The reverberation time of dense graded pavement, single layer drainage noise reduction pavement, and double layer drainage noise reduction pavement in Dahongling Tunnel 2 (long tunnel) was tested, and the reverberation time of different types of pavement conditions was 3.17s, 1.72s, and 1.55s, respectively. The typical attenuation curve calculated during the test is shown in Figure 3.1.<br>As shown in Figure 4.6, the reverberation time of the dense pavement in the Dahongling Tunnel 2 (long tunnel) was tested, and it was found that the reverberation time of the dense pavement was 3.17 seconds; The reverberation time of the single-layer drainage noise reduction road surface was tested, and it was found that the reverberation time of the single-layer drainage noise reduction road surface was 1.72 seconds; The reverberation time of the double-layer drainage noise reduction road surface was tested, and it was found that the reverberation time of the double-layer drainage noise reduction road surface was 1.55 seconds. 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.
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