When considering noise control it is important to appreciate the difference between sound absorption and sound insulation.
Sound Absorption refers to the attenuation of the reverberant noise within the same room and therefore it mostly falls outside the scope of a movable wall system. However when a sound wave hits a movable wall some of its energy will be reflected and some absorbed.
Sound Insulation, (also known as sound reduction) is the prevention of noise being transmitted from one area to another, by erecting a partition wall, for example. The ability of a partition wall to resist the passage of sound energy through it is largely determined by its mass, but structural isolation of the two surfaces and sound absorbency of the cavities in the construction are other factors which enhance the overall performance.
An Alco Wall NW100 acoustic movable wall combines these 3 factors by:
- Using dense cladding boards to add to the mass.
- Careful detailing of the internal components to isolate the boards from the inner steel frame and slabs of mineral wool infill within the cavity to increase the sound absorbency.
- Attention to detail is all important and that is why even the cavities of the seal carriers at top and bottom of the panel are filled with mineral wool and other material such as dense rubber matting.
The sound insulation level of a movable wall is graded by its Sound Reduction Index (SRI). This is usually derived from the results of laboratory tests and is expressed in terms of 'Rw dB', being a single figure based on a weighting system defined in IS0 140-3 En20 140-3
Since the results of laboratory tests are obtained in perfect conditions where there is no flanking sound leakage, they cannot be replicated on site where flanking leakage is always present at various levels. The normal loss between laboratory and site performance is 5-10 dB, depending upon how much care has been taken to eliminate sound transmission paths. There is neither a movable wall nor partitioning contractor that can guarantee any particular 'on site' performance because flanking transmission is beyond their control.
Naturally each manufacturer will try to show their product provides the best performance acoustically, but the only way each product can be compared equally is by a laboratory test result. Recently the testing method has been altered to take into account a wider range of frequencies and hence test results obtained prior to 1995 are invalid. The latest test procedures provide test results at frequencies from 100 through to 5,000 Hz and the average figure is expressed in terms of Rw. The relevant standard is now IS0 140-3 En20 140-3, 1995 in which results are expressed as Rw values only.
Alternatively, don't hesitate to contact our Sales Team on 01923 246600 e-mail Alco Walls.
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