Reverberation Time Calculator

What Is Reverberation Time?

Reverberation time (RT60) is how long sound takes to decay by 60 decibels after the source stops. Rooms with long RT60 sound echoey. Studios and classrooms often target shorter RT60 for clarity.

Sabine's Equation

$$RT_{60} = \frac{0.161\,V}{A}$$

Room volume $V$ is in cubic meters. Total absorption $A$ equals the sum of each surface area $S_i$ times its absorption coefficient $\alpha_i$. Coefficients range from 0 for hard reflective surfaces to near 1 for thick absorptive panels.

Rectangular Room Surfaces

For a box-shaped room, floor and ceiling each have area length times width. Walls contribute twice the sum of length times height and width times height. Assign one absorption value to all walls, or adjust each group for carpet, drywall, and acoustic tile.

Frequently Asked Questions

What is a good RT60 for a classroom?

Speech intelligibility is often best around 0.4 to 0.6 seconds for classrooms. Very live halls may exceed 1.5 seconds.

What does the absorption coefficient mean?

It is the fraction of sound energy a surface absorbs rather than reflects. Bare concrete might be 0.02 while thick carpet can exceed 0.5.

Why does Sabine use 0.161?

The constant comes from the speed of sound and the definition of RT60. It converts volume and absorption into seconds for metric units.

Can RT60 be too low?

Yes. Extremely dead rooms below about 0.3 seconds can feel unnatural for music. Balance absorption with the intended use of the space.

Does furniture change reverberation?

Yes. Seats, curtains, and people add absorption. Sabine estimates are a starting point before on-site measurement.

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Reverberation Time Calculator

What Is Reverberation Time?

Sabine's Equation

Rectangular Room Surfaces

Frequently Asked Questions

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