Slam Poetry Stage Acoustics Calculator
Calculate key acoustic parameters for slam poetry venues: reverberation time (RT60), speech transmission index estimate, critical distance, and recommended sound pressure level. Optimized for spoken word clarity.
Formulas Used
Room Volume: V = L × W × H
Total Surface Area: S = 2(LW + LH + WH)
Total Absorption (Sabine units): A = α·S + Naudience·0.5 [m² Sabine]
RT60 — Sabine: RT60 = 0.161·V / A
RT60 — Eyring: RT60 = 0.161·V / (−S·ln(1−αeff)) [more accurate for α > 0.2]
Critical Distance: Dc = 0.057·√(Q·V / RT60) [m]
Room Constant: R = S·αeff / (1−αeff)
Sound Pressure Level: Lp = LW + 10·log₁₀(Q/(4πr²) + 4/R) [dB SPL]
Speech Clarity C50: C50 = 10·log₁₀(e13.816·0.05/RT60 − 1) [dB] (Beranek)
STI Estimate: STI ≈ 1 / (1 + (RT60/0.65)1.5) [empirical, assumes adequate SNR]
Assumptions & References
- Sabine formula assumes diffuse sound field; valid for rooms with low-to-moderate absorption (α < 0.3).
- Eyring formula is preferred for higher absorption coefficients and is used for all primary results.
- Audience absorption: 0.5 m² Sabine per seated, clothed person (ISO 3382-1 typical value at 1 kHz).
- Critical distance formula: Dc = 0.057√(QV/RT60) — derived from Sabine reverberation theory (Beranek, 1954).
- C50 formula based on Beranek's exponential decay model; target ≥ 0 dB for speech intelligibility.
- STI estimate is empirical; full STI requires octave-band RT60 and SNR measurements (IEC 60268-16).
- Optimal RT60 for slam poetry / spoken word: 0.4–0.7 s (ANSI S12.60, classroom acoustics standard).
- Sound power level of unamplified human voice: 65–75 dB re 1 pW (Beranek & Mellow, 2012).
- Room is assumed rectangular with uniform absorption distribution.
- No HVAC noise, flanking paths, or outdoor noise intrusion are modelled.
- References: Beranek, L. (2004). Concert Halls and Opera Houses; ISO 3382-1:2009; ANSI S12.60-2010.