Regarding the sounds, it looks like the correct answer is pretty close to your first possibility: https://en.wikipedia.org/wiki/Precedence_effect
Basically, if you hear the same sound with a delay from two different directions, you will perceive it as coming from the direction of whichever arrive…
Basically, if you hear the same sound with a delay from two different directions, you will perceive it as coming from the direction of whichever arrived first, even if that's quieter. (I guess this is an adaptation we have precisely to deal with exactly the kind of situation I described!)
I'm really not sure regarding the gorillas.
Regarding the sounds, it looks like the correct answer is pretty close to your first possibility: https://en.wikipedia.org/wiki/Precedence_effect
Basically, if you hear the same sound with a delay from two different directions, you will perceive it as coming from the direction of whichever arrived first, even if that's quieter. (I guess this is an adaptation we have precisely to deal with exactly the kind of situation I described!)