Digital Microphone Array Implementation for Hearing Aids Performance Improvement in a Noisy Environment
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Traditional hearing aids do not work well in a noisy environment. In a cocktail party scenario, we receive sound from difference sources. In this case, hearing aids amplify noise and signal at the same time. As a result, the performance of hearing aids is reduced in a noisy environment. Beamforming algorithms have been applied to amplify sound from a specific direction. However, the effect of this class of algorithms is limited because the beamforming algorithms require multiple microphones. Recent performance improvements of digital micro-electrical-mechanical system (MEMS) microphones in noise level, power consumption, and form factor make them appropriate for use in hearing aids combined with the algorithms using multiple microphones. High power noise rejection ratio of MEMS microphones eliminates the needs for additional voltage regulating circuitry. In addition, digital MEMS microphones implement the mandatory analog to digital converting circuitry within the microphone. As a result, digital MEMS microphones allow the hearing aids to incorporate more microphones within a limited area. This paper presents digital MEMS microphone array implementation for hearing aids performance improvement in a noisy environment. The microphone array system is designed using Altium Designer 10 and fabricated using 2 layer printed circuit board (PCB). This array system has four digital MEMS microphones (ADMP621 from Invensense) that are 8 cm apart. The microphones are organized as a linear array. This system also has an on board power management unit to convert input voltage to 3.3V, USB B mini power input of 5V, and internal clock of frequency 3.072MHz and duty cycle of 50%. The board needs to be powered using 6.3V to 10V voltage source or exact 3.3V voltage source. This board also has one external clock input or internal clock output SMA ports, four digital data SMA output ports for each microphone, and two digital data SMA output ports for stereo output of four microphones.
Zhang, Zhenxuan (2014). Digital Microphone Array Implementation for Hearing Aids Performance Improvement in a Noisy Environment. Undergraduate Research Scholars Program. Available electronically from