Sub-project 2: Improving the practicability of the sound intensity method
The NOMAD study (2012) showed that about 80% of the noise emission data for machines, required by European Directives, in the investigated instruction manuals were not reliable. A possible cause is the high complexity of the normative measurement methods for determining noise emission values. The sound intensity measurement method according to the DIN EN ISO 9614 series of standards is ideally suited for an in-situ determination of the sound power of machines, as it does not require a background noise and an environmental correction. "In-situ" means within an industrial environment, e.g. in a factory hall, as opposed to in an acoustic test room. Larger machines and systems in particular can best be measured using these methods, as otherwise correspondingly large acoustic test rooms would be required. However, the standards of the ISO 9614 series no longer correspond to the state-of-the-art in form and content. In addition, these standards require complicated calculations and the verification of field indicators. Furthermore, it can happen that, depending on the determined field indicators, no result can be obtained despite extensive measurements.
As part of the research project, extensive calculations on model emitters and measurements were carried out. The results show that only one of the currently three field indicators is needed to assess the validity of the measurement results. In addition, the procedure was modified in such a way that at least an upper limit for the A-weighted sound power level is always obtained. In the project, drafts for a standardisation project to revise of the sound intensity measurement method and improve its practicability were prepared. In addition, it is proposed to cover the different accuracy classes in one standard each, one for measurements at discrete points and one for measurements according to the scanning method (so far two standards).
Unit 2.2 "Physical Agents"