Worked Example: MRI Suite — Patient Acoustic Comfort Design
RT60 calculation for an MRI scanner room where acoustic treatment reduces the amplification of scanner noise. Acoustic plaster and non-ferromagnetic mineral wool address the unique constraint of zero metal in the magnetic field zone.
A 120 m³ hospital ward designed to ISO-3382 requires RT60 ≤ 0.8s. With Acoustic plaster 15mm on the ceiling and Mineral wool 50mm on walls, the calculated RT60 is 0.36s — PASS.
Room Setup
Total surface area: 161.6 m². Calculation method: Sabine equation (ISO 3382-2:2008 Annex A).
Surface Materials
| Surface | Material | Area (m²) | NRC |
|---|---|---|---|
| ceiling | Acoustic plaster 15mm | 40.0 | 0.70 |
| walls-main | Painted plaster | 54.0 | 0.04 |
| walls-treatment | Mineral wool 50mm | 24.0 | 0.75 |
| floor | Vinyl/linoleum floor | 40.0 | 0.03 |
| windows | Double glazing 6mm | 0.0 | 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 × 5 × 3 = 120 m³
- 2
Total Surface Area
Stotal = 40.0 + 54.0 + 24.0 + 40.0 + 0.0 + 3.6 = 161.6 m²
- 3
Absorption per Surface at 500 Hz
ceiling: 40.0 m² × 0.65 = 26.00 Sabins
walls-main: 54.0 m² × 0.04 = 2.16 Sabins
walls-treatment: 24.0 m² × 0.70 = 16.80 Sabins
floor: 40.0 m² × 0.03 = 1.20 Sabins
windows: 0.0 m² × 0.04 = 0.00 Sabins
door: 3.6 m² × 0.08 = 0.29 Sabins
- 4
Total Absorption at 500 Hz
Atotal = 26.00 + 2.16 + 16.80 + 1.20 + 0.00 + 0.29 = 46.45 Sabins
- 5
Sabine RT60 at 500 Hz
RT60 = 0.161 × V / A = 0.161 × 120 / 46.45 = 0.42s
- 6
Compare to Target
Mid-frequency RT60 (avg of 500, 1k, 2k Hz) = 0.36s. Target: ≤ 0.8s per ISO-3382. Verdict: PASS
Octave Band Results
| Frequency | 125Hz | 250Hz | 500Hz | 1kHz | 2kHz | 4kHz |
|---|---|---|---|---|---|---|
| Total Absorption (Sabins) | 9.4 | 27.4 | 46.5 | 57.0 | 60.2 | 56.6 |
| RT60 (s) | 2.05 | 0.70 | 0.42 | 0.34 | 0.32 | 0.34 |
| Target (s) | — | — | 0.80 | 0.80 | 0.80 | — |
| Verdict | — | — | PASS | PASS | PASS | — |
Compliance Verdict
Reference: ISO 3382-2:2008; HTM 08-01 §6.2
MRI suites present unique acoustic challenges: scanner noise reaches 110+ dBA while the strong magnetic field prohibits ferromagnetic materials. Non-metallic acoustic treatments (acoustic plaster, fibreglass wool) are essential.
STI result: 0.70 (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 × 5m × 3m) and RT60 target (0.8s).
Open CalculatorField Story
An NHS hospital is installing a new 3T MRI scanner that produces peak noise levels of 118 dBA during gradient-intensive sequences. Patients already dread MRI scans due to the claustrophobic tube and deafening noise. The existing scanner room has bare plaster walls and ceiling, creating an RT60 of 1.3 seconds that amplifies the already extreme noise levels. The acoustic consultant must specify non-ferromagnetic materials — standard perforated metal ceiling tiles would become lethal projectiles in the magnetic field. The solution uses a spray-applied acoustic plaster on the ceiling and fibreglass mineral wool panels (containing no steel staples or frames) on the walls outside the 5-gauss line.
Frequently Asked Questions
What RT60 does a MRI Suite — Patient Acoustic Comfort Design achieve?
With the specified materials and dimensions (8m x 5m x 3m, volume 120m3), the calculated mid-frequency RT60 is 0.36s using the Sabine equation. The target under ISO-3382 is 0.8s or less. The result is a PASS.
What materials are used in this healthcare acoustic example?
This example uses Acoustic plaster 15mm on the ceiling (NRC 0.7), Painted plaster on the walls-main (NRC 0.04), Mineral wool 50mm on the walls-treatment (NRC 0.75), Vinyl/linoleum floor on the floor (NRC 0.03), 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 46.5 Sabins.
How much does acoustic treatment cost for this room?
The estimated treatment cost is £7,680 for 64 m2 of absorptive material at approximately £120/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.