Characteristic Of Acoustic Radiation From Concrete Cylindrical Shell With Holes

Box girder are increasingly been used to alleviate the transportation pressure caused by the increase of urban population. Thus, the problem of low frequency noises induced by box girder are gradually been highlighted. Experiments show that low frequency noise dominates the noise induced by box girder and study also shows that people too much frequently exposed to such noise may suffer from many diseases such as nausea, dizziness, memory decrease, insomnia and even neutralisms. However, few researches have been done on such problem due to the complexity of dynamic behavior and radiation condition of box girder and some indeterminate factors. Therefore, it's critical to make clear the acoustic radiation mechanism and the sound pressure distribution at various frequencies nearby the structure and hence found valid solutions for low frequency structural acoustic problems. In this paper, a preliminary simulation was carried out using a closed concrete cylindrical shell, and the closed shell is a simple and regular structure to ensure that the analytical method and further general experimental techniques are applicable. On the other hand, this experimental and theoretical analysis of the shell, especially submerged shell had better accuracy and more supporting information than the site work of viaduct. It is the fundamental study leading to measures to reducing the low frequency noise induced by the vibration of such structures, which has been keeping annoying residents living nearby and may do even greater harm to those exposing too much to it. The low frequency structure-borne noise produced by a closed finite cylindrical shell and a modified finite model under the same force excitations are examined. It is shown that modifying the structure slightly by digging some small holes on it under the premise of not affecting the bearing capacity of the structure can alleviate the annoying low frequency noise.