Search Results

Engine noise is still one of the dominating sources to vehicle interior noise. Among the engine components, engine covers are often the significant contributors to overall engine noise, requiring in-depth acoustic investigation to achieve substantial reduction. Ford Motor Company has acquired a 150 channel Nearfield Acoustic Holography (NAH) system for powertrain NVH development. This system provides new acoustic information with various metrics and visualization of non-stationary sound field in time domain to facilitate better understanding of noise generation/propagation mechanism. This paper focus on investigating the design of engine covers which radiate chain whine, fully utilizing the capability of this system including spatial transformation. Based on reconstruction of noise sources, effective design change to achieve significant reduction of chain whine is derived and then verified in very short time compared to previous methods.

An enhanced, frequency domain filtered-x least mean square (LMS) algorithm is proposed as the basis for an active control system for treating powertrain noise. There are primarily three advantages of this approach: (i) saving of computing time especially for long controller’s filter length; (ii) more accurate estimation of the gradient due to the sample averaging of the whole data block; and (iii) capacity for rapid convergence when the adaptation parameter is correctly adjusted for each frequency bin. Unlike traditional active noise control techniques for suppressing response, the proposed frequency domain FXLMS algorithm is targeted at tuning vehicle interior response in order to achieve a desirable sound quality. The proposed control algorithm is studied numerically by applying the analysis to treat vehicle interior noise represented by either measured or predicted cavity acoustic transfer functions.