On 12/07/2015 02:31 PM, Peter Lennox wrote:
But see: Localization dominance in the median-sagittal plane: Effect of stimulus duration Roberto M. Dizon and Ruth Y. Litovsky Received 19 June 2003; accepted for publication 22 March 2004
interesting! i wonder:
Lead-lag pairs of noise bursts were presented from locations spaced in 15° increments in the frontal, median-sagittal plane, with a 2-ms delay in their onsets, for source durations of 1, 10, 25, and 50-ms.
does this mean they used the same noise source, where one channel was actually delayed, or the same noise source and one channel was just faded up later ("onset delay" could be read this way), or different noise sources altogether?
in order to investigate "phantom source" mechanisms, it should be the same noise source, delayed, which is likely what they did, but i can't check this paper unfortunately.
Intermixed with these trials were single-speaker trials, in which lead and lag were summed and presented from one speaker.
Listeners identified the speaker that was nearest to the perceived source location.
so this is a simple "either/or" decision, not a continuum of possible phantom source locations. or put differently: not summing localisation, but something like a precendence effect. ok.
i could hypothesize that the initial phase of 2ms from one speaker only is enough information to localize the source, and that the lagging signal is not contributing any more cues. if so, that would not really contradict lee et al.
they go on to say
With single-speaker stimuli, localization improves as signal duration is increased.
the single speaker case is not relevant to the discussion really (although it's a nice touch to add this to the experiment). it just means that if get more time to pinpoint a single source, localisation performance improves. very well.
but this could be read as implying "in two speaker stimuli, there was _no_ improvement of localisation as the signal duration is increased". which seems to suggest that indeed, the localisation process is over and done with during the initial 2ms of only a single speaker playing.
to test this, one would need to use a coherent signal in both speakers that starts at the same time, but one is delayed relative to the other. maybe by delaying a noise source and fading it in at the same time in both speakers. otherwise, we're really only looking at onset transients.
> Furthermore,
evidence of elevation compression was found with a dependence on duration. With lead-lag pairs, localization dominance occurs in the median plane, and becomes more robust with increased signal duration.
this general statement would contradict my interpretation above. is this paper available somewhere?
this one however leaves me scratching my head:
These results suggest that accurate localization of a co-located lead-lag pair is necessary for localization dominance to occur when the lag is spatially separated from the lead.
i can't imagine what this means. -- Jörn Nettingsmeier Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487 Meister für Veranstaltungstechnik (Bühne/Studio) Tonmeister VDT http://stackingdwarves.net _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
