The Effect of Objective Room Acoustic Parameters on Auditory Steady-State Responses

Verification that Hearing Aids (HA) have been fitted correctly in pre-lingual infants and hard-to-test adults is an important emerging application in technical audiology. These test subjects are unable to undergo reliable behavioral testing, so an objective method is required. Auditory steady-state responses (ASSR), recorded in a sound field is a promising technology to verify the hearing aid fitting. The test involves the presentation of the auditory stimuli via a loudspeaker, unlike the usual procedure of delivering via insert earphones. Room reverberation clearly may significantly affect the features of the stimulus important for eliciting a strong electrophysiological response, and thus complicate its detection. This study investigates the effect of different room acoustic conditions on recorded ASSRs via an auralisation approach using insert earphones. Fifteen normal-hearing listeners were tested using narrow-band (NB) CE-Chirps centered at the octave-bands of 0.5, 1.0, 2.0 and 4.0 kHz. These stimuli were convolved with impulse responses of three rooms simulated using a Green’s function approach to recreate different sound-field conditions. Comparisons with the unmodified stimuli recordings (reference condition) quantified that room acoustics significantly affects the amplitudes of the ASSRs.