Discrimination of band-limited rippled spectra of various central frequencies in cochlear implant users Free

Sound signals with wide-band rippled spectra were used for the frequency resolving power measurements in cochlear implant users. In the present study, resolution of band-limited ripple spectra of various central frequencies and speech discrimination test (Russian language) were compared. The rippled spectra had 2-oct cosine envelope with ripples equally spaced on the logarithmic scale. The central frequencies of the rippled spectra were 1, 2, or 4 kHz. Ripple resolution was measured with a three-alternative forced-choice procedure using a paradigm of discrimination of a test signal with ripple phase reversals from a reference signals with a constant-phase ripples. The average ripple discrimination thresholds were 1.9 ripples/octave (RPO) for 1 kHz; 2.3 for 2 kHz; and 2.3 for 4 kHz. The lowest correlation between ripple discrimination limits and speech discrimination results was about 0.2 at a central frequency of 4 kHz, the highest correlation was 0.6 at 1 kHz. In all the cases, the relation between the ripple spectrum resolution and speech discrimination test had positive trends. Band-limited rippled-spectrum tests allow to reveal informative frequency bands for speech discrimination in cochlear implant users. [Work supported by the Russian Science Foundation, Grant No. 16-15-10046.]