Directional sources and listeners in interactive sound propagation using reciprocal wave field coding

Abstract

Common acoustic sources, like voices or musical instruments, exhibit strong frequency and directional dependence. When transported through complex environments, their anisotropic radiated field undergoes scattering, diffraction, and occlusion before reaching a directionally-sensitive listener. We present the first wave-based interactive auralization system that encodes and renders a complete reciprocal description of acoustic wave fields in general scenes. Our method renders directional effects at freely moving and rotating sources and listeners and supports any tabulated source directivity function and head-related transfer function. We represent a static scene's global acoustic transfer as an 11-dimensional bidirectional impulse response (BIR) field, which we extract from a set of wave simulations. We parametrically encode the BIR as a pair of radiating and arriving directions for the perceptually-salient initial ( direct ) response, and a compact 6 × 6 reflections transfer matrix capturing indirect energy transfer with scene-dependent anisotropy. We render our encoded data with an efficient and scalable algorithm - integrated in the Unreal Engine ™ - whose CPU performance is agnostic to scene complexity and angular source/listener resolutions. We demonstrate convincing effects that depend on detailed scene geometry, for a variety of environments and source types.

Interactive sound propagation for dynamic scenes using 2D wave simulation

“…The shortest path leaves the source in a radiation direction before arriving at listener. We borrow the technique from [CRG*20]. Due to reciprocity, can be estimated as opposite to the direction from which the first wavefront radiating from the listener during simulation arrives at the source location, .…”

“…Run‐time signal processing. We borrow the scalable multi‐source rendering from [RS14] via “canonical filters” for reverberation, and model source directivity on direct sound as in [CRG*20]. …”

“…where L S is the forward pointing vector of the source provided by the game thread. General frequency‐dependent radiation patterns could be straightforwardly included in our approach by a combination of lookup tables and fast equalization filters as in [CRG*20].…”

“…To address these computational challenges, we borrow ideas from precomputed parametric systems [RS14, RS18, CRG*20]. Rather than simulating wideband sound fields with immersed dynamic geometry, we take static snapshots of the scene configuration at interactive rates (10Hz).…”

“…The parameters for each source are then applied to its radiated signal using a fast multi‐source rendering pipeline borrowing from [RS14, CRG*20]. In particular, we incorporate source directivity and perform temporal interpolation of parameters that ensures artifact‐free output on geometry motion.…”