[Precedence effect at horizontal and vertical plane and moving lagging signal].

The precedence effect refers to the fact that humans are able to localize sound sources in reverberant environments. In this study, sound localization was studied with dual sound source: stationary (lead) and moving (lag) for two planes: horizontal and vertical. Duration of lead and lag signals was 1s. Lead-lag delays ranged from 1-40 ms. Testing was conducted in free field, with broadband noise busts (5-18 kHz). The listeners indicated the perceived location of the lag signal. Results suggest that at delays above to 25 ms in horizontal plane and 40 ms in vertical plane subjects localized correctly the moving signal. At short delays (up to 8-10 ms), regardless of the instructions, all subjects pointed to the trajectory near the lead. The echo threshold varied dramatically across listeners. Mean echo thresholds were 7.3 ms in horizontal plane and 10.1 ms in vertical plane. Statistically significant differences were not observed for two planes [F(1, 5) = 5.52; p = 0.07].

[Buildup of echo suppression for the high frequency signal].

The buildup of echo suppression for noise bursts in the band of 5-18 kHz was studied. Durations of the bursts were 5, 10, 20 and 100 ms. Test stimulus were preceded by a train of stimuli. The stimulus was a noise burst pair, in which the lead burst was presented from either the left (+45 deg) or right (-45 deg) side, and the lag burst was presented from the opposite side. The train consisted of 10 stimuli. The echo delays were 1, 2, 4, 8, 16, 32, 64 and 125ms. The echo threshold was measured as the minimum echo delay at which subjects reported hearing one sound rather than two sounds. The average echo thresholds were significantly elevated for all durations of bursts for buildup condition. However, despite the fact that the average threshold was slightly higher in case of the right-side lead signal presentation than that in case of its left-side presentation, there was no significant difference for the signals of 5, 10, 20, and 100 ms in duration (p > 0.05).

[Echo thresholds of the precedence effect in the vertical plane].

Echo thresholds were measured for two configurations of loudspeakers in the vertical plane. The first configuration was characterized by the lead sound presentation from a loudspeaker placed in front of a subject, whereas the lag sound was presented from the loudspeaker above the subject's head. In the second configuration, the lead and lag sounds were presented from the same loudspeakers but in reverse order. All the stimuli were broadband noise bursts in the frequency range of 5-20 kHz. Burst durations were 5, 10, 20, and 100 ms. Average echo thresholds differences were significant only for the signals of 100 ms in duration (F (1, 16) = 6.28; p < 0.05). For the other signals (5, 10, 20 ms), there was no significant effect of location of lead and lag signals (p > 0.05).

[The effect of auditory image moving in vertical plane upon posture responses of humans].

The influence of sound image motion on postural reactions was studied. The movement of sound source was created by successive switching of the loudspeakers situated over the arc in sagittal plane. Movement duration of sound stimulus was 1.6 s, 3.2 s and 4.8 s. The mean sway magnitudes decreased when the stimuli duration was 1.6 s and 3.2 s. Averaging of the wave-forms of center-of-pressure sway for signal with 4.8 s duration revealed that the sound image presentation induces body displacement in the direction opposite to that of sound image.

[Characteristics of sound source movement perception as a basis for acoustic vertical construction]. / Kharakteristiki vospiiatiia dvizheniia istochnika zvuka kak osnova sozdaniia akusticheskoi vertikali.

The subject of inquiry was perception of moving sound along the vertical at various angular velocities. The sound was switched around by 13 sequential dynamics installed on a 180 degrees arc. Threshold values for discriminating angular velocities at 150, 167, 188, 214, 250, 300, 375, and 500 degrees/s were measured with the minimal borderlines method. Six test-subjects with normal hearing participated in the experiment. Acceleration of sound movement in the range from 167 up to 500 degrees/s leads to essentially linear increases in absolute threshold values and monotonous increases in relative threshold values.