Speech intelligibility improvement of cochlear implant using release of masking

The purpose of this paper is to propose a simple technique to increase speech intelligibility for cochlear implant user to perceive speech with a competing background noise (masker). In the first experiment we processed the target speech with more channels of a voice coder (vocoder) than those of the masker speech. The performance on recognizing conversational speech with fluctuating masker was improved. The results suggest that the cochlear implant user may have access to the salient acoustical cues due to release of masking. In the second experiment, we used several well-known signal enhancement techniques on the same stimuli. For 20 channels of the target and 8 channels on the masker, the results showed that the Boll's spectral subtraction outperforms the other enhancement techniques on segmental SNR (segSNR) 8.9 dB. We also conducted subjective listening test with mean opinion score (MOS) of 3.2/5.0 from 30 normal hearing participants. This improvement may due to the lower frequencies were enhanced while eliminating the higher frequencies.