G60 Series Soundproof Windows

 Product Overview

• Dual‑window sound insulation – install a professional inward‑opening soundproof window on the inside of your existing window, creating a double‑layer system. The combined sound insulation of the two layers exceeds 48 dB(A) , with a traffic‑noise spectrum correction of Rw + Ctr ≥ 48 dB(A).

• Acoustic principle – original window + 8 cm air layer + G60 sealed soundproof window. The 8 cm air gap significantly attenuates low‑frequency noise below 250 Hz. As the air gap increases, the coincidence dip shifts downward; once it exceeds 12 cm, the dip moves below the primary energy band of traffic noise (around 125 Hz).

• Frame design guide – based on the Noise and Vibration Control Engineering Handbook (Ma Dayou, Mechanical Industry Press, 2002). Custom‑extruded multi‑cavity, equal‑surface‑density aluminium profiles designed according to the Mass Law.

• Wall thickness ≥ 2.0 mm

• Solid metal cross‑section thickness ≥ 8 mm

• Surface density ≈ 21.6 kg/m²

• Theoretical sound insulation Rw ≈ 35 dB

• Coincidence dip frequency: 1,500–1,700 Hz

• Loss factor η ≈ 0.001

• Glass options –

• Triple laminated: 6 + 1.14PVB + 8 + 1.14PVB + 6

• Quadruple laminated: 6 + 1.14PVB + 6 + 1.14PVB + 5 + 1.14PVB + 5

• Triple laminated with insulating air space: 6 + 12Air + 5 + 1.14PVB + 6

• Quadruple laminated with insulating air space: 6 + 1.14PVB + 6 + 6Air + 5 + 1.14PVB + 5

• Single‑window replacement – remove old windows and install G60 directly. Traffic‑noise spectrum correction Rw + Ctr ≈ 36–40 dB.

• Hardware –

• VOT hinges (load capacity 100 kg), 304 stainless steel transmission box, locking points, and anti‑drop cables.

• BUDUN expansion corner brackets and self‑levelling steel shims.

• Flexible windows custom CNC‑machined aluminium handles and custom‑formulated EPDM seals.

• Why choose G60? – occupies only 60 mm of sill depth. Available in inward‑opening, outward‑opening, tilt‑and‑turn, and top‑hung configurations. Can be paired with electric openers for smart operation or with our ventilation silencer for combined fresh‑air and noise control.

Core Acoustic Principles

2.1 Sound Insulation Behaviour of Thin Panels

For building fenestration, the sound insulation behaviour closely follows the frequency‑response characteristic of a typical thin plate:

Typical thin‑plate sound insulation frequency characteristic curve
(Reference: Noise and Vibration Control Engineering Handbook)

From the curve, increasing the damping of the plate suppresses the vibration amplitude at both low‑ and high‑frequency resonances, thereby improving sound insulation in the coincidence‑dip regions.

For windows, the coincidence dips typically occur at:

• Low frequencies – engine noise

• High frequencies – horn sounds

These sound waves excite forced bending vibrations in the glass. When the vibration amplitude matches an integer multiple of the sound wavelength, strong coupling occurs, allowing significant sound energy to pass through.

For roadside homes, where noise energy is concentrated in the 50–250 Hz band, we use triple or quadruple laminated glass with multiple PVB interlayers. This multi‑layer damping structure effectively suppresses the coincidence dip.

2.2 Resonance Frequency of a Thin Plate

The resonance frequency *f* of a rectangular plate is given by:

Where:

• $�$ = Bending stiffness (flexural rigidity) of the plate (N·m)  B=1/12Et3

• $�$ = Elastic modulus of the material (N/m²)

• $�$ = Thickness of the plate (m)

• $�$M = Surface density of the plate (kg/m²)

• $$$\mathrm{<br>}$a,b = Length and width of the plate (m)

• p,q = Arbitrary positive integers

Formula source: Noise and Vibration Engineering Handbook – Sound Insulation

From the formula, for a single pane of glass, different thicknesses *t* yield different resonance frequencies – and interestingly, thicker glass lowers the resonance frequency.

In practice, high‑performance soundproof windows use multiple laminated panes of varying thicknesses to achieve good insulation even below 250 Hz.

2.3 Why Windows Are the Weak Link

For a typical brick wall, the resonance frequency is below 20 Hz (inaudible). Therefore, windows are the acoustic weak link in any building. The sound insulation of a window is determined primarily by its overall surface density and damping factor (loss factor η).

2.4 How G60 Achieves Superior Performance

1. Increased frame surface density – wall thickness ≥ 2.0 mm, 4‑cavity structure → equivalent solid metal thickness ≥ 8 mm → surface density ≈ 21.6 kg/m² → Rw ≈ 35 dB.

2. Enhanced damping – multi‑layer laminated glass + flexible connections between glass and frame. Our G60 uses triple or quadruple laminated glass with PVB interlayers (minimum 1.14 mm, optionally 1.52 mm PVB or SGP). High damping effectively suppresses resonance and coincidence effects.

3. Maximised glass area – glass occupies 85–90 % of the total window surface, reducing the proportion of less‑dense frame area.

4. Dense centre seal – the opening sash is the weakest point in terms of surface density. Our triple‑seal design uses a compact EPDM gasket to improve both sealing and local surface density.

5. Minimised gaps – installation clearance between frame and wall is kept ≤ 5 mm. For gaps > 20 mm, we use micro‑expanding waterproof mortar.

6. Precision manufacturing – CNC cutting with diamond blades ensures dimensional accuracy of ± 0.5 mm, angle accuracy ± 0.3°, and on‑site vertical/horizontal alignment ± 1°. This guarantees high surface density and low porosity.

Industry Challenges We Address

1. Developer‑supplied windows – typical insulating glass (5+9Air+5) has a pronounced low‑frequency coincidence dip in the 63–250 Hz range, causing that persistent “hum” and rumbling sensation when heavy vehicles pass.
   (See the insulating glass sound insulation curve in the Handbook – regardless of air‑space thickness (6, 9, 12, 15, 18, 20 mm), dips exist at 100, 200, 300, and 2500 Hz.)

2. Mainstream window brands – focus on aesthetics, surface finishes, and branded hardware, but rarely consider acoustic coincidence dips or high‑surface‑density design. They target the premium market, not specialised roadside noise solutions.

3. Budget constraints – units closest to major roads are often sold at discounted prices. Homeowners who compromise on location usually have limited budgets for noise control. G60 was designed to maximise acoustic performance per dollar – making quiet living affordable.

4. Cost comparison – high‑end windows with excellent low‑frequency insulation cost 2,600–5,000 CNY/m². G60 costs only 1,500–1,680 CNY/m² for comparable performance.

5. Demolition is often impossible –

• Occupied homes – removing windows damages waterproofing and interior finishes.

• Curtain‑wall buildings (hotels, hospitals, offices) – exterior removal is prohibited.

• Government‑subsidised housing – original windows cannot be replaced.
  G60 can be added inside occupying only 60 mm, without altering the original structure.

6. Misconception about insulating glass – many vendors believe wider air gaps mean better sound insulation. When users find it ineffective, adding a G60 as a second layer improves insulation by 30–35 dB(A) – a cost‑effective remedy.

7. Ineffective add‑on products – soundproof curtains, seal strips, and acoustic panels ignore the Mass Law – lightweight materials cannot block low‑frequency noise (see the material sound insulation table in the Noise and Vibration Control Engineering Handbook).

8. Misleading claims about materials – some sellers say “plastic steel doesn’t transmit sound, aluminium does”. In fact, according to the Handbook, sound insulation depends primarily on surface density, not on whether the material is metal or plastic. Steel is actually used in military soundproof windows because of its high density.

Unique Advantages of G60

• 15 years in the market – over 10,000 units installed. Simple design, failure rate ≤ 0.1 %, after‑sales rate ≤ 0.1 %. Extremely durable and reliable.

• No demolition, no damage – add‑on installation occupies only 60 mm sill depth. Dry installation – no wall cutting, no damage to window frames, wallpaper, or trim.

• Preserves original window functions – your existing window continues to provide weather and security protection.

• Superimposed sound insulation – with outdoor noise at 75–80 dB(A), indoor levels drop to 35 dB(A) or below.

• Combined thermal insulation – the 8–12 cm air layer provides a thermal buffer. Typical performance:

• Traffic‑noise spectrum correction Rw + Ctr ≥ 45 dB(A)

• Thermal transmittance U‑value ≤ 0.8 W/(m²·K)
  No single‑layer window can match this dual‑window performance.

• Ideal for old‑building renovations – many old windows are 40‑ or 50‑series outward‑opening units. Replacing them with G60 fits the original opening, maximises usable sill space, and does not reduce indoor area.

• Sleek narrow‑frame design – for large windows or balcony enclosures, optional reinforced mullions withstand typhoon‑force winds (Category 9) .

Test report (2019‑03‑18) – Guangzhou Building Materials Industry Research Institute

• Sample: Skit‑03 Flexible soundproof window, quadruple laminated glass (5+0.76PVB+6+0.76PVB+5+0.76PVB+6)

• Test standard: GB/T 19889.3‑2005 / ISO 140‑3:1995, GB/T50121‑2005

• Result: Weighted sound insulation with spectrum correction: Rw(C; Ctr) = 43(‑1; ‑3) dB

• Report No.: Y03‑1900003

• Verification: Email gmlqa@gzjcs.ac.cn (online system not available in 2019)

Applicable Scenarios & Target Users

Noise sources – flight paths, subways, high‑speed rail, highways, main roads, bus depots, construction sites, square‑dance areas, and commercial districts.

Specific applications – mechanical/electrical rooms, production workshops, recording studios, home KTV, hotels – any space requiring sound containment.

Compatible window types – sliding, casement, bay, top‑hung, fixed – all can be retrofitted.

Ideal for –

• Long‑term residents of noisy roadside homes who do not want to move or renovate.

• Industrial noise‑control projects.

• Entertainment venues needing to meet boundary noise limits.

• New homeowners who cannot adapt to a noisy environment.

• Factories failing environmental noise assessments.

• Old‑building renovations – replacing all windows.

• Balcony enclosures with high acoustic requirements – connecting living room to balcony for extra space.

Theoretical Calculation – The Mass Law

Sound transmission loss through a panel is governed primarily by its surface density (thickness × density). Other parameters contribute only about ± 10 %.

For normal incidence, the theoretical sound insulation R₀ (dB) of a homogeneous single panel is:

R0=101g[1+(πfM/ρ0c)2]

Where:

• ${}_{}$${\mathrm{<br>}}_{}$ρ₀ = air density (1.18 kg/m³)

• $�$ = speed of sound in air (344 m/s)

• $�$ = frequency (Hz)

• $�$ = surface density (kg/m²)

For our quadruple laminated glass 6 + 1.14PVB + 6 + 1.14PVB + 5 + 1.14PVB + 5, surface density ≈ 57 kg/m².
Theoretical single‑window insertion loss ≈ 45 dB(A).

Laboratory Test Results

• Test signal: steady‑state white noise at 80 dB(A).

• Installation: frame sealed with cement mortar to eliminate flanking paths.

• Measured A‑weighted sound pressure level: 41.5 dB(A).

Note: This is the single‑window A‑weighted insulation, not the combined double‑window traffic‑noise correction (Rw + Ctr).

Usage Instructions

1. Add‑on installation – occupies only 60 mm sill depth. Combined with your original window, traffic‑noise spectrum correction Rw + Ctr ≥ 45 dB(A).

2. Replacement or balcony sealing – single‑window traffic‑noise spectrum correction Rw + Ctr ≥ 40 dB(A). The narrow frame offers a sleek, minimalist look.

3. Customisation – available as inward‑opening, tilt‑and‑turn, outward‑opening, or top‑hung. Can be paired with our ventilation silencer for fresh‑air supply or with electric openers for smart control.

Summary

• Through 15 years of in‑house R&D and continuous optimisation, we have refined the design while reinforcing weak acoustic points. By thickening critical materials, we eliminate every “sound‑insulation short board.” This pursuit of the optimal quality‑cost balance is why Flexible products remain highly cost‑effective.

• For any window, the glass area dominates the total surface – and its surface density far exceeds that of the frame. Maximising the glass area and embedding it deeply into the profile is the key to reducing flanking transmission.

• The measured A‑weighted value (41.5 dB) closely matches the theoretical prediction (45 dB), confirming that our design and manufacturing processes are near‑perfect.

Frequently Asked Questions

Q1: Does higher sound insulation always mean a higher price?
A: Generally, yes. Achieving higher surface density and damping requires thicker profiles, thicker laminated glass, and tighter seals. However, adding a second layer (G60) gives far better performance than a single high‑end window at a much lower cost.

Q2: Isn’t quieter always better? Can you get down to 20 dB?
A: Not necessarily. The most restful environment is a steady, low‑level pink noise around 30–40 dB(A) – like rain or fan hum. For roadside homes, dropping below 30 dB(A) is extremely difficult because structure‑borne vibration from traffic typically generates indoor noise in the 25–45 dB(A) range, concentrated in the 20–250 Hz band. Even with A‑weighted levels below 35 dB, the low‑frequency energy (50–65 dB at 50–125 Hz) can still feel very uncomfortable. We aim for an NR rating of ≤ 45 for a truly comfortable environment.

Q3: Can I use my phone’s noise‑measuring app? Is it accurate?
A: No. Entry‑grade professional meters cost around 5,000 CNY; those with 1/3‑octave analysis cost over 10,000 CNY. Phone microphones are dynamic‑type and vary widely between apps and devices. They are only useful for rough qualitative checks, not for quantitative measurement.

Q4: Does plastic steel really block sound better than aluminium?
A: No. According to the Noise and Vibration Engineering Handbook, with the same glass and sealing, sound insulation depends on surface density, not on whether the frame is metal or plastic. UPVC has a density of 1,350–1,460 kg/m³, while aluminium is 2,750 kg/m³. Plastic steel profiles are hollow with steel inserts only in cavities – not solid. About 4 mm of UPVC equals 2 mm of aluminium in terms of insulation. While some multi‑cavity UPVC windows outperform standard aluminium, they still fall short of dedicated acoustic aluminium profiles like ours.

Q5: Why does fan noise at 40–45 dB(A) feel fine, but traffic noise at the same level feels terrible?
A: A‑weighting heavily de‑emphasises low frequencies (e.g., –30.2 dB at 50 Hz, –8.6 dB at 250 Hz). Fan noise energy is mostly above 125 Hz, so the A‑weighted reading matches your perception. Traffic noise is concentrated in the 50–125 Hz range – even if A‑weighted shows 40 dB, the actual low‑frequency sound pressure may be 70 dB. Your body feels that energy, causing the “hum” that is hard to tolerate – because the human body’s natural frequencies (2–50 Hz, with internal organs at 4–12 Hz) resonate with these low waves.

Q6: Does a narrow frame (only 60 mm sill depth) mean poorer sound insulation?
A: No – sound insulation depends on surface density, not frame width. Our multi‑cavity frame has a wall thickness ≥ 2.0 mm, giving an equivalent solid thickness of 8 mm. The triple or quadruple laminated glass has a solid core thickness of about 20 mm, plus multiple PVB damping layers. The design eliminates acoustic weak points – it may look slim, but it is exceptionally “dense” and performs superbly.

Q7: What’s the process and lead time?
A: Online/phone inquiry → free on‑site measurement (dimensions and noise) → proposal and quotation → contract with 50 % deposit → production → installation. Total lead time is typically 20–25 days (extended in rainy weather for replacement jobs).

Q8: My original window is old and deformed – can I still add a soundproof window?
A: The soundproof window is completely independent of the original. Deformation of the original does not affect installation. However, if the original window is badly worn, leaks, or is hard to use, we recommend removing it and replacing it with a G60 casement soundproof window for a complete solution.

Q9: Will there be sound leakage through the installation gaps? How do you ensure an airtight seal?
A: Strictly speaking, adding a soundproof window does not improve the original window’s sealing – they are independent. Two critical factors for sound insulation are high surface density and high airtightness. Our windows feature triple seals between frames, compressed gaskets between glass and frame, and PEF backing strips plus modified silane sealant between frame and wall. After installation, there are virtually no gaps – no air leakage, no sound bypass.