NASA’s Sound of a Black Hole: An Investigation

Courtesy Event Horizon Telescope Collaboration

Are NASA not just cynically manipulating some otherwise wholly unimpressive sound wave data, mining it for clicks and likes?

Last week, NASA went viral with what purported to be the sound of a black hole. While it’s usually thought that there is no sound in space, because space is a vacuum, this is not entirely true: a ‘galaxy cluster’, apparently (a group of galaxies bound closely together by gravity), ‘has so much gas that we’ve picked up actual sound’ – from a black hole at the centre of the Perseus galaxy cluster, 240 million light years away.

And really, what is notable about this sound is… that it sounds exactly like you would expect a black hole to. Or like a huge worm screaming, Jordan Peele’s new film Nope, and the music of Björk. Personally, I think it sounds a bit like a Tim Hecker album; I would quite like NASA to release a much longer version of the black hole sound, so I could work to it (Lo-fi black hole beats to study and relax to, perhaps). But more than anything else: the black hole sound sounds exactly like space. If ‘space’ had a soul, then the black hole sound is the music it would make.

But then I thought: you know, it’s odd. ‘Space’ is this sort of utterly transcendent thing, this thing which is supposed to make us feel how intensely small we are, this great beyond we can never truly understand. No matter how much NASA explores space, we will never quite be able to grasp it. The scale of space is not a human one: there are so many stars, so many galaxies, and they are so huge, and so far away, and anyway we’re not really seeing them, we are seeing the light from how they were, many millions or even billions of years in the past (if a black hole really did make this noise, it made it at around the time the first dinosaurs were around). If we ever were to discover intelligent life on some distant Earth-like planet, our messages would surely only reach them after global warming has reduced their world to a Venusian hell-scape, and also ours (so I guess like, 2024?).

And yet: we have long been used to seeing images of space, taken by space telescopes, that look, you know, space-y. We know that there is a great deal of manipulation going on there: the visual data originally received by space telescopes is initially rendered in greyscale, which means that scientists have to choose what colours to paint it. As Pippa Goldschmidt has argued in ArtReview, NASA has historically manipulated the images their space telescopes have detected to fit the preconceptions of a public whose ideas about nature have been moulded by the romantic sublime. ‘The images from [the James Webb space telescope],’ Goldschmidt wrote, ‘show the Universe not as we actually see it, but as we might hope to.’

And now, it seems, we are hearing space, exactly as we might hope to. The viral audio, to be clear, is not a recording: it has been produced by ‘sonifying’ data taken from NASA’s Chandra X-ray Observatory (another space telescope). The audio produced was originally 57 octaves below middle C, which meant the frequency had to be raised ‘quadrillions’ of times to be heard by human ears. The sound was also apparently ‘mixed with other data’ before being amplified – although I’m not really sure what that means.

The black hole sound is not the only ‘sonification’ NASA has produced: more can be found here. But where it does differ, is that usually NASA sonifies data in order to make it sound like something closer to traditional music (see, e.g. this one). By contrast, the black hole sound has been sonified based on the ‘actual sound waves discovered in data’ from Chandra. The music-like sonifications sound a bit silly. This one sounds a lot more authentic.

At any rate, isn’t this, still, a bit too perfect? Does a black hole really ‘sound’ exactly like anyone would expect it to? Or are NASA not just cynically manipulating some otherwise wholly unimpressive sound wave data, mining it for clicks and likes?

I decided to run an experiment. I would run an mp3 of the black hole recording through the audio software program Audacity, and manipulate its speed and pitch – in an effort to see whether it would have still sounded like space, if NASA had many different aesthetic decisions.

So for context, the released recording of the black hole, sounds like this:

The first thing I did was try a simple pitch-shift up an octave, which made it sound like this:

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Not a radical difference. So then I did the same thing again:

Now, in fairness, the noise no longer really sounds like a huge worm screaming. Actually, it sounds like lots of little things screaming. But these things are still most obviously aliens. So the recording continues to sound like space. I tried shifting it up a third octave, which is the most octaves audacity would let me do:

This sounds less to me like little creatures screaming, than it does a bunch of crystals twinkling. Again though, these are clearly space crystals. Shifting the recording up in pitch only reveals different layers, as it were, of space.

So what if I pitched the black hole noise down? Here is the recording shifted down an octave from the NASA pitch:

As with the recording when it’s shifted up an octave, it sounds very similar to the original, and evokes pretty much identical things. Here it is down another half an octave (the lowest audacity would let me go):

At this point I was beginning to despair of the recording ever not sounding like space. This is a very different sort of grumble to the one heard on the original recording, but it sounds like the depths of a planet talking, or something: still a very space-y sound.

So then I tried doubling the speed instead:

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Back to sounding like a big space-worm.

Here is the speed doubled again, and pitched back up:

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This is interesting, because the recording is starting to sound less like screaming, than talking. At the original speed, the recording sounds like a big great groan, a howl – but now it’s starting to sound almost conversational. This conversation is still, however, very much happening in space. This is almost what I imagine alien language to sound like. I tried doubling the speed again:

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Yes, this is definitely an alien talking. Doubling the pitch again got me this:

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Intensifying the effect of the black hole yawn sounds like a sort of natural language. Well, if you can call something ‘natural’ language if it sounds like it’s being spoken from a galaxy several million light years away.

I doubled the pitch again:

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Gritty Clangers reboot.

Then doubled the speed:

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Tiny little bastards sent from Neptune to destroy us.

Finally, I pitched the recording right back down again – one last shot at trying to make it sound like it hadn’t come from space.

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I failed.

So: what conclusions might we draw from this? Obviously it’s difficult to definitively prove a negative. But certainly, from my experience: some rudimentary pitch-shifting will fail to make the NASA black hole sonification sound anything less like space. The black hole sound does indeed sound authentically like space. Even if NASA had presented the sound at a different pitch or speed, it would still have sounded like space – although it might have sounded like space with a slightly different affect (it could have sounded like crystals twinkling, or an alien chattering, as opposed to a huge worm).

For all this however, it remains true that NASA have manipulated the audio data they’ve picked up in order to turn something basically completely alien, inaudible to human beings and way too far away from us anyway, into comprehensible, human-level sound. The black hole sound is not entirely a fantasy. But with it, NASA have used aesthetic means – to bring the inhuman noise of space, down to earth.

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