An improved method to enhance high-frequency speech intelligibility in noise

To improve high-frequency speech intelligibility, an improved frequency compression method for high-frequency hearing-impaired patients was evaluated compared to conventional frequency compression scheme and their own hearing aids. The first step in this method was to decompose speech frame for three groups of parameters of the sinusoidal speech model: amplitudes, frequencies, and phases. Frequencies above a pre-calculated cut-off frequency (CF) were compressed and shifted to a lower frequency range to improve high-frequency intelligibility. Different from general methods, the frequency compression ratio was set according to speech intelligibility percentage in different frequency ranges. To avoid spectral distortions in the sounds, the frequency spectrum was split into six bands according to octaves. In addition, phases of compressed frequencies were randomly set to improve the envelope of the compressed signal. In subjective evaluation for Chinese speech identification, six experienced hearing aid users with a severe to profound sensorineural hearing loss were tested. After 6 weeks of training and testing, results showed the mean speech identification was improved at least 7% points in comparison with conventional frequency compression scheme.