Directional Sound Sensor With Consistent Directivity and Sensitivity in the Audible Range

Abstract

Inspired by the human cochlea, we propose a directional sound sensor using a resonator array to overcome the limitations of existing directional microphones. The proposed sensor consists of multiple cantilevers that respond to different resonance frequencies and separately acquire signals to then combine them for sound sensing. The directionality of the cantilevers is bipolar (figure -of-8) because a signal proportional to the input sound's pressure gradient is generated. We adopt multimode resonance to cover the wide frequency range of 100-8,000 Hz using few resonators. A wide-bandwidth (low-quality-factor) trenched cantilever is used to obtain a flat frequency response. Bidirectional sound sensors are tapered to achieve acoustic beamforming by simple signal processing. The directional characteristics can be easily changed according to the weighted sum of the signals acquired from a pair of sensors. We demonstrate that ambient noise can be effectively suppressed through beamforming to acquire the desired signal using the proposed sensor.

Micro-Electro-Mechanical Systems Microphones: A Brief Review Emphasizing Recent Advances in Audible Spectrum Applications

“…Inspired by the human cochlea, Kang et al [ 75 ] proposed a bipolar (figure-of-8 pattern) directional sound sensor using 16 cantilevers operating under a resonant mode, as illustrated in Figure 13 . Like the previous work of Baumgartel [ 49 ], these cantilevers have respective resonance frequencies and separately acquire signals to then combine them for sound sensing and cover a frequency range of 100 Hz to 8000 Hz, and overcome directional ambiguities introduced by bipolar directionality using a Canted Angle Design [ 63 ].…”

Dual Band MEMS Directional Acoustic Sensor for Near Resonance Operation

“…Acoustic sensors that operate near resonance have been demonstrated by other groups. Kang et al [ 47 ] demonstrated an interesting sensor consisting of multiple cantilevers that resonates in multiple frequencies with separate piezoelectric readouts allowing a broad band sensing between 100 and 8000 Hz. Their individual cantilevers were trenched to provide multimode low quality factor response.…”

Design, fabrication and experimental analysis of piezoresistive bidirectional acoustic sensor

“…Further method of directional sound detection was done by sensing acoustic flow using nanofibers, which are driven by viscous forces applied by the fluctuating medium (Ahemedali and Kumar, 2016). The research work inspired by human cochlea, proposed the sensing of directional sound using a resonator array (Kang et al , 2021).…”

“…In the dynamic mode, the resonant frequency and frequency response is measured. The detection mechanism can be by different methods such as capacitive, piezoresistive, piezoelectric, optical and electron tunneling detection methods (Kang et al , 2021). The microelectromechanical systems (MEMS) vector hydrophone sensor design, having the directional focus of the merged signal, incorporating both acoustic pressure and vibration velocity used to determine the direction of arrival (DOA), operational concept and target detection mechanism of the compound vector hydrophone.…”