HYDROPHONE TECHNIQUES FOR UNDERWATER SOUND PICKUP

With today's wide-frequency-range, extreme-dynamic-range stereo sound tracks it is appropriate to consider hydrophone techniques that can bring underwater sound pickup to the same state of the art that airborne sound pickup enjoys. Underwater sounds can be captured as accurately and easily as miking an orchestra on stage; in some cases more easily, since there is always something to hang the hydrophones from-the boat. With the right choice of hydrophones, array configuration, and preamplifiers, the sound should be captured with a minimum of trial and error and requiring little postprocessing. Stereo microphone techniques that are applicable with hydrophones underwater are reviewed; and considerations important in dealing with the underwater environment and in choosing hydrophones and preamplifiers are addressed. A state-of-the-art hydrophone is described, along with a suitable preamplifier, and for a particular recommended configuration the electrical noise floor is modeled using the equivalent circuit of the hydrophone-preamplifier interface,