- SPECIFYING SECONDARY GLAZING NOISE REDUCTION - BEST PRACTISE
- Acoustic glass windows, glazing for noise reduction, traffic noise and sound reduction
Getting the specification right is critically important, because this should be a “once only” installation that resolves the problem/s - “once and for all” - taking into account all of the following considerations:
- the type/s, frequencies and volumes of noise
- the required, or target level, of glazing noise reduction
- providing noise glazing plus insulation that also prevents heat loss
- attention to the aesthetics, to create a discreet, attractive finish
The following sections highlight the key factors involved in getting the sound reduction specification correct for each individual situation.
The Gap - for Noise Insulation
The gap between the primary window glass and the secondary acoustic glass windows (the “reveal”) is important to maximize the outside noise and sound reduction.
Standard primary window glass will usually be 4mm thick - or if very old, pre 20th century, it may be 3mm thick.
- for best glazing noise reduction using secondary glazing with 4mm glass - the gap should be 150mm
- for best glazing noise reduction using secondary glazing with 6mm glass - the gap should be 100mm
Depending upon the reveal depth of the primary window, it may not always be practicable to achieve such a gap when secondary glazing for noise reduction, but bear in mind that:
- for secondary windows using 4mm glass, each 25mm increase in the gap reduces the outside noise by approximately 0.75 dB - up to the maximum gap of 150mm
- for secondary windows using 6mm glass, each 25mm increase in the gap reduces the outside noise by approximately 1.25 dB - up to the maximum gap of 100mm
The Gap - Aesthetics
Where the primary window reveal is relatively shallow, less than 100mm, the best solution is:
- to improve the glass specification, from Float, to Acoustic Glass Windows
The alternative, “boxing-in” the secondary glazing with a deeper, extended sub-frame, may result in:
- a bulky, unattractive installation - we would identify if this is an issue on the initial site visit or survey and discuss with you to achieve the best solution
Different Types of Noise & Their Frequencies for Noise Glazing
The human ear responds differently to high and low frequency noise, filtering out the most extreme effects.
Low frequency noise includes:
- the general background “rumble” of traffic noise
- heavy goods vehicles, buses, taxis, train noise
- heavy “bass” type music from street noise
and is most effectively reduced by using a thicker glass.
High frequency noise includes:
- emergency service sirens
- jet aircraft noise
- power tools, lawnmowers
- “pop” music, etc
and is most effectively reduced by using acoustic glass windows.
General Loud Street Noise
General outside noise:
- busy street noise nearby clubs and pubs
- nearby commercial and industrial premises
- local parks, shopping centres and schools
General noise glazing is best achieved by using different thicknesses of glass in the primary window and the secondary glazing, in order to avoid resonance - which can result in:
- a high-pitched whine at high frequencies
- actual vibration of the glazing at low frequencies
The Glass - for Noise Glazing
Different types and thicknesses of glass in the secondary windows are specified to achieve the best overall glazing for noise reduction, dependent upon both the volume and the type of the outside noise.
In general order of least to most effective sound reduction, these are:
- 4.0mm Float Glass
- 6.0mm Float Glass
- 6.4mm Laminated Glass
- 6.4mm Stadip Silence Laminated Acoustic Glass
6.4mm Stadip Silence Laminated Acoustic Glass will effectively deal with traffic noise, train noise, aircraft noise and general street noise - in all city and town centres - as well as beneath flight paths and near railway lines and stations.
The Glass - for Thermal Insulation
Any of the above will also provide a dramatic improvement in thermal insulation.
See All Glass Options
Acoustic Tiles for Noise Glazing
In extreme circumstances, where the noise is really excessive and maximum sound reduction is needed, we recommend that the top and sides of the window reveals are lined with acoustic tiles for the best possible glazing noise reduction.
These are most effective for high frequencies such as aircraft noise and can improve noise reduction by up to a further 3 dB, depending upon the depth of the window reveal, the type of noise and the direction that the noise is entering the window from.
Acoustic tiles cannot be fitted to the bottom of a window onto internal cill (window board) because they are permeable and quite fragile - and therfore easily damaged.
- Noise Table & Tests
- Measuring Noise & the Human Ear Perception of Noise
- Residential Noise Levels – British Standards & World Health Organisation
Download our Secondary Glazing BrochureDownload Guidance & Info from Saint-Gobain - manufacturer of Stadip Silence acoustic glass