Source Levels for Shallow sus Charges

Abstract

Idealized source levels have been computed for sus charges (1.8 lb TNT) detonated at “standard” depths of 60, 300, and 800 ft. Spectral energy distributions were obtained by transforming quasitheoretical time functions representing the initial shock wave and first three bubble pulse phases of the explosion pressure waves. For the most part these new source level values agree well with results previously published by Weston and Christian; occasional differences of more than 5 dB occur, however, for certain frequency bands and charge configurations. One-third octave band levels have also been examined for charges detonated over the range of depths typically found in practice when the above nominal depth settings are used. This comparison shows that if the analysis bandwidth is narrow compared to the explosion spectrum pattern of peaks and nulls—and this is the case at the low-frequency end of the spectrum for these charges—such variations in depth can introduce scatter of up to 6 dB in the band level.