Research On Properties Of Vibration Reduction And Noise Absorption Of Porous Concrete Materials

This issue tried hard to exploit a kind of porous concrete material. By researching the performance of the porous concrete on road vibration and noise reduction, the issue provided a useful reference to reduce noise pollution and vehicle vibration of Modern Pavement. This issue systematic researched the effects of porous cement materials on the vibration and noise reduction properties including porosity of material, aggregate diameter, material thickness and humidity of the air.(1) Free vibration damping method was used to measure cantilever damping ratio, and three-point bending beam test was used to measure material loss factor. These two facts (damping ratio and loss fact) were used to reflect the material damping properties. The results showed that the damping property of material increase when the porosity and the aggregate diameter of the porous concrete increase.(2) The issue developed a voice absorption coefficient test device by simulation reverberation chamber method. Then the device was used to measure the sound absorption coefficient of the material. Those factors on the porous concrete absorption coefficient such as porosity, aggregates size, material thickness and air humidity were researched under different incident frequency of the acoustic. From the experiment, it was found that the absorption coefficient of the porous concrete increase with the increasing of porosity, material thickness and air humidity.(3) This issue calculated and analyzed the pore structure of the porous concrete material, by slicing porous concrete material,taking pictures of the digital camera,using MATLAB to do image processing. The mathematical statistics was done to the porosity shape factor, the area of any single pore and the effective diameter of the pore from the data which was calculated from the experiment.(4) At last, a geometric model of sound absorption properties of porous concrete is established. Then the derivation was done from the geometric model to the absorption property model which is composed by micro perforated plate and slit cavity. The process of calculating the whole absorption coefficient was transformed to the process of calculating the circuit resistance using the analogy between the electrical system and the acoustic system. Finally the model can get the absorption coefficient from the relationship between the acoustic resistance and the material absorption coefficient. In order to improve the model, to making it more close to the reality, the issue also revised the model using the pore parameters getting from the pore structure analysis. Finally the precision of the model was verified comparing the experimental results and the calculate results from the revised absorption property model of porous concrete.