Scattering in Feedback Delay Networks

TL;DR

This paper introduces a generalization of feedback matrices in feedback delay networks, enabling denser echo responses and scattering effects with minimal computational cost, advancing artificial reverberation techniques.

Contribution

It generalizes feedback matrices to lossless filter feedback matrices, including the velvet matrix, for improved echo density and scattering in FDNs.

Findings

FFMs increase echo density effectively.

Velvet feedback matrix creates dense impulse responses efficiently.

FFMs emulate scattering effects of non-specular reflections.

Abstract

Feedback delay networks (FDNs) are recursive filters, which are widely used for artificial reverberation and decorrelation. One central challenge in the design of FDNs is the generation of sufficient echo density in the impulse response without compromising the computational efficiency. In a previous contribution, we have demonstrated that the echo density of an FDN can be increased by introducing so-called delay feedback matrices where each matrix entry is a scalar gain and a delay. In this contribution, we generalize the feedback matrix to arbitrary lossless filter feedback matrices (FFMs). As a special case, we propose the velvet feedback matrix, which can create dense impulse responses at a minimal computational cost. Further, FFMs can be used to emulate the scattering effects of non-specular reflections. We demonstrate the effectiveness of FFMs in terms of echo density and modal distribution.