Effect of a contralateral masking stimulus on auditory response performance

HTLs at 1 kc/s were obtained from the L ear of 5 normal-hearing adults by Bekesy, Up-Down, and Ascending procedures, as a function of a contralateral narrow-band noise mask centered at 1 kc/s, at 70 db SL. Insert receivers were used in each ear. Bekesy tracing width was also examined, and in the Up-Down and Ascending procedures also response-level performance and the latency of the response decision. Masked and masking stimuli were presented simultaneously, both in either continuous or pulsed form. HTLs differed in quiet as a function of the temporal characteristics of the test tone, and in noise, as a function of the temporal presentation of the masked and masking stimuli. All Ss yielded higher threshold shift with contralateral (i.e., central) masking under the pulsed/pulsed than under the continuous/continuous presentation in the Bekesy procedure. The pulsed masking noise slightly decreased Bekesy tracing widths, while the continuous masking signal slightly increased them. Neither the temporal characteristics of the test tone, nor the presence/absence of the contralateral masking signal led to any systematic change in either the performance-level curves or the latency of the response decision. However, both the performance-level curves and the latency of the response decision were differentially affected by the experimental procedures. The Bekesy may be the procedure of choice for investigating central masking.