A multi-channel active noise control logic for reducing airborne noise transmission through an open car window

In this paper, a Multi-Channel (MC) Filtered-x Normalized Least Mean Square (FxNLMS) Active Noise Cancellation (ANC) system is developed and applied to the problem of open car windows. The aim is to investigate the ability of the system to reduce airborne noise radiation inside the passenger compartment, while ensuring good ventilation and perfect visibility for car users. The system under investigation consists of two reference microphones placed on the upper edge of the driver’s window, the speakers of the vehicle’s audio system serving as secondary sources and two error microphones placed on the driver’s headrest. A noise source is placed outside the car. Two different versions of the FxNLMS are implemented and compared, namely time domain and frequency domain versions. Simulation results show that satisfactory noise reduction is achieved when a stationary single harmonic signal is considered as the disturbance. The time domain version of the control algorithm is found to be preferable when the car window is open or partially open.