On the Relationship between Traffic Noise Resistance and Urban Morphology in Low-Density Residential Areas

This study aims to explore whether and how urban morphology influences the capability of a residential area on attenuating traffic noise levels. Particular attention is paid to low-density residential areas, which are more appealing for study because of their relatively low capability of noise resistance compared with the high-density morphology. Six urban morphological parameters that are accessible and commonly used in urban design and planning are selected. Noise mapping techniques have been employed and a MATLAB program has been developed to obtain the spatial noise level indices, Ln. The relationships of urban morphological parameters with the spatial noise level attenuation and the size of noisy areas were subsequently revealed. The results indicate that the spatial noise level attenuation primarily occurs on noisy façades and in noisy open areas; urban morphology influences the attenuation in open areas more than on façades. A site with quieter open areas, as measured by average spatial noise levels, such as L50, is prone to have a smaller sized 'Less Noisy Area.' A site that has greater building coverage, however, has noisy façades with higher spatial noise levels in terms of L10 and L20. With an increase of the Building Plan Area Fraction (BPAF), the spatial noise levels on noisy building façades do not decrease but increase continuously. The Complete Aspect Ratio (CAR) and the Building Frontal Area Index (BFAI) both have the greatest impact on the average spatial noise levels, such as L60 in open areas. The reduction of noisy open areas occurs with a decrease in the distance between the first-row buildings and a traffic road. It has also been revealed that the noise reduction occurs with an increase of façade areas along a road.