Hat-type hearing aid system with flexible sound directivity pattern

For speech communication, it is useful to emphasise the sound coming from a target direction. A large-scale microphone array enables a flexible design of the directivity pattern. However, it is difficult to implement a large- sale microphone array onto an ear-type hearing aid system. In this paper, we propose a hat-type hearing aid system composed of 48 MEMS microphones that can increase the flexibility of the sound directivity pattern. We found that it is possible to reduce the number of microphones to be used by considering the hat effect, without affecting the system performance. By compensating the time delays and reducing the number of microphones based on impulse response measurements, the directivity range of the sound directivity pattern was improved by 5 dB. In addition, we conducted a qualitative evaluation that resulted in an intelligibility improvement when using our hearing aid system.