At Forum Acusticum / Euronoise 2025 in Málaga, Rainer Machner presented a study that blends technical rigour with practical application. Together with Holger Brokmann and Dr. Achim Klein from Saint-Gobain Ecophon, he explored how the simplified ISO 3382-3 prediction model can support faster and more user-focused acoustic design in open-plan offices.
Traditionally, ISO 3382-3 is a measurement standard, not a calculation method. It defines how to measure parameters linked to speech propagation such as the A-weighted speech level at 4 m (Lp,A,S,4m) and the spatial decay rate of speech (D2,S) along a measurement path. Then they can be translated into DA,S, the in-situ acoustic attenuation of speech. This parameter is included in ISO 22955, which provides specific and clear guidelines on what constitutes acoustic quality in open-plan offices.
The challenge is that detailed simulations or on-site testing are often costly and time-consuming. This new approach shows how the same insights can be achieved with a simplified model.
What the study aimed to achieve
The research focused on three main objectives:
- to apply the simplified model in a real office project for around 2,000 employees
- to test whether the predicted values of Lp,A,S,4m and D2,S could reliably support planning decisions
- to assess how the resulting DA,S values align with the activity-based requirements defined in ISO 22955
How the model works
Instead of building a full simulation, the simplified model uses a small set of input variables:
- room dimensions (L, W, H)
- ceiling absorption (αc)
- vertical absorption (αv), including walls, partitions and furniture
- screen height (h)
With these values, formulas are used to predict:
- D2,S = spatial decay rate of speech
- Lp,A,S,4m = A-weighted speech level at 4 m from a talker
From these, the DA,S parameter can be derived, describing how much of the speech sound attenuates across zones. This effectively turns the method into an open-plan office calculator, allowing designers to estimate separation distances between different activities.
Key results from the project
The simplified model was applied during the fit-out phase of a new campus project. The offices followed an activity-based working concept with shared zones, quiet areas and overflow spaces.
Key findings:
- ISO 22955 room type 6 was used as a reference, linking acoustic targets to specific work modes (e.g. collaborative vs. focused).
- The model allowed quick prediction of DA,S values for different activity contrasts, such as informal meetings versus individual focus work (target 26 dB).
- The approach helped to decide minimum requirements for ceiling absorption, carpets, acoustic screens and partitions, preventing unnecessary over-design.
- After construction, on-site measurements confirmed that predicted D2,S and Lp,A,S,4m values were close to measured results.
Feedback from employees showed high satisfaction with noise levels, which contrasts with large benchmark surveys where over 35% of open-plan office workers report noise dissatisfaction.
What it means for practice
For acousticians, architects, interior designers and workplace consultants, the simplified ISO 3382-3 model offers:
- a fast, calculation-based method to predict speech propagation without full simulation
- integration with ISO 22955, ensuring planning is activity-driven and user-centric
- the possibility to act as a noise propagation calculator, translating design decisions into distances and acoustic outcomes
- efficient use of budget by matching treatment levels to actual needs
While the model is less precise than full room simulations, its accuracy is sufficient for early-stage planning. The key is to ensure realistic values for absorption and partitioning are used as inputs.
Conclusion
Presented paper demonstrated that the simplified ISO 3382-3 model is more than a theoretical shortcut. It is a practical tool that allows acousticians to predict D2,S, Lp,A,S,4m and DA,S with minimal input data, supporting better design of open-plan offices. Combined with the framework of ISO 22955, it provides a user-oriented and cost-effective way to balance acoustic quality with real workplace needs.
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Open Plan Office Calculator : https://www.ecophon.com/en/tools–services/open-plan-office-calculator
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