Inter-aural Switching with Different Fading Functions for Dichotic Presentation to Reduce the Effect of Temporal Masking in Sensorineural Hearing Loss

Sensorineural hearing loss is associated with increased temporal masking of low energy sub-segments of speech by adjacent high energy segments, resulting in increased consonant confusion. Splitting the speech into segments and presenting the alternate segments to the two ears, may help in reducing the effect of increased temporal masking in cases of moderate bilateral loss. A method of inter-aural switching with a switching frequency of 50 Hz, with step and trapezoidal “fading functions” was investigated. It has been established in our earlier work that inter-aural switching with step transition with certain overlap of segments (duty cycle of 70%) helps in improving the perceived quality, by reducing the perception of temporal gaps. Use of trapezoidal fading function during switching may help in reducing the occurrence of high frequency components and thereby further increasing the speech intelligibility. Effect of different slopes (during trapezoidal variation) in improving the speech quality was studied. Stimuli consisted of 12 English non-sense syllables in VCV context. Five normal hearing subjects with simulated hearing loss participated in the tests. Results showed that inter-aural switching with trapezoidal fading function improved the scores further, and the relative improvements were larger at higher noise levels. Thus the inter-aural switching with trapezoidal transition helps in improving the perception by reducing the effect of temporal masking.