Determining Temporal Fine Structure (tfs) Sensitivity in Individuals with Normal Hearing and Cochlear Hearing Loss through Frequency Discrimination of Complex Tones

Abstract

In a band pass filtered complex signal, Temporal fine structure (TFS) refers to the rapidly fluctuating variations in the waveform amplitude close to the centre frequency of the band, and "Envelope" refers to slower modulation superimposed on this fine structure which occurs at a rate equal to FO of the signal. A reduced ability to use TFS information could explain some of the perceptual problems of the hearing-impaired individuals. The ability to use TFS information can vary markedly across hearing-impaired individuals. The present study determined the extent to which individuals with normal hearing and individuals with cochlear hearing loss (minimal, mild & moderate degree) can use temporal fine structure information, by measuring the least amount of shift in the frequency (F} that can be detected in the harmonic complex tone containing only TFS information. TFS1 software developed by Moore & Sek (2009) was used in the study, with the task being to discriminate between harmonic complex tone (H) and frequency-shifted lnharmonic complex tone (I) under conditions where temporal fine structure cues were available, but envelope and spectral cues were limited or absent. Results revealed that individuals with normal hearing could perform the discrimination task using the TFS cues implying a superior sensitivity to TFS cues especially in the F0 of 100, 200 & 400 condition. On the other hand, cochlear hearing impairment leads to a reduction in the ability to analyze and utilize TFS cues to perform the discrimination task. The present study concludes that cochlear hearing loss significantly affects the sensitivity of the auditory system to TFS.