Worked Example: School Music Room — BB93 Acoustic Design
RT60 calculation for a secondary school music room under BB93:2015 with a higher target of 0.8-1.0 seconds. Uses partial perforated timber slat ceiling and adjustable curtains to balance musical warmth with speech clarity.
A 280 m³ classroom designed to BB93 requires RT60 ≤ 1s. With Perforated timber slats on the ceiling and Curtains (medium weight) on walls, the calculated RT60 is 0.9s — PASS.
Room Setup
Total surface area: 266.0 m². Calculation method: Sabine equation (ISO 3382-2:2008 Annex A).
Surface Materials
| Surface | Material | Area (m²) | NRC |
|---|---|---|---|
| ceiling | Perforated timber slats | 40.0 | 0.65 |
| walls-main | Plasterboard on studs | 112.0 | 0.07 |
| walls-treatment | Curtains (medium weight) | 14.0 | 0.55 |
| floor | Timber floor (sealed) | 80.0 | 0.08 |
| windows | Double glazing 6mm | 16.0 | 0.04 |
| door | Solid timber door | 4.0 | 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 = 10 × 8 × 3.5 = 280 m³
- 2
Total Surface Area
Stotal = 40.0 + 112.0 + 14.0 + 80.0 + 16.0 + 4.0 = 266.0 m²
- 3
Absorption per Surface at 500 Hz
ceiling: 40.0 m² × 0.70 = 28.00 Sabins
walls-main: 112.0 m² × 0.05 = 5.60 Sabins
walls-treatment: 14.0 m² × 0.49 = 6.86 Sabins
floor: 80.0 m² × 0.10 = 8.00 Sabins
windows: 16.0 m² × 0.04 = 0.64 Sabins
door: 4.0 m² × 0.08 = 0.32 Sabins
- 4
Total Absorption at 500 Hz
Atotal = 28.00 + 5.60 + 6.86 + 8.00 + 0.64 + 0.32 = 49.42 Sabins
- 5
Sabine RT60 at 500 Hz
RT60 = 0.161 × V / A = 0.161 × 280 / 49.42 = 0.91s
- 6
Compare to Target
Mid-frequency RT60 (avg of 500, 1k, 2k Hz) = 0.9s. Target: 0.8--1s per BB93. Verdict: PASS
Octave Band Results
| Frequency | 125Hz | 250Hz | 500Hz | 1kHz | 2kHz | 4kHz |
|---|---|---|---|---|---|---|
| Total Absorption (Sabins) | 56.4 | 45.5 | 49.4 | 51.4 | 49.1 | 46.7 |
| RT60 (s) | 0.80 | 0.99 | 0.91 | 0.88 | 0.92 | 0.96 |
| Target (s) | — | — | 1.00 | 1.00 | 1.00 | — |
| Verdict | — | — | PASS | PASS | PASS | — |
Compliance Verdict
Reference: BB93:2015 Table 1.3
BB93 specifies RT60 of 0.8-1.0s for music rooms. Unlike classrooms, some reverberation is needed for musical performance. Variable absorption via curtains allows adjustment between rehearsal and teaching modes.
STI result: 0.62 (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 (10m × 8m × 3.5m) and RT60 target (1s).
Open CalculatorField Story
The head of music at a UK secondary school complains that the dedicated music room sounds either too dead for ensemble rehearsal or too echoey for teaching music theory. The room was originally a standard classroom with an acoustic ceiling optimised for speech. A specialist music room requires a longer RT60 of 0.8-1.0 seconds for musical warmth. The solution uses partial perforated timber slats that provide diffusion and moderate absorption, while medium-weight curtains on tracks allow teachers to adjust the room's response — drawn closed for vocal instruction, open for ensemble rehearsal.
Frequently Asked Questions
What RT60 does a School Music Room — BB93 Acoustic Design achieve?
With the specified materials and dimensions (10m x 8m x 3.5m, volume 280m3), the calculated mid-frequency RT60 is 0.9s using the Sabine equation. The target under BB93 is 0.8--1s. 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), Plasterboard on studs on the walls-main (NRC 0.07), Curtains (medium weight) on the walls-treatment (NRC 0.55), 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 49.4 Sabins.
How much does acoustic treatment cost for this room?
The estimated treatment cost is £2,970 for 54 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.