Noise is the second commonest reason people give for wanting new windows and the one the trade answers worst. The usual pitch is "triple glazing", which the manufacturers' own test data does not support, and the usual figure is a percentage with no source. The glass makers publish what their units actually achieve, tested to the same British Standard, so this guide uses those numbers and shows what moves them.
The numbers: what each build of unit achieves
Sound reduction is rated as Rw in decibels, measured to BS EN ISO 10140. Higher is quieter. The figures below are Pilkington's and Saint-Gobain's own for a standard 16 mm argon cavity; they apply to air-filled units too.
| Unit build (outer / cavity / inner) | Rw | What changed |
|---|---|---|
| 4 mm / 16 mm / 4 mm (standard double) | 29 dB | The baseline in most UK homes |
| 6 mm / 16 mm / 4 mm (asymmetric) | 32 dB | Different thicknesses stop the panes resonating together |
| 6 mm / 16 mm / 6 mm standard laminate | 33 dB | Laminate damps the glass; standard interlayer |
| 6 mm / 16 mm / 6.8 mm acoustic laminate | 40 dB | Soft acoustic interlayer; the usual domestic acoustic unit |
| 8 mm / 16 mm / 8.8 mm acoustic laminate | 42 dB | Heavier panes on both sides |
| 10 mm / 20 mm / 8.8 mm acoustic laminate | 46 dB | Wider cavity adds 2 dB over the 16 mm version |
| 10.8 mm acoustic / 24 mm / 16.8 mm acoustic | 52 dB | The top of the standard range; needs a frame built for it |
Source: Pilkington Optiphon brochure (ref 8222, January 2020); Saint-Gobain STADIP SILENCE UK data. Centre-pane glass figures; the installed window is lower, see below.
Read the second column against the third and the pattern is clear. Making the two panes different thicknesses is worth 3 dB on its own. Laminating one pane is worth another. Swapping the standard laminate interlayer for an acoustic one, which Saint-Gobain tests like for like on the same 10-16-12.8 build, is worth 4 dB more: 40 against 44. Heavier glass and a wider cavity add the rest. Nothing on the list adds a third pane, and that is the point of the next section.
What the dB numbers mean at your window
Two rules of thumb. Every 10 dB is perceived as roughly a halving of loudness, so the step from a 29 dB standard unit to a 40 dB acoustic one is a little more than halving the noise that comes through the glass. And the target is an indoor level, not a reduction: the British Standard planners use, BS 8233, wants 30 dB in a bedroom at night and 35 dB in a living room by day. A busy road at the kerb is around 75 dB and the UK Health Security Agency describes 50 dB as "around the level of noise seen on a quiet street", with 40% of adults in England living above that. So on a 50 dB street a standard unit already reaches the bedroom target on paper; at 75 dB it does not, and an acoustic unit at 40 dB does, provided the rest of the window keeps up.
Why triple glazing is the wrong answer to noise
The manufacturers' data puts standard 4-16-4 double glazing at 29 dB. The lab figures installers cite for standard triple glazing are about 32 dB, a gain the asymmetric double unit above achieves without a third pane. Two equal cavities can also set up what the trade calls a drum effect, where the panes vibrate in sympathy. Where triple glazing does reach the high forties and fifties it is because acoustic laminate has been used in it, and the same laminate in a double unit gets within 2 dB: Guardian rates its acoustic laminate at up to 54 dB in triple and 52 dB in double. If an installer proposes triple glazing for a noise problem, ask for the Rw of the unit in writing. Our double vs triple guide covers the thermal case, which is where triple genuinely earns its premium, and the triple glazing cost calculator prices it.
Two more things that do not help. Argon: Pilkington states its acoustic figures apply to air or argon fills alike, because the gas changes heat transfer and not vibration. And a thicker single pane on its own: 4 mm float has a resonance around 3,000 Hz that costs it 10 to 15 dB at exactly the frequencies of traffic and voices, which is what the laminate interlayer is there to damp.
What acoustic glass costs
The premium is in the glass and nowhere else, because an acoustic unit is fitted exactly like a standard one. The trade guides quote acoustic glass at £150 to £300 per square metre. For scale, the online glass merchants sell plain 4 mm float at about £50 per square metre per pane and standard 6.4 mm laminate at about £180, so an acoustic laminated pane sits at the top of that, and a whole soundproof double glazed window is quoted at £300 to £750 against £400 to £1,000 for a standard fitted uPVC casement. On a typical casement of under a square metre that is a premium in the low hundreds per window; on a large picture window it is more. The glass specification cost guide sets it beside the other upgrades.
One saving hides in it. Laminated glass is safety glass, so on a door, beside a door or below 800 mm from the floor, where the Building Regulations already require toughened or laminated glass, the acoustic laminate replaces a cost you were paying anyway rather than adding to it. Our blown double glazing guide lists those critical locations.
The frame, the seals and the vents decide the real result
Every figure above is for the glass unit in a laboratory opening. The glass makers say so themselves: the performance "cannot be determined by the glass alone", and a 52 dB unit in a poor frame is a poor window. Three things lose the decibels you paid for. A frame that is not sealed to the wall behind the trims. Gaskets that do not compress all round; a gap of 1% of the window area can cost up to 10 dB. And the trickle vent: a standard vent left open is a hole in the window, which is why planning conditions near airports and main roads specify acoustic trickle vents, rated by their own figure (Dn,e,w), alongside the glass. Ask for the vent's rating as well as the unit's; our trickle vents guide explains why the vent has to be there at all.
When secondary glazing is the better answer
A sealed unit holds its two panes 16 to 20 mm apart, close enough that they move together. Secondary glazing, a separate pane 100 mm or more inside the original window, decouples them, and the tested figures follow: plain 6.8 mm acoustic laminate in a secondary unit reaches 40 dB at a 100 mm cavity, the same as the best domestic acoustic double glazed unit, and 42 to 43 dB at 150 to 200 mm, with heavier glass and wider cavities beyond 45 dB. It costs less per window, needs no consent on a listed building, and can be removed. Its costs are in our secondary glazing cost guide and the full comparison in secondary vs double glazing. The trade-off is a second window to open, and for a home that also needs new windows for thermal reasons, an acoustic sealed unit does both jobs in one frame.
Help with the cost near airports
If the noise is aircraft, check the airport's scheme before you pay. Stansted's sound insulation grant funds double glazing and ventilation for homes at 57 dB or above, from £5,000 to £10,000 by zone, with applications open from 1 April to 31 October. London City Airport's scheme fits secondary glazing or thermal double glazing with acoustic ventilators within its 57 dB contour, contributes £3,000 index linked toward high acoustic performance double glazing within 63 dB, and pays the full cost within 66 dB. Other airports run their own; the terms change, so go to the airport's website rather than an installer's summary of it.
The verdict on acoustic double glazing
Worth it Worth it where noise is the problem and the windows need replacing anyway: specify a 6-16-6.8 acoustic laminated unit or heavier, in writing, with the Rw figure, an acoustic trickle vent and a properly sealed frame. Not worth it as triple glazing, and not the first answer on a listed building or where the existing windows are sound, where secondary glazing does more for less.
Ask for the Rw of the unit, not the number of panes. A quote that says "triple glazed for noise" without a decibel figure is a quote from someone who has not read the glass maker's data sheet.
Double Glazing Cost Calculator Team
Get quotes with the acoustic spec written down
The benchmark is a 6-16-6.8 acoustic laminated unit at Rw 40 dB in a sealed frame with an acoustic trickle vent, priced as a standard window plus the glass upgrade. For a quote on your own openings, tell us what you have and Leads 2 Trade will arrange quotes from installers covering your postcode. Ask each one for the Rw of the unit they propose.
Frequently asked questions
On the manufacturers' tested figures, a standard 4-16-4 double glazed unit is rated Rw 29 dB. Swapping one pane for 6.8 mm acoustic laminated glass takes a 6-16-6.8 unit to 40 dB, and heavier acoustic builds reach 46 to 52 dB. Every 10 dB is perceived as roughly a halving of loudness, so 29 to 40 dB is a little better than halving the noise that comes through the glass.
Barely, unless it is built with acoustic glass. Pilkington's data puts standard 4-16-4 double at 29 dB and lab figures cited by installers put standard triple at about 32 dB. The gain in acoustic units comes from asymmetry (panes of different thickness) and laminated interlayers, not from pane count: a 6-16-4 double unit reaches 32 dB on its own, and a 6-16-6.8 acoustic unit 40 dB. The best acoustic triple and acoustic double units are 2 dB apart.
Laminated glass, two sheets bonded with a plastic interlayer, where the interlayer is a soft acoustic PVB rather than the standard one. The soft layer damps the vibration of the glass instead of passing it through. Saint-Gobain's like-for-like figures show the acoustic interlayer adds 4 dB over the same laminate with a standard interlayer. It is also safety glass, so it satisfies the rules for doors and low-level panes at the same time.
The extra is in the glass, not the fitting. Acoustic glass is quoted at £150 to £300 per square metre against around £50 per square metre per pane for plain 4 mm float, and standard 6.4 mm laminate at about £180 per square metre. A soundproof double glazed window is quoted at £300 to £750 by the trade guides, against £400 to £1,000 for a standard uPVC casement, so budget the upper half of the normal range plus the glass upgrade.
No. Pilkington states its acoustic data applies equally to air-filled and argon-filled cavities. Argon lowers the U-value; it does nothing measurable for sound.
Usually, yes. A sealed unit holds its panes 16 to 20 mm apart, so they resonate together. Secondary glazing puts 100 mm or more between the panes, which decouples them: 6.8 mm acoustic laminate in a secondary unit at a 100 mm cavity matches the best domestic acoustic double glazed unit at 40 dB, and at 150 to 200 mm reaches 42 to 43 dB, with heavier glass beyond 45 dB. It is also the route on listed buildings. The trade-off is a second window to open and clean.
A standard trickle vent left open does. Acoustic trickle vents exist, rated by their own sound reduction figure (Dn,e,w), and planning authorities near airports and busy roads commonly require them alongside acoustic glazing. Any gap matters: a 1% opening in the window area can cost up to 10 dB.