Development of experimental model-building techniques

Percy F Wang, Purdue University

Abstract

In the automobile industry, it is important to identify the major noise sources and to find the relationship between them and the interior noise of an automobile. The noise sources include engine noise and vibration, tire noise, exhaust noise and transmission noise. The objective of the research was the prediction of the sound pressure level occurring inside the passenger compartment of an automobile, by using as simple a model as possible. In building reduced models by using measurement data from an automobile, some frequency domain techniques have been used. New and extended techniques have been developed to assist building more accurate reduced models of automobile interior noise. Some time domain techniques have also been investigated. In certain applications, for example, active noise control, one would wish to predict passenger car noise in real time from measurements in the engine or from axle and spindle vibration. In other applications, for example, sound quality design, one would wish to run several predictions in a timely fashion in order to make comparisons. In these applications we derive a simple model that can predict the passenger compartment noise accurately and quickly, and has components that can be related to physical mechanisms within the car so that the effect of design changes can be embedded into the model. While including all major sources of passenger car noise, the objective in building the simplified models was to use the smallest number of transducers and the simplest models possible. Torsional vibration is an implicit excitation that exists in an operating automobile, and can be a significant noise source. Due to the difficulty of measuring torsional vibration on rotating shafts, it has not often been used as an input to noise models, although torsional vibrations could be a major cause of noise inside a passenger car. In previous studies, torsional vibration in the power train of the automobile was found to be the source of the booming noise, the correlation between the torsional vibration in the drive line and the low frequency noise in an automobile. A low cost and effective torsional vibration measurement system has been designed to assist the measurement of the torsional vibration of a shaft. The measurement system was applied to a rotating shaft on a test bench; results indicate that this method can be used on an operating automobile to measure the torsional vibration on the wheel axle.

Degree

Ph.D.

Advisors

Davies, Purdue University.

Subject Area

Mechanical engineering|Automotive materials

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