Temporal processes involved in simultaneous reflection masking

Reflection masking refers to the specific masking condition where a test reflection is masked by the direct sound. Employing reflection masking techniques, Buchholz [J. Acoust. Soc. Am. 117, 2484 (2005)] provided evidence that the binaural system suppresses the test reflection for very short reflection delays and enhances the test reflection for large delays.

Employing a 200-ms-long broadband noise burst as input signal, the critical delay separating these two binaural phenomena was found to be 7–10 ms. It was suggested that the critical delay refers to a temporal window that is employed by the auditory system to analyze the considered stimulus. In the present study, the dependency of this critical delay on the duration of the input signal (i.e., broadband noise) has been investigated.

The psychoacoustical results revealed that the critical delay decreases with decreasing stimulus duration, resulting in a critical delay of about 2–3 ms for 20-ms-long stimuli. Hence, for very short stimuli the temporal window or critical delay exhibits values similar to the auditory temporal resolution as, for instance, observed in gap-detection tasks.

It is suggested that the larger critical delay observed for longer stimuli is due to the auditory system focusing on lower signal frequencies.