Worked Example: Community Hall — BS 8233 Multi-Purpose Design
1000 m³ village hall with Rockfon ceiling, timber floor, and stage curtains
A 1000 m³ meeting room designed to BS-8233 requires RT60 ≤ 1.2s. With Rockfon Sonar 25mm ceiling tile on the ceiling and Curtains (medium weight) on walls, the calculated RT60 is 0.69s — MARGINAL.
Room Setup
Total surface area: 1005.0 m². Calculation method: Sabine equation (ISO 3382-2:2008 Annex A).
Surface Materials
| Surface | Material | Area (m²) | NRC |
|---|---|---|---|
| Ceiling — Rockfon Sonar | Rockfon Sonar 25mm ceiling tile | 180.0 | 0.82 |
| Ceiling — plaster | Painted plaster | 220.0 | 0.04 |
| Floor | Timber floor (sealed) | 400.0 | 0.09 |
| Walls — painted plaster | Painted plaster | 130.0 | 0.04 |
| Walls — curtains | Curtains (medium weight) | 20.0 | 0.56 |
| Walls — mineral wool | Mineral wool 50mm (wall) | 8.0 | 0.73 |
| Wooden chairs (100) | Wooden seats (unupholstered) | 25.0 | 0.05 |
| Stage curtains | Curtains (medium weight) | 10.0 | 0.56 |
| Windows | Double glazing 6mm | 12.0 | 0.03 |
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 = 25 × 16 × 2.5 = 1000 m³
- 2
Total Surface Area
Stotal = 180.0 + 220.0 + 400.0 + 130.0 + 20.0 + 8.0 + 25.0 + 10.0 + 12.0 = 1005.0 m²
- 3
Absorption per Surface at 500 Hz
Ceiling — Rockfon Sonar: 180.0 m² × 0.82 = 147.60 Sabins
Ceiling — plaster: 220.0 m² × 0.04 = 8.80 Sabins
Floor: 400.0 m² × 0.10 = 40.00 Sabins
Walls — painted plaster: 130.0 m² × 0.04 = 5.20 Sabins
Walls — curtains: 20.0 m² × 0.49 = 9.80 Sabins
Walls — mineral wool: 8.0 m² × 0.70 = 5.60 Sabins
Wooden chairs (100): 25.0 m² × 0.03 = 0.75 Sabins
Stage curtains: 10.0 m² × 0.49 = 4.90 Sabins
Windows: 12.0 m² × 0.04 = 0.48 Sabins
- 4
Total Absorption at 500 Hz
Atotal = 147.60 + 8.80 + 40.00 + 5.20 + 9.80 + 5.60 + 0.75 + 4.90 + 0.48 = 223.13 Sabins
- 5
Sabine RT60 at 500 Hz
RT60 = 0.161 × V / A = 0.161 × 1000 / 223.13 = 0.72s
- 6
Compare to Target
Mid-frequency RT60 (avg of 500, 1k, 2k Hz) = 0.69s. Target: 0.8--1.2s per BS-8233. Verdict: MARGINAL
Octave Band Results
| Frequency | 125Hz | 250Hz | 500Hz | 1kHz | 2kHz | 4kHz |
|---|---|---|---|---|---|---|
| Total Absorption (Sabins) | 123.1 | 182.3 | 223.1 | 242.3 | 229.8 | 225.2 |
| RT60 (s) | 1.31 | 0.88 | 0.72 | 0.66 | 0.70 | 0.71 |
| Target (s) | — | — | 1.20 | 1.20 | 1.20 | — |
| Verdict | — | — | MARGINAL | FAIL | MARGINAL | — |
Compliance Verdict
Reference:
Open the AcousPlan calculator pre-loaded with the exact room dimensions (25m × 16m × 2.5m) and RT60 target (1.2s).
Open CalculatorField Story
A village in Somerset is building a community hall to replace its Second World War Nissen hut. The 25 m by 16 m hall must serve contradictory purposes: bingo needs speech clarity, weddings need music liveliness, fitness classes demand controlled reverberation. Rockfon Sonar covers 45% of the ceiling providing the acoustic workhorse, with painted plaster on the remainder preserving liveliness. The sprung timber floor is essential for dance and badminton. Motorised curtain tracks allow drapes to be deployed for speech events. Mineral wool panels behind the stage provide permanent bass absorption. Wooden stacking chairs provide minimal absorption when deployed. BS 8233 recommends 0.8-1.2 s for multi-purpose halls; this design achieves the versatility a community facility demands.
Frequently Asked Questions
What RT60 does a Community Hall — BS 8233 Multi-Purpose Design achieve?
With the specified materials and dimensions (25m x 16m x 2.5m, volume 1000m3), the calculated mid-frequency RT60 is 0.69s using the Sabine equation. The target under BS-8233 is 0.8--1.2s. The result is a MARGINAL.
What materials are used in this performance acoustic example?
This example uses Rockfon Sonar 25mm ceiling tile on the Ceiling — Rockfon Sonar (NRC 0.82), Painted plaster on the Ceiling — plaster (NRC 0.04), Timber floor (sealed) on the Floor (NRC 0.09), Painted plaster on the Walls — painted plaster (NRC 0.04), Curtains (medium weight) on the Walls — curtains (NRC 0.56), Mineral wool 50mm (wall) on the Walls — mineral wool (NRC 0.73), Wooden seats (unupholstered) on the Wooden chairs (100) (NRC 0.05), Curtains (medium weight) on the Stage curtains (NRC 0.56), Double glazing 6mm on the Windows (NRC 0.03). The total absorption at 500 Hz is 223.1 Sabins.
How much does acoustic treatment cost for this room?
Cost data is not available for this example. Use the AcousPlan calculator to estimate treatment costs for your specific room configuration.
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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.