Resumen de `Low Noise Road Traffic'�The German research program, `LeiStra2'
LeiStra2' is a research program aimed at reducing road traffic noise at the source. It is a governmental funded program which comprises three parts: low noise tires, low noise roads and verification of results. In the course of the program it was possible to develop a new low noise truck tire, which has the potential to become the most quiet available truck tire. In another sub project a physical verified finite element method (FEM) software tool was developed, that is by now capable of simulating the structural vibration and noise emission from slick tires rolling on real road surfaces and thus can be used for the computer aided design of low noise tires. Current research in this sub program deals with the influence of the tread profile on the noise generation. In the research on a low noise road, a modified stone matrix asphalt pavement was realized that shows a noise reduction of 2 dB compared with conventional stone mastix asphalt. Furthermore, it is well know that porous asphalt layers have high sound absorption abilities, but unfortunately typically loose this ability after about eight years due to dirt clogging the pores. Within LeiStra2 we developed two measures that help to keep the sound absorbing abilities for a longer period. In particular the surface of the voids of the porous asphalt were covered with special polymeric material to prevent the voids from being clogged. In another sub project additional reactive sound absorbers were embedded in porous asphalt, which enhances the sound absorption and reduces the tire rolling noise by about 3 dB. Particularly annoying is the noise originating from vehicles rolling over expansion joints. Within LeiStra2 we succeeded in developing a new surface structure for conventional expansion joints, which substantially reduces the noise emission. These measures will be tested on various test tracks under real traffic load and environmental impact, which is the third subject of the program, the verification of the results. The program will be finished in summer or autumn 2009.
