Abstract
Reverberation is essential for the realistic auralisation of enclosed spaces. However, it can be computationally expensive to render with high fidelity and, in practice, simplified models are typically used to lower costs while preserving perceived quality. Ambisonics-based methods may be employed to this purpose as they allow us to render a reverberant sound field more efficiently by limiting its spatial resolution. The present study explores the perceptual impact of two simplifications of Ambisonics-based binaural reverberation that aim to improve efficiency. First, a "hybrid Ambisonics" approach is proposed in which the direct sound path is generated by convolution with a spatially dense head related impulse response set, separately from reverberation. Second, the reverberant virtual loudspeaker method (RVL) is presented as a computationally efficient approach to dynamically render binaural reverberation for multiple sources with the potential limitation of inaccurately simulating listener's head rotations. Numerical and perceptual evaluations suggest that the perceived quality of hybrid Ambisonics auralisations of two measured rooms ceased to improve beyond the third order, which is a lower threshold than what was found by previous studies in which the direct sound path was not processed separately. Additionally, RVL is shown to produce auralisations with comparable perceived quality to Ambisonics renderings.
Highlights
Digital reverberation was first conceived by Schroeder and Logan (1961) and has undergone continuous evolution ever since (V€alim€aki et al, 2016)
Descriptive analysis shows that the mean rating was close to zero for the null pairs, the preference between reverberant virtual loudspeaker method (RVL) and hybrid Ambisonics reverb changed depending on the room and type of audio material, and static first-order hybrid Ambisonics renderings were perceived as very similar to the dynamic renderings with a slight trend toward favouring the former
The present results suggest that when the direct sound path is rendered accurately, the degradation in both spatial and spectral qualities becomes perceptually less relevant, for more diffuse reverberant sound fields, i.e., large rooms
Summary
Digital reverberation (reverb) was first conceived by Schroeder and Logan (1961) and has undergone continuous evolution ever since (V€alim€aki et al, 2016). A “hybrid Ambisonics” method is proposed in which the direct path is rendered through convolution with head related impulse responses (HRIRs) sampled in a dense spatial grid, whereas the reverb is processed in the SH domain. The echo density increases as the wave continues to interact with the room, eventually resulting in a diffuse reverberant sound field. This process highly depends on the geometry of the room and the acoustic properties of the materials therein
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