Design of Reconfigurable Digital Filter Bank for Hearing Aid

A hearing aid is an electroacoustic device for improving the hearing ability of hearing impaired. It should be designed such that it is able to adjust the magnitude response of arbitrary input frequencies, have low power consumption for reasonable battery life, output should be provided with a low delay and the overall structure should be small in size. In a simple hearing aid gain is applied to the whole input frequency range, due to which the intensities of some speech sounds after amplification will be larger than the discomfort thresholds. To solve this problem a highly reconfigurable non-uniform digital FIR filter bank structure is proposed, where the whole frequency range is divided into several subbands and each sub band has its own amplification coefficient. The non-uniform spaced sub bands can be realized with variable bandwidth filters. Each VBF can be realized as a combination of arbitrary sample rate converters and FIR filter. The sample rate converters will be implemented using cascaded integrator comb (CIC) filters. The proposed FIR filters will be implemented using distributed arithmetic. This structure will be multiplier less to reduce the resources, thereby allowing for low power consumption. The performance is evaluated using MATLAB.