Effects of unilateral Ménières disease on masking-level differences.

Abstract

The release from masking experienced by 12 persons with unilateral Ménière's disease was compared to that of 12 normals. A noise band, 400 Hz wide centered at 500 Hz, was presented at a spectrum level of 54-dB sound-pressure level. The masked monaural threshold for a 500-Hz tone was measured in each ear under the following conditions: SmNm, SmNu, SmN0, and SmNπ. The masked binaural threshold was likewise determined during S0N0, SπNπ, S0Nu, SπNu, SπN0, and S0Nπ conditions. Alternate binaural loudness balancing and simultaneous binaural median plane localization were also explored with the 500-Hz stimulus. The persons with Ménière's disease experienced greater absolute masking and less release from masking than did the normal hearers. They also showed a tendency for the reduction in masking-level difference (MLD) to be related to degree of loss in the affected ear. A limited interdependence between reduced MLDs and either interaural threshold disparity or interaural loudness difference emerged, but these effects are attributed to the influence which degree of loss in the poor ear has on interaural imbalances in threshold and loudness. No systematic relation was observed between size of MLD and performance on the localization task. Finally, the nature of a subject's diplacusis seemed to have a bearing on MLD size.