Sabine & Eyring Reverberation Time (RT60)
Compute 60 dB acoustic energy decay time, Sabin absorption units, critical distance, and EBU studio target compliance.
How It Works & Acoustic Engineering Principles
Physical Mechanism & Theory
Reverberation Time (RT60) defines the time in seconds required for a steady-state sound field to decay by 60 dB (one-millionth of its initial acoustic energy) after the sound source abruptly stops. Wallace Clement Sabine discovered in 1898 that RT60 is directly proportional to room volume and inversely proportional to total boundary absorption.
While Sabine’s classic formula is accurate for "live" concert halls and untreated rooms where average absorption α < 0.25, it overestimates decay time in heavily treated recording studios. The Norris-Eyring equation corrects for discrete energy loss on every consecutive wall bounce using a natural logarithmic term, converging toward 0 seconds as α approaches 1.0.
Studio Bench Rules of Thumb
- 01.Control Room Target (EBU Tech 3276): Critical mastering and mixing rooms with volumes of 40–100 m³ should aim for an RT60 between 0.20 s and 0.35 s across 200 Hz – 4 kHz.
- 02.Critical Distance (d_c): Sitting closer than the Critical Distance ensures direct monitor sound dominates over diffuse room reverberation.
- 03.Avoid Over-Deadening Highs Only: Thin foam only absorbs above 1 kHz, leaving bass energy booming while making the room sound unnaturally dull and fatiguing.