Understanding fly-ear inspired directional microphones

In this article, the equivalent two-degree-of-freedom (2-DOF) model for the hypersensitive ear of fly Ormia ocharacea is revisited. It is found that in addition to the mechanical coupling between the ears, the key to the remarkable directional hearing ability of the fly is the proper contributions of the rocking mode and bending mode of the ear structure. This can serve as the basis for the development of fly-ear inspired directional microphones. New insights are also provided to establish the connection between the mechanics of the fly ear and the prior biological experiments, which reveals that the fly ear is a nature-designed optimal structure that might have evolved to best perform its localization task at 5 kHz. Based on this understanding, a new design of the fly-ear inspired directional microphone is presented and a corresponding normalized continuum mechanics model is derived. Parametric studies are carried out to study the influence of the identified non-dimensional parameters on the microphone performance. Directional microphones are developed to verify the understanding and concept. This study provides a theoretical guidance to develop miniature bio-inspired directional microphones, and can impact many fronts that require miniature directional microphones.