Modification of transducer characteristics using active feedback

Abstract

Active feedback in a hydrophone-projector system is used to modify the transmit or receive efficiency of the system. Hence, the output from the hydrophone layer can be used to broaden the bandwidth of the projector or, conversely, the driver can be used to correct the response of the hydrophone. The principal features of the system can be represented by a one-dimensional model resembling a four-media system, consisting of water, a receiver layer, a projector layer, and a backing impedance. Since the output of the receiver layer is amplified and applied to the projector layer, an active acoustic feedback system results. Experimental data using a large-area projector bonded to a transparent large area polymer (LAP) hydrophone are presented.