Say no to noise

If you live close to a main road, a railway line or airport, or if you suffer from noisy neighbours, the level of intrusive noise in your home may become intolerably high.

Fortunately, there is usually a way to bring the noise down within acceptable levels.

Noisy neighbours and noisy houses are an increasingly common cause for complaint in urban areas. Luckily, there are a number of steps you can take to insulate your home effectively against noises from without. A great deal will hinge on the type of home you live in and the type of noise concerned, but whatever the problem, there are ways of insulating your home that will bring the amount of noise down to acceptable levels, even though you might not be able to sound-proof it completely.

Airborne noises

Airborne noises are the most common invasion of your privacy and moments of relaxation, but luckily they are also the easiest to deal with. They can range from aircraft and traffic noise, to one of your neighbours hi-fi system, to the noise of children playing next door. The levels of airborne noise are determined by a number of factors that are outside of your control, including the distance from the its source, the sound absorbency of the surrounding terrain, the position of natural "screens" (such as trees, buildings and walls). In the end, your last line of defence against airborne noise is to insulate your house against it.

Improving window insulation

Airborne noises from the outside will enter buildings through the weakest links that provide the easiest access, such as windows, doors and ventilation. Consequently, the sound level close to the window will be mainly determined by the insulation value of the glazing. However, the average noise level in the room will be determined by the combination of the wall and window. In this respect, the net insulation value of the room is always closer to that of the window, than of the wall and so in general, the larger the window, the lower the insulation value.

Because of its high density, even thin glass offers some form of insulation. However, ill-fitting frames can reduce insulation values enormously. Check the seals on the casement windows. On sliding sash windows, make sure that the tolerance between the sash and the frame is no wider than it need be. If necessary, glue and pin extra timber strips to the frame side of the sashes to form a better seal.

On casement windows, over-painting of the edges will damage the effect of the seal, because the paint builds up and prevents the frame from closing properly. If this is the case, scrape, burn or chemically remove the excess paint before priming and painting both closing edges. When the paint has dried, fit one of the many types of seals that are currently available.

Seals that have been developed to save heat are useful in this respect because you can make them serve a dual purpose. Wherever possible, use compression seals, rather than brush seals, because they are more effective. Before doing so, however, make sure that the casement is capable of exerting the necessary compression force: often only metal frames are sturdy enough to seal a compression joint.

Despite the density of glass, and the use of seals, the insulation value of the window is likely to be low, unless it is double-glazed. However, while two thin sheets of glass, separated by a gap of less than 50mm, may be an efficient heat insulator, such an arrangement might let in more noise than a heavy single pane of glass. This is because if both panes are of an equal thickness, they tend to produce a "coincidence loss" for noises of a particular frequency. This will be heard as a hiss-type noise from the home's interior. Therefore, where the width of the air-gap is limited to less than 100mm for practical reasons, rather use different weights of glass. With a gap of 50mm to 80mm, and panes of different thicknesses, double glazing offers significant improvement when compared to a glass pane of the same weight.

For sound insulation of greater efficiency, use a much wider gap between panes than you would for heat-loss – if possible, as much as 200mm, and stick strips of absorbent lining in the reveals between the panes. Carpet strips, mineral-fibre board or strips of foam plastic are sufficient to reduce noise escaping into the reveals or around the frames. You can improve sound insulation of existing windows by installing secondary glazing behind them. Give the existing windows good seals first, particularly at the edges of opening casements. Use sliding panes as the secondary glazing, placing the frame at least 50mm behind the existing pane of glass.

Using heavy, line curtains could improve the sound insulation even further, though it is important to also give some thought to the loss of ventilation that this might entail. Short periods of "noisy" ventilation may be feasible, but if they are not, a ventilation gap beneath the window, with staggered openings, will baffle direct sound transmission. Line the ventilation gap with sound-absorbent material.

Improving door insulation

Like windows, doors break the insulation qualities of solid brick walls, which are normally quite efficient. And because few doors are well sealed, the insulation value of a wall can be as much as halved by the sound entering via the gaps surrounding the door. Your first concern is to make sure that the doors fit as well as possible, by fixing warped doors or frames that are out of alignment for example. Fitting seals around the edges of the doors can significantly improve their insulation value. The best seals, but also the most costly, are the magnetic type used on refrigerators. Fit them into the rebate on the door frame to protect them and to form an unobtrusive and effective seal.

The threshold is the most difficult part of the door to seal and here you should use the type of threshold seal that has a raised bar containing a rounded, resilient strip. Make quite sure that the bar is accurately aligned with the bottom of the door and that it is in contact with the complete length of the bottom rail. This will make the door more difficult to open and close, but will greatly improve the sound and heat insulation.

In particularly bad cases of traffic noise, or persistent noise from outside, a good solution is to install an extra door by building an entrance porch, which leads to the door. This will in effect, function much the same way as double-glazing for windows does. If necessary, or desirable, use sound-absorbent covering on the ceiling or walls of the entrance to form a sound lock. Alternatively, increase the sheer weight of the front door by lining it on the inside or changing the door for a heavier one.

Improving wall insulation

Brick walls offer good insulation against noise, but dry walls don't – they are relatively light and hence, airborne noise can easily pass through them. To reduce airborne noise transmission, and impact noise, construct a false wall that conceals and insulating glass blanket. Make sure that the blanket hangs from the ceiling to the floor, without resting on the floor itself or touching the wall, as the slight air gap all around is very important.

You can further increase the insulation of a wall by adding polystyrene sheets behind the false wall. Stagger the joints of the layers to avoid undue settlement and cracking. In both these cases, the system work because of the interaction of air-space and sound absorbers. As with double glazing, use surfaces of different weights on either side of the wall wherever possible to reduce the risk of "coincidence loss" by vibration. For the same reason, it is advisable to fit soft felt between the vertical wall and the top and bottom horizontal runners. – Antonella Dési

Pictures

Images courtesy of:
- Double Glazing
- Global Specialised Systems
- Home Fixers
- Nulu Doors and indows
- plastixprotal.co.za
- Swartland
- Teva
- SONDOR

For more information click here to visit the Double Glazing website.
For more information click here to visit the Global Specialised Systems website.
For more information click here to visit the Home Fixers website.
For more information click here to visit the Nulu Doors and indows website.
For more information click here to visit the plastixprotal.co.za website.
For more information click here to visit the Swartland website.
For more information click here to visit the Teva website.
For more information click here to visit the SONDOR website.

Readers' Comments
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Excellent article about the noise reduction: "Say no to noise".

Pity its just six months too late, I had to move to another house to get away from the noise.
But thank you, I will definitely bookmark it and keep it for future reference. - Vimal Morar

Nothing is mentioned about "direct noise" e.g. Footsteps etc. from above. There are some solutions for wooden floors above including "floating" ceilings. - John Crew

The article missed out a non-decor solution to noisy neighbours. You call the police to shut them up. If they don't respond to the police, you go to the local magistrate and swear out a breach of the peace complaint. Under threat of a huge fine and worse for non-compliance with the magistrate's order, the ones with brains shut up, and the ones without have to sell the house to pay the fine – win-win either way. - Chris Bennett

Thank you for your reduction of noise tips.

My understanding is there are by-laws governing acceptable noise levels. My interpretation of these laws is that those contributing to noise emissions should be part of the solution, i.e. road transport – responsibility of government, municipalities and the public – and air traffic – government and municipalities.

Some possible solutions here in Cape Town would be to improve rail transport and get the majority of the trucks off the road!

Build a suspension bridge over the harbour to feed the traffic from the city to the northern suburbs and alleviate the traffic load on the N1. This project could be a combined effort of government, the Cape Town municipality and the private sector. Property values would increase on the N1 route as traffic congestion would decrease as well as noise and pollution levels. - Beverley Stunden

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