Application of NVH Countermeasures for Cabin Boom Isolation using Hydraulic Bushing and Silicone Tuned Mass Absorber 2006-01-1681

Driveline (torque tube) boom, excited by a V6 powertrain’s 3rd order pulse signal, can produce high sound pressure levels in a vehicle’s cabin.

Past solutions that have been used as countermeasures include; adding mass, tuned mass absorbers, isolating the torque tube with cardboard or other media, and using an elastomeric isolator (between the torque tube and the body).

Specifically, we will show how to properly address temperature variation as it applies to tuned mass absorbers in driveline/torque tube applications, as well as show how to minimize production variation by using a robust design for the tuned mass absorber. Documentation will be shown detailing how higher temperature elastomers (silicon, EPDM, etc.) compare to natural rubber from a temperature variation standpoint. This is critical to the design of tuned mass absorbers as they apply to sensitive structures that require high damping levels in a narrow frequency bandwidth. We then will show how a hydraulic bushing in this position can improve the system isolation by adding more damping and reducing dynamic stiffness, relative to a conventional, passive, non-fluid design. This will be shown via acceleration data collected on the shaft, body, and sound pressure in the cabin.