Release from speech-on-speech masking by adding a delayed masker at a different location.

The amount of masking exerted by one speech sound on another can be reduced by presenting the masker twice, from two different locations in the horizontal plane, with one of the presentations delayed to simulate an acoustical reflection. Three experiments were conducted on various aspects of this phenomenon. Experiment 1 varied the number of masking talkers from one to three and the signal-to-noise (S/N) ratio from -12 to +4 dB. Evidence of masking release was found for every combination of these variables tested. For the most difficult conditions (multiple maskers and negative S/N) the amount of release was approximately 10 dB. Experiment 2 varied the timing of leading and lagging masker presentations over a broad range, to include shorter delay times where room reflections of speech are rarely noticed by listeners and longer delays where reflections can become disruptive. Substantial masking release was found for all of the shorter delay times tested, and negligible release was found at the longer delays. Finally, Experiment 3 used speech-spectrum noise as a masker and searched for possible energetic masking release as a function of the lead-lag time delay. Release of up to 4 dB was found whenever delays were 2 ms or less. No energetic masking release was found at longer delays.