ABSTRACT
Two themes frequently recur in studies of the resolution of individual components of complex sounds. Watson and Kelly (1981) have described the detrimental effects of stimulus uncertainty in the discrimination of tonal sequences. The amount of information a listener has regarding the acoustic characteristics of a sound becomes crucially important as the sound becomes more complex, and as more central processing mechanisms are involved (Watson and Foyle, 1985). Further, the magnitude of the effects of a lack of knowledge about an auditory stimulus is highly idiosyncratic across listeners. Both stimulus uncertainty effects and the large individual differences in precision of resolution of complex sounds are influenced by the distribution of auditory attention. If a listener’s attention is narrowly focussed at the temporal or spectral location of a target portion of a tonal sequence, changes in that part of the sound may be detected quite precisely. Alternatively, if attention is spread throughout the sound, or is focussed inappropriately, even quite large changes in target portions may go unnoticed. Design of the stimulus or of certain aspects of the experimental situation which directs attention to a target embedded in an acoustic surround permits the listener to ignore irrelevant, contextual information and listen specifically for the component carrying the information. The result of such focussed attention is usually improved psychoacoustic performance on tasks such as detection of low intensity components of the sound or discrimination of changes in a component along various acoustic dimensions. This paper will review some experimental methods which overcome the effects of stimulus uncertainty by directing auditory attention to selected portions of complex sounds. The value of these manipulations in improving psychoacoustic performance is partially determined by the experimental task and by individual listeners’ abilities to make use of attentional cues.
