Technical Reference
Not all glass is equal. Compare the measured acoustic performance of each glass type we specify — from basic float to our 10.8mm Ultimate Acoustic laminate — and understand the physics that delivers real-world silence.
The Science
Sound is mechanical energy — a pressure wave that travels through air at approximately 343 metres per second. When that wave strikes a window, three things happen: a portion of the energy is reflected back towards the source, a portion is absorbed by the glass (converted into negligible heat through internal friction), and the remainder is transmitted through the pane into your room. The goal of acoustic glazing is to maximise reflection and absorption while minimising transmission.
The effectiveness of any barrier against sound is governed by two fundamental principles: the mass law and the coincidence effect. Understanding these is essential to understanding why our 10.8mm specification outperforms every standard alternative on the market.
The mass law states that for every doubling of a barrier's surface mass, sound insulation increases by approximately 6 dB. A 4mm float glass pane weighs roughly 10 kg/m² and achieves an Rw of 29 dB. Our 10.8mm laminate weighs 27 kg/m² — nearly triple the mass — delivering a theoretical gain of over 8 dB from mass alone. This is why thicker, heavier glass consistently outperforms thinner panes at every frequency.
Every rigid panel has a "coincidence frequency" — the point at which bending waves within the glass match the wavelength of the incident sound. At this frequency, the panel becomes acoustically transparent, and insulation drops sharply. For 4mm float glass, coincidence occurs around 3,150 Hz — right in the range of speech, birdsong, and high-frequency traffic noise. Our laminated construction, with its viscoelastic PVB interlayer, damps this resonance by converting vibrational energy into heat, effectively eliminating the coincidence dip.
Our 10.8mm specification uses two different glass thicknesses — 6.4mm and 4.4mm — bonded with a specialist acoustic PVB interlayer. Because the two panes have different masses, they resonate at different frequencies. This asymmetry means there is no single frequency at which the entire panel becomes acoustically weak. The result is consistent attenuation from 50 Hz (deep traffic rumble) through to 5,000 Hz (high-pitched sirens and alarms).
The decibel (dB) scale is logarithmic, not linear. This is critical for interpreting the data in our comparison table. A reduction of 10 dB represents a 50% decrease in perceived loudness — not a 10% decrease. A 20 dB reduction sounds 75% quieter. And a 50 dB reduction — what our 10.8mm Ultimate Acoustic achieves — renders a thunderous 80 dB A-road into a library-quiet 30 dB. The difference between 29 dB reduction (basic float) and 50 dB reduction (our flagship) is not incremental — it is transformative.
10 dB
50% Quieter
20 dB
75% Quieter
30 dB
87.5% Quieter
50 dB
97%+ Quieter
Decibel (dB) reduction values measured as weighted sound reduction index (Rw) in laboratory conditions. Real-world performance varies with installation quality, seal integrity, and air cavity depth.
| Glass Type | dB Reduction | STC Rating | Performance | Best For |
|---|---|---|---|---|
4mm Float Glass | 29 dB | STC 28–30 | Basic | Standard single-pane glass. Minimal noise reduction — suitable only for quiet rural locations with no significant external noise sources. |
6.4mm Laminated Glass | 35 dB | STC 33–35 | Good | Two sheets of glass with a standard PVB interlayer. A measurable improvement over float glass, reducing perceived noise by roughly 50%. Suitable for light residential traffic. |
6.8mm Acoustic Laminated | 39 dB | STC 37–39 | Very Good | Acoustic-grade PVB interlayer with enhanced damping properties. Targets the coincidence dip that standard laminated glass misses. Effective for moderate urban noise. |
8.8mm Acoustic Laminated | 44 dB | STC 42–44 | Excellent | Thicker asymmetric construction (5mm + 3.8mm) with acoustic PVB. Significantly outperforms standard double glazing across all frequencies. Recommended for busy A-roads and urban environments. |
10.8mm Ultimate Acoustic | 50 dB+ | STC 48–52 | Ultimate | Our flagship specification. 6.4mm + 4.4mm asymmetric laminate with specialist acoustic interlayer. Engineered for the most demanding environments — flight paths, motorways, and high-intensity urban noise. Reduces perceived noise by over 90%. |
Reduction
29 dB
STC
STC 28–30
Standard single-pane glass. Minimal noise reduction — suitable only for quiet rural locations with no significant external noise sources.
Reduction
35 dB
STC
STC 33–35
Two sheets of glass with a standard PVB interlayer. A measurable improvement over float glass, reducing perceived noise by roughly 50%. Suitable for light residential traffic.
Reduction
39 dB
STC
STC 37–39
Acoustic-grade PVB interlayer with enhanced damping properties. Targets the coincidence dip that standard laminated glass misses. Effective for moderate urban noise.
Reduction
44 dB
STC
STC 42–44
Thicker asymmetric construction (5mm + 3.8mm) with acoustic PVB. Significantly outperforms standard double glazing across all frequencies. Recommended for busy A-roads and urban environments.
Reduction
50 dB+
STC
STC 48–52
Our flagship specification. 6.4mm + 4.4mm asymmetric laminate with specialist acoustic interlayer. Engineered for the most demanding environments — flight paths, motorways, and high-intensity urban noise. Reduces perceived noise by over 90%.
Important: These figures represent the glass panel alone. When installed as secondary glazing with our engineered air cavity, system performance increases by 8–15 dB depending on cavity depth and seal quality.
Our Flagship Glass
Our 10.8mm Ultimate Acoustic laminate is not simply thick glass. It is a precision-engineered acoustic barrier designed to address every mechanism through which sound penetrates a window. The construction consists of a 6.4mm outer leaf and a 4.4mm inner leaf, bonded under heat and pressure with a 0.76mm specialist acoustic PVB interlayer manufactured to ISO 12543 and EN 14449 standards.
The acoustic PVB interlayer is the critical component. Unlike standard PVB used in safety laminated glass, our acoustic-grade interlayer has a lower shear modulus — meaning it is "softer" at the molecular level. When sound vibrations cause the two glass leaves to flex, the interlayer deforms viscoelastically, converting mechanical energy into microscopic thermal energy. This damping effect is most pronounced at the coincidence frequency, precisely where rigid glass systems fail. The result is an Rw rating exceeding 50 dB — verified by independent UKAS-accredited laboratory testing.
In real-world terms, 50 dB of reduction means a 100 dB motorway (measured at the façade) is reduced to 50 dB indoors — quieter than a normal conversation. A 75 dB A-road becomes 25 dB — below the threshold at which the human ear perceives background noise as noticeable. This is not marketing language. These are measured values, reproducible under controlled conditions and verified post-installation with calibrated sound level meters.
Engineering Corner
The single most important factor in acoustic window performance is not the glass thickness — it's the air gap between your existing window and the secondary glazing panel. This principle, known as acoustic decoupling, is the foundation of every installation we design.
Sound travels through solid materials more efficiently than through air. When two panes of glass are close together (as in standard double glazing, with a 12–16mm cavity), they are acoustically "coupled" — vibrations pass from the outer pane, through the narrow air gap, and into the inner pane with minimal energy loss. The system behaves almost as a single mass.
By increasing the air gap to 100–150mm, we create a fundamentally different acoustic system. The two glass masses are now "decoupled" — each vibrates independently, and the large air cavity acts as a buffer that absorbs and dissipates sound energy before it reaches the inner pane. This is the same principle used in professional recording studio design.
The physics is governed by the mass-air-mass resonance formula. A larger cavity shifts the resonant frequency lower — below the range of most environmental noise — meaning the system performs well precisely where it matters. Our 100–150mm specification is optimised to push this resonance below 80 Hz, ensuring effective attenuation of traffic rumble, aircraft noise, and urban disturbance across the entire audible spectrum.
• Cavity: 12–16mm
• Resonance frequency: ~200–300 Hz
• Acoustic performance: STC 28–31
• Low-frequency weakness: Significant
The narrow cavity creates a resonance point directly in the frequency range of traffic and aircraft noise, actually amplifying sound at certain frequencies.
• Cavity: 100–150mm
• Resonance frequency: Below 80 Hz
• Acoustic performance: STC 45–52
• Low-frequency weakness: Eliminated
The wide cavity pushes resonance below the range of environmental noise. Combined with our 10.8mm laminate, the system delivers consistent attenuation across all frequencies.
When our 10.8mm Ultimate Acoustic glass (Rw 50 dB) is installed with a 150mm decoupled air cavity behind your existing window, the combined system achieves Rw 55–60 dB — performance equivalent to a solid masonry wall. This is why secondary glazing consistently outperforms replacement double or triple glazing for acoustic applications.
150mm
Optimal Air Gap
Rw 60
System Performance
95%+
Perceived Reduction
Planning a soundproofing project? These guides cover costs, regulations, and installation — everything you need to make an informed decision.
Transparent pricing for all three acoustic glazing tiers — from Essential at £350/window to Premium Heritage at £1,400/window.
How we engineer silence for A-roads and HGV rumble with 10.8mm glass and optimised air gaps.
High-frequency flight path noise from Heathrow and Gatwick — airtight seals and frequency-tuned glass.
Our acoustic engineers will assess your noise environment and recommend the optimal glass specification — no guesswork, no overselling. Free survey, no obligation.
This document provides the official UK government guidance on resistance to sound in buildings, including performance standards for windows and doors.
A technical guide detailing how to improve the acoustic performance of historic buildings through secondary glazing and window insulation.
A comprehensive report mapping noise levels and the health impacts of environmental noise, emphasizing the need for sound-insulating glazing.
An academic study providing empirical data on how different glass thicknesses and lamination improve sound insulation for building envelopes.
The primary international standard used to determine the STC rating of building partitions, including windows, in a laboratory setting.
The UK and European standard for measuring the sound insulation of buildings and building elements, often compared with STC ratings.
Citations generated with AI assistance. Please verify sources independently.