Low noise asphalt pavement Keywords: low noise; Asphalt pavement; Mix; Mix designAbstract: In order to study low noise asphalt pavement mixture gradation design method, using the aggregate gradation design and optimum asphalt content as low noise asphalt pavement mix design two major design index, adopt the token method to determine aggregate gradation design, by the means of the theoretical calculation, flow test and asphalt drop test analysis, to determine the asphalt .The best mixture asphalt content. The results show that the token method get mixture voids and target void ratio has a good linear correlation, the flow test method to determine the optimum asphalt content of asphalt mixture, more accords with the practice of engineering and easy to generalize. Low noise asphalt mixture due to different from ordinary asphalt mixture, so cant use ordinary asphalt mixture design method to study. Asphalt mix design, including aggregate gradation design and optimum asphalt content determine two content, and In China there is no mature experience. The design method, it is the study of the main problems need to be solved.Introduction:In recent ten years, thanks to the government increased the transportation infrastructure construction force and active investment policy, Chinas rapid development of highway construction, especially the main national highway construction has made great progress, road network is the total size and overall technical level have increased greatly. By the end of 2000, the national highway mileage understanding 167. 980000 kilometers, of which grade highway 131. 590000 kilometers,The national road network density up to 17. 5 km/hundred square kilometers. The rapid development of highway construction, increase transport capacity, promote regional economic rapid development speed, but also to the surrounding environment caused by a certain degree of pollution damage, traffic noise is one of the major pollution.Traffic noise as a kind of noise pollution, the residents of the interference in many countries has more than other forms of noise pollution.In France, 80% of those surveyed think noise pollution in daily life the biggest cause of interference, half of which people think that traffic noise is the main noise source. Similarly, in Beijing a survey also showed that the traffic noise pollution complaints accounted for more than 55% of the total noise complaints. The traffic noise pollution economic loss is difficult to accurately measure, in 1996 the European commission, says a report from the European Union countries home every year because of the loss caused by traffic noise estimates of GDP 0. 2% 2%.In China, with the rapid development of national economy, the appearance of a large number of new passenger and cargo traffic volume, the domestic various operating vehicles and private car society has doubled to 1990 as an example is 632. 980000 quantity, to 1999 increase to 1986. 820000 quantity. The amount of car number multiplied, plus the road mileage increase, level enhancement and the improvement of the roads, certainly will bring road traffic of rapid growth, if not take effective measures, will cause the deterioration of the road noise pollution. In urban road traffic noise as an example, according to the China environmental conditions bulletin of the data, the urban road traffic noise pollution in 2000 compared with 1999 shows ascendant trend, table 1-1 is the national 200 key city traffic noise level.Table 1-1 in 1999 and 2000, national key urban traffic noise monitoring results comparisonyearpollution levelHeavy pollution（%）Moderate pollution（%）Light pollution（%）Good（%）19995. 28. 527. 35920008. 922. 453. 315. 4In general speaking, the key urban road traffic noise pollution in mild basic state, individual main line both sides even overweight strict heavy. Beijings fourth ring road (highway standard) as an example, 2001 years of noise test results show that the average noise between day for 74. 3 77. 6 dB (A) between, night for 73. 8 77 dB (A) between. Much more than national standard day room 70 dB (A), night 55 dB (A) between the highest limit.Source to distant spread, acoustic energy with diffusion distance increases; decay rate and the shape of the wave front. However, if there is a source close to the surface, it would happen, and then the surface of the sound wave reflection appear additional sound diffusion. This kind of additional sound diffusion effect in the automobile tire noise diffusion process is very outstanding. When close to the source of the reflecting surface is porous structure, additional sound diffusion effect will occur in the table surface. At this time, the distance to receive the sound pressure level is direct diffusion acoustic and reflection of the sound wave superposition effect. When the acoustic constitute the main part of the phase difference for 180 degrees occurs when the des