Digital time delay network for active underwater acoustic coating

Abstract

A digital time delay system has recently been developed for control of an active underwater coating. The active coating contains piezoelectric polymer sensors and a piezocomposite actuator encapsulated within a host polymer. The coating is for layering on submerged objects to actively reduce underwater sound reflection. The control system incorporates time delay circuitry as opposed to the analog phase delays used in previous studies. The type of control is an open‐loop velocity feedback. This system prevents feedback instability because the acoustic reflection is decoupled from the actuator. The digital controller can characterize both the incident acoustic pressure and the reflected pressure through parallel multichannel processing. The reflected pressure is monitored at the sensors for determination of the effective sound reduction. Experimental results were obtained in a water‐filled acoustic pulse tube terminated at its boundary with the active coating. Echo reduction comparisons as functions of soun...