This might be a little presumptuous, but that seems like you are significantly overcomplicating the problem. If your target is actively sending out audio signals, then using passive sensors should be sufficient, and seems like it would be far simpler than trying to construct your own send-and-return sonar system. Using hydrophones (which look to be just microphones but designed for pressure waves in water instead of air), my background understanding is that you could set up an array of 4 and compare the timing of the signals to know exactly where the ping is coming from (time-difference-of-arrival or multilateration look like the keywords to search for). Alternatively, you could use a single directional sensor and move it around to find the “loudest” direction.
I don’t mean to be rude, but the questions you ask, as well as some of your other posts, suggest that you don’t have a lot of experience working with electromechanical systems. Jumping into a project like this with many new topics to learn may be more of a challenge than can be reasonably expected to be completed. It sounds like you have an objective and some good starting ideas, but not a clear design direction. If this is for a specific project with pre-determined tasks and constraints, knowing what those are and what you are expected to produce would be very helpful in trying to give you useful advice. If this is just an educational or side project, then I think taking more incremental steps that target a single specific aspect would serve you far more effectively. Your enthusiasm is heartening, and I certainly don’t want to squash it, but what you aiming for here might be too far a leap from where you are right now.