Minimum Phase Filter Bank with reduced delay and bandwidth extension flexibility for Audiogram matching in Digital Hearing Aids

Digital Hearing aid design requires a set of filters that gives reasonable audiogram matching for a specific case of hearing loss. Many a fixed and reconfigurable filter banks are reported for different types of sound wave decomposition plans. But the delay and hardware complexity of these structures are relatively large for a compact hearing aid system. In this paper, a minimum phase constrained least square finite impulse response filter bank with reduced group delay and low hardware complexity is proposed. Minimum phase FIR filter shows least passband group delay in the group of stable filters with the same magnitude response characteristics and the coefficients required for filter is only half of that of the prototype finite impulse response filter. Low group delay greatly influence the envelope fidelity, which is a prime factor in determining the intelligibility of speech. Multiplications per sample is considerably reduced in this method and is more suitable for systems where the spectra of desired and noise signals are overlapped. Filter coefficient decimation method is used to vary the band edge frequencies of the filters to make the system dynamic to adapt the changes in audiogram pattern which can happen in future by aging of the user. Synthesis results presented supports the theoretical claims in the proposed design.