Dichotic Presentation with Inter-aural Switching for Reducing the Effect of Temporal Masking Due to Sensorineural Hearing Loss

Synopsis Sensorineural hearing loss, is associated with increased forward and backward masking of weak acoustic sub-segments by strong ones, thereby degrading the reception of important cues for identification of consonants. Employment of inter-aural switching, by splitting the speech temporally and presenting alternate segments to the two ears may help in reducing the effect of temporal masking. A symmetrical inter-aural switching period of 20 ms was used for temporal splitting of the speech signals. Effect of different types of fading functions and overlap (duty cycle greater than 50%) in reducing the perception of temporal gaps due to switching and in improving speech intelligibility was studied. Test stimuli consisted of twelve English nonsense syllables in vowel-consonant-vowel context with vowel /a/. Four duty cycles of 100%, 75%, 70%, and 60% were used along with step transition for switching. Listening tests were conducted on three normal hearing subjects, with sensorineural loss simulated by adding broadband noise to the speech signal at different signal-to-noise ratios (∞, 6, 3, 0, and -3 dB). Test results are analyzed by comparing the recognition scores for unprocessed and processed speech, and also the relative transmission of information for consonantal features. It has been observed that, the inter-aural switching with 70% duty cycle, for dichotic presentation helps in improving the speech perception.