Implementation of adaptive IIR filter in an Active Noise Blocker to increase the controller performance and to reduce the computational load

The application of an active noise blocker (ANB) minimizes the noise energy transport in the transmission path of the window to globally calm down the adjoined room. For measuring the noise and introducing the anti-noise, several microphone-loudspeaker pairs are placed along the window frame. Each loudspeaker is driven by a finite impulse response (FIR) filter based single input single output feedback filtered-x least mean square controller (SISO FB FxLMS). The number of the sensor-actuator pairs has to be high enough to place them near each other closer than one-third of the lowest wave length in the incoming noise. However the number of controllers is limited by the computational load and the acoustical interaction of neighboring sensor-actuator pairs. Since the plant transfer functions of the closed room, considerable for the control, are described by poles and zeros, the computational load can be reduced by using infinite response (IIR) filters for the plant models. Further, usage of adaptive IIR filters for the control can improve the compensation of the acoustic interaction of the controllers similar to the cancellation of acoustic feedback in duct-noise control applications. This study compares the performance and computational load of the FIR and IIR based ANB.