Optimizing the Comb Filters for Spectral Splitting of Speech to Reduce the Effect of Spectral Masking

Sensorineural hearing impairment is associated with widening of auditory filters, resulting in poor frequency selectivity with an increased susceptibility to masking. Earlier studies have shown that binaural dichotic presentation, using critical bandwidth based spectral splitting with perceptually balanced comb filters, helps in reducing the effect of spectral masking for persons with moderate bilateral sensorineural hearing impairment In spectral splitting, the speech signal is filtered using a pair of linear phase FIR comb filters with complementary magnitude responses for binaural dichotic presentation. The objective of the present study is to optimize the comb filters with respect to the number of bands and bandwidth. Three different pairs of comb filters are investigated: constant bandwidth filters, critical band based filters, and 1/3 octave bandwidth filters. Evaluation of spectral splitting schemes, using these filters, through listening tests, indicate that 1/3 octave band and critical band based filters are superior to constant bandwidth filters.