ISO 3382-3 describes how to assess sound propagation and speech intelligibility in open-plan offices. At the recent Inter-Noise conference in Nantes, Rainer Machner presented Hongisto and Keränen’s (2013) regression-based model for predicting ISO 3382-3 parameters. By analyzing data from 10 office spaces, he evaluated the model’s performance and gave practical recommendations for its use in office design.
Open-plan office environments are prone to issues with speech propagation, which usually affect overall acoustic comfort. ISO 3382-3, introduced in 2012, provides a method for measuring key room acoustic parameters.The prediction model developed by Keränen and Hongisto (2013) simplifies the process of estimating two key acoustic parameters: the spatial decay rate of speech (D₂,S) and the A-weighted speech sound pressure level at 4 meters from the source (Lp,A,S,4m). Their regression-based equations take into account room dimensions, ceiling absorption, vertical surface absorption, and partition height to make predictions.
Application and challenges
While the model is highly beneficial for quick acoustic evaluations during the early design stages, it comes with limitations. Rooms with high ceilings (over 4m), unevenly distributed absorption surfaces, or irregular shapes tend to produce less accurate results. The model was primarily developed from data collected in larger rooms with specific absorption characteristics, so small rooms or those with unique layouts may require additional consideration or alternative methods.
Comparing predictions with real-life measurements
The results of measurements from 10 open-plan offices were compared with the model’s predicted values for both D₂,S and Lp,A,S,4m. The results indicated an acceptable level of accuracy, with deviations falling within a range of ±2 dB for D₂,S and ±3 dB for Lp,A,S,4m. These differences are within acceptable uncertainty levels based on other studies on ISO 3382-3 measurements. The measured offices ranged in size and absorption characteristics, with some deviations in room characteristics from the original dataset used to develop the prediction model. Notably, most of the measured offices had carpeted floors and varying degrees of ceiling absorption, whereas the original model was developed with less emphasis on such features.
Practical implications for acoustic design
In practice, achieving optimal acoustic conditions in open-plan offices is critical for people comfort and productivity. Acoustic standards such as ISO 3382-3, along with national guidelines like Germany’s VDI2569:2019-10 and France’s NFS31-199, offer benchmarks for designing these spaces. The simplified prediction model allows designers to quickly assess acoustic conditions and make well-informed decisions at the very early stage of the building process. Among other things, the model can help architects understand how different ceiling or partition configurations might affect speech propagation. While it cannot replace detailed simulations, it offers a quick and efficient way to compare different room configurations and make design decisions. However, designers should be cautious when applying the model to small or irregularly shaped rooms, as predictions in these spaces may be less reliable. The model’s predictions are also more reliable in rooms with consistent, evenly distributed absorption and well-defined partition heights.
Source: “Empirical Method for Predicting Speech Sound Propagation in Offices”, Machner R, Klein A., Brokmann H., Krummheuer H., Danner G., Internoise 2024 proceedings.
