Observer weighting of interaural delays in source and echo clicks

Abstract

A correlational analysis was used to assess the relative weight given to the interaural differences of time (IDTs) of source and echo clicks for echo delays ranging from 1-256 ms. In three different experimental conditions, listeners were instructed to discriminate the IDT of the source, the IDT of the echo, or the difference between the IDTs of the source and echo. The IDT of the target click was chosen randomly and independently from trial-to-trial from a Gaussian distribution (mu = 0 microsecond, sigma = 100 microseconds). The IDT of the nontarget click was either fixed at 0 microsecond or varied in the same manner as the IDT of the target. The data show that for echo delays of 8 ms or less, greater weight was given to the IDT of the source than to that of the echo in all experimental conditions. For echo delays from 16-64 ms, the IDT of the echo was weighted slightly more than that of the source and the weights accounted for a greater proportion of the responses when the echo was the target, indicating that the binaural information in the echo was dominant over the binaural information in the source. The data suggested the possibility that for echo delays from 8-32 ms, listeners were unable to resolve the temporal order of the source and echo IDTs. Listeners were able to weight the binaural information in the source and echo appropriately for a given task only when the echo delay was 128 ms or greater.

A recency effect in sound localization?

“…Consistent with previous and subsequent reports, the TWFs indicated strong onset dominance ͑in the form of increased weight on click 1͒ for click rates at or above 200 Hz ͑interclick intervals ͓ICIs͔ Ͻ =5 ms͒. This finding was similar for trains of 2 or 16 clicks and agreed closely with TWFs measured in previous studies of stimuli varying only in ITD ͑Shinn- Cunningham et al, 1993Cunningham et al, , 1995Saberi, 1996;Dizon et al, 1998;Stellmack et al, 1999͒. Different from those prior studies was the additional finding that late portions of the stimulus ͑clicks at or near the offset͒ were weighted more strongly than intermediate portionsalthough a similar result was recently reported for virtualspace localization in the vertical plane ͑Macpherson and Wagner, 2008͒. This upweighting of late-arriving sound is intriguing because it suggests that the temporal integration of auditory spatial information could be sensitive to the nature of that information, the behavioral requirements of the experimental task, or both.…”

The effect of an additional reflection in a precedence effect experiment

“…As the delay is increased, changes in the directional information of the lag become easier to discriminate. In fact, for long delays (greater than 10 ms for clicks), the directional information in the lag may be easier than the lead to discriminate (Stellmack et al, 1999) or localize (Litovsky and Godar, 2010). In these cases, Stellmack and colleagues postulated that listeners became confused about which source to report the location of, and thus often responded to the location of the most recently occurring source.…”

“…In these cases, Stellmack and colleagues postulated that listeners became confused about which source to report the location of, and thus often responded to the location of the most recently occurring source. This effect has been called "temporal-order confusion" (Stellmack et al, 1999;Litovsky and Godar, 2010).…”

“…The various phenomena of the "precedence effect" indicate that the auditory system weights the localization information in direct sound or first wavefront more heavily than that in the later arriving reflections (see Blauert, 1997;Litovsky et al, 1999 for reviews). The perceived locations of the sources change depending on the delay between the direct sound (also called the lead) and reflection (also called the lag) (Wallach et al, 1949;Zurek, 1980;Gaskell, 1983;Yost and Soderquist, 1984;Saberi and Perrott, 1990;Shinn-Cunningham et al, 1993;Tollin and Henning, 1998;Stellmack et al, 1999;Litovsky and Shinn-Cunningham, 2001). When the lead-lag delay is very short (less than 1 ms), listeners perceive a single fused sound at a location somewhere between the actual locations of the lead and lag, referred to as "summing localization" (Warncke, 1941;Blauert, 1997).…”

Psychophysical Investigation of an Auditory Spatial Illusion in Cats: The Precedence Effect

“…To do so, we took advantage of previous reports showing that, although 2 sounds can be heard near their locations, it can be difficult to accurately determine which one was actually the lead and which was the lag (Stellmack et al 1999). Here we assigned the echo threshold as the ISD at which the lagging stimulus location could be determined by the cats (e.g., Blauert 1997).…”