What Are Acoustic Design Criteria?
Acoustic design criteria are standards that control sound quality inside a space — reverberation time, background noise level, and sound isolation — so a room supports speech, music, or quiet as intended. Sabine's reverberation formula is the classic starting point.
Acoustic design criteria set target values, most commonly reverberation time (RT60), calculated with Sabine's formula RT60 = 0.161 × V / A, where V is room volume and A is total sound absorption.
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Step-by-step worked examples
A classroom has a volume of 200 m³ and total absorption of 40 m² sabins. Find the reverberation time.
RT60 = 0.161 × V / A RT60 = 0.161 × 200 / 40 RT60 = 0.805 s
A concert hall has V = 12,000 m³ and needs RT60 = 1.8 s for music. What total absorption is required?
RT60 = 0.161 × V / A 1.8 = 0.161 × 12000 / A A = 0.161 × 12000 / 1.8 = 1073.3 m² sabins
An office (V = 150 m³, A = 25 m² sabins) is compared to the same office after adding acoustic ceiling tiles (A = 55 m² sabins).
Before: RT60 = 0.161 × 150/25 = 0.966 s After: RT60 = 0.161 × 150/55 = 0.439 s Adding absorption more than halves the reverberation time.
Flashcards
Quick quiz
Q1.What does reverberation time (RT60) measure?
Q2.A room has V=100 m³, A=20 m² sabins. What is RT60?
Q3.Adding carpet and acoustic panels to a room mainly does what?
Q4.Why do classrooms typically target a shorter RT60 than concert halls?
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Common mistakes
A bigger room always has a longer RT60. — Correct: RT60 depends on the ratio V/A — a large room with lots of absorption can have a short RT60.
Hard, reflective surfaces reduce reverberation time. — Correct: Hard surfaces reflect sound and increase RT60; soft, porous materials absorb sound and reduce it.
RT60 targets are the same for every room type. — Correct: Targets vary by use — speech spaces want shorter RT60, concert halls often want longer RT60 for music.
Acoustic design only concerns reverberation. — Correct: It also includes background noise (NC/NR ratings) and sound isolation (STC/Rw) between spaces.
FAQ
What are acoustic design criteria?
Standards that set target values for reverberation time, background noise level, and sound isolation so a space performs well for speech, music, or quiet use.
What is the acoustic design criteria formula?
Sabine's reverberation time formula: RT60 = 0.161 × V / A, where V is volume and A is total absorption.
What are examples of acoustic design criteria?
Reverberation time targets (e.g., 0.6–1.0 s for classrooms), background noise ratings (NC-25 to NC-35), and sound transmission class (STC) between rooms.
How do you calculate reverberation time for a room?
Multiply the room volume by 0.161 and divide by the total absorption (sum of each surface's area times its absorption coefficient).