How Double Glazing Actually Reduces Noise, and How Much
Noise is one of the most common reasons Sydney homeowners replace their windows, and one of the most misunderstood. Adding a second pane of glass helps, but the size of the improvement depends on how the whole window is built, not just the pane count.
What actually blocks sound
Three things do most of the work. First, mass: thicker and laminated glass is harder for sound waves to move. Second, the air or gas gap between panes, which breaks the path sound travels. Third, the seal: a frame that closes tightly stops noise leaking around the edges, which is where a lot of aluminium sliders fail.
Matching the glass to the noise
Low-frequency noise, like trucks on an arterial road or aircraft overhead, needs a different specification to high-frequency noise like a nearby train squeal. Acoustic laminated glass uses a special interlayer that dampens vibration, and using two different glass thicknesses in the same unit stops both panes resonating at the same frequency. That is why we specify glazing to the noise source rather than selling one product for every home.
Realistic numbers
- Standard single glazed aluminium: little meaningful noise control
- Basic double glazing: a noticeable drop for general street noise
- Acoustic laminated double glazing in a sealed uPVC frame: up to 45dB reduction
A 45dB reduction is the difference between conversation-level noise and a quiet room. If a busy road or flight path is the reason you are considering new windows, the acoustic specification and a properly sealing frame matter more than anything else on the quote.