Right.sound absorptionPorous materials haveImpactofPerformance factorsWhat are they all?

1.Thickness to sound absorptionporous materialPerformanceYesImpact.Sound absorption coefficient of glass wool with different thickness. With the same material, the thickness is doubled, and the preferred frequency of sound absorption is shifted about one octave in the direction of low frequency. The greater the thickness, the greater the low frequency sound absorption coefficient.The sound absorption coefficient has nothing to do with the thickness of the material; increasing the thickness can improve the absorption effect of low-frequency sound, but it has little effect on high-frequency sound.

In theory, if the sound absorptionporous materialThere is a rigid wall behind the layer, and the sound absorption frequency appears when the material thickness is equal to the wavelength of the frequency sound wave.1/4 of the place. In use, considering the economy and manufacturing convenience, for medium and high frequency noise, generally can use 2~5cm thick special-shaped sound-absorbing board. When the low-frequency sound absorption requirements are high, a sound-absorbing board with a thickness of 5 to 10cm should be used.

　　2.The effect of porosity and density on sound absorptionporous materialImpact on performance.Porosity, the internal pore volume of the material as a percentage of the total volume of the material. The porosity of sound-absorbing porous materials is generallymore than 70%;When the porosity increases, the density decreases, while the density increases..The larger the pore size, the smoother the pore and the smaller the flow resistance. The ratio of the pressure gradient in the sound-absorbing material to the linear velocity of the airflow under steady gas flow conditions.Effect of 5cm thick glass wool density change on sound absorption coefficient.Too high or too low density will affect the sound absorption performance of the material. In the case of the same thickness, increasing the density of porous sound-absorbing material can improve the sound absorption coefficient of medium and low frequency, but the change is less than the change brought by increasing the thickness, and the high frequency absorption will be reduced to a certain extent. The porous sound-absorbing material has a density range corresponding to a good sound-absorbing performance.

　　3.The effect of cavity on the performance of sound-absorbing porous materials.A layer of material with a certain distance between the cavity, the air layer and the rigid wall. sound absorption coefficient with cavity depthd (air layer) increases.The cavity structure saves material and is more economical than simply increasing the material thickness.The sound absorption coefficient of porous materials increases with the increase of the thickness of the air layer, but when it reaches a certain thickness, the effect does not continue to increase.When the cavity depthWhen d is approximately equal to 1/4 wavelength or odd multiple of the incident sound wave, the sound absorption coefficient is large.The cavity depth isWhen the wavelength is 1/2 or an integral multiple thereof, the sound absorption coefficient is small.The general recommend cavity depth is5 ~ 10 cm。The depth of the cavity on the ceiling can be selected to a larger distance according to actual needs and space size.

　　4.The effect of the covering layer on the performance of sound-absorbing porous materials.In practice, porous materials with loose materials are usually subjected to a surface protection treatment in order to facilitate fixation and aesthetics.

The perforation rate of the micro-perforated plate should be greater20%, otherwise it will affect the sound absorption effect.Textiles with good air permeability have little effect on sound absorption characteristics. When brushing the surface of the formed porous material plate, water-based paint should be used instead of paint to prevent the paint from closing the pores. The influence of environment on the performance of sound-absorbing porous materials.