Initially the USN submarine doctrine pushed attacks made on hydrophone data. These were abysmally ineffective, even when the torpedoes used (primarily by the S-boats) were decent enough. The USN moved away from these rather rapidly. In WWII a hydrophone could give you bearing, some information of number of ships, and based on the proprellor(s) speed and engine noises the type of ship. Range was relatively short, and you still had to come to periscope depth to get accurate information for an attack. Submarine vs submarine attacks occurred when one was submerged and the other on the surface...