Reverberation Time (RT60)

Formula

Description

The Sabine equation calculates the reverberation time RT60, defined as the time for sound to decay by 60 dB after the source stops. It depends on the room volume, the total surface area, and the average absorption coefficient of the surfaces. Larger rooms have longer reverberation times, while more absorptive surfaces reduce it. The constant 0.161 applies when volume is in cubic meters and area in square meters. RT60 is the most important single parameter in room acoustics, determining speech intelligibility and musical character.

Variables

• RT60 — Reverberation time for 60 dB decay (s)
• V — Room volume (m³)
• α — Average absorption coefficient (0-1, dimensionless)
• S — Total surface area of the room (m²)

Practical Notes

Optimal RT60 depends on the use: 0.3-0.5s for recording studios, 0.6-1.0s for speech/conference rooms, 1.5-2.5s for concert halls, and 3-8s for cathedrals. Absorption coefficients vary with frequency: carpet absorbs high frequencies well (α≈0.5) but not lows (α≈0.05), while bass traps target low frequencies. The Sabine equation is most accurate for rooms with relatively uniform absorption.