CHRISTIAN: THE ACOUSTIC OUTPUT OF EXPLOSIVE CHARGES 



systems — you reproduce the pressure-wave output within a few per- 

 cent.* Predictability, however, is another matter. 



Given these quantitative constraints — source levels predictable 

 within 1 dB in 1/3-octave bands over the frequency range 10 to 300 Hz - 

 we are in rather poor shape for analyzing data taken with explosion 

 sources. We do not have known, standard source level values. We have 

 problems with sonar equation compatibility. And we very definitely 

 have problems with our 1 dB error allowance. 



I don't think we need much discussion on the question of known, 

 standard values. Everyone in this room who has used explosion sources 

 is aware that among the published values in the literature, the in- 

 house publications, and the backs-of -envelope working papers we all 

 turn to, a wide assortment of source level values can be found. These 

 values vary perhaps by 5 dB, perhaps more, depending upon the band- 

 width of interest. In fact, the question is so wide open that I have 

 wondered if data reduction sometimes follows the line of "when in 

 doubt, blame the source level; and then look around until you find 

 one you like better." 



To mention a few of the many names that are familiar to source 

 level seekers, we have Weston's (1960) benchmark paper that is still 

 widely used. We have Stockhausen's (1964) data, measurements reported 

 by Turner and Scrimger (1970), Maples and Thorp (1970), Buck (1974), 

 and Christian (1965, 1967). Oh, there is no dearth of source level 

 values. But they do not add up to our desired "known, standard 



* With some of the more exotic explosive materials there are problems 

 with reproducibility; the charge output may vary with charge size, 

 with the formulation, or with the density. But these materials are 

 not found among the standard acoustic sources. 



33 



