Low noise road surfaces in the Federal Republic of Germany. State of the art

The texture of road surfaces influences the rolling noise of cars and trucks. High texture depths cause high noises by the incitation of tire tread vibrations. Low depths favor the generation of aerodynamic noise sources in the tire tread, for example, air pumping. This type of noise can be suppressed by open surfaces on wearing courses with high void contents. As coatings with low diameter gritting material on worn concrete showed, air pumping noises can also be reduced on closed road surfaces. But trials on gussasphalt turned out to be not very successful thus far. The greater part of the rolling noise on such surfaces is apparently caused by a waviness with wavelengths between 3 and 6 cm, which could be caused by the embedment of chippings. A similar reason seems to be responsible for the limited noise reduction on concrete surfaces with burlap finishings. Measurements at a 5.5‐m‐diam internal drum with sandpaper surfaces and different grittings on asphalt concrete allows the hope that the rolling noise of car tires can be reduced by several decibels, if road surfaces are gritted by small diameter stones from a small fraction without oversizes.