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Response surface methodology for objective evaluation of vehicle interior noise

The importance of acoustic comfort has grown in the past few years in case of passenger cars, since regarding consumer side, the quality of the vehicle is strongly influenced by that criterion. In this paper the sound pressure level of passenger vehicle was investigated. A B-segment estate car was chosen for the acoustic experiments as sample vehicle. Input data were varied in three levels containing qualitative (working condition of the vehicle) and quantitative (excitation from the outer environment) ones as well. Pink noise was chosen as measurement signal and the values of the generated equivalent continuous sound pressure level were registered in the cabin in case of each possible combination of the levels of the input variables. Based on the measured data, a second order empirical model was constructed by help of response surface methodology (RSM).  The accuracy and the conformity of the equation were investigated by help of the residuals. The applicability of the formula was verified by further confirming measurements. Investigations revealed that the residuals follow Gaussian distribution in both cases, what is more, have small-scaled standard deviation. As a consequence, the presented formula is proper for calculating the sound pressure level of the vehicle interior with an adequate accuracy within the range of the parameters examined.