Backward and Forward Masking of Probe Tones of Different Frequencies

Abstract

Both monotic (masking and probe presented to same ear) and dichotic (masking and probe presented to opposite ears) conditions were used to investigate backward and forward masking. White noise in a 50-msec burst at 90-db SPL served as masking. Probe tones at 500, 1000, and 4000 cps with 7-msec duration preceeded or followed the masking with interspersed silent intervals ranging from 0 to 100 msec. Results showed that backward monotic masking occurred for intervals as long as 50 msec for 500 and 1000 cps and 20 msec for 4000 cps. In the dichotic condition, backward masking at 500 and 1000 cps occurred for intervals as long as 10 to 15 msec, while for 4000 cps it was observed for about 5 msec. At very brief masking intervals for the backward monotic condition, 4000 showed greater masking; however, this did not occur in the forward monotic condition nor in either of the dichotic conditions. Implications of these results are considered.