Diffraction based optical microelectromechanical systems microphone and its application to the measurement of sound intensity.

Abstract

Diffraction based optical MEMS microphones and force feedback capabilities of these microphones are presented earlier [Bicen et al., J. Acoust. Soc. Am. 123, 3230 (2008)]. Further investigation is done in order to see the capabilities of these optical microphones in measuring the sound intensity. The biomimetic diaphragms of these microphones are designed for responding to pressure gradient which can be used for extracting the particle velocity required to measure the sound intensity. In order to show the velocity measuring capability of these microphones, an impedance tube method is used because the velocity and pressure at each point in the impedance tube can be found accurately. The comparison of the measured velocities and sound intensities with the optical microphone and commercially available sound intensity probes is presented. Model results are discussed in order to show the effect of the different mode shapes on the accuracy of the pressure gradient measurements. Optimization of these biomimetic diaphragms will result in the measurement of the sound intensity in a larger bandwidth without using any spacers and additional microphone adapters like in commercial sound intensity probes. [Work supported by National Institutes of Health (NIH) and the Catalyst Foundation.]