problem is simply one of frequency – a 40-50 millihertz signal would be inaudible if sonified directly. So, instead, you need something in the range of human hearing. (It’d still be sound, just not sound you can hear.) German composer Manuel Senfft did that with this sound:

But generally speaking, we are in a world where we’re beginning to think of data and signals as something to hear as well as see. That prompted the team announcing the discovery of gravitational waves to use sound rather than just a picture. I’ve talked about the importance of that, but here you can listen to the voice of LIGO spokesperson and Professor of Physics and Astronomy Dr. Gabriela González announce it directly. (She also emphasizes that this is the real signal, just adjusted for our hearing and time scale – just like those false colors used on some space images):

ESA's horns are each tuned to simulate the low-frequency sound pressures of an actual launch.  Photo: CDM.

ESA’s horns are each tuned to simulate the low-frequency sound pressures of an actual launch. Photo: CDM.

The sounds of ESTEC

This week, with the collaboration of ESA, I’m excited to share a small sampling of additional sounds collected and recorded here on Earth. You can read about it in ESA’s blog:


The project grew out of a collaboration with the TEDxESA team from the European Space Agency. That’s Priel Manes and Angelika Daniels (from ESA’s Technology Transfer Programme Office), Marco Trovatello (ESA Communications), and Guenther Mulder. Marco also wrote up the above, and has been helpful in talking about Creative Commons licensing and access to ESA materials.

I hope it’s just the beginning. Just as important as recording these sounds themselves was the chance to communicate with the people working at ESA – with astronauts, with engineers, with people working in communications and administration – about how sound mattered and how this process might work in the future.

Inside the enormous nitrogen horns that power the LEAF, bringing its sound upwards of 156 dB. Photo credit: ESA – A. Le Floc'h.

Inside the enormous nitrogen horns that power the LEAF, bringing its sound upwards of 156 dB. Photo credit: ESA – A. Le Floc’h.

At the LEAF facility (Large European Acoustic Facility), we got to tour Europe’s largest sound facility. Imagine a giant room, several stories high, with walls of concrete reinforced with steel. Then imagine a really insane organ/calliope powered by compressed nitrogen, capable of generating 158.5 dB sound. (Standing inside with this while it was operating would actually kill you.)

Listen carefully, and you can hear the high frequency whistles early, as well as the full blast later on. Now imagine this is many, many hundreds of times louder.

Schematics in the LEAF control room show flow of compressed nitrogen into the chamber. Photo: CDM.

Schematics in the LEAF control room show flow of compressed nitrogen into the chamber. Photo: CDM.

Spacecraft have to survive both this acoustic test (the sound of a launch) and a vibration test (the shaking produced by a launch). In the case of the acoustic test, conventional microphones (albeit ones capable of responding to very high pressure levels) are used to calibrate the test. Vibration sensors on the shakers (think contact mics again) calibrate the shaker test. So in each case, there is an audio signal evaluated by the test equipment. We weren’t certain if anyone had listened to the file before, in fact. But the test equipment was capable of dumping standard wave files, so we’ve shared those.

Working with ESTEC’s Steffen Scharfenberg, an electro-mechanical engineer, we were able to understand how these test suites function and how they make use of sound.

The shaker test uses sine sweeps to test calibration of the equipment as the device is shaken. So sound is used, more or less, at both ends — it’s a source (the sine sweep), and then read again by the test equipment while the spacecraft (or other materials, including rocket propellents) are physically shaken around on the surface. Listening through the equipment, you hear not the shaking of the equipment as you would standing in the room as it operates, but as it vibrates the plate on which the test subject sits. (Again, think contact mics.) That sounds like this:

Europe is preparing for the (robotic) journey to Mars. Photo: CDM.

Europe is preparing for the (robotic) journey to Mars. Photo: CDM.

Working with the teams developing robotic prototypes in the Planetary Robotics Lab led to some different sorts of discoveries. Martin Azkarate and team got to hear their own rover hardware in a new way, as they played with Jonáš Gruska’s Elektrosluch device to listen to electromagnetic radiation emitted by various onboard instruments, including various cameras being tested. A lot of this may be distant from the hardware that actually goes to Mars, but the engineers and I got a real kick out of hearing what was emitting EMF radiation and how it sounded. It’s a bit like the acoustic version of putting on heat-sensing goggles.

Making an electromagnetic recording inside the Planetary Robotics Lab with the aid of the Elektrosluch from LOM. Photo: CDM.

Making an electromagnetic recording inside the Planetary Robotics Lab with the aid of the Elektrosluch from LOM. Photo: CDM.

What I appreciated about making acoustic recordings of the rover was that it gave a sense of the delicate pace of its travel. It wouldn’t quite sound like this if we were able to record it on Mars – Mars’ much thinner atmosphere means that the speed of sound is higher. (Think of what happens to your voice when you inhale helium.) But it does at least stimulate the imagination in a way in which a video alone (of the rover going … very … slowly …) might not.

We saw all kinds of things in the Materials & Electrical Components Laboratory that we couldn’t capture in sound, but we did get to record the signature snap of nitrogen valves going off. (In many of these facilities, security rules also dictate that you can’t take photos, so microphones are allowed where cameras aren’t.)

This was itself an interesting cross-disciplinary adventure, as we toured the facility on the invitation of Tommaso Ghidini, who has come from projects like the Airbus A380 to heading the materials lab – and now will be glad to tell you all about 3D printing on the moon.

But all in all, I think these sounds give a sense of some of the many amazing things happening at ESTEC even beyond what a picture could do. And so I hope we do more like this.

Get the audio

You can download all the audio from SoundCloud, via my own account and ESA’s:

And of course a drum kit I made with these is available here on CDM:

Download a free sampled drum kit [Ableton Live, Maschine, samples, CC-licensed]

What’s next? We hope to investigate other ways sound can help give us a better way of understanding space, technology, and space exploration, with ESA and other programs. And we hope people will respond musically to these sounds.

On ESA’s site, you’ll find lots of music inspired by space, much of it using sounds made available by the program. And ESA is collaborating with artists. I got to meet Elvire Flocken-Vitez, for instance, a young French woman who was in residence at ESTEC producing a vinyl record that sonifies the relationship of planets in the solar system. (Elvire also joined us last month in Belgium for the hacklab we hosted at Artefact Festival.) Other artists are making music both in residency programs and on their own. And other agencies are toying with this concept, too.

I believe these sorts of collaborations expand our culture and our own conception of our world. And, well, they’re a heck of a lot of fun, so there’s that, too. Let us know if you have a response of your own, and where you’d like future sonic efforts to go.

This is the result of just a couple of days spent at ESTEC (and some conversations and planning outside that). Much more can and will happen. Stay tuned.