Open Plan Office Acoustic Design Guide
Open plan offices present a unique acoustic paradox: speech must be intelligible within conversation groups but unintelligible beyond the distraction distance to preserve privacy and concentration. IS...
Requirements by Standard
The table below shows acoustic requirements for open plan office spaces across 6 applicable standards. Values are sourced from published standards documents.
| Standard | RT60 | Noise | STI | Notes |
|---|---|---|---|---|
| UnitedBS 8233:2014 | ≤0.8s | LAeq,T 45 | — | Furnished, unoccupied |
| GermanyDIN 18041:2016 | ≤0.7s | dBA 40 | — | Furnished, unoccupied, Group A4 |
| InternationalWELL v2 Feature S01 (Sound) | ≤0.6s | NC 40 | — | Furnished, unoccupied, <500 m³ |
| AustraliaNCC 2022 / AS/NZS 2107:2016 | ≤0.6s | LAeq 45 | — | Furnished, unoccupied |
| UnitedASHRAE 189.1-2020 | — | NC 40 | — | — |
| FranceNRA 2000 | ≤0.6s | dBA (NF S31-080) 42 | — | Per NF S31-080:2006 |
Recommended Acoustic Treatment
Material specifications for achieving compliance in a typical open plan office. All NRC values reference ISO 354:2003 test data.
| Surface | Material Category | Min NRC | Coverage % |
|---|---|---|---|
| Ceiling | High-performance mineral fibre | 0.90 | 85% |
| Desk screens | Absorptive fabric screens | 0.80 | 100% |
| Perimeter walls | Fabric-wrapped panels | 0.85 | 30% |
| Floor | Carpet tiles | 0.30 | 100% |
Browse the acoustic materials database for specific product absorption coefficients.
Common Design Mistakes
Poor speech privacy across workstations
Without sound masking and adequate ceiling absorption, speech remains intelligible at 8–10 metres, causing widespread distraction. ISO 3382-3 distraction distance (rD) exceeding 8 m indicates a fundamentally failing open plan acoustic design.
HVAC noise exceeding NC-40
Variable air volume (VAV) terminal units and fan coil units frequently produce NC 42–48 in open plan zones. While moderate background noise aids speech privacy, levels above NC-40 cause fatigue and annoyance per ASHRAE Handbook Chapter 49.
Insufficient desk screen height
Desk-mounted screens below 300 mm above the seated head height provide negligible acoustic benefit. Effective screens must extend 400–500 mm above desk level (1,200–1,500 mm total from floor) and be absorptive (NRC ≥0.80) on both faces.
Low-performance ceiling tiles
Standard suspended ceiling tiles rated NRC 0.55–0.65 are inadequate for open plan offices. Achieving D2,S ≥7 dB/decade requires high-performance mineral fibre or micro-perforated metal ceilings rated NRC 0.90 or above per ISO 3382-3 design guidance.
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Frequently Asked Questions
What is distraction distance (rD) in open plan offices?
Per ISO 3382-3:2012 §4.4, distraction distance (rD) is the distance from a speaker at which the STI drops below 0.50, meaning speech transitions from distracting to non-distracting. WELL v2 Feature 74 Part 3 requires rD < 5 metres. This metric is more relevant than RT60 for open plan acoustic quality.
What is the recommended RT60 for an open plan office?
Per BS 8233:2014 Table 4, large open plan offices should achieve RT60 ≤0.8 seconds. However, DIN 18041:2016 recommends ≤0.5 seconds for open plan workspaces. In practice, RT60 targets are secondary to ISO 3382-3 spatial metrics (D2,S, rD, Lp,A,S,4m) which better predict occupant satisfaction.
How does sound masking improve open plan office acoustics?
Per ASTM E1130 and ISO 3382-3:2012, sound masking raises the background noise floor with a controlled, uniform spectrum at 42–45 dBA. This reduces rD by 40–60% by lowering the signal-to-noise ratio of overheard speech. The masking spectrum should approximate pink noise shaped to match the 500–4000 Hz speech band. Systems must be professionally calibrated and zoned.
What ceiling absorption is needed for WELL v2 Feature 74?
WELL v2 Feature 74 Part 1 requires RT60 ≤0.60s in enclosed rooms. For open plan areas, achieving the Part 3 speech privacy requirements typically demands ceiling tiles rated NRC ≥0.90 covering at least 80% of the ceiling area. Class A absorptive ceilings (ISO 11654 αw ≥0.90) are the minimum specification for WELL-certified open plan offices.
What is the ABC approach to open plan acoustics?
The ABC approach, referenced in WELL v2 Feature 74 and ISO 3382-3 design guidance, stands for Absorb (ceiling and wall absorption to reduce reflected speech), Block (screens, partitions, and furniture to attenuate direct speech paths), and Cover (calibrated sound masking to raise the noise floor). All three elements must work together; addressing only one or two typically fails to achieve rD < 5 m.