Performance of small arrays of flexural disk transducers

Abstract

Trilaminar disk elements of small aperture (a = 34 mm) have been used in compact four- and six-element arrays for 2.4-kHz resonant frequency projectors with improved performance over single balanced pair (two-element) projectors of larger (a = 54 mm) elemental aperture. Several configurations of these arrays have been tested, and the results are compared to predicted values and to the larger two-element transducer. Benefits in performance are gained by improved radiation resistance and reduced radiation mass through array interaction and by the simultaneous reduction of the mechanical mass of the elements. Furthermore, the electrical impedance is reduced by the increased electrical capacity of the total array. An omnidirectional array with no dimension of the structure exceeding 110 mm performs untuned with a source level (Ss) of 141.0 dB re 1 μPa when normalized to 1 m and 1 V. The mechanical quality factor is 3.0 (untuned), and the electroacoustic efficiency is about 0.7. When series tuned, these arrays have shown bandwidths greater than 1500 Hz between −3 dB points.