III-42 



ATTENUATION 

 (db/cm) 



4 



2 



_ y^ 



10^ 



/ 



e 



— / 



6 



- / 



4 



- / 



2 



-/ 



10= 



_/ 



8 



— / 



6 



-\ 



4 



- 



2 



1 



20 40 60 80 



f= FREQUENCY (kc) 



FIGURE in-14 THEORETICAL ATTENUATION 



THROUGH A BUBBLE SCREEN WITH 

 A DISTRIBUTION OF BUBBLE SIZES 

 (AFTER MEYER AND SKUDRZYK) 



Figure III- 15 illustrates examples of damping measured on screens 

 generated by electrolysis. Physical observation showed immediately that, in this 

 case, no uniform bubble mixture was present; rather, very small bubbles of dif- 

 ferent sizes arose, together with a few large bubbles. Comparison of the curves 

 for Figures III- 15a, b, and c, with Figure III- 14 shows great similarity. In fact, 

 it is possible in both figures to connect the measured points of a series of measure- 

 ments for a fixed current density directly by a calculated curve, as shown for the 

 curves in Figure III- 15a and Figure III- 15b for 60A and 15A respectively. The gas 

 concentrations on which these calculations were based are 4.8 x 10 ^ and 9.2 x 10'^, 

 very close to the concentrations expected from a study of the electrolytic process. 



It should also be pointed out that in the electrolysis experiments Meyer 

 and Skudrzyk used the damping constant for air, although measurements were 

 actually made on hydrogen bubbles. 



Carstensen and Foldy made a series of measurements on the attenuation 

 of sound through a screen of bubbles and the amount of reflection from such a screen. 

 The measurements were made under two classes of screen conditions: relatively 

 few bubbles in the screen but all of essentially the same radius, and relatively large 

 numbers of bubbles having a considerable range of radii. The device which produced 

 the bubbles was suspended 10-1/2 feet below the surface of a lake and produced a 



Arthur Jl.littlcJnt. 



S-7001-0307 



