Perception of speaker’s facing direction: A comparison between binaural and mono recordings

“Immersive” content requires realistic auditory experiences, with attention to the directional radiation characteristics of speech production. This study investigated the role of binaural cues in perceiving a speaker's facing direction. Four types of stimuli were used: binaural recordings using dummy heads in an anechoic room and a reverberant room (RT = 1.2 s), and mono recordings in the anechoic room convolved with either a head-related impulse response (HRIR) or a binaural room impulse response (BRIR). Speech samples were recorded from nine directions on the right side of the speakers. In a listening experiment, multiple pairs of stimuli were presented to participants, with each pair consisting of front-facing speech followed by speech from one of the nine directions. Participants were asked to identify the direction of the second stimulus. For stimuli based on binaural recordings, interaural level differences were not significant, with most values below 1 dB. As a result, in anechoic conditions, no significant differences were found between binaural and mono recordings. However, under reverberant conditions with indirect sound, significant differences were observed for backward-facing directions between binaural and mono recordings. A possible explanation is that mono recordings convolved with a BRIR exhibited direction-dependent level changes in the indirect sound.