Smart sensor systems for underwater acoustic applications

A smart sensor, that can distinguish between different directional components in a superimposed acoustic pressure field, was developed as a part of the active acoustic coating system for absorbing sound energy incident on an underwater object. The smart sensor system includes a dual sensor pair encapsulated inside the coating and a multichannel digital delay-line network so that both the incident and the reflected wave signals can be extracted simultaneously. Furthermore, the delay-line network was interfaced with a personal computer to adaptively adjust the system parameters so that the performances of the smart sensor as well as the overall active system were optimized. The sensors were made of a piezoelectric polymer material known as polyvinylidene fluoride (PVDF). This flexible material offers significant advantages for underwater acoustic applications such as high and uniform sensitivity, impedance matching with water, etc. Theoretical model and experimental implementation and testing results are presented in this paper.