# Perceptual Similarities between Artificial Reverberation Algorithms and Real Reverberation
## 2 Background  
### Virtual vs. Real-World Acoustics  
In an effort to establish appropriate reference conditions for this study, prior work which has looked at comparing real-world acoustic recordings with virtual acoustic rendering from acoustic measurements is first considered.  
[PERSON] [12] compared the perceptual differences between actual acoustic recordings and 'virtual' recordings made through convolution with binaural room impulse responses (BRIRs), which represent the transfer functions between a sound source and the ears as measured in a reverberant space. He assessed the differences between real and virtual violin and female speech recordings on five subjective attributes (source width, reverberance, clarity, naturalness and source movement). It was found that, apart from the source width, which is related to the directional response of the original acoustic source and the measurement loudspeaker, there was no significant difference between actual and virtual recordings in the other attributes [12]. The virtual acoustic recordings of the violin samples had a smaller source width. For the reverberance attribute, the samples did not differ statistically. For the clarity attribute, in the case of female singing, the virtual recording showed a significant improvement in clarity over the actual recording. For both source types, no variation in source movement was perceived overall. In terms of natural timbre, no significant differences were found between the actual and virtual source recordings.  
[PERSON] et al. [13] compared the various perceptual properties of real and auraised rooms in 2018. Their results showed that when using measured BRIRs, even non-individual BRIRs, highly convincing speech auraisation is possible. Small defects in the simulations can be reliably detected. [PERSON] et al. [14] later compared the consistency of the auraisation of measurement-based binaural room impulse response with the real source (speech signal) for five attributes (reverberation, source width, source distance, source direction, and overall quality). The results showed that, although the measured BRIR set for'reverberance' was rated slightly lower than the other attributes with a median score of around 7 on a nine-point scale, for all other attributes, the agreement with the real room was rated with medians of 7.5 or higher on the nine-point scale based on the measured BRIR. The fact that the measured BRIR sets were capable of eliciting such high ratings suggests that the measured impulse response can be made realistically audible for speech. Therefore, it was concluded that close-to-real binaural auralizations of speech are possible if all modalities (auditory, visual, etc.) are appropriately reproduced [13]. Others, such as [PERSON] et al [15], have evaluated the properties of algorithmic simulations of binaural auralisation in relation to real head recordings. The results show that the spatial properties are almost identical, though there are differences in timbre. However, in general the auraisation algorithm achieves reasonable and natural binaural auraisation.  
The perceptual similarity of real and virtual recordings reported in previous work therefore justifies the use of anechoic audio samples rendered with measured binaural room impulse responses as reference conditions to represent the'real' recorded reverberation in the current study.  
It is important to note that the above experiments were all implemented in a static rendering environment and did not involve head tracking or testing in an augmented reality scenario.