Air-related mechanisms of noise generation by solid rubber tyres with cavities

There are four main air-related noise generation mechanisms at the tyre/road interface, which were all categorised more than 20 years ago. The first one is the so-called ‘air pumping’ mechanism. Two other air-related phenomena that occur when there are air movements near the contact patch of the tyre are ‘air resonant radiation’ and ‘pipe resonances’ which appear at the footprint of the tyre. In addition to these, there is a forth effect, which is mentioned in the literature, that is occurring due to turbulence effects of the air surrounding the spinning tyre. There has been less focus on the air related mechanisms than on other types of tyre noise generation mechanisms. This paper attempts to add some detail to current understanding of the air-related noise generation at the tyre road interface and gives some further information on how to identify the differences due to these mechanisms. Specifically in the present paper, a solid rubber tyre running on a vehicle chassis dynamometer is used to study the first two mechanisms. This is done with emphasis on the time history of the recorded signal and not on the frequency spectrum, as is more commonly used. A comparison with existing theoretical models of these mechanisms reveals some of the strength and weaknesses of the current understanding of these phenomena

Experimental investigations into the air pumping effect at the tyre/road interface

Introduction: Environmental noise pollution is an important issue that affects health and quality of life of millions of people in the modern world. One of the main sources of environmental noise pollution is the noise generated by road traffic. To reduce road traffic noise, the automotive industry has done a great deal of research and development in the recent decades. As a result of these efforts, such earlier important contributors to the overall automotive noise, as powertrain and exhaust noise, have been reduced considerably for nearly all driving conditions, so that the dominant contributor has become tyre/road noise. According to the tyre/road noise reference book written by Sandberg and Ejsmont, there are two different groups of generation mechanisms for tyre/road noise: (i) tyre vibrations; and (ii) aerodynamical effects in or around the tyre. In contrast to noise generated by tyre vibrations, the aerodynamical mechanisms of tyre noise generation have received relatively little attention in the past. Therefore, the main aim of the research reported in this paper was to undertake comprehensive experimental investigations of aerodynamically related mechanisms of tyre/road noise