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 exam room, step by step.
Step 1: the room
A typical exam room of 12 × 10 ft with a 9 ft ceiling has a volume of about 1,080 ft³. With hard and bare surfaces (tile, concrete, glass and little soft furniture), its echo time is about 1.67 seconds. The target for exam 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 106 ft² sabins of absorption in total. It already has about 32 from its surfaces, so the panels must add the rest.
Step 3: what one panel adds
A 24 × 48 in rectangular panel, 1 in thick has about 8.0 ft² of face. At NRC 0.80, and allowing for the surface it covers, it adds about 6.0 sabins.
Step 4: the answer
About 13 panels bring the room from 1.67 s to 0.48 s.
| Thickness | NRC | Panels needed | Echo time after |
|---|---|---|---|
| 1 in | 0.8 | 13 | 0.48 s |
| 2 in | 1 | 10 | 0.49 s |
| 4 in | 1.15 | 9 | 0.48 s |
| Room | Size | Volume | Echo time now | Panels needed |
|---|---|---|---|---|
| Small | 9 × 8 × 9 ft | 648 ft³ | 1.41 s | 7 |
| Typical | 12 × 10 × 9 ft | 1,080 ft³ | 1.67 s | 13 |
| Large | 18 × 15 × 11 ft | 2,970 ft³ | 2.30 s | 39 |
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.