Worked Example: SEN Classroom — BB93 Enhanced Acoustic Target
RT60 calculation for a Special Educational Needs classroom requiring the stricter BB93 target of 0.4 seconds. Maximum absorption on all surfaces creates an optimal listening environment for hearing-impaired students.
A 129.6 m³ classroom designed to BB93 requires RT60 ≤ 0.4s. With Ecophon Focus E on the ceiling and Fabric-wrapped panel 50mm on walls, the calculated RT60 is 0.24s — PASS.
Room Setup
Total surface area: 181.2 m². Calculation method: Sabine equation (ISO 3382-2:2008 Annex A).
Surface Materials
| Surface | Material | Area (m²) | NRC |
|---|---|---|---|
| ceiling | Ecophon Focus E | 48.0 | 0.90 |
| walls-main | Painted plaster | 47.0 | 0.04 |
| walls-treatment | Fabric-wrapped panel 50mm | 28.6 | 0.80 |
| floor | Carpet (heavy) | 48.0 | 0.30 |
| windows | Double glazing 6mm | 6.0 | 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 = 8 × 6 × 2.7 = 129.6 m³
- 2
Total Surface Area
Stotal = 48.0 + 47.0 + 28.6 + 48.0 + 6.0 + 3.6 = 181.2 m²
- 3
Absorption per Surface at 500 Hz
ceiling: 48.0 m² × 0.90 = 43.20 Sabins
walls-main: 47.0 m² × 0.04 = 1.88 Sabins
walls-treatment: 28.6 m² × 0.78 = 22.31 Sabins
floor: 48.0 m² × 0.14 = 6.72 Sabins
windows: 6.0 m² × 0.04 = 0.24 Sabins
door: 3.6 m² × 0.08 = 0.29 Sabins
- 4
Total Absorption at 500 Hz
Atotal = 43.20 + 1.88 + 22.31 + 6.72 + 0.24 + 0.29 = 74.64 Sabins
- 5
Sabine RT60 at 500 Hz
RT60 = 0.161 × V / A = 0.161 × 129.6 / 74.64 = 0.28s
- 6
Compare to Target
Mid-frequency RT60 (avg of 500, 1k, 2k Hz) = 0.24s. Target: ≤ 0.4s per BB93. Verdict: PASS
Octave Band Results
| Frequency | 125Hz | 250Hz | 500Hz | 1kHz | 2kHz | 4kHz |
|---|---|---|---|---|---|---|
| Total Absorption (Sabins) | 23.9 | 55.2 | 74.6 | 90.5 | 100.5 | 99.1 |
| RT60 (s) | 0.87 | 0.38 | 0.28 | 0.23 | 0.21 | 0.21 |
| Target (s) | — | — | 0.40 | 0.40 | 0.40 | — |
| Verdict | — | — | PASS | PASS | PASS | — |
Compliance Verdict
Reference: BB93:2015 Table 1.2 (SEN)
BB93 requires RT60 ≤ 0.4s for SEN classrooms where hearing-impaired students are taught. This demands premium ceiling tiles, extensive wall coverage, and soft flooring throughout.
STI result: 0.80 (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 (8m × 6m × 2.7m) and RT60 target (0.4s).
Open CalculatorField Story
A local authority is converting a standard classroom into a specialist SEN resource for students with cochlear implants and hearing aids. These students require exceptionally low reverberation because hearing devices amplify all sound equally — both direct speech and reflected energy. The room must meet the stricter BB93 target of 0.4 seconds, requiring approximately 60% more absorption than a standard classroom. The acoustic consultant specifies Ecophon Focus E ceiling tiles with the highest possible NRC rating, fabric panels covering most of the upper wall area, and heavy carpet throughout. Even the door is upgraded to an acoustically-rated unit.
Frequently Asked Questions
What RT60 does a SEN Classroom — BB93 Enhanced Acoustic Target achieve?
With the specified materials and dimensions (8m x 6m x 2.7m, volume 129.6m3), the calculated mid-frequency RT60 is 0.24s using the Sabine equation. The target under BB93 is 0.4s or less. The result is a PASS.
What materials are used in this education acoustic example?
This example uses Ecophon Focus E on the ceiling (NRC 0.9), 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 74.6 Sabins.
How much does acoustic treatment cost for this room?
The estimated treatment cost is £6,853 for 125 m2 of absorptive material at approximately £55/m2. Actual costs vary by region, supplier, and installation complexity.
Related Examples
UK Primary Classroom — BB93 Acoustic Compliance
UK Secondary Classroom — BB93 Marginal Result
US Classroom — ANSI S12.60 Acoustic Compliance
German Classroom — DIN 18041 Acoustic Design
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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.