WEINSTEIN: EXPLOSIVE SOUND SOURCE STANDARDS 



Dr. M. Schulkin (Naval Oceanographic Office) : What do you estimate 

 is the high frequency cutoff for your oscillograms for those charges? 



Ms. Christian: About 100 kHz. The response is flat up to about 

 100 kHz in oscilliscope readings. 



Dr. Schulkin: We found that the peak pressure that you actually 

 measure very much depended on the high-frequency response of the gage. 

 For many systems used at sea, the tape recorder itself cuts off that 

 peak. 



Ms. Christian: Right. Actually, you can get within the typical 

 reproducibility of the data points probably if your recordings are good 

 up to about 20 kHz. You don't lose much in the peak pressure above that 

 frequency. That is, you really can't see the very high-frequency spike 

 above about 20 kHz. But if you cut off at, say, 5 kHz, you can be down 

 30 percent in the peak pressure. So all of those wave functions we 

 use in the Gaspin and Shuler model require this extremely broad-band 

 recording to give a true wave form. 



Dr. Schulkin: I have seen records published where the peak and the 

 first-bubble pulse have the same amplitude. 



Ms. Christian: Oh sure, you will get to the point where the 

 bxibble peak pressure is higher than the shock if your cutoff frequency 

 is sufficiently low. As a matter of fact, I think at an upper limit of 

 about 500 Hz the bubble and shock are equal. 



Mr. G. R. Hamilton (Office of Naval Research) : What is the uniformity 

 of our standard SUS from SUS to SUS if you detonate them all at the 

 same depth? You talked about variations from variation in depth. 

 What's the variation in source level if we fire them at precisely the 

 same depth? 



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