Reverb Decay Time Calculator
Calculate reverberation decay time (RT60) for a room based on its volume and acoustic absorption. Use it when designing a studio, rehearsal space, or live venue to match reverb tail length to your musical genre.
About this calculator
Reverberation time, known as RT60, is the time in seconds it takes for a sound to decay by 60 dB after the source stops. The standard formula is derived from Sabine's equation: RT60 = (0.161 × V) / (α × S), where V is room volume in cubic metres, α is the average absorption coefficient of the surfaces, and S represents the total surface area — here consolidated into a single effective absorption term. This calculator simplifies the surface area term into the frequency-range field, allowing estimation across bass, midrange, and treble bands separately. Lower absorption coefficients (hard, reflective surfaces) produce longer decays suited to classical music, while higher coefficients (soft furnishings, acoustic panels) give the shorter, drier sound preferred in recording studios and speech environments.
How to use
Consider a rehearsal room with a volume of 200 m³, an average absorption coefficient of 0.3, and a mid-frequency range value of 1 (normalised). Apply the formula: RT60 = (0.161 × 200) / (0.3 × 1) = 32.2 / 0.3 ≈ 107.3 seconds — that result indicates the inputs are not yet scaled by surface area. In practice, if the effective absorption term (α × S) equals 32, then RT60 = 32.2 / 32 ≈ 1.0 s, a comfortable mid-range decay suitable for a jazz ensemble. Adjust absorption upward to shorten the tail for podcast recording.
Frequently asked questions
What is a good reverb decay time for a recording studio?
Most recording studios target an RT60 between 0.2 and 0.5 seconds for tracking rooms, providing a dry enough environment for clean multi-track recording without unwanted colouration. Control rooms are often even drier, around 0.2–0.3 s, so monitor speakers reproduce sound accurately. Rooms designed for live acoustic recording, such as orchestral halls, aim for 1.5–2.5 seconds to add natural warmth and blend.
How does room volume affect reverberation time?
Larger rooms have more air volume for sound waves to travel through, which inherently extends the decay time — this is why cathedrals ring for several seconds while a small bedroom sounds dead. Doubling room volume roughly doubles RT60 if absorption stays constant. This is why concert halls are engineered to precise volumes: too small and the sound feels thin, too large and it becomes muddy.
Why does reverb decay time vary across frequency ranges?
High frequencies are absorbed more readily by air molecules and soft materials, so treble reverb tails decay faster than bass. Low frequencies can resonate in room modes, sometimes sustaining longer than mid-range content. This frequency-dependent behaviour is why subwoofer-heavy genres like electronic music need careful bass trapping, and why RT60 should ideally be measured and optimised separately for low, mid, and high bands.