Determining regularities in the distribution of noise load from motorways and road bridges depending on the distance to a residential area

Abstract

This paper reports the improved model for estimating transport noise from highways at a roadside lane under the influence of noise load from traffic flow moving on an open section of the highway and over a bridge. It has been established that with an increase in the distance from the sound source to the coordinates of the noise load measurement, the noise decreases, both in the presence of a noise-protective screen and in the case of an open section of the highway. At 100 m from the sound source, the noise load level decreases by 13.4 % in the case of the car moving over a bridge, and by 13.3 % when driving a car along an open section of the road. It has been found that the noise level on bridges exceeds the level of noise pollution from the road to 10 dB, which is explained by the propagation of different frequencies of noise load from the bridge. It has been determined that due to the special nature of sound waves, diffraction through noise screens does not change all frequencies evenly. High frequencies diffract to a smaller degree while lower frequencies diffract deeper into the "shadow" zone behind the screen. Therefore, the screen is more effective at reducing sound waves with a high frequency compared to sound waves with lower frequencies. Experimental studies into the effectiveness of noise-protective screens made of metal perforated structures on sections of public roads were carried out, taking into consideration distances from noise sources to noise load measurement sites. It is established that noise-proof screens made of steel (perforated) sheet reduce the level of noise load from vehicles to the environment by up to 14 %. It was found that when driving cars on the road, the equivalent sound level at a distance of 1 m in front of the noise protection screen is 88.6 dBA while the maximum sound level at a distance of 1 m in front of the noise protection screen is 103.9 dBA. It has been established that in the presence of a drain hole in the noise protection screen, its acoustic efficiency is reduced to 3 dBA.