Digital filter bank for hearing aid application using FRM technique

A lot of effort has been devoted to the design of uniform and non-uniform filter banks for hearing aid applications. But in most of the cases, it never deals with large variation of hearing losses at mid frequencies. This paper presents a low complex design of a non-uniformly spaced digital finite impulse response (FIR) filter bank for digital hearing aid application. Frequency response masking (FRM) technique is used for the implementation of 8 non-uniformly spaced subband filters, with a single half-band filter as a prototype filter. With FRM technique and half-band filter, a drastic reduction in the number of multipliers and adders in linear phase FIR filter can be achieved. Further complexity-effective design can be achieved by producing masking filter from the prototype filter. FRM technique is achieved by cascading different combinations of prototype filter and its interpolated filters to produce subbands. The simulation results shows that, the proposed filter bank gives 120 dB attenuation with 13 multipliers only. The proposed FRM based filter bank can be effectively used for the audiogram matching with large variation of hearing threshold in mid frequencies.