Rolling noise - Influence of road pavements

For several decades now, road noise has been a major environmental nuisance in France and many other countries. Recent studies show that over 30% of the European population is exposed to levels of road traffic noise deemed hazardous to health, according to WHO limits. The stakes involved in reducing road traffic noise are therefore particularly high. While noise barriers remain the most widely used tools for combating road noise today, means of reducing noise at source have the enormous advantage of being more comprehensive (not just acting locally), less intrusive (visually) and less costly for society. Over the last twenty years, carmakers have succeeded in considerably reducing the mechanical noise of vehicles (engine, exhaust, transmission). However, the speeds considered (below 130 km/h) are too low for the aerodynamic noise associated with the vehicle's movement through the air to be significant. As a result, the noise emitted by contact between the tire and the road surface, or "rolling noise", has become predominant, even at low speeds, from 50 km/h for light vehicles (and even 30 km/h for new vehicles), and around 80 km/h for heavy goods vehicles. Practical solutions exist to reduce this rolling noise, through action on tire characteristics, on those of the road surface, or by limiting vehicle speed. The most important issue seems to be the road surface, since action on tires is limited by safety and durability concerns. For the same vehicle, a difference of the order of 2 to 3 dB(A) is obtained depending on whether or not it is fitted with acoustically optimized tires. On the other hand, gains of around ten decibels can be achieved at the roadside between the noisiest and least noisy surfacings, and some low-noise surfacings are now being proposed as road noise reduction measures in their own right.

The generation of rolling noise is a complex phenomenon which was first understood experimentally. Subsequently, a detailed analysis of the physical phenomena at play in the process of generating tire-road contact noise proved necessary in order to optimize tires and, above all, road surfaces. In fact, there is no device or scale model that can realistically reproduce rolling noise in the laboratory, and to predict the effect of a given pavement characteristic on the noise generated, it is necessary to carry out full-scale tests on several dozen meters of pavement. A predictive model involving physical pavement parameters that can be quantified in the laboratory is therefore of considerable interest.

At the same time, methods for measuring rolling noise have evolved. Essentially, two methods are currently in use: pass-by measurement and continuous proximity measurement. These measurement methods are not equivalent, but they are complementary. They enable models...