Minimum audible movement angle in vertical, horizontal, and oblique planes: Effects of velocity and frequency content

Abstract

Minimum audible movement angles (MAMAs) were measured employing a pseudo-virtual method of stimulus presentation. All stimuli were digitally recorded through KEMAR’s two ears while he was positioned in an anechoic chamber with moving loudspeakers presenting sounds in one of seven planes: frontal horizontal, lateral horizontal, median sagittal, lateral vertical, or one of three different oblique planes. These recorded binaural stimuli were subsequently played through insert earphones to subjects seated in a darkened sound-insulated room. Subjects had to say on each trial whether a single moving sound moved ‘‘left’’ or ‘‘right’’ (‘‘up’’ or ‘‘down;’’ ‘‘front’’ or ‘‘back’’). With velocity held constant during a run (from 0 to 180°/s), stimulus duration was varied adaptively to track the MAMA threshold. Stimuli were Gaussian noise bursts that were either wideband, 4-kHz low-passed, or 4-kHz high-passed. Results will be discussed in terms of human sensitivity at low and high frequencies to dynamic information provided primarily by (1) changing interaural difference cues (frontal horizontal plane); (2) changing spectral cues (median vertical plane); and (3) combinations of changing interaural and spectral cues. [Work supported by NIDCD.]