Guide

Acoustic aluminium windows: how Rw ratings work

By Paul Fradley, Founder and Technical Lead · Updated June 2026

Rw is the single-number sound reduction index, in decibels, that tells you how much airborne noise a window cuts; VitrineAlu builds acoustic aluminium windows to Rw 46 dB where specified. A higher Rw means more attenuation, but the figure is a laboratory average across frequencies, so the right glazing make-up depends on the noise source on your site. Tell us the noise problem and we quote the system and glazing that hit the target.

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Acoustic aluminium windows: how Rw ratings work, aluminium by VitrineAlu

Rw to 46 dBSound reduction where specified, by glazing make-up

22-58mm glazingAsymmetric, laminated and acoustic-interlayer build-ups by system

Class 4 air sealsAir permeability Class 4 (EN 12207) supports acoustic performance

What is an Rw rating and how is it measured?

Rw is the weighted sound reduction index of a building element, measured in decibels to EN ISO 717-1 and tested to EN ISO 10140. It compresses a window's performance across a standard spread of frequencies into one number, so a window rated Rw 46 dB attenuates more airborne noise than one rated, say, Rw 34 dB.

Because Rw is a single weighted figure, two windows with the same Rw can behave differently against a specific noise. That is what the spectrum adaptation terms C and Ctr correct for. They are quoted alongside Rw as Rw (C; Ctr).

Rw: the weighted average, good for general mixed noise
C: adaptation for mid and high frequency sources such as everyday traffic, rail at speed and conversation
Ctr: adaptation for low frequency sources such as heavy urban traffic, slow city buses and aircraft
On a flightpath or heavy-traffic site, read Rw + Ctr, not Rw alone
Figures are laboratory ratings; confirm the whole-unit acoustic result at quote

What drives the acoustic performance of an aluminium window?

Most of the sound reduction comes from the glass, not the frame. Mass, an asymmetric build-up and a laminated pane with an acoustic interlayer are the three biggest levers, and they work together rather than in isolation.

The aluminium frame, the seals and the installation then protect that glass performance. A thermally broken frame with multiple seal lines and air permeability to Class 4 (EN 12207) stops noise leaking around the glass, which is where poorly sealed windows lose most of their rating. See our energy efficiency page for how the same thermal break carries through to U-values.

Glass mass: thicker and heavier panes reduce more noise across the band
Asymmetric IGU: two different glass thicknesses defeat the coincidence dip, where matched panes resonate and let noise through
Laminated panes: a laminated leaf adds mass and damping
Acoustic interlayers: a specialist acoustic interlayer in the laminate damps vibration, lifting low-frequency performance
Frame and seals: thermally broken frame, multi-point compression seals and Class 4 air permeability stop flanking and gap noise
Glazing accommodated from 22mm up to 58mm by system to suit the target Rw

How does glazing make-up change the Rw figure?

The IGU make-up is where you buy decibels. A standard symmetric double-glazed unit sits at the lower end; an asymmetric unit with a laminated acoustic pane and a wider cavity sits at the top. The widest gains come from combining asymmetry, lamination and an acoustic interlayer rather than simply going thicker on both panes.

VitrineAlu specifies the make-up against your target. Glazing is accommodated from 22mm up to 58mm depending on the system, which gives room for laminated acoustic panes and asymmetric cavities across our window ranges.

Symmetric double glazing: baseline, matched panes share the same coincidence dip
Asymmetric double glazing: different pane thicknesses, no shared dip, a clear step up
Laminated acoustic pane: a laminate with an acoustic interlayer added on one leaf for damping
Wider or unequal cavity: helps low-frequency control, relevant for traffic and aircraft
Top of range: asymmetric make-up with acoustic-laminated glass to Rw 46 dB where specified
Triple glazing is not automatically quieter; mass, asymmetry and lamination usually beat a third pane

What real-world noise reduction can I expect by site type?

A decibel reduction is logarithmic, so a 10 dB cut sounds roughly half as loud to the ear, and 3 dB is the smallest change most people notice. Match the glazing to the dominant noise: high-frequency sources respond to mass and asymmetry, low-frequency sources need acoustic lamination and the Ctr term.

These are indicative source profiles, not a promise for your opening. The achieved result depends on the gap between your wall and window performance, the rest of the facade and the install. Confirm the whole-unit figure at quote.

Busy road, general traffic: mid and high frequency dominated, responds well to asymmetric laminated glass; read Rw + C
Heavy or slow urban traffic, buses: more low-frequency energy, prioritise acoustic interlayers and read Rw + Ctr
Rail near the line: broadband with strong low end, asymmetric acoustic-laminated make-up
Flightpath: low-frequency dominated, Ctr-led specification with acoustic lamination and wider cavity
A window only performs to its rating if the wall, trickle paths and install do not undercut it

Does the frame and installation affect acoustic results?

Yes. The best glazing in a leaky frame underperforms, because sound takes the easiest path. Aluminium suits acoustic work because a rigid thermally broken frame holds heavy laminated units flat and lets multiple seal lines compress consistently along the leaf.

Installation closes the loop. Gaps around the frame, unsealed reveals and bridged trickle vents all leak noise. Specifying Class 4 air permeability and a properly sealed perimeter keeps the installed result close to the rated glass.

Thermally broken aluminium frame carries heavy acoustic IGUs without distortion
Multi-point locking and compression seals give even seal pressure around the leaf
Air permeability to Class 4 (EN 12207) limits gap-borne noise
Weathertightness to Class 9A (EN 12208) and wind resistance to Class C5 (EN 12210) where specified
Sealed perimeter and considered trickle ventilation protect the rated performance on site

How do I specify an acoustic aluminium window?

Start from the noise, not the product. Identify the dominant source, set a target Rw with the right adaptation term, then let the glazing make-up follow. For traffic and aircraft, specify against Rw + Ctr; for general mixed noise, Rw with C is usually enough.

Give us the site and the problem and we quote the system, glazing and seals that meet it across our casement, sliding, tilt-turn and heritage ranges, with the acoustic result confirmed for your whole unit. Homeowners are routed to a vetted fitter via find an installer.

State the noise source: road, rail, flightpath or mixed
Set the target as Rw plus the relevant term, Rw + Ctr for low-frequency sources
Let us select the make-up: asymmetric, laminated, acoustic interlayer, cavity within the 22-58mm range
Specify Class 4 air permeability and a sealed install to protect the rating
Send your requirement via request a quote and we confirm the whole-unit Rw

Common questions

What Rw rating can VitrineAlu acoustic windows reach?

VitrineAlu builds acoustic aluminium windows to Rw 46 dB where specified. Rw is the weighted sound reduction index in decibels; the figure achieved depends on the glazing make-up, so the exact rating is confirmed for your whole unit at quote.

What is the difference between Rw, C and Ctr?

Rw is the single weighted sound reduction figure across a standard frequency range. C and Ctr are spectrum adaptation terms added to it: C corrects for mid and high frequency noise such as everyday traffic and rail, and Ctr corrects for low frequency noise such as heavy urban traffic and aircraft. For flightpath and heavy-traffic sites, read Rw + Ctr rather than Rw alone.

Does triple glazing make a window quieter?

Not automatically. Acoustic performance is driven mainly by glass mass, an asymmetric build-up using two different pane thicknesses, and a laminated pane with an acoustic interlayer. An asymmetric laminated double-glazed unit usually outperforms a symmetric triple-glazed one against road and rail noise.

How much glazing thickness is needed for an acoustic window?

VitrineAlu systems accommodate glazing from 22mm up to 58mm depending on the system, which gives room for laminated acoustic panes and asymmetric cavities. Thickness alone does not set the rating; asymmetry and an acoustic interlayer matter as much as overall depth. The make-up is specified against your target Rw.

Will an acoustic window fix noise on a flightpath site?

It reduces it. Aircraft noise is low-frequency dominated, so specify against Rw + Ctr with an acoustic-laminated, asymmetric make-up and a sealed install. The achieved reduction also depends on the rest of the facade and the wall, so the whole-unit figure is confirmed at quote rather than promised in advance.

Completed North West new build with VitrineAlu anthracite aluminium bifold doors, windows and dormers — The frame disappears, the view does the talking.

Proof, not promises

Specified and made by people who have fitted it

Paul Fradley, Founder and Technical Lead, has worked almost every role in windows and doors across more than twenty years: surveyed, fabricated on the floor, fitted on site, then ran the technical and operations side. He leads the spec on every project, so what we quote is what we fabricate.

4.5 / 5 from 20 Google reviews. Council for Aluminium in Building member. Tested to BS EN 14351-1 and BS EN 13830 where specified.

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