Influence of the Location of Moving and Stationary Lags on Their Suppression

Abstract

The precedence effect is a phenomenon characterizing the noise stability of the auditory system in localizing a sound source. This phenomenon is based on the ability of the auditory system to localize a direct sound in an environment of masking acoustic reflections coming from various surfaces. To create the precedence effect, we used two signals: the first was a direct signal (the lead) and the second one arriving at a delay relative to the onset of the lead was an echo signal (the lag). The signals were presented in the horizontal plane. Their duration was 1 s. Delays between the onset of the lag and that of the lead ranged from 1 to 40 ms. The suppression of the moving lag was compared in the study with that of the stationary lag. The movement of the lag was created along two paths located to the left from the subject’s head midline in the horizontal plane (–86°...–52° and –52°...–18°). The stationary lag was located at the ends of these two paths. The lag movement was simulated in opposite directions (either approaching or distancing from the lead signal). The lead was always stationary and located to the right from the head midline in the horizontal plane (15°). The lag suppression was estimated by echo suppression threshold values. It has been shown for the stationary lag that the nearer the lag was located to the lead the higher the lag was suppressed and the mean echo suppression threshold values increased from 5.1 to 7.1 ms. The location and the direction of movement of a travelling lag did not affect its suppression. The mean threshold values ranged from 6.2 to 6.9 ms. Individual differences between the threshold values were greater with moving signals than with stationary ones.