ABSTRACT
Stimulus frequency has a referent in space. When listening monaurally, the apparent location of a narrowband noise in the auditory hemifield ipsilateral to the functioning ear is governed by its frequency content, not its actual location. A spatial referent map of the different stimulus frequencies can be constructed. The pattern of the spatial map roughly is similar from one listener to the next. A seemingly related event occurs when measuring the physical acoustics of the external ear. Specifically, when recording sound pressure levels at the entrance to the ear canal for those stimuli originating in the same auditory hemifield, a pattern of maximum responses emerges. There is a place in space where, for example, a narrow noise band centered at 6.0 kHz generates a sound pressure level that is greater than it is for any other location in the hemifield. This is called the covert peak area for the 6.0-kHz centered noise. A map of a subject’s covert peak area for differently centered narrow noise bands resembles his or her spatial reference map for these stimuli. It is proposed that the spatial distribution of the covert peak areas is the acoustical basis for the spatial referents of the different stimulus frequencies. The latter serves as the primary spectral cues for both monaural and binaural localization.
