Abstract
Room acoustic synthesis can be used in Virtual Reality (VR), Augmented
Reality (AR) and gaming applications to enhance listeners' sense of immersion,
realism and externalisation. A common approach is to use Geometrical Acoustics
(GA) models to compute impulse responses at interactive speed, and fast
convolution methods to apply said responses in real time. Alternatively,
delay-network-based models are capable of modeling certain aspects of room
acoustics, but with a significantly lower computational cost. In order to
bridge the gap between these classes of models, recent work introduced delay
network designs that approximate Acoustic Radiance Transfer (ART), a GA model
that simulates the transfer of acoustic energy between discrete surface patches
in an environment. This paper presents two key extensions of such designs. The
first extension involves a new physically-based and stability-preserving design
of the feedback matrices, enabling more accurate control of scattering and,
more in general, of late reverberation properties. The second extension allows
an arbitrary number of early reflections to be modeled with high accuracy,
meaning the network can be scaled at will between computational cost and early
reverb precision. The proposed extensions are compared to the baseline
ART-approximating delay network as well as two reference GA models. The
evaluation is based on objective measures of perceptually-relevant features,
including frequency-dependent reverberation times, echo density build-up, and
early decay time. Results show how the proposed extensions result in a
significant improvement over the baseline model, especially for the case of
non-convex geometries or the case of unevenly distributed wall absorption, both
scenarios of broad practical interest.