A new multi-channel loudness compensation method based on high frequency compression and shift for digital hearing aids

At the present, multi-channel compensation is used in most of digital hearing aids. But high compensation will decrease hearing comfort, even result in negative impact when attenuation is serious. In order to improve the listening recognition of hearing-impaired patients with severe loss of high-frequency hearing, this paper proposed a new method which uses frequency compression and shift techniques for multi-channel loudness compensation. This method could reduce the negative impact during conventional loudness compensation. Firstly, high frequency portion of voice signal is compressed and shifted to the target frequency band. Then, the signal is divided into four unequal size bands via Quadrature Mirror Filter Bank. According to different hearing-impaired patients, the identity of the signal on each band is compensated and controlled. At last, the processed signal is reconstructed using perfect reconstruction filter banks. By using the proposed method, the identity of the signal is enhanced obviously and the voice is restricted within earshot of the hearing-impaired listeners. The result of the actual test of Ling'6 tone shows that the recognition rate of the voiceless increases 30 percent than conventional method. The experiment and simulation indicate that the proposed method has high practical value and improves hearing level and identification of hearing-impaired listeners, especially for voice with abundant high frequency.