| This study constitutes a proof of concept of a new feedback-controlled optical microphone for potential use in phased "beamforming" arrays utilized in aeroacoustics research. In the new microphone design, an optical sensor is employed as a means for measuring the center displacement of a stretched thin membrane caused by incident acoustic pressure. The membrane is constructed from PVDF (polyvinylidenefluoride) which exhibits piezoelectric properties allowing actuation of the membrane in a feedback system, where force feedback is used to nullify the optically detected deflection. The feedback provision was used to actively modify sensor parameters, most notably membrane stiffness, resonant frequency, and damping. A theoretical study is presented to examine the viability of two improvements that may be used in future microphone designs. Implementation of one or both of these improvements is expected to significantly increase controllability of the feedback-controlled optical microphone documented here. |
