Study On Measurement Method For Traffic Noise From Expressway

Traffic noise generated by expressway operation has unfavourable influence for residents in the surrounding region. Thus, it is needed to measure, evaluate and control traffic noise generated by expressway operation. However, the specialized measuring method of expressway noise has not been established so far. Most of the environmental monitoring departments throughout the country adopt the measuring mothods of noise along main urban roads. There are some differences in intensity of noise sources, propagation way, and influence range of noise between expressway and main urban road. So the situration of expressway noise can not be reflected accurately by the measuring mothods of noise along main urban roads. It is urgently needed to research on the change and propagation law of traffic noise along expressway, establish the unified measuring method, and standardize the measurement of traffic noise along expressway throughout the country.We monitored the traffic noise along some expressways in Shandong province using acoustical measurement technique and analyze the change law of traffic noise along expressway, relationship between the traffic noise along expressway and the number of inhale, etc. The conclusions are obtained as follows:(1) There are not notable differences in equivalent sound level of expressway between during the day and during the night. (2) The traffic noise along expressway from 7:00 tol 1:00 and from 15:00 to 18:30 are higher than other time during the day, and the traffic noise along expressway from 22:00 to 24:00 is higher than other time during the night. (3) 80 percent of the difference values between the day-time and night-time equivalent sound levels per hour, e.g. between LAeqz and L_d are less than 3 dB;.80 percent of the difference values between the night-time equivalent sound level per hour and night-time equivalent sound level e.g. between L_Aeqz and L_nare less than 2 dB. (4) The relationship between the traffic noise along expressway and the number of large inhale is the closet. To a certain extent, the changes of traffic noise are mainly controlled by the number of large inhale. (5) The noise of sensitive sites within 100 meters on both sides of expressway is generally substandard. The noise of some expressway sections with high uphill gradient even within 200 meters on both sides of expressway exceeds the standard scope.We analyzed the effect of temperature on monitoring traffic noise along expressway. In order to ensure the accuracy of monitoring data, we tried to monitor in a range of environment temperature from 10 to 30℃. If the correction difference is more than 0.5 dB(A), the monitoring data is considered to be invalid. The conclusions are obtained as follows:(1) The obtained data through combining discontinuous measurement in most of sensitive sites with continuous measurement in few sites are representative. (2) The monitoring spot should be set at more than one meter apart from noise-sensitive structures. The frequency should be set to monitor twice a day, morning and night, and twenty minutes in succession each time.At last, the detailed measurement methods of traffic noise along expressway are proposed and proved by experiment.