Arrangement of array microphones for hearing-aids based on delay-weight-sum beamforming methods

This report describes a delay-weight-sum beamforming method especially applied to hearing-aids with microphone arrays. There are many design parameters such as an aperture size, the number of microphones, and a microphone arrangement which can affect the performance of the hearing-aid. However, in this paper, the aperture size and the number of microphones were simply set to 10 cm and less than four microphones for the frequency range of between 300 Hz and 3000 Hz considering the practicality. The microphone arrangement was determined to maximize the directivity of the hearing aid so that the sound from the front would be amplified while the sound from the backward directions should be reduced. Simulations are performed using spherical head-related transfer function (HRTF) and the proper microphone arrangement is found. The performance of the proposed hearing aid achieves 34.6 dB mean reduction in frequency range of 300~3000Hz for back side sound sources compared to the front sound source. This performance is much larger than that of delay-and-sum beamformer.