How to Choose Acoustic Glass for Windows: A Practical Guide

When selecting system windows, one of the most complex choices lies in selecting the right glass configuration—How thick should the glass be? Is laminated glass better than single-pane glass for soundproofing? How wide should the air gap in insulated glazing units (IGUs) be? Should the cavity be filled with gas?

There’s no one-size-fits-all answer. Glass selection must be tailored to the window’s location and the surrounding acoustic environment. Is the window facing a bedroom or balcony? Is the property near a highway, airport, or railway? Once these variables are understood, you can follow the guidelines below to configure glass for optimal sound insulation.

1. Glass Thickness and Sound Insulation

The sound reduction capability of any material depends on mass, stiffness, and damping. For monolithic glass, the only practical way to improve sound insulation is by increasing thickness, since stiffness and damping cannot be easily changed.

However, every glass thickness has a specific critical frequency—a frequency at which the glass performs poorly in sound attenuation. For example:

• 4mm glassperforms poorly around 3500 Hz
• 6mm glassaround 2000 Hz
• 10mm glassaround 1300 Hz

The thicker the glass, the lower the critical frequency, and the fewer weak points across the sound spectrum. For instance, 25mm glass has no major weak frequency bands.

In asymmetrical IGUs, such as 6+12A+4mm, performance at high frequencies (e.g., car horns) can surpass that of 6+12A+6mm, despite the lighter glass. Conversely, 6+12A+6mm outperforms in low frequencies (125–250 Hz), such as road traffic noise. For low-frequency noise, sound insulation improves with greater mass

2. Laminated Glass vs. Monolithic Glass

Laminated glass offers better acoustic performance than monolithic glass of the same thickness.

For example:

• 2+2mm laminated glassperforms better than a 4mm monolithic pane, especially at higher frequencies, reducing sound transmission by an additional 8–10 dB.
• This is due to the PVB (polyvinyl butyral) interlayer, which provides damping and disrupts resonance at the critical frequency.

While the benefit is most noticeable at high frequencies, laminated glass still contributes positively to low-frequency attenuation, although to a lesser extent.

3. Air Gap Thickness in Insulated Glass Units (IGUs)

Contrary to common assumptions, standard IGUs provide only slight improvements in sound insulation over single glazing.

• A 6+12A+6mm IGUoffers only 2–3 dB more insulation than a single 6mm pane.
• The improvement becomes more significant when the glass thicknesses are asymmetricalor the air gap exceeds 16mm.

However, increasing the air gap from 10mm to 20mm generally shows minimal difference in acoustic performance, unless the cavity becomes substantially larger.

4. Gas-Filled IGUs and Acoustic Performance

Does filling the cavity with argon or krypton improve sound insulation?

• Theoretically, denser gases reduce sound transmission.
• In practice, argon-filled unitsshow negligible improvement in acoustic performance.
• In some cases, resonance effectsmay even become more pronounced.

Thus, while argon is beneficial for thermal insulation, its contribution to acoustic insulation is limited.

Final Thoughts

The glass you choose should match the type of noise you're trying to reduce:

• High-frequency noise(e.g., aircraft, alarms): focus on laminated glass and asymmetrical IGUs
• Low-frequency noise(e.g., traffic, trains): prioritize thicker glass, larger air gaps, and overall mass

Conclusion: There’s no one-size-fits-all solution. Innovations in glass technology continue to evolve, but the best product is always the one that suits your specific environment and comfort needs.