Musk: "Ah, yes, let me use microphones to listen for objects approaching at greater than the speed of sound"

I mean, yeah, if you control the ground in the battlespace and have microphone arrays all over the place, sure, maybe acoustic data could be... some part of... some kind of fused sensor network.

But even with perfectly smart software and shitloads of microphones over a huge radius that is going to be a very laggy and imprecise way of measuring (checks notes) objects that may be hundreds of miles away, moving nearly or above the speed of sound, using a spectrum (acoustic waves in air) that only propagates signals at the speed of sound.