Hydrophone

Article By:

Rogers, Peter H. George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia.

Trivett, David H. George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia.

Last reviewed:January 2020

DOI:https://doi.org/10.1036/1097-8542.330500

The underwater equivalent of a microphone, which generates an electrical signal as a response to the pressure component of an acoustic signal. Modern hydrophones are usually composed of piezoelectric ceramics such as barium titanate and lead zirconate titanate. The piezoelectric effect is the ability of materials to generate a voltage in response to applied mechanical stress. This effect is reciprocal in that an applied voltage will induce a small deformation in a piezoelectric material. Thus, some hydrophones can also be used as acoustic sources or projectors. In general, the capacitance of a hydrophone is relatively small, so a preamplifier is required to be placed near the piezoelectric material. The preamplifier boosts the electrical signal to allow the use of long cables without reducing the sensitivity of the hydrophone due to the added capacitance. When a preamplifier is installed in a hydrophone, the hydrophone is no longer reciprocal and may not be used as a projector. Hydrophone design requirements differ from microphones in that they must be electrically insulated from water and may need to operate at high hydrostatic pressure (deep depths). See also: Electret transducer; Microphone; Piezoelectricity; Preamplifier

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