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Frequency-specific auditory brainstem responses: Effective masking levels and relationships to behavioural thresholds in normal hearing adults.

Ipsilateral masking levels and normal thresholds for tone piip auditory brainstem responses (ABRs) were investigated in normal subjects for the purpose of establishing recording parameters and norms for frequency-specific tone pip ABR testing. White noise was found to effectively mask ABRs to tone pips at mean signal to noise ratios of between -1 and -5.5 dB [dB peak-equivalent (pe) SPL/dB SPL] depending on the tone pip frequency.

ABR thresholds were established for tone pips in the rpesence of ipsilateral masking with high pass filtered noise for 500 Hz tone pips and notched noise for tone pips from 1000 to 4000 Hz, at a nominal signal to noise ratio of -5 dB (ie with the noise SPL measured prior to filtering).

Thresholds occurred between 28.6 and 36.6 dB pe SPL, equivalent to 4.4 to 8.8 dB nHL. ABR thresholds for masked and unmasked tone pips did not differ significantly.