Efficient Nonuniform Digital FIR Filter Bank Based on Masking Approach for Digital Hearing Aid

Abstract

This paper presents an efficient linear phase nonuniformly spaced FIR digital filter bank (FIR-DFB) for hearing instrument. Two FIR halfband filters are employed as prototype filters to construct an eight band nonuniform digital filter bank (DFB). Interpolation method and frequency response masking (FRM) technique minimize required multipliers and additions in proposed nonuniform FIR-DFB. The performances of the filter and DFB are improved by optimizing filter coefficients and gain in each subband. The proposed FIR-DFB with stop band attenuation of 60 dB can be implemented with only ten multipliers and ten subfilters. In this paper, an effort has been made to reduce a computational cost and simulation work conducted on optimized magnitude response of proposed DFB. Good matching with audiogram response at low and high pitches and reasonable matching at midband frequencies has been achieved. Average matching error 1.38 dB is obtained in case of mild hearing loss.