Remarks on acoustical descriptors for explosions in air

Abstract

Currently, ISO/TC43/SC1/WG51 is collecting ‘‘experiences’’ with measuring and predicting shooting noise. One goal of this working group is to write a guideline for the measurement of source data of shooting noise, taking into account the special characteristics of these high energy, impulsive blasts. There are three special aspects with shooting noise: First, there are nonlinear effects close to the source. Second, the strong directivity of blast sources plays a very important role. Third, in contrast to most of the continuous noise sources, blasts are single events which involve coherence effects during source and receiver measurements. Therefore, a dedicated set of emission data has to be introduced to describe a blast source with respect to sound propagation models. The presentation will discuss the definition of a set of appropriate source descriptors for muzzle blasts. The source will be treated as a linear spherical source with directivity. Its intensity will be defined in the far field and its directivity pattern will describe the acoustical strength. The radius of this artificial source depends on the blast energy and is an important parameter when determining the appropriate measurement distance for source measurements.