Worked Example: Open Plan Office — BS 8233 Acoustic Design
RT60 calculation for a 300 m² open plan office under BS 8233:2014. Full Ecophon ceiling coverage with carpet flooring provides the low RT60 needed for speech privacy and reduced distraction in a 40-desk layout.
A 810 m³ open plan office designed to BS-8233 requires RT60 ≤ 0.5s. With Ecophon Focus E on the ceiling and Fabric-wrapped panel 50mm on walls, the calculated RT60 is 0.3s — PASS.
Room Setup
Total surface area: 836.2 m². Calculation method: Sabine equation (ISO 3382-2:2008 Annex A).
Surface Materials
| Surface | Material | Area (m²) | NRC |
|---|---|---|---|
| ceiling | Ecophon Focus E | 300.0 | 0.90 |
| walls-main | Plasterboard on studs | 135.0 | 0.07 |
| walls-treatment | Fabric-wrapped panel 50mm | 54.0 | 0.80 |
| floor | Carpet (heavy) | 300.0 | 0.30 |
| windows | Double glazing 6mm | 40.0 | 0.04 |
| door | Solid timber door | 7.2 | 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 = 20 × 15 × 2.7 = 810 m³
- 2
Total Surface Area
Stotal = 300.0 + 135.0 + 54.0 + 300.0 + 40.0 + 7.2 = 836.2 m²
- 3
Absorption per Surface at 500 Hz
ceiling: 300.0 m² × 0.90 = 270.00 Sabins
walls-main: 135.0 m² × 0.05 = 6.75 Sabins
walls-treatment: 54.0 m² × 0.78 = 42.12 Sabins
floor: 300.0 m² × 0.14 = 42.00 Sabins
windows: 40.0 m² × 0.04 = 1.60 Sabins
door: 7.2 m² × 0.08 = 0.58 Sabins
- 4
Total Absorption at 500 Hz
Atotal = 270.00 + 6.75 + 42.12 + 42.00 + 1.60 + 0.58 = 363.05 Sabins
- 5
Sabine RT60 at 500 Hz
RT60 = 0.161 × V / A = 0.161 × 810 / 363.05 = 0.36s
- 6
Compare to Target
Mid-frequency RT60 (avg of 500, 1k, 2k Hz) = 0.3s. Target: ≤ 0.5s per BS-8233. Verdict: PASS
Octave Band Results
| Frequency | 125Hz | 250Hz | 500Hz | 1kHz | 2kHz | 4kHz |
|---|---|---|---|---|---|---|
| Total Absorption (Sabins) | 165.3 | 276.6 | 363.1 | 449.1 | 509.4 | 509.4 |
| RT60 (s) | 0.79 | 0.47 | 0.36 | 0.29 | 0.26 | 0.26 |
| Target (s) | — | — | 0.50 | 0.50 | 0.50 | — |
| Verdict | — | — | PASS | PASS | PASS | — |
Compliance Verdict
Reference: BS 8233:2014 Table 4
BS 8233 recommends RT60 ≤ 0.5s for open plan offices to minimise speech distraction. Low ceiling height (2.7m) helps contain sound paths between workstations.
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 (20m × 15m × 2.7m) and RT60 target (0.5s).
Open CalculatorField Story
A tech company moves into a converted warehouse with exposed brick walls and polished concrete floors. Within a week, staff complaints about noise drive productivity surveys to record lows. Phone calls are impossible without booking a meeting room, and developers cannot concentrate. The measured RT60 is 1.8 seconds — nearly four times the recommended level. A comprehensive acoustic refit installs a suspended Ecophon ceiling grid below the existing roof structure, lays heavy carpet tiles, and adds fabric-wrapped panels to the end walls, transforming the space into a productive work environment.
Frequently Asked Questions
What RT60 does a Open Plan Office — BS 8233 Acoustic Design achieve?
With the specified materials and dimensions (20m x 15m x 2.7m, volume 810m3), the calculated mid-frequency RT60 is 0.3s using the Sabine equation. The target under BS-8233 is 0.5s or less. The result is a PASS.
What materials are used in this office acoustic example?
This example uses Ecophon Focus E on the ceiling (NRC 0.9), Plasterboard on studs on the walls-main (NRC 0.07), 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 363.1 Sabins.
How much does acoustic treatment cost for this room?
The estimated treatment cost is £40,548 for 654 m2 of absorptive material at approximately £62/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.