1 Department of Electrical Engineering, Technical University of Denmark2 Hearing Systems, Department of Electrical Engineering, Technical University of Denmark3 Centre for Applied Hearing Research, Center, Technical University of Denmark4 unknown
One of the most common complaints of people with impaired hearing concerns their difficulty with understanding speech. Particularly in the presence of background noise, hearing-impaired people often encounter great difficulties with speech communication. In most cases, the problem persists even if reduced audibility has been compensated for by hearing aids. It has been hypothesized that part of the difficulty arises from changes in the perception of sounds that are well above hearing threshold, such as reduced frequency selectivity and deficits in the processing of temporal fine structure (TFS) at the output of the inner-ear (cochlear) filters. The purpose of this work was to investigate these aspects in detail. One chapter studies relations between frequency selectivity, TFS processing, and speech reception in listeners with normal and impaired hearing, using behavioral listening experiments. While a correlation was observed between monaural and binaural TFS-processing deficits in the hearing-impaired listeners, no relation was found between TFS processing and frequency selectivity. TFS processing was correlated with speech reception in background noise. Two following chapters investigate cochlear response time (CRT) as an important aspect of the cochlear response to incoming sounds, using objective and behavioral methods. Alterations in CRT were observed for hearing-impaired listeners. A good correspondence between objective and behavioral estimates of CRT indicated that a behavioral lateralization method may be useful for studying spatiotemporal aspects of the cochlear response in human listeners. Behaviorally estimated filter bandwidths accounted for the observed alterations of CRTs in the hearing-impaired listeners, i.e., CRT was found to be inversely related to individual filter bandwidth. Overall, this work provides insights into factors affecting auditory processing in listeners with impaired hearing and may have implications for future models of impaired auditory signal processing as well as advanced compensation strategies.