A Hearing Device With an Adaptive Noise Canceller for Noise-Robust Voice Input

摘要

This paper presents a hearing device with an adaptive noise canceller for noise-robust voice input. The hearing device has an inner-ear and an outer-ear microphone to collect ear-canal speech signal and the outer-ear environmental signal, respectively. The environmental signal drives an adaptive filter to generate a noise replica which is subtracted from the inner-ear microphone signal to cancel the noise. Coefficients of the adaptive filter are updated by an NLMS (normalized least mean square) algorithm with an SNR-controlled stepsize for small speech distortion. The adaptive noise canceller is realized on a digital signal processor chip with 39 McPS (million cycles per second) for 64 taps. Evaluation results in speech recognition show that a word recognition rate of 89 & x0025; is achieved when the noise level is 80 dBA with 38 & x0025; improvement over the inner-ear signal without adaptive noise cancellation. DSP (digital signal processor) implementation details and two prototype devices demonstrate high feasibility.