Frequency-specific objective audiometry: tone-evoked brainstem responses and steady-state responses to 40 Hz and 90 Hz amplitude modulated stimuli.

Tone-evoked Auditory Brainstem Responses (tone-burst ABRs) and Auditory Steady-State Responses (ASSRs) with 40 or 90 Hz amplitude modulation (AM) were compared, using the same equipment and recording parameters, to determine which of these three methods most accurately approached the behavioural hearing thresholds in response to 500 Hz and 2000 Hz stimuli in eleven awake adults with normal hearing. Estimates of the thresholds obtained with the three methods were 10, 18, and 26 dB SL at 500 Hz; and 10, 12, and 22 dB SL at 2000 Hz; using 40 Hz ASSR, 90 Hz ASSR, and tone-burst ABR, respectively. ASSRs with 40 Hz AM stimuli produced significantly better results (lowest thresholds with SD=0), whereas the wave-V analysis on the tone-burst ABR produced the poorest results. In the averaged ABRs, a robust steady-state potential was also visible. Analysis of those steady-state responses showed estimated thresholds of 13 and 14 dB SL (at 500 and 2000 Hz, respectively), thus considerably better than the estimated thresholds from the wave-V analysis. It is concluded that the 40 Hz ASSR showed superior results, especially at 500 Hz.