An underwater parametric array source transducer composed of PZT/thin-polymer composite

Abstract

The source transducers for parametric array (PA) sound are required to radiate the primary wave with high intensity and directivity so as to generate nonlinear interactions between strong acoustic waves at different frequencies effectively, resulting in so-called PA sound. Thickness-mode piezoelectric transducers using 1–3 lead zirconate titanate (PZT) polymer composites were used to produce wide-bandwidth PA sound due to their ability to generate high-intensity, high-frequency sound beams over a relatively wide frequency band. The small mechanical quality factor of 1–3 PZT polymer composites results in high damping of the polymer matrix leading to a transducer with relatively flat frequency response but yet decreased-power efficiency. A PZT polymer composite that can enhance the power efficiency of a PA source transducer over a wide frequency bandwidth was proposed. This is achieved by adopting thinner polymer matrix layers and PZT rods with dual resonance frequencies. A transducer demonstrated ultrasonic sound up to 197 and 203 dB (re = 1 μP) at 98 and 135 kHz, respectively. The power efficiencies were 50% at 98 kHz and 33% at 135 kHz. PA sound was successfully generated up to 150 dB (re = 1 μP) at 30 kHz with a half-power beam width of 3.4°.