Highway Tunnel Noise Prediction And Noise Reduction Measures

Road traffic noise pollution is the main noise pollution in cities. And noise from the traffic of road tunnel, as an important part of road traffic noise pollution, has always been a problem which needs urgent solutions.The study begins with the analysis for present conditions and main courses of road traffic noise from tunnels. It is helpful for the further understanding of how the tunnel noise comes into being, which is directive for both noise prediction and also putting forward relevant control measures for tunnel and tunnel mouth.Tunnels with straight roads are objects of the study. To simply the analysis, image wall concept is introduced for noise prediction in tunnels, thus the acoustics in the long enclosure of tunnel is translated to room acoustics. Room acoustics theory is used here to study the traffic noise in tunnels with multiple paths and all kinds of vehicles with different velocities, and predicting model is given. Prediction of noise from tunnel mouth is given from the point of view of configuration of the tunnel. And the effects to mouth noise caused by shape and area of the cross-section, length of the tunnel and ratio of length to width are stressed. A uniform model is given for tunnels with rectangular or semicircle cross-sections. Some control measures are given and at the same time, noise reductions are studied when the tunnel is treated with different materials and sound absorption structures, considering their physical characteristics. Some sound absorption materials and structures are chosen for noise reduction of road tunnels.Some significant conclusions are acquired as follows,1. Given the length, noise from tunnel mouth increases with the increase of the area of the cross-section.2. Effect of the shape of cross-section can be neglected, and predicting model can be unified as one formulas concerned with the ratio of length to width.3. Noise increases with the increase of the number of road path and proportional of heavy cars.4. Different materials affect noise reduction in tunnels notably.The above conclusions help to know the characteristics of noise in tunnels. Theoretical consequence can be used to predict noise in tunnels with different traffic, and different materials can be analyzed to see if they can be used to reduce the noise in tunnels. It is theoretical directive for predicting and controlling of tunnel noise and it has practical significance.