Acoustic Privacy Calculator

This calculator estimates speech privacy between two enclosed rooms using a simplified Articulation Index (AI) model, adapting the general AI concept from open-plan-office speech-privacy research to a partition-wall scenario: below 0.05 is 'Confidential' (speech is essentially unintelligible), 0.05-0.20 is 'Normal' privacy (speech is occasionally audible but not consistently understood), and above 0.20 is 'Poor' privacy (speech is easily understood through the partition). These three break points are this calculator's own convention for the enclosed-room case, not a reproduction of a published standard — ASTM E1130 defines AI-based privacy classes, but its own scope explicitly excludes both open-plan-to-enclosed and fully-enclosed-to-enclosed spaces like the one this calculator models, so it is not cited here as the source of these specific numbers. The model chains together several real acoustic building blocks: source speech level at 1 meter (60/65/75 dB for normal, raised, and loud voice, standard reference figures in architectural acoustics), distance attenuation using the inverse-square law for a point source (a 6 dB drop for each doubling of distance), the partition's Sound Transmission Class rating (STC, the standard ASTM E413 lab metric for how much a wall assembly blocks airborne sound) degraded by imperfect sealing (gaps, unsealed penetrations, and door undercuts can bleed 10-15 dB of a wall's rated performance even when the assembly itself is well-built), and finally the signal-to-noise ratio against the receiving room's background noise level, since ambient sound masks intelligibility as much as the wall itself blocks transmission.

The resulting AI is a simplified proxy for a more rigorous measurement (real AI/STI calculations integrate performance across multiple frequency bands rather than a single broadband approximation), so treat the output as a useful design-stage estimate rather than a substitute for a certified acoustic consultant's measurement on a completed assembly. The 'STC improvement needed' and 'absorption area' outputs translate the privacy gap into two concrete design levers: upgrading the partition itself, or adding sound-absorbing treatment to raise effective masking in the receiving space.