--- title: "Secure Approval of Open-Air Events: Precise and Standard-Compliant Noise Prediction Using the APS Approach" description: Greater security for event organizers, planners and authorities. With the APS approach, IMMI and EASE bridge a key methodological gap between complex sound reinforcement planning and standard-compliant noise emission calculations. image: https://blog.woelfel.de/hubfs/Blog/2026-03-Open-Air-Veranstaltung-Lautsprecheranlage.jpg --- [![Woelfel-Logo-klein-transparent](https://blog.woelfel.de/hs-fs/hubfs/Logo/Woelfel-Logo-klein-transparent.png?width=131&height=54&name=Woelfel-Logo-klein-transparent.png "Woelfel-Logo-klein-transparent")](https://www.woelfel.de/) [IMMI](https://www.woelfel.de/) - [Industries](https://www.woelfel.de/en/industries.html) - [Wind Energy](https://www.woelfel.de/en/wind-energy.html) - [Structural Dynamics](https://www.woelfel.de/en/industries/structural-dynamics.html) - [Building Physics](https://www.woelfel.de/en/industries/building-physics.html) - [Environmental Protection and Immission Control](https://www.woelfel.de/en/industries/environmental-protection-and-immission-control.html) - [Seating Development and Comfort](https://www.woelfel.de/en/industries/seating-development-comfort.html) - 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Residents are reacting more sensitively, approval authorities are conducting more rigorous reviews and the pressure to present robust forecasts is rising significantly. ## **![Festival stage with sound system](https://blog.woelfel.de/hs-fs/hubfs/Blog/2026-03-Open-Air-Veranstaltung-Lautsprecheranlage.jpg?width=1000&height=598&name=2026-03-Open-Air-Veranstaltung-Lautsprecheranlage.jpg)** ## **The core problem: Complex sound reinforcement systems collide with simplified calculation models**    Modern sound reinforcement systems consist of numerous loudspeakers with complex directivity characteristics that are precisely coordinated with one another. However, the calculation methods used to date treat this setup in a highly simplified manner. This results in significantly differing outcomes – and therefore forecasts that are open to challenge.  ###  **Background: Legal and normative framework for noise predictions for open-air events** Noise predictions for open-air events are generally based on national environmental noise legislation. Sound propagation is typically calculated in accordance with internationally recognized standards such as ISO 9613-2. In addition, country- or region-specific guidelines – e. g. for leisure or event noise – may apply.    A calculation carried out in compliance with the applicable regulations and standards is a prerequisite for a robust and approvable forecast. ## **The solution: Aggregate Point Source (APS) – a new, scientifically validated approach for standard-compliant forecasts for complex sound reinforcement systems**    The experts from  EASE® and IMMI have combined their expertise and within the framework of a multi-year joint research project, developed a new, scientifically validated approach. Aggregate Point Source (APS) converts complex loudspeaker groups into so-called substitute point sources with realistic directivity characteristics. Internally coherent systems are combined into a modelable unit that can be used in compliance with applicable standards within existing calculation methods. This provides, for the first time, a methodological approach that integrates the actual directivity characteristics of complex line array systems into standard-compliant immission calculations. Measurements and simulations carried out as part of scientifically sound investigations show that the results are reproducible, robust and compatible with the requirements of immission control.   >> You can find out more about the APS approach and the validation studies in these specialist articles:  \[1\]: [Feistel, S., Blaul, J., Goldmann, T., and Nicht, A. (2024). *Sound immission modeling of open-air sound systems*. Audio Engineering Society 157th Convention, New York, NY, USA.](https://aes.org/publications/elibrary-page/?id=22720) \[2\]: [Blaul, J., Feistel, S., Goldmann, T., and Nicht, A. (2025). *Standard-Compliant Sound Immission Forecasts for Open-Air Music Events*. DAGA 2025, Copenhagen, Denmark.](https://pub.dega-akustik.de/DAS-DAGA_2025/konferenz-1884.html?article=268) \[3\]: [Goldmann, T., Feistel, S., Blaul, J., and Nicht, A. (2025). *Modelling and Verification of Low-Frequency Sound Systems in the Application of Noise Predictions*. Audio Engineering Society 159th Convention, Long Beach, CA, USA.](https://aes.org/publications/elibrary-page/?id=23047) \[4\]:[Blaul, J., Feistel, S., Goldmann, T., and Nicht, A. (2026). Ein softwareübergreifender Workflow zur schalltechnischen Bewertung komplexer Beschallungssysteme im Rahmen von Immissionsprognosen. DAGA 2026, Dresden, Germany.](https://pub.dega-akustik.de/DAGA_2026/konferenz-2109.html?article=157)   [![AFMG-Logo](https://blog.woelfel.de/hs-fs/hubfs/Logos%20(W%C3%B6lfel,%20IMMI...)/AFMG_Logo.png?width=118&height=43&name=AFMG_Logo.png)](https://www.afmg.eu/en/ease)    [![EASE-Logo](https://blog.woelfel.de/hs-fs/hubfs/Logos%20(W%C3%B6lfel,%20IMMI...)/EASE-Third%20Edition%20Logo.png?width=69&height=43&name=EASE-Third%20Edition%20Logo.png)](https://www.afmg.eu/en/ease) **EASE** – developed by AFMG – is established worldwide as a market-leading software solution for electroacoustic planning and enables the precise modelling of complex sound reinforcement systems, not least thanks to its extensive loudspeaker database.   [![IMMI-Logo](https://blog.woelfel.de/hs-fs/hubfs/Logos%20(W%C3%B6lfel,%20IMMI...)/IMMI.png?width=118&height=58&name=IMMI.png)](https://immi.woelfel.de/)   **IMMI** is one of the leading solutions for standard-compliant noise prediction and is used worldwide by consultants and authorities.  ## **How is the standard-compliant noise calculation for open-air concerts carried out? A seamless workflow in EASE and IMMI  ** Until now, sound reinforcement planning and noise prediction have generally been handled by separate specialist disciplines using software solutions that were not interconnected – resulting in a corresponding coordination effort and potential for errors. With the new workflow from EASE and IMMI based on the APS approach, a seamless solution is now available that efficiently and consistently integrates planning and standard-compliant noise calculation. All relevant information can be transferred via a file in APS format.  1. The event technician plans the sound reinforcement system in EASE – as usual.  **2.** Loudspeaker positions, directivity characteristics and relevant system data are exported in a file in the APS format. **3.** The complete stage and loudspeaker setup, including the alignment and relative position of each individual source, is imported into IMMI as an overall system via the APS file and can be freely positioned and aligned within the geomodel. The entire frequency range of the third-octave bands from 25 Hz to 20 kHz is supported. 4. The frequency-dependent sound power levels of the far-field directivity characteristics are determined by means of user-based input of a sound reinforcement level in the audience area (e. g. at the FOH position) as well as reference spectra of a corresponding stage programme (e. g. rock/pop). For this purpose, the APS file contains a transfer function between the complex near-field spectrum calculated in EASE 5 and the far-field spectrum of the APS sources. 5. The noise calculation in accordance with ISO 9613-2 is carried out. 6. The results are presented in a noise map or as immission point calculations. In the AFMG video, you can get an insight into the workflow:    The centralised data transfer reduces transmission errors. The entire procedure is in accordance with ISO 9613-2 and the software used is quality-assured.   ![IMMI dialogue box for defining parameters](https://blog.woelfel.de/hs-fs/hubfs/Blog/2026-03-blogbeitrag-immi-funktion-open-air-definition-der-parameter.png?width=764&height=576&name=2026-03-blogbeitrag-immi-funktion-open-air-definition-der-parameter.png)  Definition of parameters in IMMI    ![IMMI Results View](https://blog.woelfel.de/hs-fs/hubfs/Blog/2026-03-blogbeitrag-immi-funktion-open-air-ergebnis.png?width=764&height=455&name=2026-03-blogbeitrag-immi-funktion-open-air-ergebnis.png)  Result of the noise calculation displayed as IMMI noise map (in this example for the third octave band 63Hz)   The concept goes so far that a complete event schedule for the stage programme can be entered and based on this, time-assessed emission spectra are assigned to the relevant assessment periods (e. g. day/night). This enables assessments of an event to be carried out intuitively and independently of the respective national regulatory framework.  The function is available as a paid add-on starting with the current IMMI update 2025-02. [REQUEST A QUOTE](mailto:denise.mueller@woelfel.de) ## Conclusion: More planning security for event organisers, planners and authorities With the APS approach, IMMI and EASE close a key methodological gap between complex sound reinforcement planning and standard-compliant immission calculation – and set a new standard for open-air events with the associated workflow. 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