Abstract: A circuit includes an AC voltage driver configured to output an AC voltage having a given shape and given one or more frequency components. An electric field type transducer is provided including a positive voltage terminal and a negative voltage terminal. A capacitor is connected between the AC voltage driver and the positive voltage terminal of the transducer. A diode is connected across the two terminals of the electric field type transducer. The diode operates on the signal applied by the AC voltage driver so that a substantially only positive AC voltage is applied to the positive voltage terminal of the transducer. In addition, the applied positive AC voltage applied to the positive voltage terminal of the transducer has an applied shape and applied one or more frequency components that are substantially the same as the given shape and the given one or more frequency components.

Abstract: Apparatus for absorbing acoustic energy directed toward a wall. The appars includes a piezoelectric layer intermediate the wall and the source of the acoustic energy. Circuitry attached to the output of the transducer compensates blocked and motional capacitances of the transducer so that the output signal generates real current for dissipation in a resistor thereby to minimize any echo reflected from the piezoelectric layer.