| Input | Value | Notes |
|---|---|---|
| Dimensions | 12 m × 8 m × 3 m | Volume = 288 m³ |
| Method | Sabine | Good for light absorption |
| Main α | Floor 0.06, Ceiling 0.20, Walls 0.05 | Typical untreated walls, treated ceiling |
| Extra surfaces | Windows 18 m² at α 0.02; Door 4 m² at α 0.10 | Glazing and door contributions |
| Output | RT60 ≈ 1.0–1.3 s | Depends on final absorption totals |
Total absorption (in sabins) is computed as:
A = Σ (Sᵢ × αᵢ) + (people × sabins_per_person)
Sabine reverberation time:
RT60 = 0.161 × V / (A + 4mV)
Eyring reverberation time (uses average absorption ᾱ = A/S):
RT60 = 0.161 × V / ( -S ln(1 - ᾱ) + 4mV )
- Select units, method, and the room use target.
- Choose geometry input: dimensions or direct V and S.
- Pick absorption input: surfaces or total sabins.
- For surfaces, set α values and add extra surfaces.
- Press Calculate to view RT60 above the form.
- Use CSV or PDF buttons to export the report.
Why RT60 Matters on Site
Reverberation time (RT60) predicts how long sound energy lingers after a source stops. In classrooms, control rooms, and offices, long decay reduces speech clarity and increases fatigue. In atriums and worship halls, moderate decay can support spaciousness but may blur announcements. Use RT60 early to align finishes, ceiling systems, and furniture packages with acoustic targets before procurement locks choices. For retrofits, it helps justify treatments with outcomes.
Inputs That Control Accuracy
The calculator uses room volume, total surface area, and total absorption in sabins. Dimensions automatically estimate floor, ceiling, and wall areas, then multiply each by an absorption coefficient α for the selected band. Add extra items such as glazing, doors, panels, seating, and baffles. Occupant absorption can be included when modeling real use, not an empty shell. Keep α values consistent with manufacturer data and mounting conditions.
Reading Results for Room Use
RT60 should be compared to a use-based range rather than a single “good” value. Speech-led spaces often benefit from shorter decay, while music rehearsal needs longer decay with balanced diffusion. If your result is outside the range, treat it as a design signal. Review which surfaces dominate absorption and whether the selected method matches the average absorption level.
Design Levers to Tune Decay
To reduce RT60, increase absorption through acoustic ceilings, wall panels, thick curtains, carpet with pad, or suspended absorbers. To increase RT60, reduce absorptive coverage and use harder finishes, while maintaining noise control. Add diffusion to avoid flutter and dead spots. The Eyring method typically tracks better when average absorption is high, because it accounts for non‑linear absorption behavior at larger ᾱ values.
Coordinating and Reporting
Exported CSV and PDF outputs support coordination with architects, MEP teams, and contractors. Record assumptions: band, occupancy, and material α values used. During value engineering, test substitutions quickly and document impacts on RT60. Treat the result as a planning metric, then confirm with detailed acoustic modeling or measurements for high‑performance spaces and code-sensitive projects.
FAQs
Which method should I use, Sabine or Eyring?
Use Sabine for lightly treated rooms where average absorption is low. Use Eyring when absorption is higher or many surfaces are treated. If ᾱ is high, Eyring usually predicts a slightly shorter, more realistic decay.
What is a sabin in this calculator?
A sabin is one square meter of perfectly absorbing area, used as an equivalent absorption measure. The calculator totals sabins from each surface area multiplied by its absorption coefficient α.
Do I need total surface area to calculate RT60?
For Sabine, surface area helps reporting but is not strictly required when you enter total absorption. For Eyring, total surface area is required because the formula uses ᾱ = A/S.
Why does adding people change the result?
Human bodies and clothing absorb sound, especially in mid frequencies. Adding occupants increases total absorption, reducing RT60. This is useful when comparing an empty room to real operating conditions.
How can I lower RT60 without major renovations?
Add temporary absorption like movable panels, heavy curtains, acoustic baffles, rugs, or upholstered furniture. Treat first reflection areas and large parallel surfaces. Small additions distributed around the room are often more effective than one concentrated patch.
Are the target ranges guaranteed to meet codes?
No. Targets are practical design guidelines and vary by standards, room geometry, and background noise. Use this tool for early decisions, then verify with project specifications, detailed modeling, or field measurements when required.