| Summary |
Shin-han Tsai，2007.02
Graduate Institute of Traffic and Transportation Engineering and Management
Feng Chia University
While national highways being gradually integrated as a highway network, traffic noise normally becomes an annoying problem that needs to be prevented or mitigated. Highway traffic noise can be prevented by measures of blocking propagation path or controlling sound source. Noise barriers, the most prevalent measures adopted by highway authorities in Taiwan, block propagation path. On the other hand, reducing noise from running vehicles are the way of controlling sound source. Most literatures indicated that traffic noise is highly related to pavement types, and the difference of noise in decibels due to pavement types can be as high as 11 dB(A). Consequently, it is worthwhile to investigate effect of pavement types on traffic noise.
In this study, field tests and laboratory experiments/ simulation were performed to evaluate the difference between pavement types and traffic noise and its frequency. According to ISO 11819-1 “SPB Method”, ASTM E965 “Sand Patch Method”, and permeation test, suitable sites on the national highway No. 3 and 4 were selected for field measurement. By using statistics regression method, traffic noise and frequency between various pavement types were studied. From the field test data, we compare the difference among characteristic factors of pavements. For ISO 13472-1 “Extended Surface Method”, the most common surface course, open-graded friction course (OGFC), was selected. Using Superpave gyratory compactor (SGC), 6-in diameter specimens with different compact levels were produced. Sound absorption coefficients and other related characteristics of these specimens were measured for understanding variation of noise characters with respect to compaction efforts.
It was found that various pavement types do have different noise characters. The permeated rate has better representative on noise generation. With the service time increases, accumulated traffic volume will re-compact the pavement and reduce void rate, the induced traffic noise will then become louder. The test results also indicated that porous surface has the best noise reducing effect. Meanwhile, less decline on noise reducing and permeability capabilities are also observed for porous asphalt pavement. It can be concluded that porous asphalt may be the pavement type. By laboratory experiments, finding that permeation rate is highly related to porosity. Sound absorption efficiency of the specimens at low frequency is better then high frequency. Noise reduction coefficient (NRC) is approximately 0.8.
Limited to accuracy on speed measurement at field tests and the difference between pore space and aggregate on sound absorption coefficients are too large at laboratory experiments, it’s unable to find out variations in road noise and sound absorption coefficient. |
