Brake Noise Assessment by Means of Vehicle Road Tests Subjective Parameters and Objective Measurement Concepts 2005-01-3940
With a view on the statistic nature of most brake noises occurring under normal driving conditions, vehicle sign-off drives, under specific road conditions, have been established and are now state-of-the-art procedures within the automotive industry.
In contrast to the other fields of acoustical engineering, however, assessment is often based on subjective ratings rather than on measured data. This causes uncertainties in the assessment and makes it difficult to compare results of different test routes. The relation of results gained on specific routes to normal customer driving is quite unknown and cannot be clarified by means of subjective ratings.
The paper first provides an overview on psycho-acoustic findings relevant for perception and subjective assessment of brake noise. It is clarified that brake squeal must be analyzed with respect to the psycho-acoustic properties of the background noise.
Limited robustness of brake systems makes assessment difficult, causing high sensitivity to stochastic parameters of systems and environment. It is shown that objective measurements are essential to gain comparable results and to enable analysis that is reliable in terms of signal statistics.
Practical difficulties have to be solved in order for lstandards of objective brake noise measurement to be established, for example: availability of robust sensors for exterior data acquisition, appropriate detection of brake noise, verification and comparability of detection algorithms and inclusion of background noise into the assessment. Recent strategies and solutions are comprehensively reviewed.