Squeeze film damping analysis of biomimetic micromachined microphone for sound source localization

- Fly Ormia ochracea inspired perforated MEMS directional microphone is designed.
- Squeeze film damping of microphone is predicated analytically by Green's function.
- Microphone parameters are optimized in derived analytical models.
- Microphone is fabricated with PolyMUMPs process and acoustically characterized.
- The results validate the significance of critical damping in microphone response.

The trapped air between two closely oscillating MEMS devices introduces significant damping in the system. These damping effects can be modeled by designing a suitable perforation ratio in the system. Here, we design a perforated MEMS directional microphone inspired from the fly Ormia ochracea's ear anatomy. The designed microphone is circular in shape and regularly perforated with circular holes to mitigate the squeeze film damping (SFD) effects. The mathematical modeling of the fly's model demonstrates the significance of the rocking mode's critical damping in improving the cues for the directional sensitivity. To grasp the in-depth dynamics of the system damping, an analytical modeling of the SFD of both rocking and bending modes is performed by utilizing the modified Reynolds equation. The required damping formulas are extracted by using the Green's function. The derived analytical modeling results are utilized to configure the microphone parameters as to bring the damping ratio of the rocking mode in the vicinity of the critical damping. The final deduced values of the parameters are utilized to fabricate the microphone by the PolyMUMPs micromachining process. The testing of the microphone is performed in an anechoic chamber by considering a sound source having 45° incidence angle. The figured results show a substantial vibration magnitude difference and validate the significance of modeling the SFD in the dynamic response of the fly's inspired MEMS directional microphone.