Characterizing the monaural and binaural processes underlying reflection masking

Reflection masked thresholds (RMTs) for the simple scenario of a test reflection masked by the direct sound (200 ms long broadband noise) were measured as a function of reflection delay for diotic and dichotic stimulus presentations. In order to discriminate between contributions to reflection masking from simultaneous versus forward masking, the simultaneous RMT was measured in addition to the traditional RMT. Simultaneous RM was realized by truncating the offset of the test reflection such that the test reflection and the direct sound had a common offset. By comparing the experimental results for the two RMTs, it is shown that forward masking effects only have a significant effect on reflection masking for delays above 7-10 ms. Moreover, binaural mechanisms were revealed which deteriorate auditory detection of test reflections for delays below 7-10 ms and enhance detection for larger delays. The monaural and binaural processes that may underlie reflection masking are discussed in terms of auditory-modelling concepts.