A study of roadside noise barriers in a dense high-rise city

Abstract

Due to a host of factors such as fast economic growth, limited space for habitable development and concentrated road networks, road traffic noise is recognised as one of the most severe environmental impacts affecting daily livings in dense high-rise cities. The magnitude of road traffic noise impact increases enormously in the past decades due to the ever increasing demands for more transportation. More road networks are built and more vehicles are put in actions in the cities to support the economic growth and social activities. The impact is further intensified when more housing estates are constructed in cities which leads to the sharp diminish of the buffer separation between trunk roads and residential buildings. The situations even get worse when extent of hours exposed to road traffic noise goes beyond early morning and late night. There are different approaches and means to tackle the ever increasing magnitude of traffic noise problem in dense high-rise cities. Roadside noise barrier is one of the most commonly adopted measures. Because of the high density nature of high-rise cities, substantial roadside barriers like full enclosures, semi-enclosures or very high noise barriers are needed to provide necessary noise reduction. Many research works have been conducted in past decades for improving the assessment and evaluation of effectiveness; materials; and the design of roadside barriers. This study specifically investigates the accuracy of the current assessment and prediction tools, particularly in those cases where noise sensitive receivers locate near the shadow boundary of the barrier. Through theoretical and experimental evaluations, this study examines the following three aspects: a. modify the potential barrier attenuation curve in the Calculation of Road Traffic Noise (the traffic noise assessment procedures commonly adopted in the United Kingdom, Australia and Hong Kong); b. deterioration of noise attenuation effect of roadside barriers due to the presence of parallel roadside noise barriers; and c. diffraction and noise attenuation characteristics of cranked barriers. The investigations presented in the current study suggest that there are rooms for improvements in the aspects of prediction and designing of roadside barriers in dense high-rise cities.