Noise Control by Enclosure
A complete acoustic enclosure can provide noise reduction of 20 dB(A) or more. An enclosure can be used to surround either the noise source or the person exposed to it. The walls and roof should be formed from a material having a SRI exceeding the noise reduction required by at least 5 dB at all frequencies involved. To prevent build up of reverberant noise within the enclosure an internal lining of absorptive materials should be used – usually a minimum thickness of 50mm.
Direct vibration contact between enclosure and machine should be avoided by using flexible couplings and seals. Small air-gaps can seriously detract from the enclosure’s acoustic performance. Care is required when introducing services such as cooling air, power, fuel or water to an enclosure, in order to ensure its overall performance is not affected.
For all complete enclosures, attention to detail is vital to avoid weak points. Doors must be fitted with flexible seals and spring closures or compression latches. Windows must be constructed to provide the same SRI as the remainder of the structure and consideration should be given to the use of multiple glazing. In many cases a complete enclosure is not practicable, and a partial enclosure may be necessary.
In this case a lower Sound Reduction Index is provided. The SRI becomes less important than the provision of an effective sound absorbing lining. The fundamental design principle requires avoidance of direct sight lines between source and receiver.
 Noise Control by Screens
In some cases, a simple screen may provide sufficient noise control, although in general screens have very localised effects. A screen will reflect noise and if lined with an absorptive material, will provide some further reduction in the energy.
As in the case of partial enclosures, the screen may be constructed of a relatively lightweight material, since the SRI required is not high. Noise can diffract around obstacles and for maximum effectiveness, the screen should be as large as possible and placed as close as possible to either source or receiver. Screens should be both mobile and decorative.
 Noise Control by Room Treatment
Many noise problems result from the reverberant build up of noise within an acoustically “hard” building. Reductions of the order of 4 dB(A) in reverberant noise levels can often be achieved by the use of absorptive ceiling and/or wall treatments.
The products that should be specified in these applications will depend to a large extent on building type, i.e. industrial, commercial, etc.
In factories, Tap Quietair Baffles, see TAP Spec guide, suspended from the roof or ceiling, effectively reduce reverberant noise.
In offices or commercial buildings where aesthetics are of importance, reductions in reverberant noise levels can be achieved by installing a suspended ceiling incorporating Taptiles and/or Tap Quietwall panels, see TAP Spec guide. Floors may be improved by the use of Iso-barrier, see TAP Spec guide.
The reduction in noise level depends on a number of factors, but in general, for each doubling of effective absorbing area (or Sabin) in a room (effective area or Sabin = area of absorber x absorption coefficient) a reduction of 3 dB(A) in the reverberant noise level may be expected. It must be emphasised that this technique provides no reduction in the direct noise transmission path and therefore accurate identification of these is essential.
 Noise Control by Combination of ,  and 
The effectiveness of enclosures, screens and room treatment has been discussed in isolation. However it may be necessary to use a combination of two out of three or all three methods to obtain the correct noise control, e.g. Tap Laminate, see TAP Spec guide.
 Noise Control by Partition Improvement
Many cases occur where existing partitions are acoustically inadequate. In such cases it is usually possible to achieve improvement by: Stopping flanking transmission, e.g. by sealing all gaps; providing a cavity lining of Taptiles; or adding a secondary partition, separated from the original wall, again by installing Taptiles within the cavity.
 Noise Control by Ductwork Lagging
Where noise is transmitted through the walls of ductwork, very effective noise control can be achieved by an external application of 25-50mm Tap-wrap, see TAP Spec guide, with a mass layer of at least 5kg/m²)
A suitable external treatment is an application of Tap-wrap.
Where sound absorption in air conditioning equipment and distribution ductwork is required, acoustic foam or melamine should be used.