Auditorium Acoustic Design Calculator

This calculator estimates reverberation time (RT60) for an auditorium using the classic Sabine equation, RT60 = 0.161 × V / A, where V is room volume and A is total sound absorption in sabins. Absorption comes from two sources it adds together: the room's surfaces (total surface area times your chosen average absorption coefficient) and the seated audience, estimated at a flat 0.5 sabins per person — audiences are significant absorbers, so a full house sounds noticeably drier than an empty hall with the same walls. The result is compared informally against the accepted ranges for different uses: roughly 0.8–1.2 seconds for speech intelligibility, 1.5–2.5 seconds for orchestral music, and up to 4 seconds for pipe organ, though the calculator itself only returns the computed RT60 rather than auto-classifying it. Volume per seat (ideally 6–10 m³) is reported because it's a quick proxy for whether the room has enough air volume to develop natural reverberation without feeling cramped.

The calculator also derives the first axial room mode for each dimension — the lowest resonant frequency along that axis, from speed of sound divided by twice the dimension — which flags problematic bass buildup in long, narrow, or low rooms. A speech clarity index (C80) rounds out the picture, estimated directly from RT60 rather than a full impulse-response measurement. Because Sabine assumes uniformly distributed absorption and works best for reasonably live rooms, treat these numbers as first-pass design estimates: real halls with highly uneven absorption (a heavily draped stage vs. a hard rear wall, for instance) will diverge from the Sabine prediction, and detailed acoustic modeling or physical testing should follow before construction.