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Adria E. N. Hoover, Laurence R. Harris, Jennifer K. E. Steeves; Viewing condition shifts the perceived auditory soundscape. Journal of Vision 2010;10(7):880. https://doi.org/10.1167/10.7.880.
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Early-blind individuals have superior sound processing abilities compared to sighted individuals (Lessard et al., 1998 Nature 395: 278). Here we ask whether sound-processing ability was affected in normally sighted individuals by closing one or both eyes. Sound localization: Participants judged the location of ramped-onset double bursts (30 ms each separated by 30 ms) of white noise played through 16 speakers equally spaced along the azimuth (from -90 to 90 °) in a semicircular array and hidden behind a curtain. Participants listened under four viewing conditions: 1) eyes closed, 2) eyes open, 3) left eye open, and 4) right eye open. Perceived sound location was reported relative to a visual scale. Participants were more accurate in the central visual field and less accurate in the periphery with eyes closed compared to when both eyes were open. When viewing monocularly the perceived location of all sounds shifted toward the centre of the visible visual field (left for left eye viewing, right for right eye viewing) and error increased in the non-visible field. These findings suggest that the perceived position of centrally located sound sources (even when no useful visual information is available) are shifted toward the centre of the visible, visual field. Sound discrimination: Participants were asked to discriminate the relative location of two sound bursts. Two arrays of 8 speakers were equally spaced between 40 – 60 ° in the left and right periphery. Participants listened under the same viewing conditions as in the localization task. Participants had lower thresholds with both eyes open than with both eyes closed or viewing monocularly. In normally sighted individuals sound discrimination ability is not improved when eyes are closed. Viewing condition differentially affects spatial sound processing depending upon the nature of the task.
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