Acoustical performance of winter tyres on two in-service road surfaces: a frequency spectrum analysis and comparison

In order to provide appropriate performance on potentially hazardous winter or icy road surfaces, it is common to employ specific tyres developed for such conditions. Such winter tyres may contain studs embedded in the tyre tread, or they may be studless. Additionally, it is possible to use so called all season tyres which are also fitted for winter conditions. In some northern countries, the usage of winter tyres is mandatory and it is commonly assumed that studded winter tyres are significantly noisier than non-studded tyres. This paper analyses noise measurements on various types of winter tyres, both studded and studless, and the results are compared to all season and summer tyres. The measurements were carried out with the CPX method to characterize the noise performance of different tyres on in-service road surfaces. A total of approximately 50 light vehicle tyres were tested on two different road surfaces, namely an SMA 8 and a DAC 16. The analysis is focused on comparing different frequency spectra for each tyre category, providing a better understanding on how the presence of studs changes the resulting tyre/road noise in different frequencies and how winter tyres compare to all season and summer tyres regarding their frequency spectra. The results indicate how substantially the studs increase the noise level and drastically change the tyre acoustical behaviour at higher frequencies. The frequency spectra for studded tyres presented in this paper have a substantially different shape when compared to the spectra for studless tyres. The most characteristic difference between studded and non-studded tyres appears at frequencies above 4 kHz and is a result of the studs interacting with the road surface.