Case study: Reference optimization for active control of air conditioning noise at defrost mode in vehicles

Air conditioning noise at defrost mode in vehicles is annoying, especially when the fan speed is high. A case study of active control of air conditioning noise at defrost mode around the driver’s ears in an electric vehicle is reported in this paper. For the feedforward control system under investigation, coherence analysis is conducted first to optimize the location and number of the reference sensors. The simulation results show that the reference microphones should be placed around the main defrost vent toward the front windshield and the other air vents as well to achieve effective noise reduction. Based on the Wiener filtering simulations, about 10.9 dBA noise reduction can be obtained with 20 reference microphones. In the real time experiments with 12 reference microphones at optimized positions on the console, about 6.5 dBA noise reduction was obtained around the driver’s ears with little noise amplification at other seats.