Acoustic Rated · Up to Rw 44
Yes, double glazing reduces noise, and dramatically so when you specify it correctly. A standard 24mm IGU typically cuts traffic noise by around 7 to 9 dB compared with the 3mm single glazing in many older Melbourne homes. Step up to acoustic laminated glass with a 0.76mm PVB interlayer in a wider cavity, and an installed window reaches roughly Rw 42 to 44 dB, perceived as close to a quarter of the original loudness. This guide explains the Rw rating system, walks through the three IGU sizes we manufacture (24mm, 36mm, 46mm), and shows which configuration suits Melbourne's tram routes, freeways, and flight paths.
Yes. Double glazing typically reduces noise by 7 to 19 dB compared with the 3mm single glazing in many older Australian homes, depending on the glass, cavity width, and acoustic laminated specification. Because the decibel scale is logarithmic, a 10 dB drop is perceived as roughly halving the loudness, and 20 dB as roughly a quarter. The improvement comes from two glass panes separated by a sealed argon-filled cavity, which dampens sound vibration far more effectively than a single pane. The figures below are for the complete installed window in a uPVC frame, not the glass unit alone.
Yes, and the difference is measurable rather than theoretical. The 3mm single glazing common in pre-1980s Melbourne homes achieves around Rw 25 dB of noise reduction. A standard 24mm Windows Republic IGU with 4mm Low-E panes and an argon-filled cavity typically achieves Rw 32 to 34 dB. As a complete installed window, a 46mm IGU with a 12.76mm acoustic laminated outer pane reaches approximately Rw 42 to 44 dB.
What this means at home: standing in a bedroom on Sydney Road Brunswick with the original 3mm single glazing, you hear every tram, every car, every passing conversation. With a properly specified acoustic 36mm or 46mm IGU, traffic becomes a background presence rather than a foreground event. The tram bells still register but the rumble of acceleration largely disappears.
Noise reduction comes from three engineering choices stacked together: two panes of glass instead of one, a sealed argon-filled gap between them, and an acoustic laminated outer pane that absorbs the vibrations float glass transmits. Each one helps. Together they make the difference between a noisy room and a quiet one — and the same construction that blocks sound also delivers the wider thermal and comfort benefits of double glazing.
Australian acoustic ratings use the Rw value, short for Weighted Sound Reduction Index, measured in decibels. The measurement is governed by AS/NZS ISO 717.1. Rw is a single-number summary across the audible frequency range. Higher is better.
The decibel scale is logarithmic, not linear, which is the key thing to understand. A 3 dB difference is barely perceptible. A 10 dB difference is perceived by the human ear as roughly halving the loudness. A 20 dB difference is perceived as roughly a quarter of the loudness.
This is why the difference between 3mm single glazing (Rw ~25) and an acoustic laminated 46mm window (approximately Rw 42-44) matters so much in practice. The numbers show a gap of roughly 17 to 19 dB. The perceived experience is close to a quarter of the original loudness.
One refinement worth knowing about: the headline Rw is often paired with a correction factor called Ctr, the traffic-noise spectrum adjustment. Written together as Rw + Ctr, it discounts the rating to account for low-frequency sources — truck engines, distant trains, aircraft — that a single Rw figure can flatter. A window rated Rw 40 might land near Rw 35 once Ctr is applied. For homes near freeways or under a flight path, the Rw + Ctr number is the more honest predictor of real-world performance.
Windows Republic manufactures three IGU sizes across its uPVC window range: 24mm (standard double glazing), 36mm (improved acoustic), and 46mm (premium acoustic). Within each size, the glass thicknesses and whether laminated glass is used determine the final Rw value. The configuration notation reads as outer pane, air gap, inner pane.
| IGU size | Configuration | Rw rating | Best suited to |
|---|---|---|---|
| Single 3mm | Original single pane (older Melbourne homes, pre-1980s) | ~25 dB | Reference baseline |
| Single 4mm | Newer single pane in aluminium frame | 25-28 dB | Reference baseline |
| 24mm IGU | 4mm / 16mm Argon / 4mm Low-E (thermal-focused standard) | 32-34 dB | Quiet suburbs, primary thermal focus |
| 24mm IGU | 6.76mm acoustic laminated outer, argon cavity, 4mm Low-E inner | ~Rw 36-38 | Moderate traffic, inner-suburb streets |
| 36mm IGU | 10.76mm acoustic laminated outer, argon cavity, 5mm Low-E inner | ~Rw 39-41 | Tram routes, busy roads, train corridors |
| 46mm IGU | 12.76mm acoustic laminated outer, argon cavity, 5mm Low-E inner | ~Rw 42-44 | Citylink, freight routes, Tullamarine flight paths |
Note on the IGU sizes and Rw ranges: these are the three standard IGU thicknesses Windows Republic produces. The acoustic versions use acoustic laminated glass with a 0.76mm PVB interlayer that dampens sound vibration. The figures above are typical ranges for comparable configurations; exact Rw varies with the precise glass-cavity-glass combination used in your build. Where a quieter result is needed within the 46mm size, a double-laminated unit (for example 12.76 / 20 argon / 12.76) can reach around Rw 48 as an installed window. The standard 24mm IGU is our thermal-focused product. For noise problems, specify the 24mm acoustic upgrade or step up to 36mm or 46mm.
Generic acoustic advice tends to fail because it treats all noise as the same problem. A B-double truck idling outside your bedroom has a very different frequency profile from a kookaburra in the gum tree next door. The right glass depends on what you are actually trying to block.
Mid-frequency dominated. Cars on suburban Melbourne streets, courier vans, school traffic.
Low-frequency dominated. Citylink, Eastlink, West Gate, Princes Highway, freight truck routes.
Mixed-frequency with peaks from bells, brakes, rail contact. Sydney Road Brunswick, Glenferrie Road Hawthorn, Chapel Street Prahran, Lygon Street Carlton.
Intermittent high-energy noise with significant low-frequency content. Strathmore, Essendon, Pascoe Vale, Niddrie, Glenroy.
Variable. Lawnmowers, dogs, conversations, parties. Mid to high frequency dominated.
Low-mid frequency with intermittent peaks. Frankston line, Hurstbridge line, Sandringham line corridors.
The mechanism is straightforward physics. Two glass panes act as two separate barriers, with a sealed air or argon-filled cavity between them that works like a cushion. When a sound wave hits the outer pane, the pane vibrates and sheds energy. The cavity absorbs and dampens that vibration. The inner pane vibrates far less, so the sound reaching the room is significantly reduced.
Three properties of the glazing system control how much noise is actually reduced.
Glass mass. Heavier glass is harder to vibrate. A 5mm pane is meaningfully better than a 4mm pane, particularly at low frequencies, and a 6mm laminated pane is better again. This is why asymmetric configurations (6.76mm acoustic / 14 Argon / 4mm in a 24mm IGU, or 10.76mm acoustic / 20 Argon / 5mm in a 36mm IGU) outperform symmetric ones.
Gap width. A wider cavity is a softer spring, which is better for low-frequency attenuation. Our 24mm IGU uses a 14 to 16mm argon-filled gap. Our 36mm uses a 20mm gap. Our 46mm uses a 28mm gap. Beyond about 28mm the gap starts behaving like a connected air column and acoustic performance flattens.
Damping (acoustic laminated glass). Every glass pane has a natural resonant frequency where it transmits sound efficiently. An acoustic laminated outer pane with a 0.76mm PVB interlayer dampens the pane's own resonance. The PVB is engineered specifically for this, not the standard 0.38mm safety PVB used for impact resistance. This is the single highest-impact upgrade available in residential acoustic glazing.
Generic acoustic recommendations rarely match the actual noise problem outside someone's bedroom window. A few Melbourne-specific scenarios and what tends to deliver the result:
Sydney Road, Brunswick. Tram route plus through-traffic. Mixed mid-frequency with tram peaks. A 36mm IGU with 10.76mm acoustic laminated outer pane (approximately Rw 39-41) typically reduces tram noise to the point where it becomes a faint background presence in the bedroom. Sleep returns. The very low-frequency bass from Friday-night clubs further down Sydney Road is harder to fully solve at this spec.
Citylink corridor, North Melbourne / Kensington / Flemington. Heavy freight noise, low-frequency dominated, 24-hour. A 46mm IGU with 12.76mm acoustic laminated outer pane (approximately Rw 42-44) is what we typically specify for homes within 100 metres of the toll road. Standard double glazing helps but does not solve.
Tullamarine flight path, Strathmore / Pascoe Vale / Essendon. Intermittent overflight with low-frequency turbine noise. The 46mm IGU at approximately Rw 42-44 reduces in-home aircraft noise meaningfully but not entirely. Acoustic glazing addresses the windows. Full mitigation requires attention to roof and wall insulation too.
Glenferrie Road, Hawthorn. Tram plus shopping strip activity. Lower freight traffic than Sydney Road, but daytime activity is constant. The 36mm IGU acoustic laminated is the practical sweet spot here.
Inner Melbourne construction zones, Docklands / Fishermans Bend / Cremorne. Impact-heavy noise from pile-driving, cranes, and concrete pours. A 46mm IGU acoustic laminated is what is needed when construction is expected to run for years. Frame seal quality matters as much as the glass here.
Frankston / Hurstbridge / Pakenham train lines. Track-side homes within 50 metres of a train corridor. A 36mm IGU acoustic laminated reduces train rumble substantially. Homes within 20 metres typically need the 46mm IGU.
For Windows Republic's acoustic-rated window range built around these Melbourne noise problems, see the antinoise window page. We make configurations using acoustic laminated glass with a 0.76mm PVB interlayer, and double-laminated options for the hardest noise environments.
Partially, yes. The two main options for reducing noise without full window replacement are secondary glazing and acoustic film, with very different performance profiles.
Secondary glazing adds a second pane to the inside of an existing window, creating a wider air gap (typically 50-150 mm). This wider gap is acoustically beneficial because it gives more space for sound energy to dissipate. A well-fitted secondary glazing system can achieve Rw 35-40 dB in practice, broadly comparable to a 24mm acoustic upgrade IGU. Can sometimes be cheaper than full replacement and useful in heritage homes where window replacement is restricted by council overlay.
The trade-offs: secondary glazing adds an extra window to clean, can complicate the operation of the original window, and rarely matches the thermal performance of a properly specified double-glazed unit. It also requires the original window to remain serviceable. Rotten timber sashes or corroded aluminium frames undermine secondary glazing performance because air leaks around the original window.
Acoustic window film applied to existing single glazing offers marginal acoustic improvement (typically 1-2 dB) and is rarely worth the cost for noise reduction alone. Acoustic film is more meaningful for UV protection than for sound.
For most Melbourne homes outside heritage overlays, replacing single glazing with double glazed windows in Melbourne (a 36mm or 46mm acoustic laminated IGU) delivers significantly better noise reduction than secondary glazing, and combines it with thermal performance, security, and condensation control. The cost is higher upfront, but the acoustic result is meaningfully different. For homes where full replacement is the right call but the budget question matters, see the 2026 Melbourne cost guide.
Six questions worth asking any Melbourne supplier about acoustic performance:
The questions Melbourne homeowners ask us most often, with honest answers.
Yes. A standard 24mm double-glazed unit (4mm / 16mm Argon / 4mm Low-E) in a uPVC frame achieves Rw 32 to 34 dB, compared with around Rw 25 dB for the 3mm single glazing still common in older Melbourne homes. That is a 7 to 9 dB improvement on the headline number, and substantially more in real-world perception because double glazing also seals out the air-borne noise leaking around the perimeter of older frames.
Standard double glazing (24mm IGU with 4mm Low-E panes and an argon cavity) typically reduces noise to approximately Rw 32-34 dB. The 24mm acoustic laminated upgrade (6.76mm acoustic laminated outer + 4mm Low-E inner) reaches approximately Rw 36-38 dB. A 36mm IGU with 10.76mm acoustic laminated outer + 5mm Low-E inner reaches approximately Rw 39-41 dB. A 46mm IGU with 12.76mm acoustic laminated outer + 5mm Low-E inner reaches approximately Rw 42-44 dB. Higher Rw is achievable with double-laminated configurations. Each 10 dB drop is perceived as roughly halving the loudness.
Double glazing reduces noise by putting two glass panes in the path of the sound instead of one, separated by a sealed air or argon gap. When a sound wave hits the outer pane, energy is absorbed by the pane's vibration. The cavity dampens that vibration. The inner pane vibrates much less, so the sound entering the room is significantly reduced.
Adding an acoustic laminated outer pane with 0.76mm PVB further dampens pane resonance and improves performance at most frequencies. This is the single highest-impact upgrade available in residential acoustic glazing.
Yes, but the configuration matters. Standard double glazing reduces general urban traffic noise meaningfully. For homes on busy Melbourne roads like Citylink, Eastlink, or Punt Road, specify a 36mm IGU with 10.76mm acoustic laminated outer pane (approximately Rw 39-41). For homes directly beside major freight routes or freeways, a 46mm IGU with a 12.76mm acoustic laminated outer pane (approximately Rw 42-44) is what tends to deliver a genuinely quiet result.
Low-frequency truck rumble is the hardest part of traffic noise to block, which is why thicker glass and wider air gaps matter for freeway-adjacent homes.
Yes. Melbourne tram noise is mid-frequency dominated with intermittent high-energy peaks from bells, brakes, and rail-wheel contact. A 36mm IGU with a 10.76mm acoustic laminated outer pane (approximately Rw 39-41) is the typical recommendation for homes on tram routes such as Sydney Road Brunswick, Glenferrie Road Hawthorn, or Chapel Street Prahran. Standard double glazing helps but rarely solves the problem fully.
No window is truly soundproof. The accurate term is noise-reducing. A premium acoustic double-glazed window (46mm IGU with a 12.76mm acoustic laminated outer pane and 5mm Low-E inner) reduces noise by approximately 17 to 19 dB compared with the 3mm single glazing common in older Australian homes. That is perceived as a substantial reduction but not silence. For homes near airports or major freeways, acoustic glazing combined with attention to the rest of the building envelope is what delivers the closest practical result to soundproof.
Effective, with the headline numbers being: approximately 7 to 9 dB improvement at the entry level (24mm IGU standard) versus 3mm single glazing, rising to roughly 17 to 19 dB at the top end (46mm IGU with acoustic laminated glass). Because dB is a logarithmic scale, a 10 dB drop is perceived as roughly halving the loudness. The 17-plus dB improvement available from premium acoustic glazing is perceived as close to a quarter of the original loudness.
The improvement is most noticeable in mid and high frequencies and less pronounced at very low frequencies.
Partially. Secondary glazing adds a second pane to the inside of an existing window, creating a wider air gap and reducing noise transmission. A well-fitted secondary glazing system can achieve approximately Rw 35-40 in practice, broadly in the same range as a 24mm acoustic upgrade IGU. It can sometimes be cheaper and less disruptive than full window replacement, but adds an extra window to clean and can complicate the operation of the original window.
For heritage homes where full replacement is restricted by council overlay, secondary glazing is the realistic option. For most other Melbourne homes, replacing the window with a 36mm or 46mm acoustic IGU using acoustic laminated glass delivers meaningfully better noise reduction and combines it with thermal performance, security, and condensation control.
See our acoustic-rated window range, or get a free measure and quote with detailed Rw advice for your noise environment.
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