Comparative evaluation of omnidirectional and directional micro-electromechanical system microphone performance

Abstract

As the need for directionality becomes a key requirement in audio applications, directional microphones have begun to enter the micro-electromechanical system (MEMS) design and market space, and their performance is approaching that of top-of-the-line omnidirectional MEMS microphones. This presentation examines and compares the performance limitations for both types of MEMS microphones and suggests more comprehensive methods of characterization that allow the qualities of directional MEMS microphones to be fully captured. Mechanical thermal noise caused by Brownian motion of air particles, measured with a laser Doppler vibrometer system, are shared and discussed for a variety of microphones and test structures. Parameters such as signal-to-noise ratio, total harmonic distortion, and frequency response are re-examined in order to capture the value of a microphone that exhibits directional behavior. Insights and suggestions are made for improvement and future work.