The Switched Convolution Reverberator

An artificial reverberator having low memory requirements and small computational cost is presented. The reverberator consists of an equalized comb filter driving a convolution with a short noise sequence, which can consist of Gaussian or velvet noise. The reverberator equalization and decay rate are controlled by low-order IIR filters, and the echo density is that of the noise sequence. While this structure is efficient and readily generates high echo densities, if a fixed noise sequence is used, the reverberator has an unwanted periodicity at the comb filter delay length. To overcome this difficulty, the noise sequence is regularly updated or "switched." Several structures for updating the noise sequence, including a leaky integrator sensitive to the signal crest factor, and a multiband architecture, are described.