Study of the Traffic Noise Source Emission Model and the Frequency Spectrum Analysis of Electric Vehicles on Urban Roads in China

Due to the less pollution emissions while running on the road, electric vehicles are widely promoted in China. The primary objective of this study is to develop a traffic noise source emission model and analyze the noise frequency characteristics of electric vehicles on urban roads in China based on the measured traffic noise data. The noise data of two types of electric vehicles, including light and heavy electric vehicles, are collected from a noise measurement experiment conducted on urban roads. The valid measured data are used to fit the traffic noise source emission models of electric vehicles, which have passed the correlation test, t-test, and error test. Then, the analyses about the noise models and the noise frequency spectrum comparison between the electric vehicles (EVs) and the internal combustion engine vehicles (ICEs) are carried out. Finally, a traffic noise simulation is performed for presenting the noise reduction effect of different proportions of electric vehicles on traffic noise emission in a traffic flow. The results reveal the followings. The sound pressure level of EVs is lower than that of ICEs for each vehicle type and the average differences both are above 5.5 dB(A). In terms of the frequency content, the noise energy of EVs is more concentrated than that of ICEs, and the noise energy of light EVs is concentrated within the range of 500 Hz to 1,600 Hz, while that of heavy EVs is concentrated within the range of 630 Hz to 2,500 Hz; and the equivalent frequency of the traffic flow increases with an increasing proportion of electric vehicles. According to the simulation, the noise of the traffic flow decreases obviously with an increase in the proportion of EVs in the traffic flow, and the reduction effect is above 7 dB(A) with 10% reduction rate. The obvious noise reduction effect indicates that the increase of EVs can greatly improve the acoustic environment of urban areas.