Measurement & analysis of squal noise from disc brake systems

Abstract

The problem of squeal noise in car brake systems has been present since early 20th century. Many investigators have tried to solve the problem using experimental, analytical and computational methods. Still there is no known solution for suppressing squeal noise. This problem appears both when disc brakes are used, as well as with drum brake systems. This report was produced at Trelleborg Rubore AB in Kalmar Sweden. The company manufactures a laminate material called "shims", which is a noise damping composite material placed on the back plate of the braking pad of a car. This contributes to eliminate or attenuate squeal nose generated by the brake system. The goal of this project was to perform a series of experimental analysis to reveal the attenuating properties of shims when placed on a brake pad. A method to analyze and compare frequency response functions for the different parts of a brake system in parts and in whole were developed. This method makes it possible to calculate a system loss factor based on any available measurement data. Behaviour of brake system parts of a car brake system close to in situ is examined. The influence of different shims is examined both in free-free brake pads and coupled car brake systems.