A methodology for the extrapolation of coast-by noise of tyres from sound power level measurements

Abstract Traffic noise is one of the most predominant noise sources that affect citizens’ quality of life in urban areas. The increasing presence of alternative powered vehicles, such as electric or hybrid vehicles, could provide an improvement of such a situation due to the absence of internal combustion engines. However, tyre/road noise is independent of the vehicle type and still exists in alternative powered vehicles. Hence, efforts should focus also on reducing noise emission by means of new tyre designs. The tyre/road noise emission of newly produced tyres is currently evaluated by the Coast-By method, and as a result the rolling sound pressure level at the measuring distance, located 7.5 m away from the test vehicle is obtained. Such an acoustic index provides a very representative data of the annoyance that a pedestrian located at such distance could suffer. However, this value could be affected by external factors, such as environmental conditions. For that reason, this paper presents a methodology for extrapolating the sound pressure levels that are obtained in a Coast-By test, by means of the sound power level emitted by the specific tyre/road combination evaluated. This methodology could serve as the basis for defining a universal model to evaluate a tyre when rolling on a road, by using its sound power emission and predicting the Coast-By sound pressure level.