Stimulus dependencies of the gerbil brain-stem auditory-evoked response (BAER). II: Effects of broadband noise level and high-pass masker cutoff frequency across click polarity

Two experiments concerning the effects of masking noise on the gerbil brain-stem auditory-evoked response (BAER) are reported. Experiment 1 evaluated the effects of broadband masking noise on the BAER obtained to condensation and rarefaction clicks. With increasing noise level, there was an increase in BAER peak latencies, an increase in the i-v interval, and a decrease in peak amplitudes. Experiment 2 evaluated the effects of high-pass masking noise on the BAER obtained to condensation and rarefaction clicks. Both high-pass responses and derived-band responses were evaluated. For high-pass responses, with decreasing masker cutoff frequency, there was an increase in BAER peak latencies, a decrease in the i-v interval, and a decrease in peak amplitudes. For derived-band responses, with decreasing derived-band frequency, there was an increase in peak latencies and a decrease in the i-v interval. A comparison of wave i and wave v amplitudes across derived-band frequency demonstrates a greater contribution of high-frequency cochlear regions to wave i than wave v. Small, insignificant, effects of click polarity on BAER peak amplitudes were observed. These trends were in the direction seen in a companion paper [R. Burkard and H. F. Voigt, J. Acoust. Soc. Am. 85, 2514-2525 (1989)] and were, in general, reduced by the presence of broadband or high-pass maskers.