Comparing the Auditory Distance and Externalization of Virtual Sound Sources Simulated Using Nonindividualized Stimuli.
Mathieu Lavandier, Lizette Heine, Fabien Perrin
PMID 39435499WHAT IT FOUND
Perceived distance and externalization are correlated but distinct.
A sound can be judged far away yet still feel inside the head, especially with frontal or diotic cues. Clinicians should not assume that increasing simulated distance automatically externalizes a virtual sound source.
Key findings
01Distance and externalization ratings were significantly correlated, but distance only explained between 26% and 47.6% of the variance in externalization.
02A source was not rated as externalized simply because its perceived distance exceeded a threshold (e.g., head radius); only 51.3% of responses matched this hypothesis.
03Diotic reverberation influenced distance judgments but did not improve externalization, whereas adding broadband interaural cues increased externalization without affecting distance.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study used non-individualized head-related transfer functions (HRTFs) from a mannequin, which may not perfectly match the anatomy of all listeners, though previous research suggests this has a minor effect on externalization. The distance and externalization tasks were performed in separate blocks, which may have introduced contextual effects where listeners did not maintain a consistent spatial model across tasks. The simulated distances were limited to 1, 3, and 5 meters, so the findings may not generalize to very close distances (under 1 meter) where binaural cues become more dominant for distance perception. Participants were young adults with normal hearing, so the results may not directly apply to older adults or those with hearing loss who use hearing assistive devices.
Declared interests
The authors declared no potential conflicts of interest. The work was funded by Labex CeLyA, the PHC Danube program, and the Horizon Europe research and innovation program.
The easy way to misread this
Do not conclude that increasing the simulated distance of a virtual sound source will automatically make it sound externalized. The study found that many sounds perceived as distant were still rated as internalized, particularly when binaural cues were degraded or absent.