An experimental analysis of the methods for brake squeal quantification

The present paper analyzed 6 brake noise indexes (or Squeal Indexes) in order to assess the squeal produced by 4 different pad materials, which were subjected to dynamometer tests in accordance with SAE J2521 test procedure. Regardless the rating system used in the analysis, the same ranking was obtained with respect to the amount of noise produced by the brake pads selected in this study. Results from the noisiest to the quietest friction material were: pad 1 (semi-metallic) > pad 4 (low-metallic) > pad 2 (Non-Asbestos Organic) > pad 3 (a low-metallic). Besides, Squeal Indexes 2, 3 and 4 (SI2, SI3, and SI4) have shown the best ability for distinguishing friction materials with respect to the amount of brake noise. These rating systems are among the simplest methods to implement, since they consider a maximum of 2 or 3 input parameters. Finally, the histograms of friction coefficient have shown that the noisy stops have a higher average level of friction than the average result obtained for all brake stops.