Abstract
Cortical auditory evoked potentials (CAEPs) are influenced by the characteristics
of the stimulus, including level and hearing aid gain. Previous studies have measured
CAEPs aided and unaided in individuals with normal hearing. There is a significant
difference between providing amplification to a person with normal hearing and a person
with hearing loss. This study investigated this difference and the effects of stimulus
signal-to-noise ratio (SNR) and audibility on the CAEP amplitude in a population with
hearing loss. Twelve normal-hearing participants and 12 participants with a hearing
loss participated in this study. Three speech sounds—/m/, /g/, and /t/—were presented
in the free field. Unaided stimuli were presented at 55, 65, and 75 dB sound pressure
level (SPL) and aided stimuli at 55 dB SPL with three different gains in steps of
10 dB. CAEPs were recorded and their amplitudes analyzed. Stimulus SNRs and audibility
were determined. No significant effect of stimulus level or hearing aid gain was found
in normal hearers. Conversely, a significant effect was found in hearing-impaired
individuals. Audibility of the signal, which in some cases is determined by the signal
level relative to threshold and in other cases by the SNR, is the dominant factor
explaining changes in CAEP amplitude. CAEPs can potentially be used to assess the
effects of hearing aid gain in hearing-impaired users.
Keywords
Cortical auditory evoked potential - hearing-impaired - normal-hearing - hearing aid
- signal-to-noise ratio - audibility