How this calculation works
RT60 describes a sixty-decibel decay after a source stops. Sabine’s estimate links that decay to room volume and equivalent absorption area under diffuse-field assumptions, not to a direct speaker distance.
Equivalent absorption A = Σ(area × coefficient); Sabine RT60 = 0.161V/A; Eyring uses −S ln(1 − area-weighted coefficient)A worked example
The example totals 160 m² of represented surfaces. Their equivalent absorption contributions are eight, twenty and eight square metres, giving thirty-six m² sabins. For 100 m³, Sabine time is 16.1/36, about 0.44722 seconds. A 0.4-second target needs 40.25 m² sabins in that model, or 4.25 more than the entered total.
Good to know
Single-band diffuse Sabine/Eyring estimates only; no modal analysis, frequency-independent material library, air-absorption correction or acoustic compliance. Compare with appropriate room measurements and frequency-dependent data before selecting treatment. A single calculated RT60 does not establish intelligibility or listening quality.
Reference: Aalborg University thesis — diffuse reverberation model (opens in a new tab) ↗
What this calculation answers
RT60 describes a sixty-decibel decay after a source stops. Sabine’s estimate links that decay to room volume and equivalent absorption area under diffuse-field assumptions, not to a direct speaker distance.
Equivalent absorption is each represented surface area multiplied by its absorption coefficient at one chosen frequency band. Mixing coefficients from unrelated bands would not describe a single consistent room calculation.
The Speaker distance and combined sound level calculator models direct incoherent sources in a free field. Its level sum does not include the diffuse reverberant decay estimated here.
Use the right input conventions
Include the represented room surfaces once each and use coefficients appropriate to the same band and conditions. The calculator does not assign a material coefficient from its name or infer absorption from appearance.
The target time is supplied by you. The page estimates the extra Sabine absorption needed to reach it under the same model; it does not recommend a universal acoustic target or a particular treatment product.
Interpret the result
The Eyring comparison accounts differently for area-weighted absorption. At high average absorption it can diverge noticeably from Sabine, highlighting sensitivity to the simplified diffuse-field model rather than certifying one result.
The ideal Eyring expression tends to zero when mean absorption reaches one. That limit is mathematical and does not describe every transient in a fully treated room. Low-frequency modes and uneven spatial decay need more detailed analysis.
Work through the example
The example totals 160 m² of represented surfaces. Their equivalent absorption contributions are eight, twenty and eight square metres, giving thirty-six m² sabins.
For 100 m³, Sabine time is 16.1/36, about 0.44722 seconds. A 0.4-second target needs 40.25 m² sabins in that model, or 4.25 more than the entered total.
Where the model stops
Single-band diffuse Sabine/Eyring estimates only; no modal analysis, frequency-independent material library, air-absorption correction or acoustic compliance.
Compare with appropriate room measurements and frequency-dependent data before selecting treatment. A single calculated RT60 does not establish intelligibility or listening quality.
A few questions, answered
Can I use one material coefficient for every frequency?
Only if the supplied data justify it. Absorption is generally frequency-dependent, while this page models one chosen band.
Why show two formulas?
Their difference exposes model sensitivity as average absorption changes, especially away from Sabine’s usual low-absorption assumptions.