Counter detection.

Dangerous Waters can be very deep and demanding, absolutely, especially if one wants to master sonar, TMA and most importantly: Situational awareness.

Are you playing vanilla, or with the Reinforce Alert mod?

In case of RA, be aware that vanilla missions - like the campaigns - are basically broken due to drastic sensor-range changes and other things.
However, the vanilla campaign is silly and boring anyways, in this department the game fails heavily, in my opinion.

Regarding the pings, you observed that right.
The pings will, depending on the source, always sound exactly the same, so you can quickly learn to differentiate them. Torpedo-pings are higher pitched and shorter, surface vessel pings are the loooong ones that will annoy you heavily sooner or later and submarine pings you'll hardly ever hear for obvious reasons, but it can happen and sounds also very different.