Based on Cost Benefit Analysis (CBA) and acoustical view, this paper investigates the realization of an acoustical tunnel to enclose a viaduct in the vicinity of high-rise buildings in urban area. Typically, mitigation measures shall be designed and implemented according to noise predicting. While it is difficult to achieve great reduction of noise levels based on the current technology in the vehicle design, the noise reduction achieved will be offset by increase in traffic related to the growth of private car ownership. Nowadays, the traffic noise levels have exceeded the statuary noise limits in many urban areas. From this point of view, optimization of the noise control treatment shall consider concurrently with the environmental benefits, the social and economical aspects. Although mitigation measures to control traffic noise are now well-known, from the CBA point of view, acoustical efficiency to achieve required levels will be counterbalanced by heavy costs. With a non-linear relationship between efficiency and investment, a balance shall be found. Viaduct passing high-rise buildings in a city is occasionally unavoidable. For a full enclosure on such a viaduct extracted by a case study, the principles of CBA are applied to conciliate acoustics and economics. A series of predictions using software CadnaA have been conducted. While Insertion Loss is expected as high as possible, cost-efficiency of this approach is disputable, particularly in view of the contribution of ambient noise from sources other than the researched viaduct. A comprehensive approach to the mitigation solution is suggested to optimize the noise planning.
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