5. Conclusion

Lateral transmissions play a major role in some of the vibro-acoustic performances felt in the passenger compartment of an automobile. There are three main types of performance:

• low-speed hum (< 2,000 rpm), linked to engine acyclism. Engine acyclism results in pulsating torque at the crankshaft, amplified by a twisting mode in the drive train. These parasitic vibrations reach the wheels and are then transmitted to the vehicle body via the hub carrier, pivot carrier and suspension, generating noise in the passenger compartment. To improve low-speed hum, the usual solution is to reduce the stiffness of the lateral transmissions;

• high-speed hum (> 2,000 rpm) is linked to the engine rammer, i.e. to a translational movement of the latter. Lateral transmissions are transfer paths that can be amplifying if...