Shota KIDO
Noise propagation Analysis Around the Barrier using Cellular Automataon Method
Yasuyuki MIYAKI
Noise is one of the important environmental problems. Solving these problems, it has been performed Noise propagation analysis and development of noise control technology. However, the technology that have versatility and simply is not developed very. Therefore, we have been developing the 2-dimensions noise propagation analysis that is used cellular automaton (CA) method in this research. In CA method, calculation area is divided into a cell of uniform size, and state value is calculated from time to time by applying local interaction rule to each relation between notice cell and adjoining cells.
Till last year, we compared CA model with theory value, Maekawa chart and finite difference method about some phenomena of sound (the divergence decrease, the diffraction attenuation, the interference and the Doppler effect) in 2-dimensions. In addition, we examined calculation time and stable condition of calculation. As a result, we found that the precision of CA was equal with finite difference method and CA was profitable to calculation time. However, examination of versatility of CA was insufficient. The difference of effects by barrier shape is not shown definitely, either.
Therefore, this research applies CA method to 2-dimensions bridge model, and it is a last purpose to examine effects of diffraction attenuation by barrier shape. At first, plural cases are compared with Maekawa chart to check reliability of CA. Next, we compared calculation value by CA with measured value by experiment of outdoor. Afterwards, in the bridge model, we examined influence to diffraction attenuation by a difference of barrier shape. Then, it is supposed that height of barrier is constant.
As a result, the diffraction attenuation quantity by CA was distributed around the experiment curve of Maekawa. By using CA, we were able to express the experiment curve of Maekawa. In addition, the bridge model was able to show that effects of diffraction attenuation rises as frequency becomes high. In low frequency, we understood that the effects is provided when barrier shape is T or Y
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