Testing Auditory Illusions in Augmented Reality: Plausibility, Transfer-Plausibility, and Authenticity

Experiments testing sound for augmented reality can involve real and virtual sound sources.
Paradigms are either based on rating various acoustic attributes or testing whether a virtual
sound source is believed to be real (i.e., evokes an auditory illusion). This study compares
four experimental designs indicating such illusions. The first is an ABX task suitable for
evaluation under the authenticity paradigm. The second is a Yes/No task, as proposed to
evaluate plausibility. The third is a three-alternative-forced-choice (3AFC) task using different
source signals for real and virtual, proposed to evaluate transfer-plausibility. Finally, a 2AFC
task was tested. The renderings compared in the tests encompassed mismatches between real
and virtual room acoustics. Results confirm that authenticity is hard to achieve under nonideal
conditions, and ceiling effects occur because differences are always detected. Thus, the other
paradigms are better suited for evaluating practical augmented reality audio systems. Detection
analysis further shows that the 3AFC transfer-plausibility test is more sensitive than the 2AFC
task. Moreover, participants are more sensitive to differences between real and virtual sources
in the Yes/No task than theory predicts. This contribution aims to aid in selecting experimental
paradigms in future experiments regarding perceptual and technical requirements for sound in
augmented reality.