Intensity discrimination determined with two paradigms in normal and hearing-impaired subjects

The literature on auditory intensity jnd's is ambiguous with respect to the relationship between the jnd's measured with gated and continuous pedestals and with respect to changes in this relationship in the presence of loudness recruitment accompanying cochlear pathology. In an attempt to clarify these issues and to lay a foundation for systematic investigations of the dependence on the jnd's on loudness functions, the jnd's for pure tones with gated- and continuous-pedestal paradigms of two groups of subjects, one with normal hearing and one with hearing loss of cochlear origin, were measured. The experiments were performed at 0.5, 2, and 6 kHz, and at a wide range of sensation levels (SLs) by means of an adaptive two-alternative, forced-choice (2IFC) procedure. The jnd's obtained with the continuous-pedestal method were smaller than those obtained with the gated-pedestal method for both groups of subjects. They also had smaller intersubject standard deviations. When jnd's of the two groups were compared on the basis of equal SLs, the group with hearing loss showed smaller jnd values than the group with normal hearing for both pedestal paradigms. When the comparisons were made on the basis of equal sound-pressure levels (SPLs), both groups showed similar values for moderate and high SPLs. At relatively low SPLs, the group with hearing loss tended to have somewhat higher values.