Characterization For The Sound Absorption Coefficient Of Different Morphology Fiber And Arrangement Structural Needle-punched Nonwovens

Fiber assembly, referred to the fibrous body, is a porous, light, soft, sound-absorbing insulation material, and it has been widely used in various interior and the insulation material. As manual processing of needle-punched nonwovens materials is closest to the natural fibrous body state, which is only made into an assembly by a single fiber entangled with each other fibers, it is not only a low cost, high yield, small processing environmental pollution material, but also an excellent sound absorption noise reduction materials. Polyester fibers (polyester) because which has good formability, low moisture regain, high strength, high corrosion, is widely used. Needle-punched nonwovens fabric is the most important raw materials. The subject focuses on the acoustic behavior of fiber assemblies and it deals with the effect of fiber fineness and length, fiber orientation distribution, density and thickness of fiber assembly involved with the morphology of fiber assemblies, especially the effect on the structural parameters and laminated structure in order to improve sound absorption property over wide band of frequencies.Through a series of comparative experiments, it can be concluded as following:1. Natural state of the fiber assembly has a high porosity, sound absorption coefficients is up to about0.8in the high frequency; The effect of sound absorption is relatively poor at500-2500HZ. And by reducing the fiber fineness (dtex), increases the fibers and changes the orientation of fibers in the fiber assembly, using a larger bulk density and thickness of the material, which can improve the acoustic absorption coefficient and difference and achieve a good sound-absorbing effect.2. The larger the volume density is, the finer the fiber is, the sound absorption coefficient in the500-2500HZ of its fiber assembly is greater, effect of fiber volume density is smaller than the thickness,that is microfiber can receive excellent sound absorption properties in the same bulk density; Volume fraction and porosity is approximately a positive correlation and negative correlation to the sound absorption coefficient, which proves that volume fraction and porosity is another nature factor affecting the sound absorption coefficient. Specific surface area parameters of the fiber:theoretical specific surface area、the equivalent specific surface area、surface coefficient perimeter ratio are approximately linear positive correlation to the sound absorption coefficient., it proves that the specific surface area parameters are essential factors affecting sound absorption coefficient. Which also expresses the thinner fibers are, the sound absorption coefficient increases.3. Characterization of needle-punched nonwovens sound absorption behavior proves that It is consistency with the natural state of the fiber assembly, and the results are consistent with the trend of the thickness and density of fiber assembly.4. Different placement methods and the air layer will have effect on the sound absorption. The sound absorption effect of F+A is significantly than the placement of the A+F. When the needle-punched nonwoven fabric is with an air layer, which supplements the air phase of the basic unit of sound absorption, so that increase the vibration of the air layer and dissipative damping. By controlling the composition of the fibrous layer and the air layer, it is possible to enhance the sound absorbing effect of the fiber assembly. A certain size of air layer behind the textile materials can play a role in increasing thickness, so that can increase the sound absorption coefficient. There is interface between different layers. Different materials layered plus together makes interfacial friction increase, and convert it into heat or other forms of energy.5. The gradient structure combined by needle-punched nonwovens with different porosities could effectively improve sound absorption in the low-frequency. Sound absorption performance improved significantly in the low frequency (100-1000Hz).At the same time, the curve of sound absorption was relatively flat. Combining the samples with different porosities from high to low was conducive to the improvement of sound absorption.