Response of a biologically inspired MEMS differential microphone diaphragm

Abstract

The development of a novel, biologically inspired acoustic sensor is presented. The primary goal of this effort is to construct a miniature device that is capable of detecting the orientation of an incident sound source with an accuracy of 2°. The design approach follows from our investigation of the mechanics of directional hearing in the parasitoid fly, Ormia ochracea. This animal has been shown to be able to detect changes in the line of bearing of an incident sound that are as small as 2°. The tympanal structures of the ears of this animal suggest a novel approach to designing very small directionally sensitive microphones. A microphone diaphragm design is presented that has been fabricated using silicon microfabrication technology. Measurements of the static deflection due to intrinsic stress and of the response to sound are shown to be in excellent agreement with predictions. Predicted results indicate that this microphone concept could lead to a practical differential microphone with self-noise as low as 20 dBA.