In addition to simultaneous masking two time domain
phenomena also play an important role in human auditory perception,
pre-masking and post-masking. The temporal masking effects occur
before and after a masking signal has been switched on and off,
respectively (Fig. 
). The duration when pre-masking applies is less than -or
as newer results indicate, significantly less than-one tenth that of
the post-masking, which is in the order of 50 to 200 msec. Both pre
and post-masking are being exploited in the ISO/MPEG audio coding
algorithm.
