William P. Butler

Development of novel biologically inspired directional microphones

The development of novel directional microphones for hearing aids is described. The mechanisms underlying the design of these unusual microphones were inspired by our earlier study of the ears of the parasitoid fly Ormia ochracea [Miles, et al., J. Acoust. Soc. Am. 98, 3059–3070 (1995)]. The structure of Ormia’s ears inspired new approaches to the design of directional microphones that have the potential to be more sensitive and have lower thermal noise than typical miniature microphones. The mechanisms for directional hearing in this animal are discussed along with the engineering design concepts that they have inspired. Microphones have been fabricated out of silicon that employ either capacitive sensing or optical sensing to convert the diaphragm motion into an electronic signal. Measured results indicate that the directivity of these microphones is very similar to that of an ideal first‐order differential microphone. In addition, novel microphone diaphragms have been fabricated that posses a second‐or...