Reverberation Time Calculator Formula

Understand the math behind the reverberation time calculator. Each variable explained with a worked example.

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Formulas Used

Reverberation Time (RT60)

rt60 = 0.161 * volume / total_absorption

Variables

VariableDescriptionDefault
volumeRoom Volume(m3)500
total_absorptionTotal Absorption (A)(m2 Sabine)50

How It Works

Sabine Reverberation Time

RT60 is the time for sound to decay by 60 dB after the source stops.

Formula

RT60 = 0.161 V / A

  • *V* = room volume (m3)
  • *A* = total absorption (sum of surface area times absorption coefficient for each surface, in m2 Sabine)
  • 0.161 = constant derived from the speed of sound and the 60 dB decay requirement

    • Concert halls typically aim for 1.5 to 2.0 s; recording studios 0.3 to 0.5 s.

    Worked Example

    Room: 500 m3, total absorption = 50 m2 Sabine.

    volume = 500total_absorption = 50
    1. 01RT60 = 0.161 * V / A
    2. 02RT60 = 0.161 * 500 / 50
    3. 03RT60 = 80.5 / 50
    4. 04RT60 = 1.61 s

    Frequently Asked Questions

    What is a Sabine?

    One metric Sabine is equivalent to one square metre of perfectly absorbing surface. It is named after Wallace Clement Sabine, the founder of architectural acoustics.

    What is the ideal reverberation time?

    It depends on the use. Speech intelligibility requires short RT60 (under 0.8 s). Orchestral music benefits from 1.6 to 2.2 s. Churches may have 4+ seconds.

    How do I calculate total absorption?

    Sum the products of each surface area times its absorption coefficient: A = sum(S_i * alpha_i). Carpet has alpha about 0.3-0.5; bare concrete about 0.02.

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