Angle-Dependent Distortions in the Perceptual Topology of Acoustic Space.
W Owen Brimijoin
PMID 29764312WHAT IT FOUND
Listeners judge sounds at the side of the head as moving half as far as they actually do.
A 20-degree movement at the front feels like a 40-degree movement at the side. This distortion means virtual audio systems must correct for angle to sound stable.
Key findings
01Motion centered at 90 degrees required roughly twice the physical excursion to be judged as equal to motion centered at 0 degrees.
02The perceived expansion of space at the front relative to the sides causes sounds to appear to move at different velocities depending on their angle to the head.
03A mathematical model derived from these motion judgments successfully predicts previously reported errors in static sound localization.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study did not measure the minimum audible angle (spatial acuity) in the same listeners, so the direct link between the perceptual distortion and basic hearing thresholds remains theoretical. The mathematical model was only tested for the front hemifield (0 to 90 degrees); its accuracy for sounds coming from behind the listener is unknown. The range of movement excursions was not large enough to fully determine the point of subjective equality for all condition pairs, requiring some extrapolation.
Declared interests
Funded by the Medical Research Council and the Chief Scientist Office (Scotland). No other conflicts declared.
The easy way to misread this
Do not assume this distortion is a sign of pathology. The study shows that healthy listeners with normal hearing consistently perceive sounds at the side of the head as moving less than they actually do. This is a normal feature of auditory processing, not an error caused by hearing loss or brain injury.