BROOMSTICKS 
TOP VIEW 
SOFT RUBBER 
COMPLIANCE 
SIDE VIEW 
Figure A4. Monitor hydrophone rigging. 
The continuity of projector operation was shown by a strip chart recording of the 
rectified hydrophone signal. 
RESULTS 
Source Level 
MEASUREMENTS. The source level and the frequency spectrum were constant 
throughout the in-water tests. During the in-air test, the monitor hydrophone was used to 
set the frequency at 15 Hz. Figure A5 is a composite of two spectrums. The first was made 
with the monitor hydrophone lying on the wooden supports tied to the projector, and the 
second was made with the monitor hydrophone hanging from a soft rubber compliance from 
the same wooden supports. The compliance reduced the coupling between the hydrophone 
and the projector almost 40 dB in air. 
Figures A6 through A9 show that the frequency spectrum and source levels were the 
same at each depth. Figure A9 is a composite spectrum showing both the usual spectrum at 
full piston throw and the spectrum when the adjustable linkage controlling the piston throw 
was set to the extreme minimum position. Figures AlO through A16 show that the 15 Hz 
line did not change during 18 hours of operation at 500 ft but that some change occurred, 
particularly in the higher harmonic levels (slightly stronger). 
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