Evaluation of Ground Vehicle Wind Noise Transmission through Glasses Using Statistical Energy Analysis 2013-01-1930
The contribution of wind noise through the glasses into the vehicle cabin is a large source of customer concern. The wind noise sources generated by turbulent flow incident on the vehicle surfaces and the transmission mechanisms by which the noise is transmitted to the interior of the vehicle are complex and difficult to predict using conventional analysis techniques including Computational Fluid Dynamics (CFD) and acoustic analyses are complicated by the large differences between turbulent pressures and acoustic pressures. Testing in dedicated acoustic wind tunnel (AWT) facilities is often performed to evaluate the contribution of wind noise to the vehicle interior noise in the absence of any other noise sources. However, this testing is time-consuming and expensive and test hardware for the vehicle being developed is often not yet available at early stages of vehicle design. In addition, modifications of the vehicle exterior geometry that may be beneficial to interior noise are often difficult to implement during the testing or to evaluate properly via test. This paper describes a test-based approach to measuring and understanding the contribution of exterior wind noise to the interior cabin noise through the individual glasses and the development of a correlated Statistical Energy Analysis (SEA) model capable of predicting the effect of a design change to any combination of thickness or material changes to the glasses. AWT testing was performed with interior microphones, accelerometers on the glasses, and arrays of flat exterior pressure transducers to establish the acoustic and structural-acoustic transfer functions to the interior. An underbody skirt, extensive taping of exterior gaps, and “blocker” parts on the interior of the glasses were used in order to isolate the noise contribution through individual glasses. Two versions of the front side glass -monolithic and laminated - were tested to compare the effect of the glass material and damping on transmitted wind noise and to provide a reference from which the wind noise load at this important location could be inferred. The data set from this testing was processed and used to correlate an SEA model of the test vehicle capable of being used for design studies of the effect of the glasses on the interior wind noise.