Application of Nearfield Acoustic Holography for Evaluating the Design of Engine Cover

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.