THE EFFECT OF A FREE-FIELD AUDITORY TARGETS MOTION ON ITS DETECTABILITY IN THE HORIZONTAL PLANE

Masked thresholds were measured for five subjects in an anechoic chamb er. The signal (a 500-Hz tone, an 8000-Hz tone, or a broadband noise) was presented from a movable loudspeaker located in the horizontal pla ne at ear level. A continuous noise masker came from two fixed loudspe akers at +/- 14 degrees azimuth. In different threshold runs the signa l was either stationary (positioned at 0 degrees or at 15 degrees azim uth), or it moved during its on-time (at a velocity of 30 degrees/s or 90 degrees/s) through an are from -15 degrees to + 15 degrees. There was no evidence that any of the moving signals was more detectable tha n a stationary signal when threshold variation due to position changes of the stationary signal was taken into account. Likewise, there was no evidence that signal velocity affected detectability when signal du ration was taken into account. These results agree with previous repor ts obtained with simulated moving signals presented via earphones and suggest that if horizontal motion-sensitive mechanisms exist in the au ditory system, such mechanisms do not contribute to signal detectabili ty. (C) 1997 Acoustical Society of America.