Contralateral Masking and the Sisi-Test in Normal Listeners

Abstract

The influence of contralateral white-noise masking on the DLI was studied in 10 normal listeners. Measurements were undertaken by means of the SISI procedure with different increment magnitudes so that psychometric functions could be determined at various levels of masking. At 4 Kc, even the lowest level (50 dB) caused a significant improvement of the DLI, and with 70 dB contralateral masking 5 subjects had positive SISI scores. At 1 Kc, the effect was less pronounced and only significant from the 70 dB noise level. At .25 Kc the changes were in opposite direction, but also statistically significant already in the 50 dB masking condition. This definite influence of contralateral stimulation on the performance of normal ears can only be explained by a neural, interaural interdependence, possibly in connection with adaptive mechanisms.