Find the tested specimen first
- Identify the laboratory, report reference, date and stated method.
- Read whether the specimen is glass, a complete window or another assembly.
- Check dimensions, glazing, cavity, frame, opening style and operating condition.
- Ask the supplier to explain any differences between that specimen and your proposed system.
A summary graphic can omit important qualifications. Request the relevant report or an authorised extract and check it alongside the actual quotation. A brand name alone does not establish that every configuration has the same performance.
Keep the labels attached to the numbers
| Label | How to approach it |
|---|---|
| dB | A decibel is a unit used for sound-related quantities. Ask which quantity was measured, where and under what conditions. |
| Rw | A weighted sound reduction index. Check the tested specimen and method rather than treating it as a guaranteed room reduction. |
| C and Ctr | Spectrum adjustment terms used with the relevant rating. Saint-Gobain explains Ctr in relation to low-frequency noise such as road traffic. |
| STC and OITC | Different rating methods. Keep the original method and report attached; do not convert between them with an informal rule. |
The underlying method and applicable standard govern a rating. This checklist helps you ask questions; it is not a substitute for interpreting the full test report.
Compare like with like
Before comparing two numbers, check that the methods, specimen scope and relevant configurations are comparable. If one proposal quotes a glass result and another quotes a complete-window result, ask for an explanation rather than ranking the numbers.
For a demanding noise problem, ask whether a qualified acoustics professional should assess the site and the evidence. Do not subtract a laboratory rating from a phone reading to predict your future room level.
Ask what a percentage measures
For a claim such as “80% noise reduction,” ask what quantity is expressed as a percentage, the comparison baseline, the operating conditions and the test method. Without those details, the percentage does not tell you what change to expect in your room.
Treat an open-window versus closed-window recording as a demonstration of those conditions. It does not isolate the difference between an old and a new closed window.
Use recordings for listening, not certification
Device microphones, automatic processing, editing and playback affect recordings. Our project films are labelled as on-site recordings, not certified acoustic tests. Keep your playback volume steady if you listen, and treat the experience as illustrative.
Where site measurements are supplied, ask for the instrument, settings, measurement locations, source conditions and comparison method. A site observation should not be relabelled as an accredited laboratory test.
Common questions
Can I compare a glass report with a complete-window report?
They describe different specimens. Ask how each report supports the proposed complete configuration before comparing headline figures.
Does a project video prove a decibel reduction?
A recording illustrates its capture and playback conditions. Numerical claims require an appropriate measurement method and supporting records.
Sources & context
References support the general explanations or official requirements identified above. Manufacturer sources describe their own systems; they do not certify Victorious Windows products, imply a supply relationship or predict your home’s result.
Source pages checked 31 October 2026. Recheck current property requirements and the exact product specification for your project.
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