Development and Application of an Objective Metric for Transient Engine Clatter Noise

Several powertrain noise phenomena have been studied over the years. Sound quality metrics, like loudness, sharpness, modulation, and tonality, among others, have been developed to characterize powertrain noises. While these readily available metrics work well on steady state and some transient noises, they do not correlate directly with subjective impressions. Moreover, it is difficult to assign a meaningful single rating for time varying noises that may also be associated with simultaneous variations in frequency content. This paper summarizes the process of creating a vehicle level objective metric and its application to blind noise samples to verify correlation with subjective impressions, particularly in association with clatter noise at moderate engine speeds (2000-3500 rpm) with light to moderate throttle tip-ins. The main results include a single number rating and a rating curve as a function of engine speed useful for comparative NVH assessments of multiple vehicles or of multiple hardware iterations on a development vehicle with objectionable clatter content. The latter application is particularly useful since it gives correct feedback to an uninitiated engineer about the hardware changes he or she is proposing. Further this could help in data driven decision making during cost versus benefit assessments.