ROBUST DETAILS - SOUND PROOFING

Sound plays a key part in maintaining a good quality of life. Poorly acoustically insulated properties will feel uncomfortable, as noise will easily penetrate the structure. The sound experienced within a building will vary from type to type. A detached house will mainly need sound proofing to prevent internal noise from transferring between rooms.

An apartment will require sound insulation to prevent footsteps from being transmitted through to the lower flat ceiling. This can be eliminated through the use of appropriate sound insulation. There are three main areas of a building that will require sound insulation - walls, floors and ceilings.

UK building codes require walls to be rated to 45Db and 62Db for impact noise to prevent noise from transmission between dwellings.

Robust Details is the UK standard for sound insulation. New buildings can either be tested using microphones, called pre-completion sound testing, or use standard thicknesses of defined materials to provide insulation. The latter is the usual method as it takes the guessing out of the process.

See www.robustdetails.com

Interior stud walls are normally designed purely as a method of dividing a structure into rooms. These often consist of 12.5mm plasterboard either side of a 50mm stud frame. These walls typically have a sound rating of 40Db (the level to which noise is blocked by the wall) and will allow TV and conversational noise to pass through. In order to insulate these walls sound proofing will need to be installed under the plasterboard.

This can take the form of a mineral or natural wool pressed into the cavities to increase the density and therefore sound proofing of a wall. A further method of sound insulation is to provide an absorbing sound membrane between the plaster board and stud wall frame. This can be made from materials such as recycled rubber and help to cushion against the vibrations which are caused by sound.

Interior brick walls will require some form of cladding to help prevent sound transfer. In high noise areas such as a practice room sheeting similar to a bedding duvet can be laid around the walls, this can be made from many environmentally friendly and recycled materials with common materials being hemp, wool and even recycled denim!

Exterior wall soundproofing is normally achieved by the choice of construction. Thick and dense rammed earth and cob walls not only use naturally sustainable materials but are also great sound insulators. Where dealing with an existing cavity wall filling the cavity with insulating foam or loose fill wool insulation will further increase the density of the wall. External cladding and render can be added to further enhance a walls sound insulation.

Noises transmitted through floors are caused by two methods, airborne and impact. Airborne noise consists of general noise created above the floor seeping through, impact noise is created by footsteps and other movements that impact on the floor transmitting sound downwards. Laying acoustic wool insulation underneath floorboards can cut airborne noise by up to 24Db but only reduces impact noise by 4Db, it should be noted though that sound insulating floorboards will help keep heat in as well.

Where impact noise is a particular problem matting solutions can be used to reduce impact noise. These are placed above the floor and can be made from recycled rubber. The absorption rate of matting can be as much as 30+ Db of impact noise.

Ceilings can be insulated from noise by fitting acoustic absorbing panels and insulation underneath a false ceiling layer. This may take up to 30mm off of the height of a room but will offer sound absorption qualities of around 17 + Db to both impact and airborne noise.

The type of insulation used in sound insulation installations will be of interest to a green builder. These often contain rubber, which is sustainable, but try and find companies that use a high percentage of recycled rubber from waste such as tyres.

Natural wool is not as efficient as mineral wool but if other methods of design are used which themselves reduce sound (such as cob building etc) then less dense wool insulation can achieve similar results to synthetic insulation. Mineral wool can contain a high percentage of recycled glass so if it is to be used make sure that a wool with a high recycled material content is chosen.

Wood based products such as fibreboards are also good insulators of sound and when sourced from sustainable forests are environmentally friendly.

Most heating insulation will also double as sound insulation. This means that making sure exterior cavity walls and interior walls have as many gaps as possible filled with insulation either sound or heat types. This is because air is a good conductor of sound allowing it to pass through it with ease, in contrast wool and foam based insulations provide a barrier slowing down the sound as it penetrates through them reducing its volume.