Noise shielding system utilizing a thin piezoelectric membrane and elasticity control

Abstract

The description and theoretical analysis of a noise shielding system are presented. In this system, the noise and/or sound are transmitted through the piezoelectric curved membrane, which is connected to an external feedback circuit. Using the principle of elasticity control, i.e., utilization of both direct and inverse piezoelectric effects simultaneously, the movement of the membrane as well as the sound pressure of the transmitted wave can be controlled to a large extent. Transmission loss of an audible sound through the membrane in such a system is expressed as a function of a sound frequency, geometrical properties of the membrane, and parameters of the feedback circuit. It is used for the comparison of theoretical predictions and experimental data. Using this technique, the increase of the transmission loss of about 60 dB in a narrow frequency range or about 7 dB in the broad frequency range has been achieved. The performance of this system is discussed.

A theory of sound transmission through a clamped curved piezoelectric membrane connected to a negative capacitor

“…3(b). Date et al (2000) and Mokrý et al (2003a) showed that the complex input capacitance of such a circuit is equal to C NC ¼ ÀR 2 C 0 =½R 1 ð1 þ jxC 0 R 0 Þ. The values of circuit parameters R 2 , R 1 , C 0 , R 0 of the negative capacitor are chosen in a way to achieve the desired matching of the membrane and circuit capacitances at a given frequency x 0 , i.e.…”

Feedback Control of Piezoelectric Actuator Elastic Properties in a Vibration Isolation System

“…The detailed theoretical analysis of the described mechanism and further experimental investigation were needed to improve this technology for practical applications. The theoretical analysis of these systems was performed later by Mokrý et al [5,6] and the various applications of active elasticity control technique in noise and vibration control devices were demonstrated by Fukada et al [7]. Results of these works have shown that the crucial point in the successful realization of the SMNC method is the accurate matching the capacitances of the external electric circuit and the piezoelectric element.…”

Elasticity Control of Curved Piezoelectric Polymer Films

“…The circuit works as a negative capacitance, which generates negative charge upon receiving positive voltage. It has been found that the thickness and the radius of curvature of the film give the influence on the vibration amplitude, and thus affect the efficiency of the sound transmission and the feedback voltage required to obtain the maximum attenuation [3,4]. …”