NVH Refinement of Passenger Vehicle for In-cab Boom Noise Using Experimental Operational Deflection Shape and Full Vehicle Acoustic Sensitivity Simulations

This paper discusses combined experimental and simulation approach used for NVH refinement of Passenger Vehicle for in-cab Boom Noise. On initial testing of Proto Vehicles a boom was identified in the speed range of 1300-1600 rpm in all the gear conditions. Investigations through measured Vibrations and Operational Deflection Analysis (ODS) identified that the rear axle had a vibration mode of the axle on the trailing arm bushes at around 43 Hz excited by the engine combustion forces. This finding was concurred by predicted full vehicle level modal and acoustic response analysis results. Based on simulation findings, conceptual change of rigid attachment between rear axle and trailing arm suppressed the vehicle boom. Using simulation approach a realistic design solution was worked out in terms of optimization of trailing arm rear bush stiffness values. Benefits of same were confirmed on the vehicle.

Investigation approach applied through simulation and experimental tools towards root cause identification of boom noise issue, correlation of predicted vs measured results, optimization of trailing arm bush stiffness values and its effect on improving vehicle subjective rating etc. is discussed in the present paper.