Equalized Algorithm for a Truck Cabin Active Noise Control System

The noise inside a truck cabin is caused by various sources such as the engine, transmission, wheel vibrations, wind, and some other external sources. In general, the interior noise of vehicles is composed of two components: one is synchronized with the engine rotation or other periodic noise, while the other is caused by stochastic sources [1]. For most midsized trucks with an in-line four-cylinder engine, periodic noise is the dominant part of the internal noise. Such periodic noise is a combination of the harmonic noise components, also known as noise orders. Furthermore, the order frequency range is relatively low, typically below 500 Hz. That makes Active Noise Control (ANC) effective in attenuating the order-related noise. The most commonly used strategy is narrowband feedforward ANC with a Filtered-x Least Mean Squares (FXLMS) algorithm [1]. The FXLMS algorithm, first derived by Widrow in 1981, has been used successfully for many applications, such as broadband noise in an enclosure [2], single frequency noise in a duct [3], multiple frequency noise in a helicopter [4], and timevarying noise in a tractor [5].