Understanding Decibels (dB)
The decibel scale is logarithmic, not linear. This means that a 10dB reduction represents a 50% reduction in perceived loudness, and a 20dB reduction means the noise seems 75% quieter.
Common Noise Levels
Key Insight: Secondary glazing typically achieves 35-45dB reduction, meaning a busy road at 80dB would sound like a quiet conversation at 35-45dB.
Acoustic Performance by Configuration
| Configuration | Gap Size | Glass Type | Rw (dB) |
|---|---|---|---|
| Single glazing only | N/A | 4mm float | 25-28 |
| Standard double glazing | 12-16mm | 4mm-4mm | 28-32 |
| Secondary glazing (standard) | 100mm | 6mm float | 40-43 |
| Secondary glazing (acoustic) | 100mm | 6.4mm laminated | 43-45 |
| Secondary glazing (premium) | 150mm | 10.8mm laminated | 47-50 |
*Rw = Weighted Sound Reduction Index, the single-number rating for acoustic performance
Acoustic Glass Specifications
Standard Float Glass
- Thickness: 4mm, 6mm, or 10mm
- Performance: Good for general noise
- Best for: Moderate traffic noise
- Cost: Most economical
Laminated Acoustic Glass
- Thickness: 6.4mm, 8.8mm, 10.8mm
- Performance: Superior for all frequencies
- Best for: Heavy traffic, railways, aircraft
- Bonus: Enhanced security, UV protection
Why Laminated Glass Works Better
Laminated acoustic glass contains a special PVB (polyvinyl butyral) interlayer that absorbs sound vibrations. This is particularly effective at blocking low-frequency noise like bass from traffic, trains, and aircraft that standard glass struggles with.
The Importance of Air Gap Size
The air gap between your original window and secondary glazing is crucial for acoustic performance. Unlike double glazing (12-16mm gap), secondary glazing creates a much larger cavity.
Minimum effective gap
Basic improvement, suitable where space is limited
Optimal gap (recommended)
Best balance of performance and practicality
Maximum performance
Ideal for severe noise problems, where space allows
Noise Frequency Considerations
Low-Frequency Noise is Harder to Block
Bass frequencies from HGVs, trains, and aircraft require thicker glass and larger air gaps than high-frequency noise.
Low Frequency (20-250Hz)
HGVs, trains, bass, aircraft
Solution: 10.8mm laminated + 150mm gap
Mid Frequency (250-2000Hz)
Cars, voices, general traffic
Solution: 6.4mm laminated + 100mm gap
High Frequency (2000Hz+)
Sirens, alarms, birdsong
Solution: 6mm float + 100mm gap
Testing Standards & Certifications
Our acoustic performance claims are verified according to international standards:
- BS EN ISO 10140: Laboratory measurement of sound insulation
- BS EN ISO 717-1: Rating of sound insulation (Rw calculation)
- BS 8233:2014: Guidance on sound insulation in buildings
Related Resources
Acoustic Glass Specifications
Technical specifications for acoustic glass options and their performance data.
Understanding Low Frequency Noise
Why bass frequencies from traffic and trains are harder to block and what works.
Understanding Decibel Reduction
What does dB reduction actually mean? A guide to acoustic performance measurements.
Noise Reduction Calculator
Calculate your potential noise reduction based on your current glazing and noise sources.
Get a Free Acoustic Assessment
Our specialists can measure your current noise levels and recommend the optimal solution.