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Calculating Noise

As NVH is a key concern at Ford Motor Co.—Derrick Kuzak, Ford group vice president of Global Product Development, recently stated that they are working to “Understand every noise path,” as quiet vehicles are desirable—when a transmission prototype had sound pressure levels of 10 to 15 dB greater than the nominal values, Jack S.P.

As NVH is a key concern at Ford Motor Co.—Derrick Kuzak, Ford group vice president of Global Product Development, recently stated that they are working to “Understand every noise path,” as quiet vehicles are desirable—when a transmission prototype had sound pressure levels of 10 to 15 dB greater than the nominal values, Jack S.P. Liu, Das Ramnath, and Rajesh Adhikari worked to (1) determine the source of the noise, which was in the 1,800 to 1,900 Hz range, and (2) to develop simple analytical models to quickly compute the transmission chain drive system resonances. It had been determined that chain-sprocket meshing noise was the most significant noise source. So the team worked to analytically predict chain drive system resonance, as they assumed that the existence of chain resonances can amplify radiated chain meshing noise.

Needless to say, this was a complex task, involving complex calculations and analysis. The engineers deployed mathematical software from Maplesoft (www.maplesoft.com) to model the physical system so as to gain an understanding of the vibrational behavior. They used Maple software to validate mathematical model predictions against both an ABAQUS CAE model and experimental test results. Additionally, they created a predictive design tool to develop analytical models and predict chain drive dynamics.

Bottom line, they accurately determined the exact locations of the 1,800-Hz noise source and the problematic noise peak. This information is important in developing quiet, smooth chain drive systems.