A simple geometrical model is proposed to describe the phenomenon of sonic boom of projectiles fired from weapons. In this model the trajectory of the projectile is conceived as a coherent fine source in which the proper temporal and phase relationships stemming from the projectile travel are maintained. In the calculation algorithm the coherent line source is approximated by point sources along the trajectory that emit an impulse when being reached by the projectile. The sound pressure at a receiver point is obtained as the phase sensitive addition of the contributions from the individual sources along the trajectory. It is shown that this integration can be simplified considerably by applying the concept of Fresnel zones. Based on a number of examples it will be demonstrated that the model correctly reproduces the observed properties of sonic boom. In addition it offers the possibility of investigating problems which cannot be handled by conventional models, for instance the sound pressure at points outside of the main region of sonic boom. The simulation model was confirmed through measurements at locations on the borderline of the sonic boom region. Neither non-linear effects nor the influence of turbulence are considered. The attenuation with distance is therefore influenced solely by geometry and the speed profile of the projectile. It is shown that higher decelerations of the projectile lead to greater geometric attenuation. Furthermore the attenuation per doubling of distance is not constant, but increases at greater distance from the trajectory. [References: 4]
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