Scientific Article

Uncertainty and environmental effects in outdoor firearm noise propagation

¹ Department of Mechanical Engineering, Royal Military Academy, avenue de la Renaissance 30, 1000 Bruxelles, Belgium
² Faculty of Engineering (General Physics Unit), University of Mons, Place du Parc 20, 7000 Mons, Belgium

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 14 March 2025
Accepted: 27 August 2025

Abstract

Outdoor noise measurement is highly uncertain due to its strong dependence on environmental conditions. In firearm noise studies, these uncertainties are amplified by the impulsive nature of the noise and the lack of large datasets, making long-term meteorological averaging and stochastic techniques impractical. Numerical models also face limitations, with most commercial software relying on coefficient-based environmental predictions. This study investigates uncertainties and environmental effects in outdoor firearm noise propagation, combining experimental and numerical approaches to understand their impacts. The expanded uncertainty of systematic (Type B) uncertainties contribute up to ±4.1 [dB], while random (Type A) uncertainties, influenced by environmental variability, range from ±0.5 to ±10 [dB], predominantly affecting mid- to high-frequency bands at extended distances. A refined 2D Nonlinear Progressive Equation (NPE) model is used to simulate varying terrains and atmospheric conditions. Results reveal that sound-dampening terrains, such as grass, cause significant amplitude and spectral shifts compared to asphalt, with attenuations up to 10 [dB] at specific frequencies and distances. Downwind conditions enhance high-frequency propagation, while upwind scenarios reduce signal strength, with notable effects indicatively happening beyond 65 [m]. The findings highlight the importance of environmental characterization and advanced modeling as complementary tools for understanding and contextualizing uncertainties in firearm noise studies, supporting the development of improved methodologies for military and civilian acoustic applications.