i would guess that for a simulation... the depth charge blasts
should ruin hydrophone acoustics for about 40 to 60 seconds... i dont know how long this effect runs in SH3.
the baffels are modeled pretty well... I have charged right up on a slow moving destroyer from his six o'clock position at ahead flank and periscope depth and he didnt even flench until it was too late

i would estimate it is about a 20 to 30 degree arc off the rear of every ship.
thermal layers are NOT modelled in SH3 - this is only modelled by using SH3 with "SH3 Commander" (a third party program)