What reverberation time tells you
When you clap in an empty room, the sound keeps bouncing between hard surfaces before it dies away. Reverberation time (RT60) is the time it takes for sound to fall by 60 dB after the source stops. Too much reverberation makes speech hard to understand, blurs music and turns restaurants into noisy halls. Too little makes a room feel dead. Each kind of space has a sweet spot.
RT60 = 0.161 × volume (m³) ÷ total absorption (m² sabins)
This is the Sabine formula. Each surface absorbs a share of sound energy given by its absorption coefficient: painted drywall reflects about 95 % of mid-frequency sound (coefficient 0.05), while a 2-inch fiberglass panel absorbs nearly all of it (0.95 or more). EchoLess adds up the absorption of your floor, ceiling, walls and furniture to estimate the current reverb time, then calculates how much absorption you need to reach the target.
Target reverberation times
| Room | Target RT60 (mid frequencies) |
|---|
| Mixing / control room, vocal booth | 0.2 – 0.3 s |
| Home theater, podcast studio | 0.3 – 0.4 s |
| Hi-fi listening room | 0.4 – 0.5 s |
| Office, conference room | 0.5 – 0.7 s |
| Classroom | 0.6 – 0.7 s (ANSI S12.60) |
| Restaurant | 0.8 – 1.0 s |
| Church, concert hall | 1.2 – 2.0 s |
Where to put acoustic panels
- First reflection points: the spots on the side walls where a mirror would show you the speakers from your listening position.
- Ceiling cloud: a panel or two suspended above the listening or mixing position.
- Rear wall: absorption or diffusion behind the listener to reduce echoes.
- Corners: thick bass traps (4 – 6") where low frequencies build up.
- Offices and restaurants: spread panels evenly across walls and ceiling – coverage matters more than exact position.
Choosing panels
Look for panels made from rigid fiberglass or mineral wool (6 – 8 lb/ft³ density) wrapped in breathable fabric. Thickness determines how low the absorption reaches: 1" panels work mainly above 1 kHz, 2" panels down to about 250 – 500 Hz, and 4" panels or bass traps lower still. The NRC (Noise Reduction Coefficient) averages absorption across speech frequencies – 0.8 or higher is good. Check fire ratings (Class A / ASTM E84) for commercial spaces.
Absorption is not soundproofing
Acoustic panels improve how a room sounds inside, but they do almost nothing to stop sound leaking to neighbors. Blocking sound needs mass, airtight seals and decoupled construction – a different job entirely.
Frequently asked questions
How many acoustic panels do I need for a home studio?
A typical 12 × 10 ft room usually needs about 8 – 14 panels of 2 × 4 ft, 2" thick, plus bass traps in the corners, to reach 0.3 s.
Do acoustic panels block sound from neighbors?
No. They reduce echo inside the room. Stopping sound transmission requires soundproofing: mass, sealing and decoupling.
Is foam as good as fiberglass panels?
Thin foam absorbs mainly high frequencies. 2" mineral wool or fiberglass panels absorb a much wider range and are more effective per dollar.
What is a good RT60 for a room?
About 0.3 – 0.4 s for studios and home theaters, 0.5 – 0.7 s for offices and classrooms, and around 0.8 – 1.0 s for restaurants.
Where should acoustic panels go first?
At the first reflection points on the side walls, then a ceiling cloud and the rear wall, with bass traps in corners.
About EchoLess
EchoLess is an independent, free acoustic treatment calculator for home studios, home theaters, podcast rooms, offices, classrooms and restaurants, based on the Sabine reverberation formula and typical absorption coefficients. We are not affiliated with any acoustic panel manufacturer.
Every formula on this page runs entirely in your web browser. The numbers you type are never uploaded, stored or shared. Our goal is simple: give you an honest starting point so you can compare product specifications with confidence and avoid paying for capacity you do not need – or buying something too small to do the job.
The methodology combines widely published engineering rules of thumb, manufacturer data sheets and the electrical code practices that installers use every day. We review the assumptions regularly and update the calculator when typical product specifications change.
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Last updated: October 28, 2026
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