Efficient Synthesis of Room Acoustics via Scattering Delay Networks

Abstract

An acoustic reverberator consisting of a network of delay lines connected via scattering junctions is proposed. All parameters of the reverberator are derived from physical properties of the enclosure it simulates. It allows for simulation of unequal and frequency-dependent wall absorption, as well as directional sources and microphones. The reverberator renders the first-order reflections exactly, while making progressively coarser approximations of higher-order reflections. The rate of energy decay is close to that obtained with the image method (IM) and consistent with the predictions of Sabine and Eyring equations. The time evolution of the normalized echo density, which was previously shown to be correlated with the perceived texture of reverberation, is also close to that of IM. However, its computational complexity is one to two orders of magnitude lower, comparable to the computational complexity of a feedback delay network (FDN), and its memory requirements are negligible

Directional Feedback Delay Network

“…Individual delay lines are expanded into a set of multichannel signals by encoding a mono input signal in the SH domain, as in Eq. (11). A directional energy weighting function is included in the recirculating path to modify the direction-dependent energy decay T 60 (φ, θ ), which can be tuned to resemble the anisotropic energy decay behavior of an existing space.…”

“…For multichannel sound reproduction Gerzon [6], as well as Stautner and Puckette [8], presented a method that distributes the decorrelated output of different delay lines to a set of spatially arranged loudspeakers. In [11], De Sena et al introduced a physically informed recirculating delay system, using digital waveguide networks, capable of positioning the output at the location of the first-order early reflections in a virtual shoebox. This design was further expanded to include physically informed second-order reflections [12].…”

Perceptual Spatial Audio Recording, Simulation, and Rendering: An overview of spatial-audio techniques based on psychoacoustics

“…An artificial reverberator that inherits all its parameters from physical characteristics of the room it simulates was recently proposed [12]. This reverberator, termed scattering delay network (SDN), is a modified DWN where the length of the digital waveguides and the topology of the network, as illustrated conceptually in Fig.…”

“…Full-blown room auralization systems typically aim to render each and every reflection and diffraction up to a given order for each source [10], [11]. More recent methods achieve remarkable computational savings by rendering accurately only first order reflections, while replacing higher order reflections with their progressively coarser approximations [12]. Further computational savings are possible by eliminating sources whenever they are inaudible, a process referred to as audio source culling.…”

Localization Experiments with Reporting by Head Orientation: Statistical Framework and Case Study

“…The subjects could choose between two conditions-an anechoic condition, where the sound source was placed in free field at the same height as the listener and at a distance of 1.4 m, and a reverberant condition, where the room acoustic response was simulated in real-time using a scattering delay network (SDN) [19]. SDN was chosen to generate the reverberation because of its ability to reproduce faithfully the important physical (e.g., early reflections, reverberation time) and perceptual features (e.g., normalized echo density) while running in real-time.…”