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How to soundproof windows

How to soundproof windows

Noise or the modern term noise pollution is a real frustration for a lot of people today.  Whether it is at home or in the workplace, it causes a range of problems including sleep deprivation and anxiety, fortunately you do not have to put up with it.

In this blog article, we’ll take a closer look at noise pollution and why installing the right specification of soundproof windows are crucial to stopping it.

Noise pollution from airports

Problems with noise pollution

While it can seem trivial to those who have not experienced it, noise pollution can be a serious problem with real consequences. At the very least, it can act as a disturbance at home, making it difficult to concentrate whether you are watching TV, reading a book or just trying to get a good night’s sleep.

This can become even more problematic away from your home, impacting the quiet environment of classrooms, places of work including the office environment and boardrooms. Working from home is on the increase, it now accounts for more than 1 in 10 UK workers, so a quiet area of your home is becoming a lot more crucial.

Exposure to prolonged or excessive noise ‘pollution’ has been shown to cause a range of health problems ranging from poor concentration, stress,  productivity losses in the workplace, communication difficulties and fatigue from lack of sleep. This can lead to more serious issues such as cardiovascular disease, cognitive impairment, tinnitus and hearing loss.

In 2011 the World Health Organization WHO released a report titled ‘Burden of disease from environmental noise’. The study collated data from various large-scale epidemiological studies of environmental noise in Western Europe, collected over a 10-year period.

The studies analysed environmental noise from transport modes like planes, trains and motor vehicles, as well as other typical city noise sources. It also looked at links to health conditions such as sleep disturbance, cardiovascular disease, tinnitus, cognitive impairment in children and importantly annoyance. The WHO team used the information to calculate the disability-adjusted-life-years or DALYs—basically the healthy years of life―lost to ‘unwanted’ human-induced encounters. The results might surprise you.

The WHO found that at least one million healthy years of life are lost each year in Europe alone due to noise pollution, an alarmingly high figure. The authors of the report concluded that “There is overwhelming evidence that exposure to environmental noise has adverse effects on the health of the population.” They ranked traffic noise second only to air pollution among environmental threats to public health

What is sound/noise? The Science

Sound travels through air, liquids and solids like the ripple seen on the surface of a pond when a stone is thrown into it. Sound waves emanate from the source in all directions, gradually reducing in intensity the further away you are from the source. It is these waves of sound that cause our ear drums to vibrate and are interpreted by the brain as sound. So a question commonly asked is 'if a tree falls in the woods and nobody is there to hear it, does it make a sound'  That is a deep subject, sound is a wave for sure, I will leave the rest up to you. 

Frequency of sound is defined as the number of vibrations per second. The higher the number of vibrations per second, the higher the pitch. The pitch is the way we perceive the frequency of sound. Tones that are high in pitch are high frequency and tones that are low pitch are considered low frequency. The sound intensity describes how soft or loud the sound is (this is measured in decibels dB). A low dB value indicates a soft sound and a high dB value a loud sound. Amplitude is loudness. A given change in amplitude is not necessarily perceived as being proportionate to the change in loudness. This is because loudness is also effected by the frequency of the sound. Loudness is measured as sound pressure level in decibels (dB).

Noise Cancelling

So we have all heard of noise cancelling headphones, how do they work?  A speaker emits a sound wave with the same amplitude, however with an inverted phase (known as antiphase) to the original sound. The waves combine to form a new wave that causes interference. The waves effectively cancel each other out – an effect which is called phase cancellation that results in noise cancellation. The science can be quite complex!

Causes of noise pollution

Common sources of nuisance noise in the home or work place

  • Transport including road traffic, planes and trains
  • Pets
  • Neighbours
  • Passers-by on public footpaths
  • Restaurants, bars, clubs and pubs
  • General town/city noise
  • Industrial sites, like factories or bus stations
  • Maintenance and building (like road works or building projects)

So why does the type of windows matter?

There is more to the cause of noise pollution than where the source of the noise actually originates. It is worth considering why your home is letting that noise in. Common weak spots include trickle vents, letter boxes, fireplaces, ill-fitting windows, keyholes and cat flaps. But in most cases, it is down to your windows and the type of glass used.

Windows are one of the weakest points in a property because the glass is thin and taut pieces of material. This readily influences by sound wave energy. Without the right protection, they essentially behave like a speaker to transmit noise. Windows that do not close properly because they are not well sealed, will also be a major cause of ‘sound leakage’

This just does not apply to old single-glazed windows, standard double or even triple glazing often struggles to offer a notable reduction as the vibration of the glass compresses the internal air or gas in the sealed unit. Because of the close proximity of glass layers in double or triple glazing (it is often no more than 16mm or 20mm) this allows the sound wave energy to continue without much interference. So how can this be improved?

Acoustic glass helps soundproof windows 

Acoustic glass is a sandwich of two or more sheets of glass. These are either heat or pressure bonded together with one or more acoustic polyvinyl  butyral (PVB) interlayers. The interlayers act like a noise damper, weakening the energy of the sound waves as they travel through the glass.

Acoustic glass is designed to absorb and dissipate sound more effectively than standard glass options. Using a combination of laminated glass and different thicknesses of glass reduces vibrations and noise, so less sound travels through your double or even triple glazed window. Acoustic double glazed windows can reduce sound by up to 30-40dB

In simple or layman’s terms , noise reduction can also be expressed in terms of distance. Every 3dB reduction in noise in effect doubles the distance from the source of the noise. So if you have a noisy road 10m from the front of your property and can get 3db reduction, this would theoretically double the source of the noise to 20m away.

Improving the sound insulation of a double glazed window can be achieved by:

  • Having the widest possible cavity between panes of glass
  • Differing the thicknesses of the two glass panes used
  • Using thicker glass
  • Using an efficient insulating window frame
  • Using specially laminated acoustic glass

Our glass supplier uses SGG STADIP SILENCE. This is Saint-Gobain's best solution for acoustic insulation glazing. It reduces 3 dB acoustic compared with laminated glass of a similar thickness. At equal weight, the acoustic comfort is therefore significantly improved. As mentioned earlier 3 dB in effect double the distance of the source of the noise!

Acoustic performance of glass is not affected by

  • The position of the two panes of glass, whether they are placed on the interior or exterior of the glazing.
  • Using argon gas to improve the thermal insulation

Please remember the acoustic qualities of windows are determined by the glazing but also by the type of frame and how they are installed. Acoustic insulation glazing must be mounted in an effective and well-installed frame.

Secondary glazing and soundproofing

If you really want to reduce the amount of noise getting through your windows (assuming the primary window is in reasonable condition) secondary glazing is proven to be the most effective solution. Why you might ask? The gap between the existing window and secondary glazing panel is bigger than the gap you get in between double glazing.

The larger gap between the primary window and the secondary glazed unit creates a more significant barrier for sound waves to pass through. This means the sound waves are much weaker by the time they get to the other side.  The results can be incredible; it can be as much as five times more effective than double glazing. With the right design using acoustic glass and a good size gap, it is possible to reduce noise by as much as 75%.

The gap between the original window and the new secondary glazing is one of the most important things to consider regarding sound insulation. The most common thickness of glass in the original household single glazing would typically be around 4mm, unless the property is pre 20th century, then it could be 3mm. Double glazing cavities are generally smaller on older double glazing and are usually constructed with 4mm glass.

  • So if the original house glazing is 4mm and the secondary glazing is 4mm, the gap would need to be around 150mm between the original window and the new secondary glazing for optimal sound insulation.
  • With 6mm glass in the secondary glazing this gap could be reduced to 100mm.
  • If the reveal (or window cill depth) cant accommodate a 100mm gap then laminate or acoustic glass like Stadip should be considered for maximum sound insulation.
  • Acoustic glass is always the best option – the downside is the increased cost

In general terms the larger the gap between the primary window and secondary glazing the better the sound insulation.

The benefits of secondary glazing:

  • Secondary glazing is one of the best ways to reduce noise and soundproof your windows, it can reduce external noise by around 75%. This can be enhanced further by specifying either laminate glass or Stadip acoustic glass.
  • Draught Proofing is another reason to install secondary glazing.
  • Low E Pilkington K glass (option) for better heat insulation
  • Extra security (if specified with locking catches)
  • Retains the exterior look/character of the property

Secondary Glazing Options

The following designs can normally be suited to your existing primary windows to allow ventilation and egress

  • Horizontal slider
  • Side Hinged
  • Vertical Sliding
  • Fixed Units/Lift Out

Secondary glazing case study


Noise and your windows – my closing thoughts

In conclusion sound is an important and valuable part of everyday life. It is how we communicate and can warn us of danger.  But when sound becomes noise and becomes a nuisance it can negatively affect our mental and physical health. The realities of modern life mean the noises created in our world are not going to suddenly fall silent and if anything are growing every day, as the population continues to increase at an alarming rate. So we need to recognise that noise pollution is a serious health concern worthy of our attention, find realistic and sustainable ways to manage and reduce it. The truth is that external noise is very hard to manage and it will take many years of governments dithering to do so. However changing what can be heard in your home can be regulated by installing good double glazing and for extreme circumstances installing secondary glazing. This is how you soundproof your windows.

Useful information

Glass and Glazing Federation guide to acoustics

Our soundproof windows web page

Our secondary glazing web page

Saint Gobain high performance glazing brochure


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