Application of active noise control to car intake system

Engine intake noise of automobile is another important noise that irritates drivers and passengers. The intake noise is narrow-banded low frequency noise. And it varies with engine rpm and throttle condition. Active Noise Control (ANC) technique is superior to passive noise control for this low-frequency noise. ANC is applied to four-cylinder automobile engine intake system. Normalized FXLMS (Filtered-X Least Mean Square) algorithm is used to suppress the intake noise. Two loudspeakers are used for actuator and microphone is used for error signal and reference signal. For stationary case, descending and ascending rpm condition and various throttle opening conditions are applied. ANC successfully suppresses engine intake noise emission. For stationary rpm case, the loudest second order component is attenuated by 20dB. For RPM transition rate of 200rpm/sec case, second order component is attenuated by 10dB.