SOUND INSULATION

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SOUND INSULA T ION

JARGON BUSTE R

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OV ERV IEWA QUICK

Airborne NoiseImpact NoiseAvoiding FlankingThe Difference Between Rw and Dw 

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BUILDING STYP E S OF SOUND INSULATION IN

There are two main types of noise that are of concern when it comes to sound insulation in buildings.

Airborne NoiseImpact Noise 

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NOIS EAIRBORNE

E XAMP LE S OF AIRBORNE NOISE

Someone's voice

Music from a loudspeaker 

Sound from a television

Airborne noise is any unwanted noise that travels or transfers through the air. It is most relevant when constructing partitions between rooms. 

This is defined as a variant of either Rw or Dw, and isusually specified as a minimum value of insulation which must be achieved.

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NOIS EIMP ACT

Impact noise occurs when energy passes into a partition from an impact, and re-radiates as noise on the other side. The example of this you will likely be most familiar with is footsteps on a floor that can be heard in the room below - especially concerning in domestic situations.    Impact is a form of structure-borne noise, which many of us have also experienced when neighbours decided to get the drill out and do some DIY too early on a Sunday morning! This is specified as a variant of Lw and, in contrast to airborne sound insulation, is specified as an upper limit which must not be exceeded.

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INSULA T IONSOUND

Avoiding Flanking and The Difference Between Rw and Dw

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SOUND F LANKINGAVOID ING

D UCTWORK

Ductwork passing from room to room may also prove an issue, but cross-talk attenuators (prefabricated sections of ductwork with acoustic lining) can be used to stop ducting acting like a “speaking tube”, and allowingspeech to transfer from room to  room.

Flanking is sound that transfers from Room A to B through a route other than directly through the partition. This might include junctions of walls with ceilings or floors, if the partition isn’t properly detailed and sealed. It's also common for a hole to be drilled through the partition, for example for cables, then not be properly sealed, leading to excessive flanking.

Products like expanding foam won't stop noise from passing through; in any case, the key to sound insulation is mass. To stop sound flanking, small openings need to be properly stopped up with mineral wool and mastic. Larger openings may require a cover plate to perform as intended. 

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Rw and DwTHE   D IFFE RE NCE BE TWE E N

RwThe laboratory stated value of the sound reduction index of a building. It can, for example, apply to walls, ceilings, floors, doors, windows, etc.

D wThe on-site measured values of the sound insulation. This is the target used to measure against in pre-completion testing.

Both Rw and Dw are ways of rating the performance of a partition in terms of Sound Insulation which must be achieved.

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SOUND INSULATION?SO, YOU WANT TO ACHIEVE DECENT

FOLLOW THE " GOLDEN RULES"

Get some help on specification from an acoustic consultant - it's not just about the wall / floorBuild it properly - sound can be like water, it'll trickle through any holes you leaveThrow that expanding foam in the bin... Please?

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