A low-noise bio-inspired piezoelectric MEMS directional microphone for noise monitoring

摘要

According to world health organization (WHO), about 5% people are having hearing disabilities, and one of the biggest reasons is the inter-layer unwanted noise from apartments and houses. To monitor the unwanted noise, the literature is abundant with various approaches, however, the majority of them are reported using pair or array of omnidirectional microphones, and most importantly, their cumulative internal noise is higher than human-hearing threshold, i.e., 32 dBA at audio bands or 25 dB SPL at 1 kHz frequency. Here, we present an optimized fly Ormia ochracea's ears-inspired piezoelectric MEMS directional microphone with bare minimum self-noise. The optimization was carried out in terms of sensor dimensions, sensing, and processing circuitry. Accordingly, the developed device showed 25.52 dB SPL self-noise at 1 kHz frequency. The A-weighted noise was measured relative to the angular rotation of sound under audio frequency, and found 19.91 dBA, and 21.61 dBA, respectively for 0~°, and 45~° of incidence of sound. The measured results are the lowest ever reported by a similar device in the literature. With this lowest noise-in addition to its directionality, the developed device can be extended for simultaneous noise monitoring and source localization.