That is apparently the sound gravitational waves would make if gravitational waves could make a sound.

We know this because scientists around the world are emulating this sound with their mouths and posting it online with the hashtag “#chirpforLIGO”. Astrophysicist Katie Mack was the first to sound off:

The sound comes from a signal – converted for demonstration purposes into a sound wave – detected by a team at the Laser Interferometer Gravitational-Wave Observatory (LIGO) project.

The world’s greatest minds began chirping Wednesday in anticipation of the evidence for gravitational waves being formally announced.

The signal was created by two black holes colliding about 1.3 billion light years away from the Earth. In September, LIGO detected a signal from this collision that – when interpreted as a sound wave -- began as a low rumble before culminating in a higher-pitched “chirp”.

On social media, the scientific community applauded the first evidence of Einstein’s long-theorized gravitational waves, with scientists sharing videos of themselves chirping for everyone to enjoy.