Noise Reduction of a Digital Hearing Aid for Continuous Speech Based on Spectral Harmonic Structure
Koichi Yanagisawa, Kyoko K. Tanaka, Itsuo Yamaura · IEEJ Transactions on Electronics Information and Systems · 2000
A noise reduction method of a hearing aid is developed for continuous speech under noisy environment. We make use of a comb filter for the noise reduction. The comb filter requires a fundamental frequency of the voice. A property of continuity in a power spectrum envelope(PSE) is applied for noise-proof fundamental frequency detection. The comb filter for continuous speech with noise often makes strange sound because the harmonic structure at higher frequency is disturbed by the noise. The disturbed frequency band is detected by using two types of PSE, and an estimated noise level is subtracted from the spectrum at this band. Accuracy of the fundamental frequency needed for the comb filter is obtained from these processing. Efficiency of noise reduction was evaluated by normal listeners, and the results showed good performance in the noise reduction. In conclusion, the present noise reduction method is useful for the hearing aid in continuous speech including strange sound suppression.