Aspects of Powertrain Noise with Special Emphasis on Impulsive Noise

NVH refinement is an important aspect of the powertrain development process. Powertrain NVH refinement is influenced by overall sound levels as well as sound quality. The sound quality and hence the level of powertrain NVH refinement can be negatively affected by the presence of excessive impulsive noise. This paper describes a process used to develop an understanding of impulsive powertrain noise. The paper begins with an introductory discussion of various sources of impulsive noise in an automotive powertrain. Following this, the paper outlines a process for identifying the source of the impulsive powertrain noise using examples from case studies. The remainder of the paper focuses on certain examples of impulsive noise such as Diesel knocking noise, injector ticking, impulsive cranktrain noise, and gear rattle. For these examples, the development of key objective metrics, optimization measures, and improvement potential are examined. Where possible, the metric development process considers correlation with subjective studies. The optimization process outlines the various engineering possibilities to control the specific impulsive powertrain noise issues. Finally, the findings from the discussed studies are summarized and appropriate conclusions are drawn with respect to understanding, characterizing, and solving impulsive powertrain noise issues.