Sabine's Reverberation Time Formula
Calculate reverberation time using Sabine's formula T60 = 0.161V/A.
Essential for designing concert halls, studios, and classrooms.
The Formula
Sabine's reverberation time formula predicts how long sound lingers in an enclosed space after the source stops. The result, T60, is the time it takes for sound to decay by 60 decibels, which is roughly the point where it becomes inaudible.
Wallace Clement Sabine developed this equation in the late 1890s while studying the acoustics of lecture halls at Harvard University in the United States. He discovered that reverberation depends on just two factors: the volume of the room and the total sound absorption of all surfaces inside it. His work laid the foundation for the entire field of architectural acoustics.
The constant 0.161 has units of seconds per meter and is derived from the speed of sound in air at room temperature. If you work in imperial units (feet), the constant changes to 0.049. This formula assumes the sound field is diffuse, meaning sound energy is evenly distributed throughout the space.
Rooms with hard, reflective surfaces like concrete and glass have low absorption, producing long reverberation times. Rooms with soft, absorptive materials like carpet, curtains, and acoustic panels have high absorption, producing short reverberation times. Concert halls typically aim for a T60 of about 1.5 to 2.0 seconds. Recording studios need much shorter times, often 0.3 to 0.5 seconds, for clear sound reproduction. Classrooms work best around 0.4 to 0.7 seconds so speech remains intelligible.
Variables
| Symbol | Meaning |
|---|---|
| T60 | Reverberation time (seconds) — time for sound to decay by 60 dB |
| V | Room volume (cubic meters, m³) |
| A | Total absorption (sabins, m²) — sum of each surface area multiplied by its absorption coefficient |
| 0.161 | Constant derived from the speed of sound (use 0.049 for imperial units in feet) |
Example 1
A small recording studio measures 6 m × 5 m × 3 m. The total absorption from all surfaces, furniture, and acoustic treatment is 45 sabins. What is the reverberation time?
Calculate volume: V = 6 × 5 × 3 = 90 m³
Apply formula: T60 = 0.161 × 90 / 45
T60 = 14.49 / 45
T60 ≈ 0.32 seconds — excellent for a recording studio
Example 2
A concert hall has a volume of 12,000 m³ and total absorption of 1,100 sabins. Is the reverberation time suitable for orchestral music?
Apply formula: T60 = 0.161 × 12,000 / 1,100
T60 = 1,932 / 1,100
T60 ≈ 1.76 seconds — within the ideal range of 1.5 to 2.0 seconds for orchestral performance
When to Use It
Use Sabine's reverberation time formula whenever you need to predict or control how sound behaves in an enclosed space.
- Designing concert halls, theaters, and auditoriums for optimal musical sound
- Treating recording studios and home studios with acoustic panels
- Improving speech intelligibility in classrooms, lecture halls, and conference rooms
- Evaluating the acoustic impact of interior design choices (hard floors vs. carpet, glass walls vs. curtains)
- Meeting building codes and standards for room acoustics in public spaces