Localizing the end position of a circular moving sound source near masked threshold

Abstract

This study investigates the influence of motion of a sound source on localization performance in the presence of a binaurally correlated noise masker in the free field. For moving sources, the interaural differences in time and level are time varying which might influence localization performance. Four subjects localized the static position and the trajectory?s end position of a 500 Hz sine tone, both with a constant duration of 300 ms, in the presence of an octave-band noise from the front. All tones were presented 5 dB above the masking threshold obtained at the end position of the moving trajectory. The simulated velocities ranged from m 0°/s to 200°/s. Static stimuli where positioned at azimuthal angles from 0° to 60°. Both types of stimuli were simulated with 17th order Ambisonics and played on 36 horizontally arranged loudspeakers in an anechoic chamber. Without the noise masker, localization bias is small and about 3.5� for the moving and 2� for the static sine tones. If a noise masker at 0° is presented with the target sine tone slightly above masking threshold, the overall localization error increases for both static and moving signals. For more lateral positions, caused by higher velocities, the localized direction seems to saturate around 35� for stimuli moving faster than 100°/s. This results in an increasing underestimation of the laterality of the tone?s end position for increasing velocities. The tendency for underestimating the most lateral position of the sound source is more pronounced for moving sound sources than for static ones. The results indicate a sluggish integration of sound source location in the auditory system in presence of a noise masker.