Browse Publications Technical Papers 2019-01-1532

Vibro-acoustic transfer function measurement in vehicles using dodecahedral sound source and its application for material assessment 2019-01-1532

NVH is an important aspect of vehicle design since it is one of the highest priorities and biggest influencing factors for customer while making decision to buy a vehicle. Hence, automotive engineers strive to design the superior cabin compartment to maintain pleasant levels of noise, vibration and the overall experience within the vehicle. To quantify the amount of energy transmitted between source and receiver region, transfer function analysis is primarily used. The focus of this paper is to measure vibro-acoustic transfer function using reciprocity approach instead of direct impact test measurement. It is found that the vibro-acoustic reciprocity holds true even for non-linear system like vehicle. The reciprocal measurement involves usage of dodecahedral sound source to acoustically excite the cabin from desired seating location and accelerometers are placed at all the locations of interest on vehicle body. In case of direct measurement, vehicle body is excited using impact hammer and acoustic pressure is measured at desired seating location. It is observed that transfer function calculated with direct and reciprocal measurements showed a good match with overall deviation of less than 8 %. The linearity of the reciprocity measurement is checked for various locations in vehicles and found to be working satisfactorily in frequency range of 80 - 5000 Hz. The validation helps in optimizing the traditional approach for measuring structural response using vibro-acoustic transfer function in frequency range of 80 - 5000 Hz. The traditional method involving impact hammer test for predicting response at various points in vehicles is a time taking process and inaccessible measurement locations are prone to error. The overall broad frequency range analyzed is further analyzed in spectral plot to closely understand sensitive frequency zones to tackle different contributing noises. The linearity advantage of this reciprocity approach is further utilized in this paper in an application to characterize a highly damped acoustic material which is difficult to characterize using direct impact based measurement. These material test results are used for assessment and will serve as an input for its development.


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