通过分析可知，由于排水降噪路面为大孔隙结构能有效吸收隧道内的交通噪声，

通过分析可知，由于排水降噪路面为大孔隙结构能有效吸收隧道内的交通噪声，排水降噪路面的混响时间短。对于密级配路面，单层排水降噪路面的混响时间减少了约1.45s，双层排水路面的混响时间减少了约1.62s。因此，采用排水降噪路面能有效缓解隧道内噪声混响效应，极大提高司乘人员行车安全性与舒适性。<br><br>大洪岭2号隧道内（长隧道）密级配路面、单层排水降噪路面及双层排水降噪路面噪声纵向衰减规律进行测试，得到隧道内三种类型路面工况的噪声衰减特征规律，具体噪声测试结果如表4.3所示。其中双层排水降噪路面第一个测试截面距离声源为25 m，由于在30 m位置存在一个隧道通道，将该测试截面向声源位置移动了5米，对于单层排水降噪路面及密级配路面测试截面均在距离声源30 m位置处。<br>沿隧道纵向声压级值大小进行线性拟合，得出沿纵向的衰减率。纵向分布曲线如图4.8所示，通过线性拟合(y= a*x+b)后得出的隧道不同路面的纵向衰减率。<br><br>通过试验测试，得到隧道不同路面的纵向衰减率如图4.7所示，三种路面衰减率有显著的差异，密级配路面的纵向衰减率为0.076dB/m，单层排水降噪路面的纵向衰减率为0.100dB/m，双层排水降噪路面的纵向衰减率为0.1316dB/m。得到在同一隧道环境内，密级配路面的噪声纵向衰减率最小，双层排水降噪路面的噪声纵向衰减率最大，单层排水降噪路面的噪声纵向衰减率居中。因此，采用排水降噪路面能够有效提高噪声的纵向衰减率，以降低隧道噪声和改善隧道声环境。

Through analysis, it can be concluded that due to the large pore structure of the drainage noise reduction pavement, it can effectively absorb traffic noise in the tunnel, and the reverberation time of the drainage noise reduction pavement is short. For dense graded pavement, the reverberation time of single-layer drainage noise reduction pavement has been reduced by about 1.45 seconds, and the reverberation time of double-layer drainage pavement has been reduced by about 1.62 seconds. Therefore, using drainage noise reduction pavement can effectively alleviate the reverberation effect of noise in tunnels, greatly improving the safety and comfort of drivers and passengers during driving.<br>The longitudinal noise attenuation characteristics of dense graded pavement, single-layer drainage noise reduction pavement, and double-layer drainage noise reduction pavement in the Dahongling Tunnel 2 (long tunnel) were tested to obtain the noise attenuation characteristics of three types of pavement conditions in the tunnel. The specific noise test results are shown in Table 4.3. The first test section of the double-layer drainage noise reduction road surface is 25 meters away from the sound source. Due to the presence of a tunnel channel at a distance of 30 meters, the test section was moved 5 meters towards the sound source position. For the single-layer drainage noise reduction road surface and the dense graded road surface, the test sections are all located at a distance of 30 meters from the sound source.<br>Perform linear fitting along the longitudinal sound pressure level value of the tunnel to obtain the attenuation rate along the longitudinal direction. The longitudinal distribution curve is shown in Figure 4.8, and the longitudinal attenuation rates of different road surfaces in the tunnel are obtained through linear fitting (y=a * x+b).<br>Through experimental testing, the longitudinal attenuation rates of different road surfaces in the tunnel are shown in Figure 4.7. There are significant differences in the attenuation rates of the three types of road surfaces. The longitudinal attenuation rate of the dense graded road surface is 0.076dB/m, the longitudinal attenuation rate of the single-layer drainage noise reduction road surface is 0.100dB/m, and the longitudinal attenuation rate of the double-layer drainage noise reduction road surface is 0.1316dB/m. Within the same tunnel environment, the longitudinal attenuation rate of noise on densely graded pavement is the smallest, the longitudinal attenuation rate of noise on double-layer drainage noise reduction pavement is the largest, and the longitudinal attenuation rate of noise on single-layer drainage noise reduction pavement is in the middle. Therefore, using drainage noise reduction pavement can effectively improve the longitudinal attenuation rate of noise, reduce tunnel noise and improve the tunnel acoustic environment.

Through the analysis, it can be seen that the drainage and noise reduction pavement has a large pore structure, which can effectively absorb the traffic noise in the tunnel and the reverberation time of the drainage and noise reduction pavement is short. For dense graded pavement, the reverberation time of single-layer drainage noise reduction pavement is reduced by about 1.45s, and that of double-layer drainage pavement is reduced by about 1.62s s. Therefore, the drainage noise reduction pavement can effectively alleviate the reverberation effect of noise in the tunnel and greatly improve the driving safety and comfort of drivers and passengers.<br> <br> 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.