D. Schofield 
17 
Fig. 1.8. Array of 5-kcps transducers, 
the water. The presence of these cavities or bubbles sets an upper limit to the 
power transferred from a vibrating piston tothe water since they reflect, scatter, 
and absorb the incident energy. At the same time, the radiation resistance 
changes and the acoustic waveform is distorted. The latter occurs because the 
amplitude of the acoustic signal is not symmetrical about the zero axis and a form 
of rectification takes place. Considerable erosion of the transducer face can 
occur. 
_ Assuming that water does not exhibit a cohesive force and equating the atmos- 
pheric pressure to the peak acoustic pressure, we find that the intensity to pro- 
duce cavitation at shallow depths is 0.3 w/cm?. As is well known, a sound intensity 
R= 313002 
fo 
Qm 
Fig. 1.9. Calibration results k 
of 5-kcps transducer. PRO SENS fo 
H/P SENS fo 
Nea 
ma 
= 
K=.00183 pf 
N=520mh 
Sw=34102 
S| = 340 
5.1 KC/S 
4.9 
0.17 
217 #BAR/ VOLT AT 3° 
370 4 VOLT/ p» BAR 
81% 
90% 
