New Technologies of Directional Microphones for Hearing Aids

This paper describes new technologies of directional microphones for the practical hearing aids, referring to a front-delay direction microphone (DM), narrow beam DM, and minimum variance distortionless response (MVDR) beamformer. Each of the DM technologies was researched against weaknesses of those existing DMs, such as imperfection in low level noise, short suppression to adjacent interference, and failing to simultaneously perceive multiple target voices. In order to eliminate them, the conventional DM architectures have been innovated: the front-delay DM exchanged the elements’ positions; the narrow beam DM employed binaural DMs to composite a relatively narrow lobe; the MVDR beamformer combined two types of processing in spatial and frequency domains; and the novel technologies are state-of-the-art beamformers for hearing aids. Based on some references related to the DM technologies and operation principles of the latest beamformers, we further researched the DM technologies, first proposed the implementing architectures, derived new gain equations of the relevant polar plots, accomplished the extensive experiments, and evaluated advantages and disadvantages of the DMs by the obtained evidences; then we confirmed that the new technologies could reach their expected goals. Meanwhile, we used the latest simulating software, Simulink of MatLab R2018b and audio edition software, SoundBooth, in our Lab computers.