AN INVESTIGATION OF ACOUSTIC PHASE-SHIFT NETWORKS IN THE DESIGN OF UNIDIRECTIONAL, UNDERWATER SOUND TRANSDUCERS
PENNSYLVANIA STATE UNIV UNIVERSITY PARK ORDNANCE RESEARCH LAB
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A low-frequency, underwater sound transducer model was developed which utilized a liquid-filled, acoustic phase-shift network to obtain a unidirectional cardioid directivity response over a prescribed frequency range. A number of analytical relationships between certain physical parameters of the device, its environment, and the acoustic phase shift network were studied to determine just how they should interact for the transducer to function as specified. A search was directed at finding and choosing an inert fluid which would satisfy the required acoustic phase-shift network parameters and also be relatively insensitive to a change in pressure hence depth and temperature. A study of the transducer design was carried out and a trilaminar, piezoceramic pressure-gradient element was selected in the final design of the model. When the completed transducer model was configured as specified, a unidirectional cardioid response was achieved consistently between 4000 Hz and 6000 Hz. Front-to-back discriminations ranging between 15 dB and 22 dB were recorded over the upper half of the frequency range 5000 Hz to 6000 Hz, while 10 dB to 15 dB discriminations were recorded over the lower half 4000 Hz to 5000 Hz of the frequency range.
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