Voyager 1 was able to record the sounds of interstellar space. This helped the Voyager science team calculate the density of interstellar plasma.

Listen to the Sounds of Interstellar Space, Recorded by Voyager 1

click on link for audio

Plasma wave frequencies are quite interesting. Plasma are akin to electromagnetic waves but have frequencies akin to those of sound waves (A few Hertz to a few kHz) rather than normal electromagnetic waves (typically 3 kHz and much higher). We’ve heard sounds from the Voyager spacecraft before, as they have crossed through various parts of the outer solar system.

Here’s a website that gives a spectrogram of the Voyager 1 sound as it crossed Jupiter’s bow shock. Voyager at Jupiter