The number of panels depends on three things: the room's volume, how much its surfaces already absorb, and how short you want the echo to be. Here is the calculation for a typical conference room, step by step.
Step 1: the room
A typical conference room of 20 × 14 ft with a 9 ft ceiling has a volume of about 2,520 ft³. With hard and bare surfaces (tile, concrete, glass and little soft furniture), its echo time is about 2.11 seconds. The target for conference rooms is 0.50 seconds.
Step 2: how much absorption is missing
Sabine's formula says RT60 = 0.161 × V ÷ A, with V in cubic meters and A, the total absorption, in square-meter sabins. To reach 0.50 s, the room needs about 247 ft² sabins of absorption in total. It already has about 59 from its surfaces, so the panels must add the rest.
Step 3: what one panel adds
A 24 × 21 in hexagon panel, 2 in thick has about 2.6 ft² of face. At NRC 1.00, and allowing for the surface it covers, it adds about 2.5 sabins.
Step 4: the answer
About 77 panels bring the room from 2.11 s to 0.50 s.
| Thickness | NRC | Panels needed | Echo time after |
|---|---|---|---|
| 1 in | 0.8 | 97 | 0.50 s |
| 2 in | 1 | 77 | 0.50 s |
| 4 in | 1.15 | 67 | 0.49 s |
| Room | Size | Volume | Echo time now | Panels needed |
|---|---|---|---|---|
| Small | 15 × 11 × 9 ft | 1,485 ft³ | 1.83 s | 43 |
| Typical | 20 × 14 × 9 ft | 2,520 ft³ | 2.11 s | 77 |
| Large | 30 × 21 × 11 ft | 6,930 ft³ | 2.86 s | 228 |
These are estimates for speech frequencies (500–1,000 Hz). Use the room calculator with your own measurements, then load the result into the designer.