10 



u 



u 



fe 



10 



























































































































>3 



^ 

































^y^ 





























^ 



^ 



^ 



^ 























^ 



^ 



^ 



























^ 



^ 











































Avg 

 1 



r_ 



1 1 1 

 Sj^ 105 db above 1 mic 



at 1 meter (peak level) 



1 III 



1 1 



robar 



1 1 1 



10 



10^ 

 Depth in Feet 



10^ 



Figure 29. Plot of frequency vs. depth for pneumatic sound 

 source (3- inch OD sphere inflated with compressed air). 

 Heavy wall thickness. 



Figure 30. Typical waveform produced by 1. 3- inch OD pneumatic 

 sphere; no filtering used. The sine wave at the bottom is that of 

 a 50-c/s calibrate signal. 



53 



