Tire/pavement noise characteristics of HMA pavements

In today's society, traffic noise is a serious problem. The term "noise" should not be confused with the term sound. Noise is the generation of sounds that are unwanted. With respect to traffic, noise would be the generation of sounds that affect the quality of life for persons near roadways. Therefore, traffic noise can be considered an environmental pollution because it lowers the standard of living. Research in Europe and in the United States has indicated that it is possible to build pavement surfaces that will reduce the level of noise generated on roadways. Use of hot mix asphalt to reduce noise levels could potentially save millions of dollars by reducing the number or height of noise wall barriers alongside highways. For this reason, in January of 2002 the National Center for Asphalt Technology initiated a research study with the objective to develop safe, quiet and durable asphalt pavement surfaces. This paper provides a basic understanding of the nature of noise, how it is measured, and how the vehicle and the pavement affect noise. The study has shown that it is possible to construct low-noise HMA mixes and that in general the smaller the nominal maximum size for those mixes (regards whether the pavements are dense graded, SMA or OFGC mixes) the lower the noise level. It is also concluded that for OGFC mixes the higher the air voids the lower the noise level. It is recommended that controlled experiments where HMA pavement surfaces using the best available technology are built and the noise level be monitored over time.