Worked Example: Church — ISO 3382 Liturgical Music Acoustics
2500 m³ stone church with timber roof, stone floor, cushioned pews, and carpeted aisles
A 2500 m³ worship space designed to ISO-3382 requires RT60 ≤ 2.5s. With Timber floor (sealed) on the ceiling, the calculated RT60 is 2.39s — PASS.
Room Setup
Total surface area: 1490.0 m². Calculation method: Sabine equation (ISO 3382-2:2008 Annex A).
Surface Materials
| Surface | Material | Area (m²) | NRC |
|---|---|---|---|
| Ceiling — timber barrel vault | Timber floor (sealed) | 500.0 | 0.09 |
| Floor — stone nave | Terrazzo/marble floor | 300.0 | 0.01 |
| Floor — carpet aisles | Heavy carpet | 200.0 | 0.29 |
| Walls — stone | Stone/granite wall | 280.0 | 0.04 |
| Walls — painted plaster | Painted plaster | 100.0 | 0.04 |
| Pews (with cushions) | Upholstered seating | 60.0 | 0.55 |
| Stained glass | Single glazing | 30.0 | 0.16 |
| Organ casework | Timber floor (sealed) | 20.0 | 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 = 25 × 20 × 5 = 2500 m³
- 2
Total Surface Area
Stotal = 500.0 + 300.0 + 200.0 + 280.0 + 100.0 + 60.0 + 30.0 + 20.0 = 1490.0 m²
- 3
Absorption per Surface at 500 Hz
Ceiling — timber barrel vault: 500.0 m² × 0.10 = 50.00 Sabins
Floor — stone nave: 300.0 m² × 0.01 = 3.00 Sabins
Floor — carpet aisles: 200.0 m² × 0.14 = 28.00 Sabins
Walls — stone: 280.0 m² × 0.03 = 8.40 Sabins
Walls — painted plaster: 100.0 m² × 0.04 = 4.00 Sabins
Pews (with cushions): 60.0 m² × 0.56 = 33.60 Sabins
Stained glass: 30.0 m² × 0.18 = 5.40 Sabins
Organ casework: 20.0 m² × 0.10 = 2.00 Sabins
- 4
Total Absorption at 500 Hz
Atotal = 50.00 + 3.00 + 28.00 + 8.40 + 4.00 + 33.60 + 5.40 + 2.00 = 134.40 Sabins
- 5
Sabine RT60 at 500 Hz
RT60 = 0.161 × V / A = 0.161 × 2500 / 134.40 = 2.99s
- 6
Compare to Target
Mid-frequency RT60 (avg of 500, 1k, 2k Hz) = 2.39s. Target: 1.5--2.5s per ISO-3382. Verdict: PASS
Octave Band Results
| Frequency | 125Hz | 250Hz | 500Hz | 1kHz | 2kHz | 4kHz |
|---|---|---|---|---|---|---|
| Total Absorption (Sabins) | 113.5 | 109.5 | 134.4 | 173.4 | 214.9 | 228.0 |
| RT60 (s) | 3.55 | 3.68 | 2.99 | 2.32 | 1.87 | 1.77 |
| Target (s) | — | — | 2.50 | 2.50 | 2.50 | — |
| Verdict | — | — | FAIL | PASS | PASS | — |
Compliance Verdict
Reference:
Open the AcousPlan calculator pre-loaded with the exact room dimensions (25m × 20m × 5m) and RT60 target (2.5s).
Open CalculatorField Story
A 19th-century Anglican parish church in Bath is installing a hearing loop after parishioners complained about sermon intelligibility. The church is constructed of hard reflective materials: Bath stone walls, stone nave floor, and timber barrel-vault ceiling. Cushioned pew seats (added in a 1990s refurbishment) and carpeted aisle runners provide the only significant absorption alongside the stained glass windows which vibrate as panel absorbers at low frequencies. This calculation quantifies the challenge: the long RT60 is magnificent for organ music and choral evensong but makes unamplified speech from the pulpit difficult beyond the first five rows. ISO 3382 classifies this within the acceptable range for liturgical music, but a speech reinforcement system with carefully aimed loudspeakers is essential.
Frequently Asked Questions
What RT60 does a Church — ISO 3382 Liturgical Music Acoustics achieve?
With the specified materials and dimensions (25m x 20m x 5m, volume 2500m3), the calculated mid-frequency RT60 is 2.39s using the Sabine equation. The target under ISO-3382 is 1.5--2.5s. The result is a PASS.
What materials are used in this performance acoustic example?
This example uses Timber floor (sealed) on the Ceiling — timber barrel vault (NRC 0.09), Terrazzo/marble floor on the Floor — stone nave (NRC 0.01), Heavy carpet on the Floor — carpet aisles (NRC 0.29), Stone/granite wall on the Walls — stone (NRC 0.04), Painted plaster on the Walls — painted plaster (NRC 0.04), Upholstered seating on the Pews (with cushions) (NRC 0.55), Single glazing on the Stained glass (NRC 0.16), Timber floor (sealed) on the Organ casework (NRC 0.09). The total absorption at 500 Hz is 134.4 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.