The longitudinal noise attenuation laws of dense graded pavement, single-layer drainage and noise reduction pavement and double-layer drainage and noise reduction pavement in Dahongling No.2 tunnel are tested, and the noise attenuation characteristics of three types of pavement in the tunnel are obtained. The specific noise test results are shown in Table 4.3. Among them, the first test section of the double-layer drainage and noise reduction pavement is 25 m away from the sound source. Because there is a tunnel at the position of 30 m, the test section is moved to the sound source position by 5 m. For the single-layer drainage and noise reduction pavement and dense graded pavement, the test sections are at the position of 30 m away from the sound source.<br> Linear fitting is performed along the longitudinal sound pressure level of the tunnel, and the attenuation rate along the longitudinal direction is obtained. The longitudinal distribution curve is shown in Figure 4.8, and the longitudinal attenuation rate of different road surfaces of the tunnel is obtained by linear fitting (y= a*x+b).<br> <br> Through the test, it is found that the longitudinal attenuation rates of different pavements in the tunnel are as shown in Figure 4.7, and there are significant differences among the three pavements. The longitudinal attenuation rate of dense graded pavement is 0.076dB/m, that of single-layer drainage noise-reducing pavement is 0.100dB/m, and that of double-layer drainage noise-reducing pavement is 0.1316 dB/m.. It is concluded that in the same tunnel environment, the longitudinal attenuation rate of noise of dense graded pavement is the smallest, that of double-layer drainage and noise reduction pavement is the largest, and that of single-layer drainage and noise reduction pavement is in the middle. Therefore, the drainage noise reduction pavement can effectively improve the longitudinal attenuation rate of noise, so as to reduce tunnel noise and improve tunnel acoustic environment.
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