Worked Example: Baby Nursery — BS 8233 Sleep Environment
25 m³ nursery with heavy carpet, blackout curtains, and plasterboard walls
A 25 m³ residential living designed to BS-8233 requires RT60 ≤ 0.4s. With Painted plaster on the ceiling, the calculated RT60 is 0.38s — PASS.
Room Setup
Total surface area: 56.6 m². Calculation method: Sabine equation (ISO 3382-2:2008 Annex A).
Surface Materials
| Surface | Material | Area (m²) | NRC |
|---|---|---|---|
| Ceiling | Painted plaster | 12.5 | 0.04 |
| Floor | Heavy carpet | 12.5 | 0.29 |
| Walls — plasterboard | Plasterboard on studs | 16.0 | 0.07 |
| Curtains (blackout) | Curtains (medium weight) | 5.0 | 0.56 |
| Soft furnishings | Upholstered seating | 3.0 | 0.55 |
| Walls — painted plaster | Painted plaster | 4.0 | 0.04 |
| Window | Double glazing 6mm | 2.0 | 0.03 |
| Door | Solid timber door | 1.6 | 0.09 |
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 = 5 × 2.5 × 2 = 25 m³
- 2
Total Surface Area
Stotal = 12.5 + 12.5 + 16.0 + 5.0 + 3.0 + 4.0 + 2.0 + 1.6 = 56.6 m²
- 3
Absorption per Surface at 500 Hz
Ceiling: 12.5 m² × 0.04 = 0.50 Sabins
Floor: 12.5 m² × 0.14 = 1.75 Sabins
Walls — plasterboard: 16.0 m² × 0.05 = 0.80 Sabins
Curtains (blackout): 5.0 m² × 0.49 = 2.45 Sabins
Soft furnishings: 3.0 m² × 0.56 = 1.68 Sabins
Walls — painted plaster: 4.0 m² × 0.04 = 0.16 Sabins
Window: 2.0 m² × 0.04 = 0.08 Sabins
Door: 1.6 m² × 0.08 = 0.13 Sabins
- 4
Total Absorption at 500 Hz
Atotal = 0.50 + 1.75 + 0.80 + 2.45 + 1.68 + 0.16 + 0.08 + 0.13 = 7.55 Sabins
- 5
Sabine RT60 at 500 Hz
RT60 = 0.161 × V / A = 0.161 × 25 / 7.55 = 0.53s
- 6
Compare to Target
Mid-frequency RT60 (avg of 500, 1k, 2k Hz) = 0.38s. Target: 0.25--0.4s per BS-8233. Verdict: PASS
Octave Band Results
| Frequency | 125Hz | 250Hz | 500Hz | 1kHz | 2kHz | 4kHz |
|---|---|---|---|---|---|---|
| Total Absorption (Sabins) | 6.5 | 5.6 | 7.5 | 12.1 | 14.9 | 15.3 |
| RT60 (s) | 0.62 | 0.72 | 0.53 | 0.33 | 0.27 | 0.26 |
| Target (s) | — | — | 0.40 | 0.40 | 0.40 | — |
| Verdict | — | — | FAIL | PASS | PASS | — |
Compliance Verdict
Reference:
Open the AcousPlan calculator pre-loaded with the exact room dimensions (5m × 2.5m × 2m) and RT60 target (0.4s).
Open CalculatorField Story
New parents in a Victorian terrace in Bristol are preparing the smallest bedroom as a nursery. Infant sleep research indicates reverberation amplifies intrusive noise — a door closing elsewhere sounds louder and persists longer in a reverberant room, disrupting sleep cycles. The 5 m by 2.5 m room uses heavy carpet for warmth and absorption, with a thick wool rug beside the cot. Blackout curtains serve dual purpose of light blocking and acoustic absorption, particularly important as the room faces a busy road. An upholstered nursing chair provides mid-frequency absorption. Plasterboard walls absorb low-frequency traffic rumble. BS 8233 recommends the lowest practical reverberation for bedrooms where noise sensitivity is highest; the calculation shows typical nursery furnishings achieve this without dedicated acoustic products.
Frequently Asked Questions
What RT60 does a Baby Nursery — BS 8233 Sleep Environment achieve?
With the specified materials and dimensions (5m x 2.5m x 2m, volume 25m3), the calculated mid-frequency RT60 is 0.38s using the Sabine equation. The target under BS-8233 is 0.25--0.4s. The result is a PASS.
What materials are used in this residential acoustic example?
This example uses Painted plaster on the Ceiling (NRC 0.04), Heavy carpet on the Floor (NRC 0.29), Plasterboard on studs on the Walls — plasterboard (NRC 0.07), Curtains (medium weight) on the Curtains (blackout) (NRC 0.56), Upholstered seating on the Soft furnishings (NRC 0.55), Painted plaster on the Walls — painted plaster (NRC 0.04), Double glazing 6mm on the Window (NRC 0.03), Solid timber door on the Door (NRC 0.09). The total absorption at 500 Hz is 7.5 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.