A detector that is sensitive to variations in pressure, as opposed to a geophone that is sensitive to particle motion. Used when the detector can be placed below a few feet of water, as in marine or marsh work or as a well seismometer.
The sensing element is usually a piezoelectric ceramic material such as barium titanate, lead zirconate, or lead metaniobate. Piezoelectric hydrophones are high-impedance devices and signals may be passed through preamplifiers or impedance-matching transformers before transmission through the streamer to the recording instruments. Compare geophone.