Shifts in Air-Conduction Thresholds Produced by Pulsed and Continuous Contralateral Masking

Abstract

Auditory threshold shifts for either constant or pulsed pure tones were observed while a steady or pulsed narrow band of white noise was delivered to the contralateral ear. A narrow-band masker, centered around 4000 cps, was presented at intensity levels of 50, 70, and 80 db [decibels] while thresholds were obtained from the test ear at 4000, 1000, and 250 cps. Larger threshold shifts occurred when the test signal and the masker were pulsed simultaneously than when the masker was continuous. A continuous masker was as effective as the pulsed masker if the test tone was also continuous. More contralateral masking was found when the test tone and masker were close in frequency. A small increase in the average threshold shift occurred as the intensity level of the masker increased. Several interpretations are offered in explanation of the threshold shifts for the continuous- and pulsed-pulsed conditions.