What is Rw in acoustic glazing?

Rw is the weighted sound reduction index measured in decibels (dB). It represents the overall ability of the glazing to reduce airborne sound transmission across a range of frequencies. A higher Rw means better noise reduction. Standard double glazing achieves about 29 dB Rw, while specialist acoustic units can reach 42+ dB.

What noise level should a bedroom achieve?

BS 8233:2014 recommends internal ambient noise levels of 30 dB LAeq for bedrooms at night and 35 dB LAeq for living rooms during the daytime. Planning conditions for new developments near noise sources typically require compliance with these standards.

Does laminated glass improve acoustic performance?

Yes, laminated glass with a PVB (polyvinyl butyral) or specialist acoustic interlayer significantly improves sound reduction. A 6.4mm laminated pane (two 3mm panes with 0.4mm interlayer) outperforms a single 6mm pane acoustically because the interlayer dampens vibration transmission.

Why use asymmetric glass thicknesses?

Asymmetric glass (different thicknesses in each pane) avoids the coincidence dip where both panes resonate at the same frequency. For example, a 6/16/4 unit performs better acoustically than 4/16/4 or 6/16/6 because the resonance frequencies differ between panes.

How much does acoustic glazing cost in the UK?

Standard acoustic DGUs (6/16/6.4 laminated) cost approximately £200-£300/m² supply and fit. High-performance units (10/16/8.8 laminated) cost £350-£500/m². Secondary glazing with a 100mm+ air gap is often the most cost-effective acoustic solution at £150-£250/m².

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Acoustic Glazing Calculator

Calculate noise reduction from acoustic glazing options and check compliance with BS 8233 internal noise level targets for UK residential properties.

Noise Source

Typical external noise level

Glazing Specification

Laminated panes give best acoustic results

Number of Windows

Windows facing the noise source

Average Window Area

Per window glazed area

Price per m²

Supply and install cost

How We Calculate This

This calculator estimates the internal noise level achieved by different acoustic glazing options based on the external noise source and installation quality.

The formula

Internal level = External noise (dB) - Glazing Rw + Vent penalty + Seal penalty

Rw = weighted sound reduction index of glazing
Vent penalty: open window -15 dB, trickle vent -5 dB, acoustic trickle -2 dB
Seal penalty: poor seals -5 dB, average -3 dB

BS 8233 targets

Living rooms (daytime): ≤35 dB LAeq
Bedrooms (night): ≤30 dB LAeq

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.