Simulating the effects of aging and hearing loss on the masking-level difference
Meyer, Ted Albert
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Permalink
https://hdl.handle.net/2142/21392
Description
Title
Simulating the effects of aging and hearing loss on the masking-level difference
Author(s)
Meyer, Ted Albert
Issue Date
1995
Doctoral Committee Chair(s)
Bilger, Robert C.
Department of Study
Speech and Hearing Science
Discipline
Speech and Hearing Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Health Sciences, Audiology
Psychology, Experimental
Language
eng
Abstract
When testing binaural hearing under headphones, the stimulus (signal and noise) delivered to the two ears can either be the same (diotic) or different (dichotic). Once any part of the stimulus is changed between the ears, the signal becomes easier to detect compared to the diotic condition. The difference in masked threshold between the diotic condition and the dichotic condition has been termed the masking-level difference (MLD) (Webster, 1951).
In general, a listener with impaired hearing has smaller MLDs than the mean MLD of a group of listeners with normal hearing. Thresholds are identical under the diotic condition, while thresholds under dichotic conditions are elevated for the listeners with impaired hearing compared to the listeners with normal hearing, thus reducing their MLDs. There is a great deal of variability in the data from listeners with hearing losses, however, and many people with various degrees and types of hearing loss demonstrate MLDs that are equal to the MLDs of listeners with normal hearing.
Many reasons have been suggested for the decreased MLD in listeners with impaired hearing including the listener's age and changes associated with aging, the type of hearing loss, the amount of hearing loss, and asymmetries between the ears. Those who model the auditory system suggest that listeners with hearing impairments have a greater amount of internal interaural variability in the information coming from the two ears than do listeners with normal hearing.
MLDs were obtained from listeners with normal hearing and listeners with impaired hearing using a number of interaural correlation conditions. The results from the two groups were quite different. Three of eight listeners with impaired hearing demonstrated smaller MLDs than did the listeners with normal hearing. Modifications were then made to the stimulus to simulate temporal jitter by increasing the amount of external variability in the stimulus through the use of attenuators and filters.
The results from the listeners with normal hearing under the modified conditions were similar to the results from the listeners with impaired hearing under normal conditions.
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