How does double glazing block out noise?

Many people will turn to double glazing as a way to block out noise from their homes as well as to keep the heat in; if you live on a busy road or near to a pub, airport or other source of sound adding double glazing to your windows will cut down the racket from outside your home. There are a few things to bear in mind if you want your double glazing to be an effective barrier for sound, using the wrong material or having windows that don’t fit correctly will not have the desired effect on the noise inside your home.

The first step to reducing outside noise is to understand how sound travels, then you can create a more effective barrier for it. Sound travels in waves, similar to the way that light travels but much, much slower; light travels at over 650 million miles an hour, whereas light potters along at just over 750 miles per hour (the exact speed depends on air pressure and composition). It is much easier to block out the shorter, faster waves of light than the slower sound waves, as anyone who has tried to make a room both pitch black and silent will know.

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The noise created by sound waves is due to the vibrations of the air and other materials that they travel through, eventually reaching our ears and vibrating our ear drums in a way that sends messages about the sound to our brains. So the way to stop noise is to stop the sound waves reaching our ears, which is more difficult than it seems. Light waves can be stopped by most opaque solid materials, whereas sound actually travels better through steel than through air, and those long sound waves can bend round corners and squeeze through tiny gaps.

Sound travels through solid objects by making them vibrate and in turn making the air on the other side of them vibrate, passing the sound on. Sound waves pass through a pane of glass quite easily, but with a double glazed unit they also have to navigate a pocket of gas such as argon, which slows down the sound waves meaning that less get to the second pane of glass, creating fewer vibrations and less noise. Thicker panes of glass and a larger gap between them will have a greater noise reducing effect, and having panes of different thicknesses can help as they will affect different sound wavelengths.

Double glazing can be a really effective way to reduce the outside noise getting into your home, but it is important to remember that the sound waves will find the path of least resistance, so there is no point in having double glazed windows if they do not fit properly; the tiniest air gap is a channel for noise. Channels for cabling to get into the house which tend to be cut through window frames need to be properly sealed, and the seals where the windows fit into their frames need to be as airtight as possible; even ventilators need to be tightly shut for the best results.

Basically if air can get in, sound can too so as we are unlikely to live in a completely air tight house there is little chance every bit of outside noise can be filtered out, but a well fitted double glazing unit can make a big difference to your peace and quiet at home.

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