SECT. 1] 



OONTINtrOUS REFLECTION PROFILING 



51 



signal. Frequency selection is accomplished with filters following the hydro- 

 phone pre-amplifier, as shown in Fig. 2. Broad-band filters have been used ; 

 obviously at any frequency a band as wide as the order of an octave will be 

 required if the response time of the filter (taken as the reciprocal band-width) 

 is not to limit resolution. 



All designers have used graphic recorders which record intensity changes as 

 relative darkening of an electro-sensitive recording paper. Cathode-ray-scope 

 visual presentations are included in all the systems, and, at least experimentally, 

 long sequences of oscillograms have been recorded photographically. In the 

 case of the new Marine Seismic System of the Field Research Laboratory, 

 Socony Mobil Oil Company, photographic recording with the much-used 

 galvanometer camera has been employed to compare with the variable density 

 recording. It seems obvious that oscillographic recordings will be needed for 



SPARK ER (KNOTT) 





THUMPER (EDGERTON) 



DETONATION GUN 

 (SOCONY-MOBIL) 



ABSCISSA: 1 XIO'^SEC/DIV 

 0RDINATE:0.35X105 DYNES/CM2 

 SEPARATION: 4 METERS 



2X10"' SEC/DIV 

 0.7X 10^ DYNES/CV|2 

 6 FEET 



5X 10"3 SEC/DIV 

 NOT GIVEN 

 16 FEET 



PNEUMATIC SOUND SOURCE (PADBERG) 



PASS (BECKMAN ETALJ 



\t 



g^/f^T-^-KlT^^^; 



ABSCISSA: 20X10-3SEC/DIV 

 0RDINATE:O.7X105dYNES/CM2 

 SEPARATION: NOT GIVEN 



1X10-5 SEC/DIV 

 0.7X105 DYNES/CM2(107dB//B) 

 16 FEET 



Fig. 3. Pressure-time curves of continuous profiling sources. 



completely quantitative study of transmission and reflection jjrocesses, but it 

 seems equally obvious that the automatic correlation provided by the graphic 

 recorder together with the ease of measuring precise travel time with it will be 

 useful for some time to come. 



The following is a summary of the principal individual characteristics of the 

 several instruments. 



(a) The Sonoprobe: a directional magnetostrictive transducer. Acoustical 

 pulse described as "one complete cycle of a 3800-cycle sine wave" (McClure 

 et al., 1958). 



(b) Padberg {in lift.): short-pulsed strongly directional magnetostrictive 

 transducer. Padberg has also experimented with spark and pneumatic sources 

 (see Fig. 3). 



