Theater Calculators
Soundproofing STC Estimator
https://www.theatersizing.com/calculators/soundproofing-stc/
Estimate only — not a calibrated SPL meter, an acoustic report or an electrical design. Confirm with measurement.
Soundproofing STC Estimator
STC ≈ 13.5 log10(mass) + 13 + 5 log10(1 + gap/20). It is a speech-range single number. Subwoofer rumble is another fight.
Inputs
Results
- Estimated STC
- 34
Calculation method
Mass law plus a crude air-gap bonus. Use it to compare “one sheet vs two with a gap”, not to pass a lab.
Exact formula
STC ≈ 13.5 log10(m) + 13 + 5 log10(1+g/20). Limits: no flanking, no coincidence dip, no doors/windows, speech band only.
Frequently asked questions
Is STC isolation?
It is a lab number for airborne speech. Impact and bass are different tests.
More gap always better?
A damped cavity helps; an undamped 300 mm cavity can ring.
Doors?
The leaky door sets the wall. Seal it or the STC is fiction.
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