With the WWII technology your hydrophones would have to be pointing at the U-boat to hear the launch. The sound man would need to be trained to interpret the sound.
The sight of the wake of the steamers allowed a warship to turn and avoid the incoming "kiss."
Nevertheless, on stock and GWX, the escorts will head for datum point (the location you launched your torpedoes from).
Thus, a small suggestion: get away from datum, do the wiggle-waggle and dive deep after launching.
