Calculate RT60 reverberation time using Sabine and Eyring equations. Add room surfaces with absorption coefficients, assess speech intelligibility, and reference α values.
Reverberation time (RT60) is the time it takes for sound in a room to decay by 60 dB — roughly the time from when a sound stops until silence. The Sabine equation, RT60 = 0.161V/A, relates room volume (V) to total absorption area (A, in sabins) to predict how "live" or "dead" a room sounds.
This calculator lets you build up a room model by adding surfaces with their areas and absorption coefficients (α). It computes RT60 using both the Sabine equation (accurate for low to moderate absorption) and the Eyring equation (more accurate when absorption is high). It also estimates speech intelligibility and classifies the room from "very dry" to "extremely reverberant."
Four presets cover common scenarios: a small classroom, a concert hall, a recording studio, and a church — each with realistic surface types. The absorption coefficient reference table lists α values at six octave bands for common materials from concrete to acoustic foam.
This tool is indispensable for architects, acoustic engineers, AV integrators, recording studio designers, and anyone who needs to predict or fix room acoustics.
Acoustic calculations with multiple surfaces and materials are tedious by hand. This calculator lets you model rooms interactively and instantly see the effect of adding treatment.
The speech intelligibility estimate and quality classification help non-expert users understand whether the room needs acoustic treatment. Keep these notes focused on your current workflow. Tie the context to real calculations your team runs.
Sabine: RT60 = 0.161 × V / A, where A = Σ(Sᵢ × αᵢ). Eyring: RT60 = 0.161 × V / (−S × ln(1 − ᾱ)), where ᾱ = A/S. 1 sabin = 1 m² of perfect absorption (α = 1). Open window has α = 1 (perfect absorber).
Result: RT60 (Sabine) = 0.73 s — moderate, suitable for multipurpose
RT60 = 0.161 × 100 / 22 = 0.73 seconds. This is typical of a treated classroom. Adding 10 m² of acoustic panels (α=0.7) would reduce it to 0.57 s.
Use consistent units, verify assumptions, and document conversion standards for repeatable outcomes.
Most mistakes come from mixed standards, rounding too early, or misread labels. Recheck final values before use. ## Practical Notes
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Track units and conversion paths before applying the result. ## Practical Notes
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For speech clarity: RT60 < 0.6s in small rooms, < 0.8s in lecture halls. Longer reverberation smears consonants, reducing intelligibility. Amplification systems need even shorter RT60.
Orchestral concert halls: RT60 = 1.5-2.2s at 500 Hz. Chamber music: 1.2-1.5s. Opera: 1.0-1.5s. Rock/pop studios: 0.3-0.5s. The ideal depends on the musical genre.
Use Eyring when the average absorption coefficient exceeds 0.2. Sabine overestimates RT60 when absorption is high. For very absorptive rooms (studios), Eyring is needed.
Volume = Length × Width × Height for rectangular rooms. For irregular shapes, estimate or use 3D modeling. Furniture reduces effective volume by 5-10%.
Thin absorbers (foam, panels) mainly work above 500 Hz. Bass absorption requires thick materials, membrane absorbers, or Helmholtz resonators. RT60 should be calculated per octave band for accurate design.
Add absorptive materials: acoustic panels on walls, carpet on floors, acoustical ceiling tiles. Focus on the largest reflective surfaces first. Each doubling of absorption area halves RT60.