sound insulation part 2

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What are the Options?​

The science of sound is quite complicated and acoustic insulation is therefore a relatively complex field, as far as housebuilding is concerned. Noise is routinely referred to in decibels (dB), and soundproofing tends to be measured in decibel reduction. But the decibel scale is not easy to understand and there are different ways of measuring sound reduction.

Sound itself moves in different ways: airborne sound is easy to understand, impact sound less so, as apparently small sounds can carry and even amplify as they travel through solid materials like pipes or across hard surfaces. Flanking sounds are ones which arrive by indirect routes, such as through side walls or floors. The frequencies of sound also matter: measures to stop a high-pitched whine may not be effective against a deep-thumping bass sound.
What acoustic insulation hopes to do is to reduce the overall effect of a cocktail of sounds. There are three basic methods of improving sound insulation:
  • One is to add mass – heavy layers – which naturally absorb sound better.
  • The second is to provide separated layers so that an air gap is formed, which dampens sound.
  • The third is to compartmentalise, which means to make sure that rooms are fully separated from one another and penetrations are kept to a minimum.

The insulation suppliers have many materials and solutions for the first two methods: acoustic insulation, sound-blocking boards and planks, resilient bars and much more. Compartmentalisation, on the other hand, is about not leaving holes in floors or walls. It’s all to do with build quality.

When the original research was being carried out for the rewriting of Part E, it was found that many beam and block middle floors, which had been specified because of their superior mass and soundproofing characteristics, were in reality performing rather badly. Closer investigation found that plumbers were routinely taking out blocks in order to run pipes through the floor, and not bothering to fill in the voids afterwards. This causes a sound pathway, thus making a perfectly good idea ineffective.