Undirectional, Underwater-Sound, Pressure-Gradient Transducer

Abstract

Results are presented for the design, construction, and calibration of an experimental, low-frequency, pressure-gradient, underwater sound transducer that utilizes a liquid-filled, acoustic phase-shift network to obtain a unidirectional (cardioid) directivity response over a prescribed frequency range. A solution for satisfying a number of analytical relationships, which are known to exist among certain physical parameters of the device, its environment, and the acoustic phase-shift network, is outlined. Design specifications defining the over-all physical configuration of the transducer, the acoustic phase-shift network parameters, and the piezoceramic pressure-gradient element, are given. Presentation of experimental data, in the form of azimuth directivity responses, demonstrates that a unidirectional (cardioid) response was achieved consistently between 4000 and 6000 Hz. Front-to-back discriminations ranging between 15 and 27 dB were recorded over the upper half of the frequency range (5000–6000 Hz), while 10- to 15-dB discriminations were recorded over the lower half (4000–5000 Hz) of the frequency range. In addition, a nominally flat free-field voltage response (M0) of −85 dB +2 dB re 1 V//μbar was achieved over the frequency range of 4000 to 6000 Hz.