On the human ability to auditorily perceive human speaker's facing angle

Abstract

This paper summarizes an empirical study exploring whether or not human listeners can tell the facing direction of a human speaker solely by the auditory sense, and if so, how accurately they are able to do it. The purpose is to find the sound information necessary for ultimately realistic and human-centered telecommunications. The study consists of two parts: listeners' performance and acoustic analysis. The first part describes the methodologies of assessing human perception and the results obtained. The second part provides the candidates of sound information that convey speaker's facing angles. Twelve blindfolded listeners were tested on their ability to sense the facing angle of a male who spoke a sentence in an anechoic chamber. The listeners were able to indicate the speaker's facing angles with a reasonably high confidence. The average response errors were 23.5 degrees for horizontal angles and 12.9 degrees for vertical angles. To estimate acoustic cues that the listeners exploited, the acoustic transfer characteristics from the speaker's mouth to the listener's ears were measured for all the facing angles tested. The results suggested that the overall level and spectral tilt were used for the listeners' judgment along the frontback axis, and the level difference between left and right ears was used for the judgment along the left-right axis.

Effect of Masker Head Orientation, Listener Age, and Extended High-Frequency Sensitivity on Speech Recognition in Spatially Separated Speech

“…It is well known that EHF content provides cues to elevation and front/back location for both speech (Best et al 2005; Monson et al 2014) and environmental sounds (Heffner & Heffner 2008). Human listeners can also judge orientation of a talker or a loudspeaker presenting speech based entirely on acoustic properties of sound (Kato et al 2010; Imbery et al 2019), with the greatest sensitivity around 0° (i.e., with the sound source facing the listener). The just noticeable difference in head orientation relative to 0° is better for full bandwidth stimuli than for stimuli that have been low-pass filtered at 8 kHz (Monson et al 2019).…”

On the effect of the acoustic environment on the accuracy of perception of speaker orientation from auditory cues alone

“…Kato and colleagues later took the potential relevance for realistic human-to-human telecommunication as their main motivation to perform similar studies. [5] and [6] both report on a study where a male speaker poised on a pivot chair in an anechoic chamber speak utterances at different horizontal and vertical angles. We focus on the horizontal angles here.…”