Responses to speech signals in the normal and pathological peripheral auditory system.

The responses to single (/a/ and /i/) and double vowel (/a,i/) stimuli of normal guinea pig cochlear nerve fibres are compared with those from animals with a cochlear hearing loss. When the threshold losses are sufficient to exclude the higher harmonics of the /i/, the temporal representation of the second and higher formants is lost. Smaller threshold elevations allow a representation of the second formant when the vowel /i/ is presented alone. However, under double vowel stimulation wider auditory filters allow the capture of the synchrony of high characteristic frequency fibres by lower frequencies thereby losing the higher formants of the /i/ and also much of the information about its fundamental frequency.