A hydrophone for the detection of sound or vibrational waves, comprising a piezo electric transducer within a Faraday cage such that it is in contact with and yet isolated from a deformable pressure transmitting medium that carries vibrations. The Faraday cage reduces noise interference. The deformable medium is usually a fluid and preferably a vegetable oil, but can also include a silastic compound couple. One side of the Faraday cage is a ground plane of a surface-mount printed circuit board. Components of an electronic circuit for conditioning the signal are mounted on the printed circuit board and include a buffer having an ultra-high impedance input and a very low impedance output. The circuit has a low power draw and is powered by a replaceable battery.