Broadband multimode piezoelectric spherical shell transducers are investigated for underwater sound by exciting the zeroth and/or first order (0 + 1) extensional modes of vibration with and without acoustical baffles of different types. Measurements of the frequency response (transmit pressure per volt or TVR), radiation patterns and electromechanical impedance reveal useful tradeoffs and design guidance for many practical applications. Measurements are in good agreement with theoretical closed form analytical results.
Active spiral-wave active localization is a technique for determining location of acoustic targets [after Dzikowicz et al., JASA 146, 4821–4830 (2019)], which relies on measuring the phase difference between a reference and spiral wavefronts. This research presents a monostatic model of spiral detection and tracking for multiple targets in sparse noise limited environments. Simulation and experimental results from an acoustic spiral wave beacon in a small underwater test tank will be presented. Results show good agreement to resolve targets in horizontal and vertical dimensions with a compact aperture. [Work supported by ONR 321MS.]
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