Applications of FDNs

• In FDN reverberation applications, $\mathbf{A}={\bm \Gamma}\mathbf{Q}$, where $\mathbf{Q}$ is an orthogonal matrix, and ${\bm \Gamma}$ is a diagonal matrix of lowpass filters, each having gain bounded by 1.

• In certain applications, the subset of orthogonal matrices known as circulant matrices have advantages.