Theoretical active control analysis of low frequency noise in a mining vehicle cabin: Part 1

摘要

The effectiveness of an active noise control system in globally and locally controlling lowrnfrequency noise in a rectangular enclosure used to simulate a mining vehicle cabin wasrninvestigated theoretically. A numerical model of the sound field within a rectangularrnenclosure was created based on excitation by a point source within the enclosure. Usingrntotal average acoustic potential energy as a measure, the maximum achievable noisernreductions over the total internal volume of the enclosure with an ideal active controlrnsystem were calculated. A small volume within the enclosure was used to simulate the spacernthat may be occupied by a driver’s head in a vehicle cabin, and the levels of noise reductionrnpossible within this volume were compared to those achievable over the entire enclosure.rnWhile the levels of achievable noise reduction were greater over the smaller volume,rncontrolling just the smaller volume resulted in a net increase in the total enclosure acousticrnpotential energy. The effect of using multiple control sources as well as varying the criticalrndamping ratio of the enclosure on the possible noise reductions was also investigated. Thernuse of multiple control sources increased the bandwidth over which significant noisernreductions were possible, although the magnitude of the noise reductions did not greatlyrnincrease. Increasing the damping of the enclosure walls limited the effect of active control,rngiving lower levels of noise reduction, and lowering the frequency range over whichrnsignificant reductions were possible compared to the undamped case.