Attenuation of the sound transmitted through the piezoelectric curved membrane: the effect of the electrically controlled elasticity

Principles of the sound transmission control using a thin curved membrane made of piezoelectric polymer are presented in this paper. Utilizing both the direct and inverse piezoelectric effects simultaneously, which is realized by connecting the external circuit with a negative capacitance, the elastic properties of piezoelectric materials can be controlled. The effective value of the Young's modulus of the PVDF and P(VDF/TrFE) films can be governed to a large extent (theoretically in the range from -/spl infin/ to /spl infin/). Calculation of the transmission loss of an audible sound through the curved piezoelectric membrane is used for the theoretical analysis of the application of this phenomenon in acoustics. Transmission loss is expressed as a function of frequency, radius of curvature, Young's modulus and the capacity of the external circuit. The effects of the values of these variables on the transmission loss and related aspects are described. The comparison of theoretical predictions and experimental results is discussed.