Sound Absorption Performance of Glass Wool
Centrifugal glass wool has better sound absorption performance to high frequency sound.The main factors affecting the sound absorption performance of centrifugal glass wool are thickness, density and air resistance.Density is the weight of material per cubic meter.Airway resistance is the ratio of static air pressure difference on both sides of the material to air velocity per unit thickness.Airway resistance is the most important factor affecting the sound absorption performance of centrifugal glass wool.The flow resistance is too small, indicating that the material is sparse and the air vibration is easy to pass through,so that the sound absorption performance decreases.The flow resistance is too large, indicating that the material is dense, the air vibration is difficult to be absorbed,so that the sound absorption performance is also decreased.For centrifugal glass wool, sound absorption performance has the best flow resistance.
In practical engineering, it is difficult to measure airway resistance, but it can be roughly estimated and controlled by thickness and bulk density.
1.With the increase of thickness, the sound absorption coefficient of medium and low frequency sound increases significantly, but that of high frequency sound changes little (the high frequency absorption is always large).
2.The thickness remains unchanged, the bulk density increases, and the sound absorption coefficient of medium and low frequency sound also increases;However, when the bulk density increases to a certain extent, the material becomes dense, the flow resistance is greater than the optimal ones, and the sound absorption coefficient decreases instead.For centrifugal glass wool with a bulk density of 16Kg/m3 and a thickness of over 5cm, the sound absorption coefficient of 125Hz at low frequency is about 0.2, and that of medium high frequency (>500Hz) is close to 1.When the thickness continues to increase from 5cm, the sound absorption coefficient of the low frequency will gradually increase. When the thickness is more than 1m, the sound absorption coefficient of the low frequency 125Hz will also be close to 1.When the thickness remains unchanged and the bulk density increases, the low-frequency sound absorption coefficient of the centrifugal glass wool will also continuously increase. When the bulk density approaches 110kg/m3,at 50mm thick , the sound absorption performance reaches the maximum value and is close to 0.6-0.7 at 125Hz frequency.When the bulk density exceeds 120kg/m3, the sound absorption performance decreases instead, because the material becomes dense and the sound absorption performance of medium and high frequency is greatly affected. When the bulk density exceeds 300kg/m3, the sound absorption performance decreases a lot.The thickness of sound absorbing glass wool commonly used in architectural acoustics is 2.5cm, 5cm and 10cm, and its bulk density is 16, 24, 32, 48, 80, 96 and 112kg/m3. 5cm thick, 12-48kg/m3, centrifugal glass wool is usually used.
The sound absorption performance of centrifugal glass wool is also closely related to the installation conditions.When there is an air layer behind the glass wool board, the sound absorption effect is similar to that of the glass wool board without air layer of the same thickness.In particular, the sound absorption performance of medium and low frequency will be greatly improved compared with that of the material actually attached to the hard bottom, and the sound absorption coefficient will increase with the increase of the thickness of the air layer, but the effect will not be obvious after increasing to a certain value.
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