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Workshop on the Auditory Basis of Speech PerceptionKeele University, UK |
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Workshop on the Auditory Basis of Speech PerceptionKeele University, UK |
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Cochlear hearing impairment is associated with reduced frequency selectivity and with loudness recruitment. This paper describes a series of studies that assess the importance of these factors for speech intelligibility by simulation of their effects, either singly or in combination. The effects of reduced frequency selectivity are simulated by spectral smearing, using the overlap-add method. The smearing has adverse effects on speech intelligibility especially at adverse speech-to-background ratios. The effects of loudness recruitment combined with threshold elevation are simulated using fast-acting expansion applied independently in thirteen frequency bands. The intelligibility of speech in quiet at low levels and in noise at higher levels is adversely affected. The adverse effects in quiet and in speech-shaped noise are overcome by frequency-selective amplification applied prior to the simulation. However, the effect in a background of a single talker is not compensated by linear amplification. Recently, the combined effects of reduced frequency selectivity and loudness recruitment have been simulated in the normal ears of subjects with unilateral cochlear losses. Generally, the performance with stimuli simulating impairment in the normal ear was somewhat better than that obtained in the impaired ear. We are currently investigating the possibility that the worse performance in the impaired ear can be attributed to "dead" regions in the cochlea, where there are no functioning inner hair cells or auditory neurones.
Bibliographic reference. Moore, Brian C. J. / Baer, Thomas / Glasberg, Brian R. / Vickers, Deborah A. (1996): "Simulations of the effect of hearing impairment on speech perception", In ABSP-1996, 273-278.