A Demonstration of Active Noise Reduction in a Cabin Van

In recent years the automotive industry has focused attention on the alleviation of interior vehicle noise since it affects passenger comfort and can be a factor of substantial importance to safety. In this work, an active system has been implemented inside an eight-seat four-cylinder engine van to control the booming produced when the second order harmonic of the engine excites normal modes of the passenger compartment. Using six microphones as error sensors and six loudspeakers as secondary sources, it is possible to reduce the interior sound pressure level over the 50–150 Hz frequency range. The positions for the transducers have been selected between the physically available locations to avoid the acoustic cavity nodes. The electronic control system is accomplished using a commercial system based in a Texas Instruments TMS320C40 DSP. The experimental verification has been made within a semi-anechoic room, with the engine running under hard acceleration in third and fourth gears.