Intake noise cancellation using a manifold bridging technique

Abstract

Automobile manufacturers have expended considerable efforts to attenuate the many noise sources perceived within the passenger compartment with varying degrees of success. Given that these dominant noise sources have been attenuated, induction noise has become more noticeable. The present study investigates the feasibility of using a non-conventional noise cancellation technique. The investigation has attempted to improve the acoustic performance of the induction system by introducing a bridge between the exhaust and intake manifolds. The effectiveness of such a technique is investigated using Ricardo WAVE, a computational engine simulation technique that uses a one-dimensional finite-difference formulation. Graphical results using 1/12^th octave frequency spectra and three dimensional colour maps of both an unmodified and abridged engine are presented for both steady state and transient engine cases. A sound quality analysis is also presented using the psychoacoustic metrics of Loudness, Fluctuation Strength and Articulation Index. While a reduction in overall sound level was achieved, an additional benefit of this technique proved to be in the realized sound quality of the induction noise with the implementation of the manifold bridge. This investigation continues with verification of the theoretical model to experimental measurements on a dynamometer.