Worked Example: Call Centre — BS 8233 Speech Privacy Design
RT60 calculation for a 100-seat call centre requiring maximum absorption to prevent cross-talk between operators. Full Ecophon ceiling with carpet and strategic wall panels achieve the stringent 0.5s target for sustained speech environments.
A 1215 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 0.31s — PASS.
Room Setup
Total surface area: 1185.8 m². Calculation method: Sabine equation (ISO 3382-2:2008 Annex A).
Surface Materials
| Surface | Material | Area (m²) | NRC |
|---|---|---|---|
| ceiling | Ecophon Focus E | 450.0 | 0.90 |
| walls-main | Plasterboard on studs | 163.8 | 0.07 |
| walls-treatment | Fabric-wrapped panel 50mm | 68.4 | 0.80 |
| floor | Carpet (heavy) | 450.0 | 0.30 |
| windows | Double glazing 6mm | 50.0 | 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 = 25 × 18 × 2.7 = 1215 m³
- 2
Total Surface Area
Stotal = 450.0 + 163.8 + 68.4 + 450.0 + 50.0 + 3.6 = 1185.8 m²
- 3
Absorption per Surface at 500 Hz
ceiling: 450.0 m² × 0.90 = 405.00 Sabins
walls-main: 163.8 m² × 0.05 = 8.19 Sabins
walls-treatment: 68.4 m² × 0.78 = 53.35 Sabins
floor: 450.0 m² × 0.14 = 63.00 Sabins
windows: 50.0 m² × 0.04 = 2.00 Sabins
door: 3.6 m² × 0.08 = 0.29 Sabins
- 4
Total Absorption at 500 Hz
Atotal = 405.00 + 8.19 + 53.35 + 63.00 + 2.00 + 0.29 = 531.83 Sabins
- 5
Sabine RT60 at 500 Hz
RT60 = 0.161 × V / A = 0.161 × 1215 / 531.83 = 0.37s
- 6
Compare to Target
Mid-frequency RT60 (avg of 500, 1k, 2k Hz) = 0.31s. Target: ≤ 0.5s per BS-8233. Verdict: PASS
Octave Band Results
| Frequency | 125Hz | 250Hz | 500Hz | 1kHz | 2kHz | 4kHz |
|---|---|---|---|---|---|---|
| Total Absorption (Sabins) | 232.3 | 402.3 | 531.8 | 660.5 | 749.3 | 749.2 |
| RT60 (s) | 0.84 | 0.49 | 0.37 | 0.30 | 0.26 | 0.26 |
| Target (s) | — | — | 0.50 | 0.50 | 0.50 | — |
| Verdict | — | — | PASS | PASS | PASS | — |
Compliance Verdict
Reference: BS 8233:2014 Table 4
Call centres require the most stringent acoustic treatment of any office type. BS 8233 recommends RT60 ≤ 0.5s, and sound masking systems are typically also needed to ensure speech privacy between adjacent operators.
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 (25m × 18m × 2.7m) and RT60 target (0.5s).
Open CalculatorField Story
An insurance company's call centre has the highest staff turnover in the building. Exit interviews reveal that constant noise exposure is the primary complaint — operators cannot hear callers clearly and must raise their voices, creating a vicious cycle of escalating noise. The Lombard effect causes each person to speak 3-6 dB louder for every 10 dB increase in background noise. The open plan room has basic ceiling tiles with NRC 0.55 and hard flooring. A comprehensive refit with premium Ecophon tiles (NRC 0.90) and heavy carpet reduces the RT60 to under 0.5 seconds. Combined with desk-mounted screens and a sound masking system, staff satisfaction surveys improve dramatically within three months.
Frequently Asked Questions
What RT60 does a Call Centre — BS 8233 Speech Privacy Design achieve?
With the specified materials and dimensions (25m x 18m x 2.7m, volume 1215m3), the calculated mid-frequency RT60 is 0.31s 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 531.8 Sabins.
How much does acoustic treatment cost for this room?
The estimated treatment cost is £56,167 for 968 m2 of absorptive material at approximately £58/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.