Anactive underwater acoustic reflection control system

In this paper, an active underwater acoustic reflection control system is investigated experimentally in a water-filled pulse tube using samples with two layers of 1-3 piezocomposites, one as pressure sensor and another as cancelling acoustic transmitter. A one-dimensional electroacoustic model is first developed for multi-layer sensor-actuator system to simulate the frequency responses of both the sensor and actuator. The controller transfer function of the closed-loop feedback control using a single pressure sensor is then derived. Significant echo reductions to harmonic incident waves in low frequency band are achieved experimentally by directly phase-shifting the sensor signal and amplifying it to drive the canceling actuator.