Worked Example: School Library — BB93 Quiet Study Space
RT60 calculation for a school library under BB93:2015 targeting 0.6 seconds. Heavy carpet and extensive ceiling treatment create a quiet study environment suitable for individual work and small group reading sessions.
A 360 m³ library designed to BB93 requires RT60 ≤ 0.6s. With Rockfon Sonar 25mm on the ceiling and Fabric-wrapped panel 50mm on walls, the calculated RT60 is 0.31s — PASS.
Room Setup
Total surface area: 393.6 m². Calculation method: Sabine equation (ISO 3382-2:2008 Annex A).
Surface Materials
| Surface | Material | Area (m²) | NRC |
|---|---|---|---|
| ceiling | Rockfon Sonar 25mm | 120.0 | 0.85 |
| walls-main | Painted plaster | 87.0 | 0.04 |
| walls-treatment | Fabric-wrapped panel 50mm | 45.0 | 0.80 |
| floor | Carpet (heavy) | 120.0 | 0.30 |
| windows | Double glazing 6mm | 18.0 | 0.04 |
| door | Solid timber door | 3.6 | 0.08 |
Absorption coefficients sourced from manufacturer datasheets and ISO 354 test reports. Browse the full acoustic materials database.
Step-by-Step Calculation
- 1
Room Volume
V = L × W × H = 12 × 10 × 3 = 360 m³
- 2
Total Surface Area
Stotal = 120.0 + 87.0 + 45.0 + 120.0 + 18.0 + 3.6 = 393.6 m²
- 3
Absorption per Surface at 500 Hz
ceiling: 120.0 m² × 0.82 = 98.40 Sabins
walls-main: 87.0 m² × 0.04 = 3.48 Sabins
walls-treatment: 45.0 m² × 0.78 = 35.10 Sabins
floor: 120.0 m² × 0.14 = 16.80 Sabins
windows: 18.0 m² × 0.04 = 0.72 Sabins
door: 3.6 m² × 0.08 = 0.29 Sabins
- 4
Total Absorption at 500 Hz
Atotal = 98.40 + 3.48 + 35.10 + 16.80 + 0.72 + 0.29 = 154.79 Sabins
- 5
Sabine RT60 at 500 Hz
RT60 = 0.161 × V / A = 0.161 × 360 / 154.79 = 0.37s
- 6
Compare to Target
Mid-frequency RT60 (avg of 500, 1k, 2k Hz) = 0.31s. Target: ≤ 0.6s per BB93. Verdict: PASS
Octave Band Results
| Frequency | 125Hz | 250Hz | 500Hz | 1kHz | 2kHz | 4kHz |
|---|---|---|---|---|---|---|
| Total Absorption (Sabins) | 49.2 | 115.2 | 154.8 | 198.2 | 223.1 | 223.3 |
| RT60 (s) | 1.18 | 0.50 | 0.37 | 0.29 | 0.26 | 0.26 |
| Target (s) | — | — | 0.60 | 0.60 | 0.60 | — |
| Verdict | — | — | PASS | PASS | PASS | — |
Compliance Verdict
Reference: BB93:2015 Table 1.2
School libraries require RT60 ≤ 0.6s under BB93 for combined speech and quiet study use. Bookshelves on walls provide additional scattering that improves perceived acoustics.
STI result: 0.74 (per IEC 60268-16:2020)
Cost Estimate
Costs are indicative and vary by region, supplier, and installation complexity. For a detailed cost breakdown, use the AcousPlan calculator.
Open the AcousPlan calculator pre-loaded with the exact room dimensions (12m × 10m × 3m) and RT60 target (0.6s).
Open CalculatorField Story
A new-build secondary school includes a 120 m² open-plan library designed as both a study space and a venue for author visits and reading groups. The architect's initial plan features a polished concrete floor to match the school's contemporary design language. Acoustic modelling shows this would produce an RT60 of 1.4 seconds, making quiet study impossible. After negotiation, a heavy-pile carpet is agreed with the architect choosing a design pattern that complements the concrete aesthetic. Combined with full ceiling treatment, the library achieves a RT60 well within the BB93 limit.
Frequently Asked Questions
What RT60 does a School Library — BB93 Quiet Study Space achieve?
With the specified materials and dimensions (12m x 10m x 3m, volume 360m3), the calculated mid-frequency RT60 is 0.31s using the Sabine equation. The target under BB93 is 0.6s or less. The result is a PASS.
What materials are used in this education acoustic example?
This example uses Rockfon Sonar 25mm on the ceiling (NRC 0.85), Painted plaster on the walls-main (NRC 0.04), Fabric-wrapped panel 50mm on the walls-treatment (NRC 0.8), Carpet (heavy) on the floor (NRC 0.3), Double glazing 6mm on the windows (NRC 0.04), Solid timber door on the door (NRC 0.08). The total absorption at 500 Hz is 154.8 Sabins.
How much does acoustic treatment cost for this room?
The estimated treatment cost is £12,540 for 285 m2 of absorptive material at approximately £44/m2. Actual costs vary by region, supplier, and installation complexity.
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All calculations are advisory and based on the Sabine equation (ISO 3382-2:2008 Annex A). Results require professional verification for compliance submissions. Absorption coefficients are sourced from manufacturer datasheets and ISO 354 test reports.