Worked Example: Hotel Lobby — ASHRAE RC 35-40 Design
600 m³ luxury lobby with terrazzo floor, stone walls, and perforated metal ceiling
A 600 m³ restaurant designed to ASHRAE requires RT60 ≤ 1.2s. With Perforated metal ceiling on the ceiling, the calculated RT60 is 1.03s — PASS.
Room Setup
Total surface area: 502.0 m². Calculation method: Sabine equation (ISO 3382-2:2008 Annex A).
Surface Materials
| Surface | Material | Area (m²) | NRC |
|---|---|---|---|
| Ceiling — perforated metal | Perforated metal ceiling | 80.0 | 0.78 |
| Ceiling — plaster | Painted plaster | 70.0 | 0.04 |
| Floor | Terrazzo/marble floor | 150.0 | 0.01 |
| Walls — stone | Stone/granite wall | 120.0 | 0.04 |
| Walls — plasterboard | Plasterboard on studs | 30.0 | 0.07 |
| Seating areas | Upholstered seating | 16.0 | 0.55 |
| Feature curtains | Curtains (medium weight) | 12.0 | 0.56 |
| Glazed entrance | Double glazing 6mm | 24.0 | 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 = 15 × 10 × 4 = 600 m³
- 2
Total Surface Area
Stotal = 80.0 + 70.0 + 150.0 + 120.0 + 30.0 + 16.0 + 12.0 + 24.0 = 502.0 m²
- 3
Absorption per Surface at 500 Hz
Ceiling — perforated metal: 80.0 m² × 0.80 = 64.00 Sabins
Ceiling — plaster: 70.0 m² × 0.04 = 2.80 Sabins
Floor: 150.0 m² × 0.01 = 1.50 Sabins
Walls — stone: 120.0 m² × 0.03 = 3.60 Sabins
Walls — plasterboard: 30.0 m² × 0.05 = 1.50 Sabins
Seating areas: 16.0 m² × 0.56 = 8.96 Sabins
Feature curtains: 12.0 m² × 0.49 = 5.88 Sabins
Glazed entrance: 24.0 m² × 0.04 = 0.96 Sabins
- 4
Total Absorption at 500 Hz
Atotal = 64.00 + 2.80 + 1.50 + 3.60 + 1.50 + 8.96 + 5.88 + 0.96 = 89.20 Sabins
- 5
Sabine RT60 at 500 Hz
RT60 = 0.161 × V / A = 0.161 × 600 / 89.20 = 1.08s
- 6
Compare to Target
Mid-frequency RT60 (avg of 500, 1k, 2k Hz) = 1.03s. Target: 0.8--1.2s per ASHRAE. Verdict: PASS
Octave Band Results
| Frequency | 125Hz | 250Hz | 500Hz | 1kHz | 2kHz | 4kHz |
|---|---|---|---|---|---|---|
| Total Absorption (Sabins) | 52.8 | 75.1 | 89.2 | 99.4 | 93.2 | 84.3 |
| RT60 (s) | 1.83 | 1.29 | 1.08 | 0.97 | 1.04 | 1.15 |
| Target (s) | — | — | 1.20 | 1.20 | 1.20 | — |
| Verdict | — | — | PASS | PASS | PASS | — |
Compliance Verdict
Reference:
Open the AcousPlan calculator pre-loaded with the exact room dimensions (15m × 10m × 4m) and RT60 target (1.2s).
Open CalculatorField Story
A five-star hotel chain is constructing a flagship property in downtown Chicago with a quadruple-height lobby featuring Italian marble floors and granite feature walls. The interior architect insists on maintaining the luxurious hard-surface aesthetic, making the ceiling the only viable location for significant treatment. A perforated aluminium ceiling system with concealed mineral wool absorber covers just over half the ceiling area — the remainder left as painted plaster where decorative coffers are featured. Clustered seating areas with deep upholstered armchairs create localised absorption zones. Full-height curtain panels at the mezzanine level provide tunable mid-frequency absorption. The ASHRAE RC 35-40 target ensures the lobby feels serene despite the adjacent bar, concierge activity, and luggage handling at the bell desk.
Frequently Asked Questions
What RT60 does a Hotel Lobby — ASHRAE RC 35-40 Design achieve?
With the specified materials and dimensions (15m x 10m x 4m, volume 600m3), the calculated mid-frequency RT60 is 1.03s using the Sabine equation. The target under ASHRAE is 0.8--1.2s. The result is a PASS.
What materials are used in this hospitality 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), Terrazzo/marble floor on the Floor (NRC 0.01), Stone/granite wall on the Walls — stone (NRC 0.04), Plasterboard on studs on the Walls — plasterboard (NRC 0.07), Upholstered seating on the Seating areas (NRC 0.55), Curtains (medium weight) on the Feature curtains (NRC 0.56), Double glazing 6mm on the Glazed entrance (NRC 0.03). The total absorption at 500 Hz is 89.2 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.