Worked Example: Bar/Lounge — NRA French Acoustic Regulation
300 m³ Parisian bar with acoustic plaster, exposed concrete, and timber floor
A 300 m³ restaurant designed to NRA requires RT60 ≤ 0.9s. With Acoustic plaster 15mm on the ceiling and Fabric-wrapped panel 50mm on walls, the calculated RT60 is 0.53s — MARGINAL.
Room Setup
Total surface area: 390.0 m². Calculation method: Sabine equation (ISO 3382-2:2008 Annex A).
Surface Materials
| Surface | Material | Area (m²) | NRC |
|---|---|---|---|
| Ceiling — acoustic plaster | Acoustic plaster 15mm | 70.0 | 0.66 |
| Ceiling — exposed concrete | Exposed concrete | 80.0 | 0.02 |
| Floor | Timber floor (sealed) | 150.0 | 0.09 |
| Walls — exposed concrete | Exposed concrete | 42.0 | 0.02 |
| Walls — fabric panels | Fabric-wrapped panel 50mm | 16.0 | 0.78 |
| Bar front (leather) | Leather/vinyl seating | 8.0 | 0.15 |
| Seating (40 seats) | Upholstered seating | 12.0 | 0.55 |
| Window | Single glazing | 12.0 | 0.16 |
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 × 2 = 300 m³
- 2
Total Surface Area
Stotal = 70.0 + 80.0 + 150.0 + 42.0 + 16.0 + 8.0 + 12.0 + 12.0 = 390.0 m²
- 3
Absorption per Surface at 500 Hz
Ceiling — acoustic plaster: 70.0 m² × 0.65 = 45.50 Sabins
Ceiling — exposed concrete: 80.0 m² × 0.02 = 1.60 Sabins
Floor: 150.0 m² × 0.10 = 15.00 Sabins
Walls — exposed concrete: 42.0 m² × 0.02 = 0.84 Sabins
Walls — fabric panels: 16.0 m² × 0.78 = 12.48 Sabins
Bar front (leather): 8.0 m² × 0.15 = 1.20 Sabins
Seating (40 seats): 12.0 m² × 0.56 = 6.72 Sabins
Window: 12.0 m² × 0.18 = 2.16 Sabins
- 4
Total Absorption at 500 Hz
Atotal = 45.50 + 1.60 + 15.00 + 0.84 + 12.48 + 1.20 + 6.72 + 2.16 = 85.50 Sabins
- 5
Sabine RT60 at 500 Hz
RT60 = 0.161 × V / A = 0.161 × 300 / 85.50 = 0.56s
- 6
Compare to Target
Mid-frequency RT60 (avg of 500, 1k, 2k Hz) = 0.53s. Target: 0.6--0.9s per NRA. Verdict: MARGINAL
Octave Band Results
| Frequency | 125Hz | 250Hz | 500Hz | 1kHz | 2kHz | 4kHz |
|---|---|---|---|---|---|---|
| Total Absorption (Sabins) | 40.2 | 60.1 | 85.5 | 93.6 | 94.7 | 91.2 |
| RT60 (s) | 1.20 | 0.80 | 0.56 | 0.52 | 0.51 | 0.53 |
| Target (s) | — | — | 0.90 | 0.90 | 0.90 | — |
| Verdict | — | — | MARGINAL | MARGINAL | MARGINAL | — |
Compliance Verdict
Reference:
Open the AcousPlan calculator pre-loaded with the exact room dimensions (15m × 10m × 2m) and RT60 target (0.9s).
Open CalculatorField Story
A cocktail bar in the Marais district of Paris occupies the ground floor of a Haussmann-era building with original exposed concrete columns and beams that the architects wish to celebrate. French NRA regulations impose strict limits on sound levels in hospitality venues, requiring adequate absorption to control internal noise. The acoustic plaster ceiling — finished to match the raw concrete tone — covers under half the ceiling, delivering invisible treatment while leaving exposed concrete beams visible between. Fabric-wrapped panels behind banquette seating absorb speech frequencies at ear level. The sealed parquet timber floor, original to the building, provides modest low-frequency absorption through flexural vibration. Single-glazed shopfront windows facing the street contribute useful low-frequency absorption through panel vibration. Music playback noise is managed by keeping RT60 within NRA limits.
Frequently Asked Questions
What RT60 does a Bar/Lounge — NRA French Acoustic Regulation achieve?
With the specified materials and dimensions (15m x 10m x 2m, volume 300m3), the calculated mid-frequency RT60 is 0.53s using the Sabine equation. The target under NRA is 0.6--0.9s. The result is a MARGINAL.
What materials are used in this hospitality acoustic example?
This example uses Acoustic plaster 15mm on the Ceiling — acoustic plaster (NRC 0.66), Exposed concrete on the Ceiling — exposed concrete (NRC 0.02), Timber floor (sealed) on the Floor (NRC 0.09), Exposed concrete on the Walls — exposed concrete (NRC 0.02), Fabric-wrapped panel 50mm on the Walls — fabric panels (NRC 0.78), Leather/vinyl seating on the Bar front (leather) (NRC 0.15), Upholstered seating on the Seating (40 seats) (NRC 0.55), Single glazing on the Window (NRC 0.16). The total absorption at 500 Hz is 85.5 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.