Myths and realities

At this conference, the subject of tyre/road noise is on the agenda to a greater extent than ever before. This paper aims at giving an insight into the past, present and future of tyre/road noise emission in the society as well as its control. This is made by means of exploring some myths and realities related to the subject. The following myths are explored: 1. Tyre/road noise has become a concern only during the last decades, say from the 1970's. It is shown that already long ago tyre/road noise was an important issue. 2. Tyre/road noise is an important part of vehicle noise at speeds above 50 km/h (70 for trucks). The truth is that nowadays tyre/road noise dominates during almost all types of driving for cars and down to about 40 km/h for trucks (vehicles meeting EU requirements). 3. Manufacturers have done a lot to reduce vehicle and tyre/road noise. Yes, in some respects; but yet it seems that vehicle noise sometimes has increased rather than decreased. 4. The speed influence is large but not very interesting. It is shown that there are unexpected relations between speed-related factors and that these can be useful in data presentation. 5. Different road surfaces may give a large variation in noise levels. True, the variation is very large, albeit the most common and useful surfaces are close together on the noise scale. 6. Tyres do not differ very much in noise emission. This is not true, the variation is large if sufficiently many tyre types are included in the data set. 7. Winter tyres are much more noisy than summer tyres. This is a myth based on the past. Currently, winter tyres may be the "quiet" tyres. 8. The width of the tyre is a very influential factor. Essentially true: A noise-width relation covering the range from "tiny" bicycle tyres to large truck tyres is presented. 9. Tyre/road noise from a heavy truck is far above that of a typical car. Not true, one may find heavy trucks that emit lower tyre/road noise than some cars. 10. Tyre/road noise is very broadband nowadays. True and not true current tyres emit noise very much concentrated within the 1 kHz octave. Tone correction may be considered. 11. Quiet tyres are possible only if sacrificing safety. Recent results show that there is no tradeoff between low noise emission and high safety; neither with rolling resistance. 12. We cannot afford to reduce tyre/road noise. Calculation exercises are presented that suggest that low-noise tyres as well as low-noise road surfaces may be very cost efficient. 13. Tyre/road noise will be substantially reduced by the introduction of noise emission limits. Not true; the new EU emission tyre noise limits will be almost totally ineffective.