Spectral Analysis of the Acoustical Performance of Winter Tires for Different Road Textures, Test Speeds and Tire State-of-Wear

Under winter conditions, in which ice or snow may be present on the road, different tire designs may be used to provide suitable friction levels. One alternative is to have studs embedded in the tire tread to increase friction. Another alternative is to use a studless tire with materials and tread pattern optimized for winter conditions. There is also a hybrid alternative, which is the use of small hard particles instead of regular studs. When considering the acoustical performance, these three different alternatives have different acoustical performances and the studded tires will result in significantly different noise spectra. Results from CPX measurements at different speeds and different road sections indicated that the studded tires spectral response is different in two major aspects: (i) a plateau instead of a decreasing trend is found for frequencies higher than 4 kHz, and (ii) overall increased noise levels, resulting in a spectrum that is shifted upwards. This paper analyses how the frequency spectra of winter tires are affected by different road surfaces, test speeds and tire wear. It also attempts to relate the observed behaviour to different contact and noise generation mechanisms to provide a better understanding of the acoustical performance of such tires.