Localisation dominance for long lead-lag stimuli in background noise
Stefan Kerber and Bernhard U. Seeber


The precedence effect describes the ability of the auditory system to integrate sounds 
reaching the ear directly with their various reflections into a single sound event. The 
first arriving sound determines the perceived location of a source regardless of present 
reflections which was named "localization dominance". In the laboratory this is studied by 
playing a leading sound from one location followed by its delayed copy, the lag, from a 
different location. Only few studies examined if the effect functions in the presence of 
background noise, particularly for stimuli other than clicks. 
We studied the localization of long-duration lead-lag stimuli in the presence of diffuse 
background noise. Lead and lag were identical copies of noise played from loudspeakers at 
±30° in an anechoic chamber. The signal-to-noise ratio was varied. Subjects pointed to the 
perceived location(s) of the lead-lag pairs with a light pointer. Preliminary results show 
that the maximum delay time for which lead and lag form one image at the lead position (echo 
threshold) increases through the presence of diffuse background noise.  This is surprising 
since most models explain the precedence effect through the suppression of binaural cues in 
the lag which are made here less accessible by the noise.