The four post buzz-squeak-rattle system is a fully mechanical rig that simulates both high and low frequency rattles (that might be encountered on the test track) by increasing or decreasing the driving speed on the specially designed bump cam rolls. Rattle force is variable—simply driving from one side of the rolls to the other creates variability due to rolls that are paved with bump cams that increase in size from left to right. These variable rolls are mechanically coupled, meaning no expensive motor and drive systems are required.