Worked Example: School Assembly Hall — BB93 Multi-Use Space
RT60 calculation for a school assembly hall used for assemblies, drama, and PE. Perforated timber slat ceiling and targeted wall treatment balance speech clarity with the timber floor required for sports use.
A 1080 m³ gymnasium designed to BB93 requires RT60 ≤ 1.2s. With Perforated timber slats on the ceiling and Fabric-wrapped panel 50mm on walls, the calculated RT60 is 0.86s — PASS.
Room Setup
Total surface area: 770.0 m². Calculation method: Sabine equation (ISO 3382-2:2008 Annex A).
Surface Materials
| Surface | Material | Area (m²) | NRC |
|---|---|---|---|
| ceiling | Perforated timber slats | 216.0 | 0.65 |
| walls-main | Painted plaster | 276.0 | 0.04 |
| walls-treatment | Fabric-wrapped panel 50mm | 24.0 | 0.80 |
| floor | Timber floor (sealed) | 216.0 | 0.08 |
| windows | Double glazing 6mm | 30.0 | 0.04 |
| door | Solid timber door | 8.0 | 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 = 18 × 12 × 5 = 1080 m³
- 2
Total Surface Area
Stotal = 216.0 + 276.0 + 24.0 + 216.0 + 30.0 + 8.0 = 770.0 m²
- 3
Absorption per Surface at 500 Hz
ceiling: 216.0 m² × 0.70 = 151.20 Sabins
walls-main: 276.0 m² × 0.04 = 11.04 Sabins
walls-treatment: 24.0 m² × 0.78 = 18.72 Sabins
floor: 216.0 m² × 0.10 = 21.60 Sabins
windows: 30.0 m² × 0.04 = 1.20 Sabins
door: 8.0 m² × 0.08 = 0.64 Sabins
- 4
Total Absorption at 500 Hz
Atotal = 151.20 + 11.04 + 18.72 + 21.60 + 1.20 + 0.64 = 204.40 Sabins
- 5
Sabine RT60 at 500 Hz
RT60 = 0.161 × V / A = 0.161 × 1080 / 204.40 = 0.85s
- 6
Compare to Target
Mid-frequency RT60 (avg of 500, 1k, 2k Hz) = 0.86s. Target: 0.8--1.2s per BB93. Verdict: PASS
Octave Band Results
| Frequency | 125Hz | 250Hz | 500Hz | 1kHz | 2kHz | 4kHz |
|---|---|---|---|---|---|---|
| Total Absorption (Sabins) | 87.6 | 154.0 | 204.4 | 212.9 | 190.0 | 169.4 |
| RT60 (s) | 1.99 | 1.13 | 0.85 | 0.82 | 0.92 | 1.03 |
| Target (s) | — | — | 1.20 | 1.20 | 1.20 | — |
| Verdict | — | — | PASS | PASS | PASS | — |
Compliance Verdict
Reference: BB93:2015 Table 1.3
BB93 targets 0.8-1.2s for multi-use assembly halls. The timber floor is acoustically reflective but operationally essential. Perforated timber slat ceiling provides moderate absorption while maintaining visual warmth.
STI result: 0.60 (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 (18m × 12m × 5m) and RT60 target (1.2s).
Open CalculatorField Story
A school's assembly hall doubles as a gymnasium, drama space, and dining area — a common compromise in UK schools where space is at a premium. The timber sprung floor is non-negotiable for sports and dance, but its reflective surface adds to the acoustic challenge of a 1,080 m³ volume. During morning assembly, the head teacher's voice becomes a muddy wash of reflections, and children at the back cannot follow announcements. The solution uses perforated timber slats on the ceiling to provide moderate absorption while maintaining visual warmth, supplemented by fabric panels on the rear wall behind portable staging.
Frequently Asked Questions
What RT60 does a School Assembly Hall — BB93 Multi-Use Space achieve?
With the specified materials and dimensions (18m x 12m x 5m, volume 1080m3), the calculated mid-frequency RT60 is 0.86s using the Sabine equation. The target under BB93 is 0.8--1.2s. The result is a PASS.
What materials are used in this education acoustic example?
This example uses Perforated timber slats on the ceiling (NRC 0.65), Painted plaster on the walls-main (NRC 0.04), Fabric-wrapped panel 50mm on the walls-treatment (NRC 0.8), Timber floor (sealed) on the floor (NRC 0.08), 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 204.4 Sabins.
How much does acoustic treatment cost for this room?
The estimated treatment cost is £12,480 for 240 m2 of absorptive material at approximately £52/m2. Actual costs vary by region, supplier, and installation complexity.
Related Examples
UK Primary Classroom — BB93 Acoustic Compliance
UK Secondary Classroom — BB93 Marginal Result
School Gymnasium — BB93 Non-Compliant Case
Physiotherapy Gym — Excessive Reverberation
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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.