Abstract
This study characterizes changes in response properties of toneburst-evoked auditory
brainstem responses (ABRs) and/or middle latency responses (MLRs) as a function of
perceived loudness and physical intensity of these stimuli and delineates the range
of levels corresponding to categorical loudness judgments for these stimuli. ABRs/MLRs
were recorded simultaneously to 500- and 2,000-Hz tonebursts in 10 normal-hearing
adults at levels corresponding to each listener's loudness judgments for four categories
on Contour Test of Loudness. Group mean ABR wave V and MLR wave Pa latency values
increased significantly as loudness judgments decreased. Group mean amplitude values
for ABR wave V-V′ and MLR wave Na-Pa increased as the listeners' categorical judgments
increased. Listeners assigned a broad range (30 to 40 dB) of stimulus intensities
when judging loudness of these stimuli within a specific loudness category. This was
true for all four loudness categories and both frequencies. Thus, it appears that
tone-evoked ABR/MLR response measures reflect, in part, the listener's perception
of loudness. Response latencies are a more sensitive indicator of listener's loudness
percept than corresponding response amplitudes. An appreciable range of signal levels
was judged to be categorically equivalent across listeners. Thus, limiting how loudness
judgments can be applied to prescriptive hearing aid fittings in individuals who cannot
provide accurate loudness judgments.
Keywords
Auditory evoked potentials - and categorical loudness judgments
