THE STUDIO JOURNAL / Test data
Why frequency matters when choosing acoustic curtains
Explore Acoustic Molton’s published practical absorption coefficients from 125 Hz to 4 kHz and understand their limits.
THE SHORT ANSWER
One headline rating cannot show how a fabric behaves across the frequency range.
The data, explained.
Swipe the diagram or table sideways to see all the detail ↔
| Frequency | Practical coefficient αp |
|---|---|
| 125 Hz | 0.25 |
| 250 Hz | 0.65 |
| 500 Hz | 0.85 |
| 1000 Hz | 1.00 |
| 2000 Hz | 1.00 |
| 4000 Hz | 1.00 |
Single layer, 50% fullness, 350 mm cavity. Data Sheet 8 / Test 9, page 1. Values transcribed from the practical coefficient column, not estimated from a graph. View the sources ↓
01 / THE DETAIL
Read across the spectrum
The table shows that the reported response changes with frequency. This matters when the brief is more specific than “make the room quieter”. A room dominated by low-frequency problems should not be designed solely around a high-frequency result. The measured assembly has to suit the actual issue.
These values belong to Acoustic Molton at the stated mounting condition. They should not be applied to another Molton product, a different fullness or an added lining without supporting evidence.
02 / THE DETAIL
Know which column you are using
The original report contains more than one type of absorption coefficient. Here we use the practical octave-band values. The adjacent measured one-third-octave series is a different set of data. Mixing the two can create a chart that appears precise but does not represent a consistent series.
See how to read a test report for the difference between band values, αw, NRC and an absorption class. The source link below lets you inspect the original table.
03 / THE DETAIL
A coefficient of 1 is not a silent room
A band coefficient describes absorption under the test conditions. It does not mean that all sound in an occupied room disappears, that a microphone captures no reflections, or that the curtain blocks sound reaching a neighbouring space. Untreated surfaces, furniture, positions and the room’s volume remain important.
Likewise, a lower coefficient at one band is a reason to review the wider treatment design rather than a reason to turn a single fabric into an all-purpose solution.
04 / THE DETAIL
Use band data in a consistent room estimate
For a worked reverberation estimate, select a band and use room inputs appropriate to the same band. Do not insert αw into a calculator field labelled “500 Hz coefficient”. If you need a target across several bands, repeat the design review across those bands and have the final room performance assessed for the project.
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.