Noise emission limits usually highlights the noise emitted from the power-train units of the vehicles. However, to obtain further reductions, limits for tire/road noise and noise influences by road surfaces could be introduced. A work item of the International Organization for Standardization (ISO) focuses on measurement methods for comparison of noise on different road surfaces, one of the major candidates considered by the ISO-group is the trailer method which is reviewed in this report. Nine trailers used for tire/road noise measurement have been reviewed. Two of them have been used for testing of truck tires and the remaining seven have been intended for passenger car tires. All of them would be possible to us also for testing road surfaces. The review includes the most important technical data of the trailers as well as the microphone position used during the measurement, one of the most important factors that must be considered before the trailer method can be recommended for evaluation of the road surface influence on traffic noise is its relation to other measuring methods, especially to the statistical pass-by method. In the latter method, peak pass-by levels of vehicles in actual traffic are recorded together with data about vehicle type and speed, the results of which are then averaged to obtain noise levels typical of each vehicle type and speed. This method is probably the closest one can come to actual road-side listening conditions. The comparison of the results presented in the report shows that the trailer method correlates well with the statistical pass-by method if drainage pavements are excluded. If drainage pavements are included then the trailer method underestimates their noise reduction in comparison to the pass-by method. However if tires for use with the trailer method are selected in an appropriate way, then the underestimation have a systematic character, so it is probably possible to correct the results to some degree. (A)
Samenvatting