Quieter cabins are indispensable in today’s evolving automobile industry. The effective isolation of vehicle noise and vibrations are essential to achieve the above. Since, low frequency powertrain induced NVH has been one of the major contributors affecting noise and vibration levels inside the passenger cabin. Thus, use of hydraulic mounts is a natural choice for all major OEMs. The objective of this study is to optimize the design of the hydraulic mount de-coupler unit, to reduce the abnormal noise felt inside the cabin. This condition was observed when the vehicle was driven at 20~30 km/h over undulated road surface, found very often in Indian drive conditions.
Due to lack of accuracy and repeatability errors during NVH data acquisition in actual driving condition, the above road profile was captured and subsequently simulated in an acoustically treated BSR (Buzz, Squeak and Rattle) four poster simulator. Problem investigation and countermeasure validation were also performed in this facility.
A significant improvement in cabin noise level by ~6 dB(A) in the problematic frequency zone, with the countermeasure, without negatively affecting any other NVH performance parameters, was achieved.
A novel test methodology has been established for expedited root cause investigation & counter-measure validation of the problem statement. Design modification of the de-coupler membrane for eliminating such noise is a new approach.