Rw, the weighted sound reduction index calculated to ISO 717-1, is a single-number rating of how well a wall or door blocks airborne sound. The higher the number, the better the insulation. Reading it well means checking three things: whether the figure is laboratory tested rather than estimated, where the weak points such as doors and junctions sit, and how laboratory values relate to what you will hear on site.
Where the Rw value comes from
The standard procedure mounts the wall or door element in an acoustic laboratory, measures its sound insulation across frequencies to BS EN ISO 10140-2, then weights the result to ISO 717-1 to produce a single comparable figure. As a working rule of thumb, a 10dB difference reads as roughly half the perceived loudness, though the actual impression depends on background noise and the type of sound.
Tested and estimated values are not the same thing
Catalogue acoustics come in two kinds: laboratory tested (Lab Tested) and extrapolated from similar constructions (Estimated). They can display identical numbers, but only tested values come with evidence. The British Optima systems we represent publish each tested figure with a Summary of Evidence reference, so you can request the document that stands behind any number in the specification.
Laboratory-tested reference data
| Configuration | Laboratory-tested Rw |
|---|---|
| Single glazed wall with 14.8/16.8mm acoustic laminated glass | 40dB |
| Single glazed wall, slim-profile system | 38dB |
| Double glazed wall (12.8mm + 12.8mm) | 43dB |
| Double glazed wall (Revolution 100, 12.8mm + 12.8mm acoustic laminate) | Rw 51dB lab tested; up to Rw 52dB assessed with 12.8 + 16.8mm |
| Double glazed door | 42dB |
| Single glazed sliding door | 36dB |
All values measured to BS EN ISO 10140-2 and calculated to ISO 717-1; actual performance varies with system, configuration and site conditions. For range-by-range details, see the Optima systems overview.
Doors and junctions: the weakest link sets the result
A wall tested at Rw 43dB paired with a much weaker door, or with poorly detailed junctions, performs close to its weakest element. Treat the wall, the door, the ceiling line and the floor junction as one system at the planning stage instead of comparing wall figures alone. On the relationship between sound and focus at work, see Sound Management is the Key to Creating a Focused and Comfortable Work Environment.
Frequently asked questions
How much Rw does a meeting room need?
There is no single number. It depends on what sits next door and on background noise levels: a confidential meeting room needs more than a general discussion room, and a room beside open desks needs more than one against a wall. Have the layout assessed and map requirements room by room.
How much lower will on-site performance be than the laboratory value?
Site results are typically lower because of flanking paths through ceilings, raised floors and services, plus workmanship variables. That does not make the data useless; it means choosing systems with verified test evidence and paying equal attention to the installation team and junction detailing.
Does thicker glass always mean better insulation?
Not necessarily. Acoustic laminated glass and double glazed cavities are more effective than simply adding thickness, which is why two walls of similar thickness can test very differently. The principle holds: read the tested data, not the intuition.
Next step
Designing acoustics in at the planning stage costs far less than fixing them afterwards. Book a site survey, or browse the partition systems overview for tested performance by configuration.