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.
Room divergence effect decreases externalisation.
The specific acoustic differences that cause the effect are unknown. Towards determining thresholds for room divergence: A pilot study on detection thresholds and Towards determining thresholds for room divergence: A pilot study on perceived externalization try to determine detection thresholds between sound sources recorded under different acoustic conditions in a variable acoustics room. The aim is to predict situations where divergence effects can be expected.
Reverberation time is an important parameter. Just noticeable difference values vary from 5% to as high as 25%. For reverberation time, the studies focus on RT30.
Externalisation degrades significantly and progressively for BRIRs presenting a T30 lower than 90% and higher than 125% of those of the real room.
Our perception is strongly influenced by the comparisons that listeners can conduct. Both external and internal references are used for comparison. Internal references are based on our previous experience, and give us a sense of the kind of acoustics we can expect from the visual appearance of a room.
Linearly increasing absorptive surfaces does not linearly change the reverberation time.
Less repetitive signals are more difficult to detect. For speech, room divergence is difficult to detect.
Distance does not appear to affect detection thresholds.
In [7] it is reported that the externalization ratings do not improve further when comparing renderings produced using full Binaural Room Impulse Responses (BRIR) as compared to BRIRs truncated after 80 ms.
Head movement contributes to a reduction in front-back confusion, more accurate sound localisation and improved externalisation.
Externalisation is better in situations where the user can see the room. Dark or incogruent rooms have poorer externalisation.
It is known that in situations of room divergence listeners experience adaptation to virtual sounds, resulting in an increase of externalization [14]. However, because of the small sample size in the test it is unclear whether this phenomenon is due to adaptation or a statistical artifact.
A Summary on Acoustic Room Divergence and its Effect on Externalisation of Auditory Events and Adjustment of the direct-toreverberant- energy-ratio to reach externalization within a binaural synthesis system focus on investigation of the effect of direct-to-reverberant ratio on externalisation.
Manipulating RT30 affects other perceptually relevant parameters such as Center Time, Clarity and Direct-to-Reverberant Ratio.