Localization of narrow-band sounds in the medial sagittal plane.

Abstract

Many experiments have shown that sources in the medial sagittal plane are localized by human listeners according to spectral cues. Therefore, narrow-band sounds in different frequency ranges are perceived as originating from different vertical locations. To further elucidate the cues involved in this effect, listeners were asked to localize two kinds of sound; a sine tone and one-third-octave band of noise. Stimuli were presented, at random, from one of three sources: front, overhead, and rear. The listener’s task was to identify the source. The experimental results supported the spectral theory of localization in that, for both kinds of sound, judgments depended more upon frequency than upon actual source location. However, the results also showed that judgments were considerably more stable and consistent with the one-third-octave bands of noise than with the sine tones. It is suspected, therefore, that the spectral theory of vertical localization is true but that it is incomplete. The results are interpreted to mean either that listeners are capable of using head-related transfer-function cues on a band that is as narrow as one-third octave or else that listeners gain vertical-plane localization information from spectral fluctuations, present in the noise but not in the sine tone. [Work supported by the NIDCD, DC00181.]