IIR Biquad Controllers for Low Frequency Acoustic Resonance

Low frequency normal modes of an enclosed soundfield introduce unwanted frequency, spatial and temporal artefacts to reproduced electroacoustic signals. A novel control approach is presented based on an analytical modal decomposition, which incorporates a low-frequency soundfield model formed from the sum of a number of second-order IIR filter sections. It is shown that within constraints determined by the model accuracy, IIR controllers may be constructed and may be applied to control tasks such as point pressure cancellation and the reduction of modal quality factor.