Using Rumble Strips for Buzz, Squeak and Rattle (BSR) Evaluation of Subsystems or Components 2007-01-2267
Many car companies use rumble strips to evaluate Buzz, Squeak & Rattle (BSR) performance of vehicles. Some call these surfaces by other names such as chatter bumps or wake-up strips. But regardless of what they're called, these surfaces are characterized by a uniform spacing of bumps or strips which are driven over at a particular speed(s).
This is a relatively easy way to generate relatively high vibration levels so these surfaces are often favorites of the team doing total vehicle evaluation for BSR. If this is the case, then it is essential that a rumble strip evaluation be performed at the subsystem or component level when certifying that a particular item will not generate BSR problems in the vehicle.
One of Siemens' customers uses Rumble Strips to evaluate the Radio/CD player that Siemens supplies. Carefully defined test track tests showed that the particular dynamic characteristics of the Rumble Strip surface made it very challenging to have a repeatable, realistic test. Very small variations in the actual speed (of only 1 mph!) could cause the difference between having a quiet radio/CD or a noisy radio/CD. Furthermore, the troublesome speed varies depending on the resonances of the I-P so what's a radio/CD supplier to do?
If at all possible, Siemens wants to supply radio/CD units that will not have BSR issues at any speed or when mounted in any reasonably stiff Instrument Panel in any vehicle. However in order to pursue that goal it's necessary to have a reasonable worst case lab BSR test for the radio/CD unit that is repeatable.
This paper describes the considerable challenges presented by a rumble strip surface and presents one innovative solution that Siemens is using to overcome those challenges.