Sound source localization by Ormia ochracea inspired low–noise piezoelectric MEMS directional microphone

Abstract

The single-tone sound source localization (SSL) by majority of fly Ormia ochracea’s ears–inspired directional microphones leaves a limited choice when an application like hearing aid (HA) demands broadband SSL. Here, a piezoelectric MEMS directional microphone using a modified mechanical model of fly’s ear has been presented with primary focus to achieve SSL in most sensitive audio bands to mitigate the constraints of traditional SSL works. In the modified model, two optimized rectangular diaphragms have been pivoted by four optimized torsional beams; while the backside of the whole structure has been etched. As a result, the SSL relative to angular rotation of the incoming sound depicts the cosine dependency as an ideal pressure–gradient sensor. At the same time, the mechanical coupling leads the magnitude difference between two diaphragms which has been accounted as SSL in frequency domain. The idea behind this work has been analytical simulated first, and with the convincing mechanical results, the designed bio–inspired directional microphone (BDM) has been fabricated using commercially available MEMSCAP based on PiezoMUMPS processes. In an anechoic chamber, the fabricated device has been excited in free-field sound, and the SSL at 1 kHz frequency, rocking frequency, bending frequency, and in-between rocking and bending frequencies has been found in full compliance with the given angle of incidence of sound. With the measured inter-aural sensitivity difference (mISD) and directionality, the developed BDM has been demonstrated as a practical SSL device, and the results have been found in a perfect match with the given angle of incidence of sound. Furthermore, to facilitate the SSL in noisy environment, the noise has been optimized in all scopes, like the geometry of the diaphragm, supportive torsional beam, and sensing. As a result, the A-weighted noise of this work has been found less than 23 dBA across the audio bands, and the equivalent-input noise (EIN) has been found to be 25.52 dB SPL at 1 kHz frequency which are the lowest ever reported by a similar device. With the developed SSL in broadband–in addition to the lowest noise–the developed device can be extended in some audio applications like an HA device.

A biologically accurate model of directional hearing in the parasitoid flyOrmia ochracea

“…O. ochracea's hearing system has repeatedly served as a source of inspiration for bio-inspired designs for directional microphones and hearing aids (22)(23)(24)(25)(26)(27)(28)35). Including the angle-dependent behavior of the expanded q2D model in future Ormia-inspired device designs may also provide significant avenues for improvement in device performance, or may expand the functionality of devices like acoustic sensors through miniaturization and tunable frequency sensitivities.…”

Mathematical Analysis and Micro-Spacing Implementation of Acoustic Sensor Based on Bio-Inspired Intermembrane Bridge Structure

“… Typical bionic structure design based on the O. ochracea ear system. ( a ) Diffractive grating structure [ 15 , 16 ]. ( b ) Circular support structure [ 9 , 10 ].…”

“…Different diaphragm designs, including rectangular [ 6 , 7 , 8 ], circular [ 9 , 10 , 11 ] ( Figure 1 b), square [ 12 ] ( Figure 1 d), perforated [ 11 , 12 , 13 ], and gimbal [ 14 ] designs, have been fabricated and tested. Readout schemes, including capacitance [ 11 ], diffraction grating [ 15 , 16 ] ( Figure 1 a), comb finger [ 7 , 17 ] ( Figure 1 e), optical fiber [ 18 ] ( Figure 1 c), and most recently piezoelectric [ 19 , 20 ], have been deployed to monitor diaphragm displacement. Scholars have carried out various designs and research work on miniature bionic acoustic localization structures based on this research work.…”

Cues for Directional Hearing in the Fly Ormia ochracea

“…Efforts to design biomimetic antenna arrays (BMAAs) have applied the principle of coupled detectors to electromagnetic signal localization (Grüner et al, 2019). Much of this work has focused on quantifying the contribution of sensor coupling to directional resolution (Akçakaya and Nehorai, 2008;Grüner et al, 2019), tuning the effective bandwidth of the system (Rahaman and Kim, 2020), extending the mechanism to more than one axis (Lisiewski et al, 2011), and optimizing noise-robustness and sensitivity in the readout of ILDs and ITDs (Miles et al, 2009). Previous work has shown that directional information is represented in the fly auditory system by amplified ITDs in the responses of auditory receptors (Mason et al, 2001).…”