Speech enhancement in digital hearing AIDS: An active noise control approach

Digital hearing aid is one of the most widely used assistive listening device. A basic digital hearing aid consists of a microphone, a loudspeaker, a processing unit and a battery. In order to avoid occlusion effects in digital hearing AIDS, an open fitting scheme is usually followed. This leads to issues of acoustic feedback between the loudspeaker and the microphone. In addition, it reduces the effectiveness of noise reduction schemes which are implemented in digital hearing AIDS to improve speech quality. Open fitting also results in scenarios in which the ambient sound directly reaches the ear drum along with the sound produced by the hearing aid. The noise reduction capability in hearing AIDS is also affected by the secondary path, which is the path from the input of the loudspeaker to the ear drum. In order to overcome these limitations of noise reduction techniques, a reduced complexity integrated active noise cancellation approach has been introduced in this paper along with noise reduction schemes. The new scheme has been shown to effectively handle undesired leakage signals as well as the secondary path effects in comparison with traditional noise reduction schemes.