The 'meaning' in noise—Evidence for bottom-up information masking of within channel modulation coding of speech

Spectro-temporal variations are a consequence of dynamic structural variations of a sounding body. The human auditory system is highly optimized for the detection, segregation and analysis of one class of such variations—speech. Here, we will examine some consequences of this optimisation in the context of complex listening involving multiple concurrent talkers. In such conversational settings, listeners rapidly shift their attention from one to another talker so foreground and background are defined dynamically by listener intent. Up-regulation of the attended-to talker is generally thought to result from endogenous, top-down attention. Here, we review a recent report indicating that substantial informational masking between concurrent talkers may result from bottom-up interactions between sources within frequency modulation channels. This indicates that temporally dynamic aspects of within-frequency channel processing plays a very important role in speech masking by the sort of “noise” most commonly enc...