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Delay-and-sum beamforming for a hearing-aid technique
A novel hearing-aid which attaches microphone arrays to temple bows of eye-glasses or a headphone body was proposed to solve the problem of existing hearing-aids. Existing hearing aids are basically worn in ears, which has restrictions of an aperture s ize and the number of microphones. When microphone arrays are attached to glasses or a headphone, an aperture size of microphone array can be longer. To boost the frontal sound using microphone array, delay-and-sum beamforming method is adopted since it is the most popular and the simplest method to use. Three design parameters, an aperture size, the number of microphones, and a microphone arrangement of microphone arrays, were chosen to develop the proposed hearing-aid. An aperture size and the number of microphones were simply set to 10 cm microphone array with four microphones for the frequency range of between 300 Hz and 3000 Hz. To decide the optimal microphone arrangement, index of the efficiency of hearing-aids was determined by front-back difference. With this index, simulations are performed using spherical head-related transfer function(HRTF) and the best microphone arrangement is found. Using finalized design parameters, the final design of the hearing aid achieves the best performance when delay-and-sum beamforming method is used to boost the signal.

In this webpage, you can download a source code to calculate spherical HRTF and find proper arrangement of microphones for using this technique.

Source Code