1. Thickness and mounting
Thin panels fixed directly on a wall absorb mostly high frequencies. Thicker panels, or panels with an air gap behind them, do much more in the speech range. Decide where and how they will be mounted before comparing prices.
2. A test report for that setup
Ask for an ISO 354 report with the thickness and mounting you plan, and the αw class to EN ISO 11654. A single NRC figure without mounting tells you little; see our guide to NRC and αw.
3. Fire classification
Public buildings, schools and offices often require a reaction-to-fire class to EN 13501-1. Classes differ between products, so ask for the report for the product you buy.
4. Coverage
One wall seldom fixes a room. An acoustician can estimate how many square metres are needed for the room’s purpose.
5. Colour and cutting
PET felt can be CNC-cut into shapes and grooves. Check colour consistency across batches if you will reorder.
6. Recycled content
Many acoustic felts contain about half recycled PET. Ask for the share and the certificate rather than accepting “made from bottles”.
See acoustic panels and offices and architects.
