Order Analysis

To accurately measure noise and vibration from different parts of the vehicle, understanding the different measurement tools and the techniques is important. Once the noise and vibrations are accurately measured, the components that are contributing to the noise can then be individually identified using order analysis. 

In this project, I measured the noise and vibration data of a vehicle in a chassis dynamometer to analyze the order of vibrations and resonances of various sources present in a vehicle. 

Method:

For the test, a BMW 530 with inline 6-cylinder engine was used. The vehicle was operated in a chassis dynamometer and it was operated in 3 main conditions. Wide open throttle and Partial Open Throttle (done in 2nd and 3rd gear). The vehicle was run from 850 to 5000 Rpm. The engine speed was measured using an optical tach, with 79 pulses/rev on the crankshaft. Several accelerometers were placed on the valve cover, front of the cylinder head, alternator, driver front seat track. Linear and A weighted microphones were mounted near the driver’s right ear position. An artificial Aachen head was placed on the front passenger seat. The data from these sensors were collected and analyzed through the SCADAS data analysis system and Siemens Testlab was used for time data processing.

Results:

The concepts of A- weighting and linear microphones were understood. Creating 1/3rd octave plots and order plots were also done. Color maps were generated for the various sensors placed on the vehicle. The difference between the color plots from the accelerometers placed on the different points on the vehicle and the plots from the microphones were analyzed and documented.