Design of Filter Length of Order Filter and Its Application to Filtered-X Algorithm for Active Noise Cancellation of Interior Noise Inside an Excavator Cabin

초록

This paper presents a novel method to determine the filter length. Major interior noises inside an excavator cabin are hydraulic pump noise. The filtered x-LMS (FxLMS) algorithm using a notch filter has been widely applied to ANC of engine noise inside the cabin of a passenger car. A notch adaptive filter is a comb-type filter and is useful to attenuate a steady-state pure tone. When the rotating speed of the crankshaft accelerates steadily in sweep mode, instantaneous frequencies of the hydraulic pump noise and cooling fan noise inside an excavator cabin increase steadily. The FxLMS algorithm using a notch filter can be stably applied to the ANC of the interior noise inside an excavator cabin in steady sweep mode. However, when a hydraulic pump is operated in dynamic mode, the rotating speed of the crankshaft fluctuates rapidly due to rapid change of the working load, and instantaneous frequencies of the hydraulic pump noise are also periodic and fluctuate rapidly. The FxLMS algorithm using an order filter is effective for ANC of the noise in which the instantaneous frequency rapidly fluctuates. For effective application of the order filter to ANC of non-stationary noise, the filter length should be optimally determined.

키워드