Acoustic curtains: how to read a datasheet (absorption, weight, fire rating)

"Acoustic curtain" has become a sales claim that everyone makes and almost no one quantifies. For an architect, an operator or a contractor, the only protection against disappointment is knowing how to read a datasheet. Here are the four indicators that matter — and the most common reading traps.

First, clarify the problem: absorb or insulate?

Absorbing means reducing reverberation inside a space — the noisy restaurant, the tiring open-plan office. Insulating means stopping sound travelling from one space to another. A curtain excels at absorption; for insulation it provides a modest complement but will never replace a partition. Any salesperson promising otherwise should show you measurements.

The indicators to demand on the datasheet

1. The alpha-w coefficient (weighted absorption)

The king indicator, lab-measured to ISO 354 and weighted to ISO 11654. It runs from 0 (reflective) to 1 (total absorption) and translates into classes A (0.90 and above) to E. A good acoustic curtain reaches 0.5 to 0.8 depending on fullness — the equivalent of proper absorbent panels, over a much larger surface.

2. The measurement conditions — trap number one

The same fabric can show 0.35 hung flat and 0.80 with 100% fullness and a wall gap. Always check the gather ratio and the fabric-to-wall distance stated in the test report. A datasheet that says nothing about them is probably quoting the most flattering figure.

3. Surface weight

Expressed in g/m², it drives low-frequency performance and the insulation complement. Below 300 g/m², expect no miracles; genuine heavy acoustic curtains often exceed 500 g/m².

4. The fire rating — non-negotiable in public buildings

An acoustic curtain in a meeting room, restaurant or hall must be M1/Euroclass compliant, certificate in hand. Acoustic performance and flame retardancy combine very well — see our guide to acoustic fabrics in public spaces.

Turning figures into an audible result

What your client will hear is the drop in reverberation time. In a very reverberant restaurant, going from 1.5 s to under 1 s transforms the experience — conversations become possible, staff fatigue drops. The calculation uses the alpha-w values, treated surfaces and room volume: it is an engineering sizing, not a hunch. We run it systematically at study stage.

Checklist before signing an "acoustic" quote

• ISO 354 test report available, with installation conditions stated?
• Alpha-w quoted at the fullness actually planned in your make-up?
• Surface weight consistent with the promise?
• Fire certificate in the exact name of the fabric delivered?
• A quantified reverberation or ambience target, written into the offer?

If any answer is missing, demand it — or change supplier. For a reasoned sizing of your project, our thermal and acoustic technical curtains page describes our engineering method.

See also our dedicated page: Thermal & acoustic technical curtains →