Frequency compression of critical band for digital hearing aids

The auditory filter of hearing impaired is wider than that of normal hearing people. Thus, the frequency selectivity decreases because of increased of masking effects. We have focused on this wider auditory filter shape and developed a method in which the critical band is compressed along the frequency axis. We also implemented a system based on the proposed algorithms using "SIMULINK. " To test our method, we conducted two experiments. The first evaluated the Mean Opinion Score (MOS) and the second was an articulation test. The quality and intelligibility of speech sounds were improved in Exp.1. In Exp.2, the articulation score was also improved when frequencies were compressed. These results show the feasibility of frequency compression algorithm for the hearing impaired people. There were many studies on the human auditory filter and the critical band (e.g., Fletcher [1] and Zwicker [2]). Patterson measured an auditory filter using notched-noise method [3]. Glasberg and Moore measured an auditory filter of hearing impaired an