# Study on Noise Reduction with Paving Different Low Noise Pavement Materials
## 4 Measurement Results
### Speed of the Trailer at 100 km/h  
Figure 8 shows the measurement results with CPX using the trailer at the speed of 100 km/h. For the inner lane, before the pavement maintenance, with the ECA-10, the average equivalent sound pressure level of typical light vehicle tire/road noise is 121.2 dB,  
Figure 7: Tire/road noise for different pavements at 80 km/h.  
and that of typical heavy vehicle tire/road noise is 122.5 dB, so the tire/road noise of heavy vehicles is about 1.3 dB higher than that of light vehicles. After the pavement maintenance, both the tire/road noise of light vehicle and that of heavy vehicles have decreased. For the inner lane, with 2.5 cm PUC-10, the tire/road noise of light vehicles has decreased by 0.3 dB on average, and that of heavy vehicles has decreased 1.9 dB. With 4.5 cm PAC-13+2.5 cm PUC-10, the light vehicle tire/road noise has decreased by an average of 2.1 dB, and the heavy vehicle tire/road noise has decreased by an average of 4.2 dB. With 2.5 cm PUC-10, the average light tire/road noise has decreased by 1.3 dB, and the heavy vehicle tire/road noise has decreased by 1.2 dB. With 4.0 cm PAC-13, the light vehicle tire/road noise has decreased by 1.0 dB, and the heavy vehicle tire/road noise has decreased by an average of 2.3 dB.  
For the outer lane, before the pavement maintenance, with the ECA-10, the average equivalent sound pressure level of typical light vehicle tire/road noise is 121.7 dB, and that of typical heavy vehicle tire/road noise is 122.0 dB. The tire/road noise of heavy  
Figure 8: Tire/road noise equivalent sound pressure level at 100 km/h before and after road maintenance (RM): inner lane (**Upper**); outer lane (**Lower**).  
vehicles is similar to that of light vehicles. After the pavement maintenance, the tire/road noise of light and heavy vehicles has decreased. With 2.5 cm PUC-10, the tire/road noise of light vehicles has decreased by an average of 1.7 dB, and that of heavy vehicles has decreased 0.3 dB. With 4.5 cm PAC-13+2.5 cm PUC-10, the light vehicle tire/road noise has decreased by an average of 3.6 dB, and the heavy vehicle tire/road noise has decreased by 3.0 dB on average, and the heavy vehicle tire/road noise has decreased by 3.2 dB. With 4.0 cm PAC-13, the light vehicle tire/road noise has decreased on average at 1.3 dB, and the heavy tire/road noise has decreased by an average of 2.0 dB.  
When comparing the tire/road noise measurement results of the inner lane with that of the outer lane at 100 km/h, with the ECA-10, one can see that the tire/road noise of heavy vehicles is higher than that of light vehicles. With 2.5 cm PUC-10, the average tire/road noise level of light vehicles is 120.5 dB, and that of heavy vehicles is 121.4 dB, so the tire/road noise of heavy vehicles is 0.9 dB higher than that of light vehicles. With 4.5 cm PAC-13+2.5 cm PUC-10, the light vehicle average tire/road noise is 118.7 dB, and the heavy vehicle tire/road noise level is 118.6 dB, which has nearly the same value. With 4.0 cm PAC-13, the average tire/road noise is 119.7 dB, and the heavy vehicle tire/road noise is 119.9 dB, which can be seen in Figure 9.  
From the experimental results at 100 km/h, one can see that both the tire/road noise of the light and heavy vehicles becomes the lowest when using the double-layer pavement among these four kinds of pavement materials. Compared with 4.0 cm PAC-13, for light vehicles, the 2.5 cm PUC-10 road noise is 0.8 dB higher, while for heavy vehicles, 2.5 cm PUC-10 road noise is 1.5 dB higher. Therefore, at a driving speed of 100 km/h, the noise reduction performance of 4.0 cm PAC-13 is much better than that of 2.5 cm PUC-10.