Prediction of coast-by tyre/road noise based on equivalent monopoles synthesised from indoor tests

Tyre/road interaction is the main source of environmental noise pollution, particularly in urban and suburban areas, even at moderate speeds. Its impact is further emphasised by the growing presence of electric vehicles, which significantly reduce the engine's contribution to overall vehicle noise. Indoor testing of tyres is a common practice in the tyre industry during product design stages, as it provides an initial understanding of noise performance. However, outdoor tests are required to assess the noise performance of tyres. For this reason, this study presents a methodology for the prediction of coast-by tyre/road noise based on equivalent sources identified from indoor tests, including the effect of sound reflections due to the vehicle's presence in an outdoor environment. The equivalent monopoles are identified from standalone tyre rolling noise measurements on a test rig equipped with a road replica in a semi-anechoic chamber. To conduct outdoor simulations, acoustic transfer functions are measured on the test track through an omnidirectional acoustic source, with the vehicle positioned on the track. This paper details the experimental setup, data processing, and methodology for carrying out coast-by tyre/road noise simulations based on these equivalent monopoles while accounting for vehicle motion, followed by a comparison with experimental measurements performed using an electric vehicle.