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The elements of noise control
When approaching a noise control problem, the difference between sound
absorption and sound insulation should be appreciated.
Sound Absorption
Sound absorption refers to the attenuation of reverberant noise within the
same room or area as the noise source. This normally involves lining all or
part of the room surfaces with a material which absorbs sound.
In most houses and flats, the soft furnishings provide a good degree of sound
absorption. Adding additional sound absorbent material is unlikely to lower
the noise level in the room significantly and will not produce a corresponding
reduction in the noise being transmitted to neighbouring premises.
Sound Insulation
Sound Insulation, otherwise know as sound reduction, is the prevention of
noise being transmitted from one part of a building to another, for example by
erecting a partition or wall.
Improving the sound insulation of walls and floors between dwellings is the
main way in which the noise transmission between dwellings can be reduced.
When considering sound insulation in existing buildings, three methods of
sound transmission need to be considered:
Airborne sound
Impact sound
Flanking sound
The air tightness of the construction is also important.
Increasing the mass of a wall or floor will improve its sound insulation.
However, the amount of extra weight that can be safely supported by an
existing construction is often limited so other design approaches are usually
employed in remedial work i.e, isolation, absorbent materials and resilient
layers.
Airborne sound sources produce noise by vibrating the air immediately around
them. Typical sources include the human voice, musical instruments, home
entertainment systems and noisy dogs.
The ability of an element of construction to resist the passage of airborne
sound energy through it is largely determined by three factors:
1. The sound absorbency of any cavities in the construction.
2. The structural isolation between the two outer surfaces.
3. Its mass.
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