True (though stealth bombers are subsonic, just). What about headings that are not straight at you though? May still have value detecting things passing by?
When I was at military I attended a few exercises where jets were involved. They don’t go supersonic but pretty close to it so usually once you start hearing something it’s almost over. It’s actually quite terrifying to have a jet coming at you at 800 km/h at low altitude. Very surprising, then very loud and incredibly fast. You also hear passing by jets only once they are long gone. I assume radar is just much better than sound.
Then it becomes a battle between the detection range of the audio sensors vs how long the attacking craft can spend supersonic. They could spend the last phase of the approach supersonic and even transition then turn to make any tracking useless.
If they are supersonic, would you just need to increase how much you lead the weapon. Supersonic doesn't mean they're quiet, they're just further ahead than where you are hearing them. Or am I just totally making stuff up?