SURFACE AND OTHER EFFECTS 



Fig. 10.3 which were obtained by a vertical sound ranging system com- 

 prising five gauges at 200-foot intervals to a depth of 815 feet, and 

 illustrate the order of agreement found. 



As compared to a sound ranging method, bubble period measure- 

 ments offer the advantage that very much simpler equipment and gear 



40 



30 



^ 25 

 6 



UJ 



20 



15 



10 

 200 300 400 500 600 700 800 



DEPTH (FT.) + 33 FT. 



Fig. 10.3 Bubble pulse period plotted against set depth and sound ranging 



depth. 



is needed. Only a single gauge need be used and it can be placed at 

 any point which is close enough for the pulses to be picked up and not 

 so close to boundary surfaces that reflections distort the pulse. Sound 

 ranging gauges, however, must be relatively close to the source and ac- 

 curately placed relative to each other and to reference points. If these 

 conditions can practically be satisfied (and this is not easy in open 

 water), the sound ranging method is more powerful because calibration 

 is not as essential and distances other than depth can be determined. 



10.4. Pressures near Yielding Surfaces 



The analysis of damage caused by underwater explosions is, as has 

 been suggested at several points, a very complicated one in all its rami- 



