THE STUDIO JOURNAL / Acoustics
Estimating room reverberation with acoustic curtains
A transparent worked Sabine estimate using documented 500 Hz fabric data, with assumptions and limits explained.
THE SHORT ANSWER
A room calculation is an estimate. Keep its frequency, coverage area and installation assumptions visible.
The data, explained.
Swipe the diagram or table sideways to see all the detail ↔
| Input or calculated result | Value |
|---|---|
| Room / volume | 8 × 6 × 3 m / 144 m³ |
| Assumed baseline reverberation time | 1.80 s |
| Projected treatment area | 18 m² |
| Assumed existing coefficient / tested curtain coefficient | 0.05 / 0.85 |
| Initial equivalent absorption | 12.88 m² |
| Added equivalent absorption | 14.40 m² |
| Estimated reverberation time | 0.85 s |
Curtain coefficient: Acoustic Molton at 500 Hz, single layer, 50% fullness, 350 mm cavity. Other inputs are illustrative assumptions. Sabine model; no room performance guarantee. View the sources ↓
01 / THE DETAIL
Start with the room, not the rating
Reverberation time describes how sound decays in a space. To estimate a change, you need the room volume, a baseline time and the absorption being changed. The example assumes a baseline at 500 Hz; it is not a measurement taken in a customer project.
The selected 0.85 coefficient comes from a documented Acoustic Molton test configuration at that band. It is not the brochure’s single-number SAC classification. The fullness and cavity must remain attached to the value when evaluating a proposed installation.
02 / THE DETAIL
Follow the arithmetic
Using the simplified Sabine relationship, equivalent absorption A₀ = 0.161 × volume ÷ baseline time. Here that gives 12.88 m². The illustrative change is 18 × (0.85 − 0.05) = 14.40 m² of added equivalent absorption.
The new estimate is 0.161 × 144 ÷ (12.88 + 14.40) = 0.85 seconds. This comparison assumes the treatment replaces the existing surface contribution over that projected area. It is not a universal formula for adding a freestanding curtain to every room.
03 / THE DETAIL
Avoid counting fullness twice
Use the projected area covered by the tested arrangement, not the total unfolded cloth area multiplied again for fullness. The coefficient already belongs to a specimen with the stated folds. Doubling both the area and the tested coefficient’s fullness benefit would exaggerate the prediction.
If you need 18 m² of projected coverage, use the quantity configurator separately to determine how much cloth is needed to make it. Acoustic coverage and purchasing area answer different questions.
04 / THE DETAIL
Know when the model needs more work
This is a simplified diffuse-field room estimate. Unusual geometry, strongly localised treatment, uneven sound fields, room modes and other surfaces can make the real result differ. A single band does not describe the whole listening experience.
Use our reverberation calculator to explore assumptions, then obtain a project-specific acoustic assessment where a performance target must be met. Read the frequency-data guide before carrying the same coefficient into another band.
Sources & further reading
Technical figures come from the linked manufacturer documents. Worked examples are Studio Curtains calculations with their assumptions shown. Product data and availability should be checked again when specifying.
YOUR NEXT STEP
Turn the detail into a specification.
Share your dimensions and intended use. Stock availability and the final order are confirmed by email.