Résumé
This project delves into applied research on the fundamental mechanisms of high-intensity impulsive sound propagation, concentrating specifically on small and large calibre firearms. Present models used for noise impact studies are essentially based on linear propagation. These models fail to predict accurately the propagation of sound from military sources such as jet noise, or impulse noise from firearms, guns, detonations and explosions. The broad spectrum, the directivity and the duration are specific to military noise sources. The large discrepancies observed with experimental data or within results from civilian noise propagation models are related to the nonlinear propagation behaviour. This research intends to develop a in-house numerical solver and the related expertise on the subject of firearm noise propagation. The outcome is a toolkit to be used by Belgian Defence to make assessments of the impact of military noise emissions with respect to international and regional regulations and optimize the mitigation the measures, by shielding and/or by adapting the existing procedures. The methodology leverages on the unique opportunity to access military shooting ranges and to collect on-field acoustic measurements during live fire exercises with various weapon systems and calibres. This way, the raw signals and the sound levels close to the gun and at further locations can be measured, serving as an important validation and comparison tool for the in-house numerical model. The latter is able to simultaneously take into account the complex physics of firearm noise as well as to model the effects of the environmental conditions. Through the use of different time and frequency domain metrics, it was shown that, although the approach based on rule of thumbs and semi-empirical corrections proposed by commercial off-the-shelf software and standards may be sufficient in certain conditions, it most certainly leads to miscalculations when compared to real measurements. When nonlinearity is accounted for in the numerical model, the nonlinear prediction of the high-frequency spectrum can outperform the linear solution by more than 30 dB, when large calibres are involved.The effects of acoustic nonlinearity are shown to persist at least up to a distance of 300 m from the source, demonstrating that, if an accurate and physically consistent noise exposure prediction is sought, modelling firearm noise propagation in all its complexity is the recommended approach. Ultimately, the study contributes to the existing body of knowledge on environmental acoustics by shedding light on the mechanism of acoustic nonlinearity and by offering new insights into firearm noise propagation.
| la date de réponse | 4 sept. 2024 |
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| langue originale | Anglais |
| L'institution diplômante |
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| Superviseur | Benoît Marinus (Promoteur), Kristof Harri (Promoteur) & Francis Moiny (Promoteur) |