Design Of A DSP Based Digital Hearing Aids Developing System

The Independent R&D of digital hearing aids has great significance in audiology research of China. This paper designs and implements a DSP-based digital hearing aids developing system. The system consists of acoustic part, digitalization part and digital signal processing part. The input part of the referred acoustic part implements the acoustic-electro converter of sound pressure signal in clinical hearing test frequency-domain; the digitalization part which consist of the audio codec implements the digitizing processing of the voice signal; the system implements the control and communications of hardware, digital filtering of voice signal and hearing compensation function by using Fir Filters in the DSP environment of the referred digital signal processing part. The output part of the referred acoustic part implements the playback of the compensated voice signal with a protective measure. In software, considering the microphone and headphones amplitude-frequency response curve, as well as the patient's pure tone test gram factors, it designs the Hearing compensation curve by setting the transition zone frequency sampling value which is equal 1/2 of two adjacent frequency sampling value in frequency sampling method, and tests the algorithm with an instance of hearing loss, result shows that the system implements the hearing loss compensation with a small range of error. The system has advantages of low power consumption, and small size which is close to BTE (Behind the Ear) digital hearing aids, it can be further solidified as a special chip for the hearing aids, combined with the system software package, and it will meet the requirements of compensation for different patients with hearing loss. Therefore, this paper is helpful for the research of digital hearing aids in China.