Towards determining thresholds for room divergence: A pilot study on detection thresholds

In binaural rendering, the room divergence effect refers to the decrease in perceived externalization due to a mismatch between the room acoustics of the virtual sounds and those of the listening space. However, it is currently unknown which specific acoustic differences cause this effect. In this work, we present a pilot study to determine detection thresholds between sound sources recorded under different acoustic conditions in a variable acoustics room. These results are intended to predict situations where divergence effects can be expected. The participants had to perform a triangle test where they could listen to three sound sources placed at different positions in the room. The test design was motivated by the fact that sound sources are not placed at the same position in real acoustic scenes. One sound source was recorded under different acoustic conditions than the other two, and the task for the participant was to detect the differing source. The test was conducted in the measured room using 3 DoF binaural reproduction and using a virtual reality (VR) headset to display a visual 360 capture of the room enabling the subjects to see the positions of the sources in the room. Detection rates are signal-dependent and increase with differences in reverberation time (RT). For the most critical signal in the test (castanets), an RT difference of 8% was detectable, while the difference was 15% across all conditions. Furthermore, we discuss the influence of sound source distance and absorption configuration (symmetric or asymmetric) on detection thresholds.