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 home office, step by step.
Step 1: the room
A typical home office of 12 × 10 ft with a 8 ft ceiling has a volume of about 960 ft³. With typical surfaces (drywall, a rug and some furniture), its echo time is about 0.80 seconds. The target for home offices is 0.45 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 0.45 s, the room needs about 105 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 × 48 in rectangular panel, 2 in thick has about 8.0 ft² of face. At NRC 1.00, and allowing for the surface it covers, it adds about 7.2 sabins.
Step 4: the answer
About 7 panels bring the room from 0.80 s to 0.43 s.
| Thickness | NRC | Panels needed | Echo time after |
|---|---|---|---|
| 1 in | 0.8 | 9 | 0.43 s |
| 2 in | 1 | 7 | 0.43 s |
| 4 in | 1.15 | 6 | 0.43 s |
| Room | Size | Volume | Echo time now | Panels needed |
|---|---|---|---|---|
| Small | 9 × 8 × 8 ft | 576 ft³ | 0.68 s | 3 |
| Typical | 12 × 10 × 8 ft | 960 ft³ | 0.80 s | 7 |
| Large | 18 × 15 × 10 ft | 2,700 ft³ | 1.10 s | 25 |
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.