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

Abstract

In the present investigations, 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 via an insert receiver. The narrow-band masker, centered around 4000 cps, was presented at intensity levels of 50, 70, and 90 dB SPL while thresholds were obtained from the test ear at 4000, 1000, and 250 cps. The results demonstrate, first, that larger threshold shifts occur when the test signal and the masker are pulsed simultaneously than when the masker is continuous; second, that a continuous masker may be as effective as the pulsed masker if the test tone is also continuous; third, that more contralateral masking is found when the test tone and masker are close in frequency; and, last, that a small increase in the average threshold shift occurs as the intensity level of the masker increases. Several interpretations are offered in explanation of the threshold shifts for the continuous continuous and pulsed pulsed (simultaneous) conditions.