Spatial unmasking of circular moving sound sources in the free field
* Presenting author
This study investigates the contribution of interaural phase and level differences to the unmasking of a moving tonal source in noise under free-field presentation.Thresholds of static and circular moving 500 Hz sine tones presented in octave-band noise from the front were measured with seven normal hearing listeners with an adaptive forced choice method. The stimuli were generated with 17th order Ambisonics and played via 36 horizontally arranged loudspeakers in an anechoic chamber. Six velocities were tested from 10°/s to 200°/s.Spatial unmasking increased with increasing velocity up to 11 dB for 200°/s but unmasking remained lower than for static sound sources at the most lateral position reached in the movement trajectory. This is consistent with observations in the literature on binaural sluggishness. Even for a small velocity of 30°/s and therefore relatively slow changes in interaural phase, spatial unmasking decreases by 5.3 dB. This velocity is comparable to that of a walking person in 2 meters distance. It seems that in the free field, the auditory system cannot fully exploit interaural phase differences even when they are only changing slowly. This finding is important for extending binaural models to more realistic, dynamic listening situations in the free field.