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A subjective in-vehicle evaluation system is generally used to evaluate brake noise. This approach is quite dependent on analysis procedure, individual hearing abilities, individual tolerance level to the noise, the vehicle condition, road conditions and weather conditions. Due to the resultant subjective rating's dependence on these non-controllable factors, it was decided to develop an empirical laboratory technique using the brake dynamometer with sensitive noise measuring equipment to collect sufficient data on brake noise to allow engineers to study brake noise problems.

A drag test method for the quantification of front disc brake squeal which uses a brake dynamometer and noise analysis equipment was developed and previously reported in SAE Paper 820037. Subsequently, the dynamometer procedure was revised to a variable stop method which allows a wider study range in less test time while still providing sufficient information to determine the noise character influence of design changes. In conjunction with this revised dynamometer operation, a systematic vehicle test procedure was developed to more clearly define vehicle/dynamometer noise character correlation and in-vehicle noise sensitivity.