It's kinda like all those clever hacks that use audio to figure out keystrokes.
> the study of sound associated with laser impacts on Martian rocks to better understand their mechanical properties, the improvement of our knowledge of atmospheric phenomena at the surface of Mars such as atmospheric turbulence, convective vortices, dust lifting processes and wind interactions with the rover itself. The microphone also helps our understanding of the sound signature of the different movements of the rover: operations of the robotic arm and the mast, driving on the rough surface of Mars, monitoring of the pumps, etc
https://hal.science/hal-03977124/document
There were some scientists who believed that the recordings would be useless. A waste of payload space. The experiment had to be done to demonstrate, with data, just how versatile audio can be.
There's only one The Jim Green, but we need more Jim Greens in the world.
IIRC we would've actually had audio to accompany video of the skycrane landing, but the mic had an issue at that time.