(in English) |
The ability to auditorily perceive the facing direction of a human speaker was assessed. A male speaker sat on a pivot chair in an anechoic chamber and spoke a short sentence (3.9 s to 6.0 s long) while facing one of eight azimuthal angles (0° (listener's direction), 45°, 90°, 135°, 180°, -135°, -90°, or -45°) or one of three elevation directions (0° (level), 45° (up), or -45° (down)). The azimuthal angle was set solely by turning the pivot chair. Twelve blindfolded listeners heard the spoken sentence at a distance of either 1.2 or 2.4 m from the speaker and were asked to indicate the speaker's facing angle. In separate sessions, the speaker changed angles while speaking and the listeners indicated the perceived direction of horizontal rotation (clockwise or counter-clockwise) or vertical rotation (upward or downward). The overall results showed that the listeners' average response errors were 23.5° for azimuth and 12.9° for elevation. The average correct-response rates for rotation direction (either horizontal or vertical) were equal to or more than 80%. Effective acoustic cues were then discussed on the basis of the transfer characteristics from the speaker's mouth to the listener's ears measured by the cross-spectral method using the speaker's own voice. The results finally suggested that potentially effective cues included but were not limited to the overall level, spectral tilt (for the front-back or up-down judgment), and interaural level difference (for the left-right judgment). |