Delay Network Architectures for Room and Coupled Space Modeling
Feedback delay network reverberators have decay filters associated with each delay line to model the frequency dependent reverberation time (T60) of a space. The decay filters are typically
designed such that all delay lines independently produce the same
T60 frequency response. However, in real rooms, there are multiple, concurrent T60 responses that depend on the geometry and
physical properties of the materials present in the rooms. In this
paper, we propose the Grouped Feedback Delay Network (GFDN),
where groups of delay lines share different target T60s. We use the
GFDN to simulate coupled rooms, where one room is significantly
larger than the other. We also simulate rooms with different materials, with unique decay filters associated with each delay line
group, designed to represent the T60 characteristics of a particular
material. The T60 filters are designed to emulate the materials’ absorption characteristics with minimal computation. We discuss the
design of the mixing matrix to control inter- and intra-group mixing, and show how the amount of mixing affects behavior of the
room modes. Finally, we discuss the inclusion of air absorption
filters on each delay line and physically motivated room resizing
techniques with the GFDN.