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Auditory Spatial Stream Segregation

Dear All,

            I was looking for a task to assess spatial auditory stream segregation  (sequential stream segregation based on localization and/or lateralization cues) in literature and found an experiment done by Judd T.(1979):(Spatial stream segregation in The Journal of the Acoustical Society of America 1979;65(S1):S122 - S122). According to him when the tones of a slow (e.g., 1 tone/s) tone sequence alternate between widely placed speakers, observers report hearing a single melody which moves back and forth between the speakers like a pingpong game. When the same sequence is presented more rapidly (e.g., 8 tones/s), observers report hearing two independent melodies or streams, one from each speaker (Spatial Stream Segregation). The other studies that I found to study spatial stream segregation were those which used presentation of multitalker babble or other noise through two or three loudspeakers in free field and then present a target speech stimulus (word/sentence) through any one speaker the position of which can or cannot be known by the listener, the task of the listener is to identify the target correctly in presence of the spatial noise. I tried simulating the experiment by Judd using slow and fast alternating tones between two widely placed speakers, although I could hear the galloping like/ping pong like rhythm for the slow tone presentation but then could not actually get the split stream percept (I am comparing these percepts to the typical sequential stream segregated percepts based on fundamental frequency or other strong spectral or temporal cues, especially the primitive stream segregation percepts as demostrated by Bregman and colleagues)  in the faster tone presentations. I could not get access to the entire study or article as it was just the online abstract which was available. I was wondering  if this task is really efficient to assess spatial auditory stream segregation. Moreover I also wanted any suggestions regarding any difference in efficacy of assessment of stream segregation if the target positions for presentations of target speech stimuli are same or different on each presentation, and if the target position is either known/predictable or unpredictable by the listener. Also in this task will roving the noise/babble across different speakers (eg. speakers 3,4,5 for the first trial and speaker 6, 7, 8 for the next trial) will give any addtional information regarding auditory stream segregation ? I would also request everyone to share if any other tasks that would be more efficient or appropriate to assess the spatial stream segregation ability. 

Best Regards,
Imran Dhamani
PhD. Student (Audiology).
$$$$$ monty@@@@

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