system
Given the following post, respond as if you're commenting on Reddit:
human
Why are acoustically guided weapons an option in the ocean but not in the air?

For example, most modern stealth warplanes take great care to minimize their infrared and radar signatures,  but are still quite loud.  Would it be possible to track these planes acoustically?
gpt
Ships are extremely slow (say 15 m/s / 30 knots) compared to the speed of sound in water (1500 m/s). What that means is that acoustic detection is practically instantaneous -- when the sound waves hit you, the target hasn't moved far.

Warplanes travel a significant fraction of the speed of sound (or well above it) so acoustic tracking isn't ever going to be very good. In fact for an approaching supersonic aircraft, you literally cannot hear it at all, so it's physically impossible to track it acoustically. There's also a lot of attenuation of acoustic waves in air -- you certainly can't hear an airliner cruising overhead at 30,000 feet.

I'll add that there is significant effort put into reducing the acoustic noise generated by aircraft for stealth reasons. It's especially a big deal with helicopters which are loud as hell, typically fly very close to the ground, and are desirable for clandestine use.