This paper presents the measurement & analysis procedures and the results of a complete road noise identification and reduction project on a midsize passenger car.
Operational interior noise signals and structural accelerations are measured for several test conditions. The operating data are decomposed into sets of mathematically independent phenomena by Principal Component Analysis. Operating Deflection Shape Analysis and Transfer Path Analysis are applied to each of these independent phenomena. Critical transfer paths are thus identified and quantified.
The interior sound level is amplified when the frequency content of the transmitted energy coincides with structural resonances or standing waves of the interior car cavity. The vehicle is dynamically characterized by Experimental Structural Modal Analysis and by Acoustic Modal Analysis.
The insights gained into the noise generation and transmission process that result from these analyses, are “materialized” into realistic design modifications. An analysis method to predict the acoustic efficiency of structural modifications using experimental modal models and measured vibro-acoustic transferfunction data is presented.
Eventually, prototype structural modifications are implemented and evaluated by measurements on a test track.