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In this paper, we discuss methods used to investigate a clearly audible gear whine problem in a modern automobile. Currently available PC-based computer software, coupled with more traditional engineering tools, such as spectrum analyzers, are employed to efficiently observe noise and vibration phenomena. Jury evaluations are conducted, using in-vehicle noise data, to rank actual gear whine levels. Additional jury studies using synthesized gear whine help us further understand listener preferences. Unloaded gear transmission error testing is explored as a means of predicting gear whine levels under light loads, such as those seen during highway cruising. We finally correlate many results to better understand the source and paths of the gear noise, and make recommendations for further exploration of this type of problem.

This paper describes the procedures used to reduce the tonal noise of a class eight truck engine timing gear train that was initially found to be objectionable under idle operating conditions. Initial measurements showed that the objectionable sounds were related to the fundamental gear mesh frequency, and its second and third harmonics. Experimental and computational procedures used to study and trouble-shoot the problem include vibration and sound measurements, transmission error analysis of the gears under light load condition, and a dynamic analysis of the drive system. Detail applications of these techniques are described in this paper.