The design and evaluation of a noise suppression system for custom-made digital hearing aids
Yoshiyuki Yoshizumi, Shigekiyo Fujii · The Journal of the Acoustical Society of America · 2006
A noise suppression system, which has the inbuilt feature to adapt to the local environment, for custom-made digital hearing aids has been developed. The signal process is based on spectral subtraction technology with 32 bands in the frequency domain. The signal-to-noise ratio was improved by an average of 7.5 dB in rms level. Its effectiveness was evaluated using the seven-point rating scale method for nine normal-hearing subjects and six hearing impaired subjects. Test speech is presented under three different environments, which consist of a car, a duct, and a crowded place. As a result of the assessment, the same tendency is observed between normal and hearing-impaired subjects and there were two good points that were found. First, the noise suppression system makes them more comfortable to listen to speech with the statistical significance of p=0.05. Second, the noisiness is reduced with the statistical significance of p=0.01. It should be noted that there is a scattering of the plotted data; however, statistically, the data result is quite acceptable.