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 living room, step by step.
Step 1: the room
A typical living room of 18 × 14 ft with a 9 ft ceiling has a volume of about 2,268 ft³. With typical surfaces (drywall, a rug and some furniture), its echo time is about 1.03 seconds. The target for living 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 223 ft² sabins of absorption in total. It already has about 108 from its surfaces, so the panels must add the rest.
Step 3: what one panel adds
A 24 × 48 in arch panel, 2 in thick has about 7.6 ft² of face. At NRC 1.00, and allowing for the surface it covers, it adds about 6.8 sabins.
Step 4: the answer
About 17 panels bring the room from 1.03 s to 0.50 s.
| Thickness | NRC | Panels needed | Echo time after |
|---|---|---|---|
| 1 in | 0.8 | 22 | 0.50 s |
| 2 in | 1 | 17 | 0.50 s |
| 4 in | 1.15 | 15 | 0.49 s |
| Room | Size | Volume | Echo time now | Panels needed |
|---|---|---|---|---|
| Small | 14 × 11 × 9 ft | 1,386 ft³ | 0.90 s | 9 |
| Typical | 18 × 14 × 9 ft | 2,268 ft³ | 1.03 s | 17 |
| Large | 27 × 21 × 11 ft | 6,237 ft³ | 1.40 s | 58 |
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.