What does a black hole sound like?

Scientists are learning more about black holes every day, and today is no exception: According to a new study published in Science Advances, researchers have discovered that the flickering light of accretion disks surrounding black holes, stellar objects, and white dwarfs can also emit sound.
Discovered by Simone Scaringi, a postdoctoral researcher at the Max Planck Institute in Germany, and his team of fellow researchers, the studying of accretion disks shows that while the mechanics behind this phenomenon are still unknown, stellar objects such as black holes can emit variable amplitudes of sound.
Basically, a black hole sounds like the white noise static of your old radio.
So, what is an accretion disk?
When looking at a photo of a black hole, it is easy to identify the accretion disk as the disk-like structure formed by diffuse material and gas orbiting around the epicenter of the stellar object—in this case, the black hole. However, accretion disks can also form around smaller stars and stellar remnants, and can form on a larger or smaller scale.
You can think of accretion disks like a gramophone record: The needle begins on the very outer edge of the record disk and slowly makes its way inward, increasing its speed the closer it gets to the center of the disk.
Scaringi and his team began studying these accretion disks using observations from NASA’s Kepler space telescope, the European Space Agency’s XMM-Newton satellite, and ground-based instruments. The team noticed that the flickering light produced from released energy by material in accretion disks which falls toward the center was found in both the visible brightness of young stellar objects and the light emitted from the accretion process of black holes or white dwarfs.
“The seemingly random fluctuations we see from the black holes and white dwarfs look remarkably similar to those from the young stellar objects—it is only the tempo that changes,” explained Dr. Simon Vaughan, Reader in Observational Astronomy at the University of Leicester’s Department of Physics and Astronomy.
Taking it to the next level, the scientists found it’s possible to turn this flickering into sound.
Turning light into sound
By using NASA’s Kepler/K2 telescope, Scaringi and his team were able to “listen” to the variations of brightness produced by accretion disks by treating the light flashes’ frequency like a sound wave. Then they had to scale these frequencies into the range of human hearing.
The result? On a small scale we learned that black holes sound like static, similar to the sounds emitted from the accretion disks surrounding other stellar objects.
On a bigger scale, the team established the universality of accretion physics from stars that are still growing to supermassive black holes found at the centers of some galaxies.
As one of the main findings, Scaringi and his team found that the physics of accretion disks can scale up and down and remain for the most part the same, no matter how large the object found at the center of the disk is. The next step would be to uncover the mechanisms behind this universal basic law which can apply to a black hole, a galaxy, or even a young solar system.
“As far as the detailed modeling is concerned, we’re still not there,” Scaringi told Space.com in an interview. “We seem to observe that it turns out that they all seem to scale, but the detailed physics as to why the scaling relation holds is not clear yet.”