III-39 



Experimental Evidence 



The expressions for the phase velocity and attenuation are generally 

 in good agreement with experiment. In particular, we have the following body 

 of experiments: 



(1) Meyer and Skudrzyk (Ref. III-29) calculated the theoretical at- 

 tenuation for uniform bubble mixtures which were resonant at 12 kc and for a 

 mixture having a uniform distribution of bubble sizes. These agreed qualita- 

 tively quite well with experimental results . 



(2) Carstensen and Foldy (Ref. Ill- 3) measured attenuation and re- 

 flection for a bubble screen in a lake. Screens of both constant and varying 

 bubble sizes were used. The results agreed qualitatively with the theory. 

 The mixtures were generally resonant at 15 kc. 



(3) Laird and Kendig (Ref. Ill- 19) measured attenuation in a bub- 

 ble screen having various sizes of bubbles. Although the reported results ap- 

 pear to be in good agreement with the theory, the nature of the experiment 

 was such that there may be considerable error in the results. The screen as 

 a whole was resonant at 8 kc. 



(4) Fox, Curley and Larson (Ref. III-9) measured phase velocities 

 and attenuation for a bubble screen resonant at 60 kc. The results agreed 

 quantitatively with the theory. 



(5) Macpherson (Ref. III-26) measured attenuation for a very care- 

 fully controlled, almost idealized, bubble screen. The bubbles were all of the 

 same size and were resonant at 30 kc. The results agreed very well with the 

 theory. 



(6) Silberman (Ref. Ill- 37) measured attenuations and phase veloc- 

 ities for screens which were resonant in the range 1 kc to 10 kc. The results 

 generally agreed well with the theory. 



The net result is that the theory for propagation of sound through an 

 air bubble-water mixture is well supported by experimental work. Deviations 

 from the theory can usually be explained by experimental conditions or im- 

 proper use of a parameter, such as the damping constant, in comparing the 

 theory with measurements. The following gives details on the experimental 

 work. 



S-7 001-03 07 



