Not all double glazing is equal for noise. Standard IGUs reduce sound, but for Melbourne homes on tram routes, arterial roads, or near rail lines, the difference between "some improvement" and "genuinely usable room" comes down to which glass you specify.
How Sound Reduction Is Measured
The Rw (Weighted Sound Reduction Index) is the single-number rating used on window specifications. Higher is better.
| Rw | Typical reduction | Context |
|---|---|---|
| 25–29 | ~3 dB effective | Single-pane standard |
| 30–34 | ~6–8 dB effective | Standard double glazing |
| 35–39 | ~10–12 dB effective | Good general noise reduction |
| 40–44 | ~15–18 dB effective | Meaningful acoustic performance |
| 45+ | ~20+ dB effective | Specialist acoustic specification |
Note: Rw is measured in a laboratory. Real-world performance depends heavily on frame sealing, window reveals, and flanking paths (gaps under doors, ceiling voids, etc.).
Standard Double Glazing vs Acoustic Laminated
A standard 24mm IGU (4mm glass + 16mm cavity + 4mm glass) typically achieves Rw 30–34.
An acoustic laminated IGU using 6.38mm PVB laminated glass on one pane and asymmetric glass thicknesses (e.g. 6.38mm lam + 12mm cavity + 5mm clear) typically achieves Rw 40–44.
That 10-point Rw difference corresponds to roughly 12–15 dB of additional reduction — a clearly perceptible change, typically perceived as halving the loudness of traffic.
Why Asymmetric Panes Matter
When both panes are the same thickness, they have the same resonant frequency. They vibrate in unison at certain frequencies — the "coincidence dip" — which reduces performance in that frequency band.
Using different thicknesses (asymmetric IGU) shifts the resonant frequencies apart, smoothing the acoustic performance across the spectrum. This is why serious acoustic IGUs never use identical glass on both panes.
What Melbourne Noise Sources Require
Different noise sources have different frequency profiles:
Tram noise peaks in the low-to-mid frequency band (63–250 Hz) — the grinding and rumble. Academic and laminated PVB glass performs significantly better here than standard float.
Road traffic noise spans 125–2000 Hz. Standard acoustic laminated IGUs handle this well.
Aircraft noise is more complex: broadband with significant low-frequency energy. Near flight paths, specialist high-mass IGUs (typically 8mm+ panes) are worth specifying.
Human voices and music are mostly in the 500–4000 Hz range. Almost any double glazing makes a meaningful difference here.
Getting the Right Specification
For a bedroom on Sydney Road or a lounge that faces a tram route, specify acoustic laminated glass as the inner pane, asymmetric configuration, with a 12–16mm cavity minimum. This consistently delivers Rw 40–44 in practice.
For general background noise reduction without a specific noise source, standard Low-E double glazing is sufficient and more cost-effective.
The Soundproof Windows page has full specification guidance and pricing. Use the Instant Estimate tool to price your specific configuration.
See also: Double glazing for tram and traffic noise in Melbourne
Main service
Soundproof Windows Melbourne →