Worked Example: Emergency Room Waiting Area — ASHRAE NC 35-40
500 m³ waiting space with perforated metal ceiling and wipe-clean surfaces
A 500 m³ hospital ward designed to ASHRAE requires RT60 ≤ 1s. With Perforated metal ceiling on the ceiling and Mineral wool 50mm (wall) on walls, the calculated RT60 is 0.63s — PASS.
Room Setup
Total surface area: 640.0 m². Calculation method: Sabine equation (ISO 3382-2:2008 Annex A).
Surface Materials
| Surface | Material | Area (m²) | NRC |
|---|---|---|---|
| Ceiling — perforated metal | Perforated metal ceiling | 120.0 | 0.78 |
| Ceiling — plaster | Painted plaster | 130.0 | 0.04 |
| Floor | Vinyl/linoleum floor | 250.0 | 0.04 |
| Walls — painted concrete | Painted concrete block | 105.0 | 0.07 |
| Walls — mineral wool panels | Mineral wool 50mm (wall) | 8.0 | 0.73 |
| Reception window | Single glazing | 8.0 | 0.16 |
| Seating (60 seats) | Leather/vinyl seating | 15.0 | 0.15 |
| Entrance doors | Double glazing 6mm | 4.0 | 0.03 |
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 × 10 × 2 = 500 m³
- 2
Total Surface Area
Stotal = 120.0 + 130.0 + 250.0 + 105.0 + 8.0 + 8.0 + 15.0 + 4.0 = 640.0 m²
- 3
Absorption per Surface at 500 Hz
Ceiling — perforated metal: 120.0 m² × 0.80 = 96.00 Sabins
Ceiling — plaster: 130.0 m² × 0.04 = 5.20 Sabins
Floor: 250.0 m² × 0.03 = 7.50 Sabins
Walls — painted concrete: 105.0 m² × 0.06 = 6.30 Sabins
Walls — mineral wool panels: 8.0 m² × 0.70 = 5.60 Sabins
Reception window: 8.0 m² × 0.18 = 1.44 Sabins
Seating (60 seats): 15.0 m² × 0.15 = 2.25 Sabins
Entrance doors: 4.0 m² × 0.04 = 0.16 Sabins
- 4
Total Absorption at 500 Hz
Atotal = 96.00 + 5.20 + 7.50 + 6.30 + 5.60 + 1.44 + 2.25 + 0.16 = 124.45 Sabins
- 5
Sabine RT60 at 500 Hz
RT60 = 0.161 × V / A = 0.161 × 500 / 124.45 = 0.65s
- 6
Compare to Target
Mid-frequency RT60 (avg of 500, 1k, 2k Hz) = 0.63s. Target: 0.6--1s per ASHRAE. Verdict: PASS
Octave Band Results
| Frequency | 125Hz | 250Hz | 500Hz | 1kHz | 2kHz | 4kHz |
|---|---|---|---|---|---|---|
| Total Absorption (Sabins) | 70.6 | 106.7 | 124.5 | 136.7 | 126.0 | 114.8 |
| RT60 (s) | 1.14 | 0.75 | 0.65 | 0.59 | 0.64 | 0.70 |
| Target (s) | — | — | 1.00 | 1.00 | 1.00 | — |
| Verdict | — | — | PASS | MARGINAL | PASS | — |
Compliance Verdict
Reference:
Open the AcousPlan calculator pre-loaded with the exact room dimensions (25m × 10m × 2m) and RT60 target (1s).
Open CalculatorField Story
A Level I trauma centre in Houston is redesigning its emergency department waiting area after patient complaints about excessive noise stress. The elongated 25 m by 10 m space has a low 2 m ceiling to control reverberation. Perforated metal ceiling with mineral wool backing covers roughly half the ceiling area, with the remainder left as painted plaster above mechanical service runs. Wipe-clean vinyl flooring and painted concrete block walls meet stringent infection control requirements. A narrow band of mineral wool panels behind protective grilles on one wall targets mid-frequency speech noise. Leather seating for 60 patients provides modest absorption. ASHRAE guidelines recommend NC 35-40 for hospital waiting areas; this acoustic treatment aims to reduce the Lombard effect that causes voices to escalate in crowded emergency departments while keeping surfaces hygienic.
Frequently Asked Questions
What RT60 does a Emergency Room Waiting Area — ASHRAE NC 35-40 achieve?
With the specified materials and dimensions (25m x 10m x 2m, volume 500m3), the calculated mid-frequency RT60 is 0.63s using the Sabine equation. The target under ASHRAE is 0.6--1s. The result is a PASS.
What materials are used in this healthcare acoustic example?
This example uses Perforated metal ceiling on the Ceiling — perforated metal (NRC 0.78), Painted plaster on the Ceiling — plaster (NRC 0.04), Vinyl/linoleum floor on the Floor (NRC 0.04), Painted concrete block on the Walls — painted concrete (NRC 0.07), Mineral wool 50mm (wall) on the Walls — mineral wool panels (NRC 0.73), Single glazing on the Reception window (NRC 0.16), Leather/vinyl seating on the Seating (60 seats) (NRC 0.15), Double glazing 6mm on the Entrance doors (NRC 0.03). The total absorption at 500 Hz is 124.5 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.