Fixed windows
No opening joint, so the highest airtightness and acoustic performance. Ideal for façades where ventilation is provided mechanically. See fixed windows.
Acoustic window systems
Aluminium Soundproof Window Systems
An aluminium soundproof window cuts outside noise by combining acoustic glass, a stiff thermally broken frame, compression seals and careful installation; thicker glass alone does very little. A good acoustic window reduces noise by about 38 – 45 dB (Rw), compared with roughly 30 dB for ordinary double glazing. Metline supplies acoustic window profiles, thermal-break sections and accessories to window fabricators for traffic, railway and airport noise projects worldwide.
- Typical rating
- Rw 35 – 45 dB (system dependent)
- Window types
- Fixed, casement, tilt-turn, sliding
- Glass
- Acoustic laminated, asymmetric IGU
- Ratings
- Rw + Ctr · STC · OITC
How a soundproof window actually works
Sound reaches a room through a window in two ways: through the glass and frame as vibration, and through any air gap. The second route is the one most often overlooked. A gap of only a fraction of a percent of the window area can let through as much sound as the rest of the window combined, which is why an expensive acoustic glass in a poorly sealed sliding sash often disappoints.
A soundproof window therefore works as a system. The glass provides mass and damping. The frame and sash must be stiff enough to carry heavy glass without twisting, because a distorted sash no longer presses evenly on its seals. The seals and hardware close the air paths: multi-point locks pull the sash tight against two or three lines of EPDM gaskets. Finally, the installation joint between frame and wall must be filled and sealed, or noise simply goes around the window.
Aluminium is well suited to acoustic windows because its stiffness supports heavy laminated and triple glazing in slim, accurate sections, and modern thermally broken profiles with insulated chambers combine acoustic and thermal performance. The frame contributes little of the acoustic rating directly, but it decides whether the glass and seals can do their job.
STC, OITC and Rw: how to specify acoustic performance
Acoustic performance is expressed as a single-number rating derived from laboratory measurements of sound transmission loss across a range of frequencies. Different regions use different ratings, and they are not interchangeable, so the specification must name the rating and the test standard.
| Rating | Standard | Frequency range | Best describes | Used in |
|---|---|---|---|---|
| Rw | ISO 717-1 (tests to ISO 10140) | 100 – 3150 Hz | General airborne sound, voices, mixed noise | Europe, UK, Australia, Asia, Middle East |
| Rw + Ctr | ISO 717-1 | As Rw, weighted to low-frequency urban traffic spectrum | Road traffic, low-frequency rumble | Facades facing roads, rail and aircraft |
| Rw + C | ISO 717-1 | As Rw, weighted to pink noise | Speech, TV, rail at speed | Europe |
| STC | ASTM E413 (tests to ASTM E90) | 125 – 4000 Hz | Speech and mid-frequency noise | United States, Canada |
| OITC | ASTM E1332 | 80 – 4000 Hz | Outdoor transport noise: traffic, rail, aircraft | US façade acoustics |
Because Ctr is usually between −3 and −8 dB for glazing, a window rated Rw 40 might only achieve about 34 – 35 dB against traffic noise (Rw + Ctr). OITC values for the same window are typically several points below its STC. For street-facing bedrooms, specify Rw + Ctr or OITC rather than Rw or STC alone.
Decibels are logarithmic: a 10 dB reduction is perceived as roughly halving loudness, and a 3 dB change is just noticeable. Moving from ordinary double glazing (about Rw 30) to a good acoustic window (about Rw 40) makes traffic noise sound roughly half as loud.
Glass build-ups and typical performance
Three mechanisms drive glass performance: mass (heavier glass blocks more, especially at low frequency), asymmetry (panes of different thickness have different coincidence frequencies, so one covers the other's weak spot) and damping (an acoustic PVB interlayer absorbs vibration energy). Cavity width helps too, but a normal 12 – 20 mm cavity has a mass-air-mass resonance in the low-frequency range that limits traffic-noise performance.
| Glass build-up | Indicative Rw | Indicative Rw + Ctr | Comment |
|---|---|---|---|
| 4 / 16 / 4 mm double glazing | 30 – 32 dB | 26 – 28 dB | Standard thermal unit; poor acoustic choice |
| 4 / 12 / 6 mm asymmetric | 33 – 34 dB | 29 – 30 dB | Cheap improvement from asymmetry |
| 6 / 16 / 10 mm asymmetric | 36 – 38 dB | 32 – 34 dB | Good value for moderate traffic noise |
| 8 / 20 / 8.8 mm laminated | 37 – 39 dB | 33 – 35 dB | Heavier; laminate adds security |
| 10 / 20 / 8.8 mm acoustic laminated | 40 – 42 dB | 35 – 38 dB | Strong performance for busy roads |
| Acoustic laminated both panes, e.g. 10.8 / 20 / 8.8 | 42 – 46 dB | 37 – 41 dB | Rail, airports, major roads |
| Primary IGU + secondary pane, 100 – 200 mm gap | 45 – 55 dB | 40 – 48 dB | Highest performance; two separate frames |
Glass-only indicative values from published manufacturer data ranges. A complete window usually rates 1 – 4 dB below its glass because of the frame and seals; always ask for a whole-window test report to ISO 10140 or ASTM E90.
Low-E coatings and argon fill do not improve acoustic performance on their own; they are added for energy efficiency and can be combined with any acoustic build-up. Triple glazing is not automatically quieter than a well-designed asymmetric laminated double unit, because its two narrow cavities each have their own resonance.
Choosing a configuration by noise source
| Noise source | Character | Recommended configuration |
|---|---|---|
| Urban street, voices | Mid-frequency, intermittent | Asymmetric or laminated IGU, standard compression seals; Rw about 34 – 38 |
| Busy road traffic | Continuous, strong low-frequency rumble | Acoustic laminated asymmetric IGU, wide cavity, multi-point locks; target Rw + Ctr 35 or more |
| Railway and metro | Low-frequency rumble plus wheel and brake noise | Heavy acoustic laminated glass both sides, stiff frame, fixed or tilt-turn windows |
| Airports and flight paths | Very low-frequency, high level | Double-frame or secondary glazing system, acoustic laminated glass, mechanical ventilation so windows stay shut |
| Construction sites | Impact, high-frequency | Laminated glass, robust frame; temporary secondary glazing is an option |
| Industrial plant | Tonal, mechanical, vibration | Multi-layer heavy glazing, resilient fixings, review with an acoustic consultant |
Typical indoor targets help set the window rating. The UK guidance in BS 8233, for example, suggests about 30 dB LAeq at night in bedrooms and 35 dB by day in living rooms. If outdoor night-time noise at the façade is 70 dB, the window must remove around 40 dB of traffic-weighted noise, which points to an acoustic laminated build-up with excellent sealing.
Which window type performs best acoustically?
Casement windows
Compression closing onto two or three gasket lines with multi-point locks gives stable, high performance. The mainstream choice for acoustic residential and hotel projects. See casement windows.
Tilt-turn windows
Compression sealing like a casement, plus a secure tilt position for ventilation. Common in European apartments, schools and hospitals.
Awning windows
Top-hinged and compression sealed; good acoustic results in smaller openings and as vents above fixed lights. See awning windows.
Sliding windows
Brush and fin seals cannot compress, so performance is limited, usually to around 30 – 35 dB even with good glass. Use lift-and-slide or compression sliders where a sliding action is essential. See sliding windows.
Secondary glazing
A second window fitted inside the first with a wide air gap. The most effective upgrade for existing or heritage buildings and airport zones.
Frame, seals, hardware and installation
| Element | What to specify | Why it matters |
|---|---|---|
| Profile system | 6063-T6 or 6060-T66 thermally broken profiles, deep glazing rebate, insulated chambers | Stiffness for heavy glass; room for thick units |
| Glazing gaskets and beads | EPDM gaskets on both sides, setting blocks sized for the glass weight | Isolates glass vibration, keeps the unit seated |
| Sash seals | Two or three continuous EPDM seal lines with welded or moulded corners | Closes the air path, which limits performance |
| Hardware | Multi-point locks with adjustable cams, hinges rated for sash weight | Even seal compression around the whole perimeter |
| Ventilation | Acoustic trickle vents or mechanical ventilation | Rooms must be ventilated with windows closed |
| Installation joint | Expanding foam or mineral wool plus inner airtight and outer weatherproof sealing tapes | Prevents flanking around the frame |
| Reveals and shutters | Avoid hollow roller-shutter boxes above acoustic windows, or use insulated boxes | Shutter boxes are a common weak point |
Most acoustic shortfalls trace back not to the glass but to the details: an untested sliding sash, an open trickle vent, foam left unsealed at the reveal or a roller-shutter box with a thin cover. A small leak can halve the benefit of the acoustic glass, so these details deserve as much attention as the glass build-up.
Common mistakes in acoustic window projects
Specifying Rw for traffic
A window chosen on Rw alone can fall well short against road noise, because the Ctr correction for low frequencies is often 5 dB or more. Use Rw + Ctr or OITC on traffic-facing façades.
Thicker symmetric glass
Two equal panes resonate together. Changing 6/16/6 to 8/16/8 adds weight but little benefit; 6/16/10 or a laminated pane usually gains more.
Ignoring ventilation
If occupants must open the window to get fresh air, the acoustic rating is irrelevant at night. Plan acoustic trickle vents or mechanical ventilation from the start.
Testing the glass, not the window
Glass data sheets describe a pane in a laboratory frame. Ask for whole-window tests, at a size close to what will be installed.
Weak installation joints
Unsealed foam, gaps behind trims and hollow shutter boxes create flanking paths that bypass the window altogether.
Oversized opening sashes
Very large sashes with heavy glass deflect and lose seal pressure over time. Split large openings into fixed lights with smaller opening vents.
Where acoustic aluminium windows are used
- Hotels and serviced apartments: casement or fixed windows with acoustic laminated asymmetric units on road- or airport-facing elevations, and standard units on quiet sides to control cost.
- Roadside apartments: bedrooms on the street side with tilt-turn windows and acoustic trickle vents, living rooms with fixed lights and casement vents.
- Schools and libraries: classroom windows rated to keep internal noise low enough for teaching, often with mechanical ventilation.
- Hospitals and care homes: patient rooms where quiet sleep matters, using compression-sealed windows and laminated glass for safety.
- Offices and meeting rooms: fixed curtain wall or window wall glazing with acoustic laminate on noisy frontages.
- Homes near rail lines or airports: secondary glazing or double-frame systems in noise-insulation schemes.
RFQ checklist for soundproof windows
- Project and noiseCountry, building type and main noise source (road, rail, aircraft, urban), with measured levels or an acoustic report if available.
- Window scheduleWindow types (fixed, casement, tilt-turn, sliding) and sizes, quantities and positions.
- Acoustic targetRequired Rw, Rw + Ctr, STC or OITC; if none, the expected improvement or indoor target level.
- Glass and hardwarePreferred build-up, safety glass needs, multi-point locks, ventilation requirement.
- Finish and deliveryColour and coating standard, packing and destination; profiles ship with EN 10204 3.1 certificates.
References and standards
- ISO 717-1 – Acoustics: rating of sound insulation in buildings and of building elements, airborne sound
- ISO 10140-2 – Acoustics: laboratory measurement of sound insulation, airborne sound
- ASTM E413 – Classification for Rating Sound Insulation (STC)
- ASTM E1332 – Classification for Rating Outdoor-Indoor Sound Attenuation (OITC)
- EN 12758 – Glass in building: glazing and airborne sound insulation
- BS 8233 – Guidance on sound insulation and noise reduction for buildings
Aluminium (aluminum) soundproof windows: FAQ
How much noise do soundproof windows reduce?
A good acoustic window with laminated asymmetric glass and compression seals typically achieves Rw 38 – 45 dB, against about 30 dB for standard double glazing. Secondary glazing systems with a wide air gap can reach 45 – 55 dB.
Is triple glazing better for soundproofing than double glazing?
Not necessarily. Triple glazing improves thermal performance, but its narrow cavities limit acoustic gains. An asymmetric double unit with acoustic laminated glass and a wider cavity often performs as well or better for traffic noise.
Can sliding windows be soundproof?
Only to a degree. Standard sliders rely on brush seals that cannot be compressed, so they usually reach around 30 – 35 dB. Where high acoustic performance is needed, casement, tilt-turn or fixed windows are recommended.
What rating should I specify for traffic noise?
Specify Rw + Ctr (or OITC in the US), because these weight the low-frequency rumble of traffic. A busy urban road often needs Rw + Ctr of 35 dB or more for bedrooms.
Why do windows with similar glass test so differently?
Because the frame, seals, hardware and installation decide how much sound leaks around the glass. A stiff, airtight frame with continuous gaskets and multi-point locks preserves the glass rating; a weak or leaky one can lose several decibels.
Can you quote without a defined acoustic target?
Yes. Describe the noise source, the building use and approximate sizes, and we will suggest glass build-ups and profile series, which can then be confirmed against an acoustic consultant's report.
Dealing with traffic, rail or aircraft noise?
Send the noise source, target rating and window schedule to sales@metline.in. We will propose acoustic window profiles and a delivered price.
