Sound in Space: The Eerie Noise From a Black Hole

16th Sep 2022
Sound in Space: The Eerie Noise From a Black Hole

Back in August, NASA shared the “sound of a black hole”. Somehow, it is exactly what you would expect. Eerie, a little futuristic, and pretty unsettling. The short clip has since been circulated online and watched many millions of times.

But how is the sound travelling? How was this creepy noise from a black hole recorded, and how long am I going to have nightmares about it? NASA also went on to explain this, too.

While people tend to think that there is no sound in space, this isn’t strictly true. It is true, though, that sound that has originated does not travel in the vacuum of space. There is no way for the sound to travel in large parts of space. Within a galaxy cluster, though, there is a lot of gas, giving sound a passage to travel.

Sound travels in the form of waves. Effectively, these are just vibrations, and they travel as disturbances in a medium. That medium is any series of connected particles, including gases and liquids. This is why, even though the atmosphere is so different through space, in a location with a gaseous surrounding, the waves can emanate. Even though some of the gases are incredibly low-density, they are usually charged, so particles can also interact at a distance using magnetic fields, which provides another way to measure the waves. So, there are multiple ways to interpret data and turn it into a space sound.

Can you actually hear noise from a black hole?

In this clip, what you’re actually hearing has gone through a process of “sonification” which means that the data has been turned into sound after being collected from space. It has been released as a part of the NASA “Black Hole Week” event to help build interest and give a unique perspective on black holes.

The black hole itself is the one at the centre of the Perseus cluster, and was first linked with sound back in 2003, when astronomers worked out that the pressure waves the black hole was sending out made ripples in the gases surrounding the nearby galaxies. This could be translated, not just into a noise, but into an actual musical note.

The note sits somewhere around 57 octaves below middle C on a piano, so it is way out of the human hearing range, but through this interpretation and “sonification” we now have a sound to associate with the Perseus black hole.

The sonification involved extracting the sound waves in radial directions, measuring them outwards from the centre of the black hole. They were resynthesized, scaled up 57-58 octaves above the original pitch to make them audible. 57 octaves is a lot, but when you put this in terms of the original frequencies of the sound, the audio has been pitched up 144 quadrillion times higher than its original.

You can see from NASA’s visualisation that there are blue and purple lines, showing the data that has been captured and then turned into audible sound waves.

More Sounds of Space

Sonification of the sounds of space is not a totally new concept, and though this particular sound is noteworthy (pun intended) due to the fact that it has a rough, specific pitch to it, there have been plenty of other sounds released by NASA in the past, as well as the ESA, and plenty of educational establishments.

The University of Iowa has made its collection of space sounds available. These have been collected over a period of 40 years.

In 2017, NASA released some sounds for Halloween, and you can see why they chose the spookiest time of year to put these in the public domain.

These sounds include NASA’s spacecraft Juno recording the crossing of the boundary of Jupiter’s magnetic field.

There is also the rhythmic, driving sound of the plasma waves, recorded using an EMFISIS instrument aboard NASA’s Van Allen Probes.

Radio emissions from Saturn, related to auroras and solar weather, and a flyby sound of the comet Tempel 1 are also in the sample pack. You can hear the craft getting hit by rocks and making its way through a cloud of matter.

All of the sounds are incredibly interesting, and somehow exactly appropriate. If you heard any one of them in the latest sci-fi blockbuster film, you would not be taken aback by any of the noises. It seems sound designers have created pretty good approximations.

The Music Industry Responds

You can rely on musicians to experiment with weird audio, and the collection of space sounds online has already been dissected for parts and turned into compositions. 

Alternative duo Beach House were somewhat ahead of the curve, in 2014 they released “Saturn Song” which featured samples of radio waves that were collected and recorded by the Voyager 1 and Voyager 2 spacecraft. Beach House took these sounds and turned them into audio, providing a soundscape for their haunting song. This was part of the “Space Project” which was a compilation album where 14 different bands and artists interpreted these recordings to create music. Youth Lagoon, Jason Pierce, Mutual Benefit, the Antlers, and more joined Beach House in the project.

Plenty of electronic musicians have been inspired by the audio samples put into the public domain by space agencies, and used them as source material. The genre that can make use of the noise from a black hole is still under consideration, however.

All of this opens up an existential question of what sound really is anyway. Are these “sonifications” really the sound of space?

The fact that these are all sonifications and therefore interpretation means that we don’t know the exact sound of many aspects of space, rather a technologically-aided perception of data. Still, it makes for some pretty interesting sounds and another way to understand the data, as well as sample fodder for musicians everywhere.

The sound of the black hole is relatively new, but let’s face it, with such a dense sound and fascinating depth, it is inevitable that it will be used by musicians in the coming months, especially with Halloween just around the corner. 

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