Sound Absorption Properties Of Flexible Needle-Punched Nonwoven And Its Composite Structrues With Wood-Based Board

With the development of modern technology and industry, noise pollution has become one of the three major sources of pollution along with air pollution and water pollution. Thus, noise reduction has been gradually evolved into an important issue need to be addressed urgently, which involves high tech, the environment and the coordinated development of the human need. At present, traffic noise and construction noise are particularly acute, most commonly used high-density materials such as iron and steel, metal sheet often have good sound insulation property whereas poor sound absorption property. That's because when sound waves come into contact with these materials, a large number of noise will reflect into the environment, resulting in noise pollution once again. Application of fiber or fabric reinforced composite or composite structure has been proved to be effective ways to reduce noise. Flexible nonwoven composed of fibrous bundles, which has a network of interlocking pores and high total fiber surface area, is a kind of typical porous sound-absorbing material. Compared to high-density materials, flexible nonwoven materials not only overcome the major disadvantage of high cost and high density, but also have the advantage of relatively simple to process, easy to shape and convenient to install. Therefore, this kind of material in recent years is concerned by public gradually.On the basis of previous studies, this paper mainly includes two aspects as bellows:Firstly, several needle-punched nonwoven samples are tested through Impedance Tube Methods and some factors such as fiber type, fiber size, thickness, bulk density, air gap, air permeability and pore structure affecting the sound absorption properties are discussed. The research results indicate that the thickness and bulk density play more important roles. The relation between thickness and sound absorption coefficient is a positive linear correlation and that between bulk density and sound absorption coefficient is a quadratic correlation under different frequencies.Secondly, in order to achieve complementary strengths and enhance the sound absorption performance, we innovatively paste flexible needle-punched nonwovens into rigid wooden sound-absorbing materials using adhesive to make a new composite structure. Three types of wood-based boards along with several needle-punched nonwovens are made into composite structure and their sound coefficients are measured in this paper. The results show that the type of wood, fabric paste manner, the fabric thickness, fabric density and the cavity can all influence the sound absorption performance, reasonable adjusting and arranging these factors can significantly improve the sound absorption property of the composite structure. Non-woven material paste into wood materials can increase the acoustic properties in varying degrees, in which the average absorption coefficient of wooden perforated board affixed before the nonwovens, wooden fiberboard after the nonwovens both increase by 0.35. The average absorption coefficient of the composite structures made by partt board and wooden fiberboard can increase up to 0.868, 0.862 from 0.409, 0.306.