How Is Reverberation Time Engineering Done in Practice?

Reverberation time engineering sets a target RT60 for the room's use, calculates existing absorption with the Sabine equation, and sizes acoustic treatment to hit the target. It balances speech clarity against musical fullness and verifies the result with field reverberation measurements. Reverberation is the room's signature. It determines whether a space feels intimate or grand, clear or lush — and it's set by just two things: the room's volume and its total absorption. The engineer controls the second one.

The absorption tally is the core calculation: every surface — ceiling, walls, floor, windows, doors, furnishings — contributes its area times its absorption coefficient, summed across octave bands. The Sabine equation converts that total into a predicted RT60 per band, which is compared against the target. The shortfall becomes the treatment schedule. Frequency balance is the subtlety. A room can hit its mid-frequency RT target while booming in the bass (too little low-frequency absorption) or sounding harsh up top. The design selects treatment with the right absorption profile — membrane absorbers and thick panels for bass, standard panels for mids — so the RT curve is smooth, not just correct on average.

RT designs fail when finishes change after the calculation. The acoustic plaster becomes painted drywall, the carpet becomes polished concrete, and the absorption tally quietly collapses. The finish schedule is an acoustic document. Here's what I guard on RT designs.

• Lock the finish schedule: every surface change re-runs the absorption tally
• Design for occupied conditions: people are absorbers — empty-room numbers mislead
• Balance the frequencies: bass control needs different treatment than midrange
• Treat the right surfaces: parallel hard walls cause flutter that average RT hides
• Measure the finished room: RT testing verifies the calculation survived construction