Аннотация:Improvements of the sensitivity of piezoelectric microphones based on charged cellular polymer films are reported. The improvements are achieved by (1) an increase of the piezoelectric d33-coefficient of the cellular polypropylene films by pressure expansion and (2) stacking of the films. Microphones consisting of a single film of such material have sensitivities of about 2 mV/Pa at 1 kHz, independent of size, while for a microphone with five stacked films a sensitivity of 10.5 mV/Pa was measured. The equivalent noise level is about 37 dB(A) for the single-film transducer and 26 dB(A) for the stacked version. Advantages of these new piezoelectric transducers include their simple design, low cost, and small weight, as well as a large range of shapes and sizes possible.
