Source and Listener Directivity for Interactive Wave-Based Sound Propagation

Abstract

We present an approach to model dynamic, data-driven source and listener directivity for interactive wave-based sound propagation in virtual environments and computer games. Our directional source representation is expressed as a linear combination of elementary spherical harmonic (SH) sources. In the preprocessing stage, we precompute and encode the propagated sound fields due to each SH source. At runtime, we perform the SH decomposition of the varying source directivity interactively and compute the total sound field at the listener position as a weighted sum of precomputed SH sound fields. We propose a novel plane-wave decomposition approach based on higher-order derivatives of the sound field that enables dynamic HRTF-based listener directivity at runtime. We provide a generic framework to incorporate our source and listener directivity in any offline or online frequency-domain wave-based sound propagation algorithm. We have integrated our sound propagation system in Valve's Source game engine and use it to demonstrate realistic acoustic effects such as sound amplification, diffraction low-passing, scattering, localization, externalization, and spatial sound, generated by wave-based propagation of directional sources and listener in complex scenarios. We also present results from our preliminary user study.

Investigation of Auditory Objects Caused by Directional Sound Sources in Rooms

“…This is known to be the case whenever the level of a reflected sound exceeds the echo threshold of the preceding sound. The knowledge of the localization itself is still rough and can often only be guessed from what is known [2,3,[14][15][16]. A more specific but still coarse description of the perceived direction was given in [13,17].…”

Local Time-Domain Spherical Harmonic Spatial Encoding for Wave-Based Acoustic Simulation

“…In this work, instead of following the array processing paradigm, the encoding process is formulated and integrated directly in the FDTD scheme, operating with very low latency and without extensive pre-computation. We demonstrate that this is possible through the relation between spherical harmonic encoding and the local pressure gradients of the sound-field, through a representation first presented by Dickins and Kennedy [23], and also employed in non-volumetric frequency-domain techniques by Mehra et al [24]. In the present setting of volumetric time-domain methods, the resulting procedure selects explicit compact grid point sets for each encoded signal and is recursive in the time-domain.…”

Spatial Sound Rendering – A Survey

“…In comparison with the better-known FEM, the BEM differs in the element structure [20]. Specifically, the algorithm can be divided in the follow steps: (1) the Helmholtz equation is transformed into the boundary integral equation; (2) pressure and velocity are solved on the boundary, as a result of that the pressure is calculated at any point in the domain [21].…”