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Recent trends show a growing demand for improved powertrain NVH and sound quality. In particular, there is little customer acceptance of tonal annoyances under any driving condition. Thus, powertrain NVH and product development engineers have a strong need to confidently determine acceptable noise levels for commodities that produce narrow band noise. Components such as power steering, transmission gears, pumps, engine timing chains, axle gearing, etc., all may produce significant tones under various vehicle conditions. The perception of the tone is highly influenced by its frequency and background noise. Background noise is composed of wind, road, and engine noise. A methodology and toolset of masking perception algorithms has been developed to meet these needs. The Masking Perception Analysis Software (MPAS) is used to address the development and verification of acceptable powertrain tonal levels as well as the diagnosis of tonal-related issues.

Numerous authors have previously published on the effects of system dynamics on gear noise in automotive applications [1,2]. It is now widely understood that the torsional compliances and inertias of propeller shafts and pinion gear sets are a controlling factor in final drive gear noise for rear wheel drive vehicles. Considerable progress has been achieved in using finite element simulations of the driveline dynamics to improve the system in regards to gear noise. However very few published results are available showing the application of dynamic simulation methods to automatic transmissions which require considerations of the complications due to epicyclical gear sets. This paper documents the successful application of finite element dynamics modeling methods to the prediction of gear noise from the gear set in a rear wheel drive automatic transmission. The model was used to investigate the effects of component inertias, stiffnesses, and resonances.

The Ford GT is the modern re-creation of the 60's era supercar. The powertrain sound quality of the vehicle must enhance its powerful nature, meet regulatory requirements, and maintain a targeted level of refinement. The Ford GT acoustic engineering team used time domain sound decomposition and sound synthesis techniques to determine the sub-system source sounds from surrogate vehicles. The donor source sounds (e.g. exhaust system) are recombined to produce the customer perceived vehicle listening experience from these sub-systems. Target sounds are developed by modifying sub-systems by level, frequency dominance, and order balance. Proposed target sounds are verified by a jury and the results are used for early target agreement and cascading to component targets. This exercise allows development of a customer focused powertrain target sound based on realistic hardware assumptions before any prototypes are available.

Gear whine can be reduced through a combination of gear parameter selection and manufacturing process design directed at reducing the effective transmission error. The process of gear selection and profile modification design is greatly facilitated through the use of simulation tools to evaluate the details of the tooth contact analysis through the roll angle, including the effect of gear tooth, gear blank and shaft deflections under load. The simulation of transmission error for a range of gear designs under consideration was shown to provide a 3-5 dB range in transmission error. Use of these tools enables the designer to achieve these lower noise limits. An equally important concern is the dynamic mesh stiffness and transmissibility of force from the mesh to the bearings. Design parameters which affect these issues will determine the sensitivity of a transmission to a given level of transmission error.