A Zone-of-Quiet Based Approach to Integrated Active Noise Control and Noise Reduction for Speech Enhancement in Hearing Aids

This paper focuses on speech enhancement in hearing aids and presents an integrated approach to active noise control and noise reduction which is based on an optimization over a zone-of-quiet generated by the active noise control. A basic integrated active noise control and noise reduction scheme has been introduced previously to tackle secondary path effects and effects of noise leakage through an open fitting. This scheme however, only takes the sound pressure at the ear canal microphone into account. For an integrated active noise control and noise reduction scheme to be efficient, it is desired to achieve active noise control at the eardrum which in practice is away from the ear canal microphone. In some cases, it can also be desired to achieve noise control over a zone not limited to a single point. Two different schemes are presented. The first scheme is based on a mean squared error criterion expressed at a remote point (RP) away from the ear canal microphone and the second scheme is based on an average mean squared error criterion over a desired zone-of-quiet. They are both compared experimentally with the original scheme for both active noise control and integrated active noise control and noise reduction, respectively. The remote-point approach then allows to restore the performance of the original scheme at the desired remote point while the zone-of-quiet approach allows to increase performance up to 3 dB on the desired zone-of-quiet.