How to calculate RT60 from materials?

Sabine: T60 = 0.161V/A. Multiply each surface area by its alpha, sum = A. Predicts per octave band. Use Eyring when average alpha exceeds 0.2 for accuracy.

NRC 0.80+ for effective treatment. 50mm mineral wool: 0.80-0.95. Thicker or air-gapped panels improve bass. Check per-band alpha at needed frequencies.

Why is bass absorption hard?

Long wavelengths (3.4 m at 100 Hz). Porous absorbers need quarter-wavelength depth: 860mm at 100 Hz. Membrane, bass traps, Helmholtz provide practical alternatives.

Sabine assumes low absorption (alpha below 0.2). Eyring uses -ln(1-alpha) for better accuracy at high absorption. Use Eyring in treated rooms, studios, anechoic spaces.

How to calculate RT60 from materials?

Sabine: T60 = 0.161V/A. Multiply each surface area by its alpha, sum = A. Predicts per octave band. Use Eyring when average alpha exceeds 0.2 for accuracy.

NRC 0.80+ for effective treatment. 50mm mineral wool: 0.80-0.95. Thicker or air-gapped panels improve bass. Check per-band alpha at needed frequencies.

Why is bass absorption hard?

Long wavelengths (3.4 m at 100 Hz). Porous absorbers need quarter-wavelength depth: 860mm at 100 Hz. Membrane, bass traps, Helmholtz provide practical alternatives.

Sabine assumes low absorption (alpha below 0.2). Eyring uses -ln(1-alpha) for better accuracy at high absorption. Use Eyring in treated rooms, studios, anechoic spaces.

Sound Absorption — NRC, Sabine & Material Selection

Sound Absorption — NRC & Materials

Sound absorption converts acoustic energy to heat through porous material friction, membrane vibration, or resonance. Alpha ranges 0-1.0. NRC averages alpha at 250, 500, 1000, 2000 Hz per ASTM C423 for single-number material comparison.

ISO 354:2003ASTM C423:2017ISO 3382-1:2009§3.1

Sabine Equation

T60 = 0.161V/A. V = volume (m3), A = total absorption (sabins = sum of alpha_i times S_i). Eyring more accurate when average alpha exceeds 0.2.

Absorber Types

Porous: mineral wool, foam. Mid/high frequency, proportional to thickness. Quarter-wavelength rule. Membrane: plywood+gap, tuned low-frequency. Helmholtz: specific frequency resonance.

NRC/SAA

NRC: average at 4 frequencies, rounded to 0.05. SAA per ASTM C423: 12 bands. NRC above 0.70 = good absorber. Check per-band alpha for targeted treatment.

Selection

Calculate deficit: A_required = 0.161V/T60_target minus existing. Select materials matching deficit frequency profile.

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Sound Absorption — NRC & Materials

Sabine Equation

Absorber Types

NRC/SAA

Selection

Frequently Asked Questions

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→Complete Guide to Room Acoustics Measurement — ISO 3382

→Room Modes & Standing Waves — Calculation & Treatment

→Acoustic Treatment vs Soundproofing