A STUDY ON THE NOISE BARRIER WITH SOFT SURFACE

软表面声屏障的研究

• 批准号: 04650542
• 负责人: FUJIWARA Kyoji
• 金额: $ 1.34万
• 依托单位: KYUSHU INSTITUTE OF DESIGN
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1992
• 资助国家: 日本
• 起止时间: 1992 至 1993
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04650542/
• 关键词: ROAD TRAFFIC NOISE; NOISE BARRIER; SOFT SURFACE

As the most convenient method for traffic noise control, we have a method to build noise barrier along the road sides. This method have been used for a long time until now. The surface of the noise barrier currently used is absorptive because of getting large shielding efficiency. But the efficiency is not so large, therefore the efficiency is not taken into account for barrier design. On the other hand, it is not very known that a barrier with "soft" surface reduces noise more than one with absorptive surface does. This study is aimed to make clear theoretically and experimentally how this barrier with soft surface can reduce noise.In 1992 it was studied whether it satisfies the soft boundary condition to cover the noise barrier surface with array of one quarter wave length acoustic tubes, as the result it was found theoretically and experimentally that this structure satisfies the boundary condition approximately. When one third octave band noise was used as a signal, the same result was obtained. But following the experimental result the array of acoustic tubes did not satisfy the boundary condition perfectly, a little more study was left for the next year.In 1993 the two dimensional sound field behind the barrier covered with acoustic tubes stood "on the reflective ground" was studied theoretically using Boundary Element Method. Following the result this surface also satisfies the soft boundary condition and it was found that this barrier can reduce the noise more than the absorptive noise barrier can. The same result was also obtained experimentally. Even in this year the perfectness of the soft surface has not been realized.There is one peak in the frequency characteristics of the road traffic noise, and when the design frequency of the acoustic tube is tuned at the peak frequency, then the noise reduction efficiency of the soft barrier is 3 to 5 dB greater than that of the absorptive one.

在道路两侧沿着设置声屏障是控制交通噪声最方便的方法。这种方法一直沿用至今。目前使用的声屏障表面是吸收性的，因为可以获得很大的屏蔽效率。但是效率不是很大，因此在屏障设计中没有考虑效率。另一方面，具有“软”表面的屏障比具有吸收性表面的屏障更能降低噪声，这一点还不是很清楚。为了从理论和实验上阐明这种具有软表面的声屏障的降噪效果，1992年曾研究过用四分之一波长的声管阵列覆盖声屏障表面是否满足软边界条件，结果从理论和实验上发现这种结构近似满足边界条件。当三分之一倍频程带噪声被用作信号时，获得了相同的结果。1993年，作者用边界元法对“反射地面”上的声屏障后的二维声场进行了理论研究，并在此基础上提出了声屏障后的二维声场的边界元法。结果表明，该表面也满足软边界条件，并且该声屏障比吸收式声屏障具有更好的降噪效果。实验也得到了同样的结果。道路交通噪声的频率特性存在一个峰值，当声管的设计频率调谐在峰值频率时，软质声屏障的降噪效率比吸收式声屏障的降噪效率高3 ~ 5dB。