Simulation of Gear Rattle to Aid in the Development of Sound Quality Metrics for Diesel Engine Component Specification

Noise produced by components in a diesel affect the quality of the engine noise. One component source related to consumer complaints is gear rattle. Gear rattle is caused by gear tooth impacts resulting from fluctuations in differential torsional acceleration of the driving gears. Previous work in this area has focused on rating the overall sound quality of diesel engines without specifically focusing on models for predicting the perception of gear rattle. Here, a method to generate sounds having different levels of gear rattle is described. First, diesel engine noise recordings were analyzed to determine the engine speed time histories; they were then used to guide gear impact timing and to generate gear noise components. The gear noise transfer paths were then tuned to improve the quality of the gear noise predictions. The gear noise simulation tool is presently being used to generate sounds for subjective tests designed to quantify the detectability, perception of growth, and annoyance of gear rattle. The noise prediction coupled with the sound quality models based on the analysis of the subjective data will provide a way to predict how people perceive gear rattle so that component noise targets can be set directly related to human perception