Bubbles should have the greatest effect when the sound 

 frequency matches the resonant frequency of the bubble. 

 The resonant frequency of a spherical bubble is given by 



/ D = 652 



where D is the bubble diameter in cm and f is the reso- 

 nance frequency in cycles per second. A bubble resonat- 

 ing at 5.2 kc/s accordingly has a diameter of 1.25 mm 

 and is therefore easily visible. This is pertinent to the 

 interpretation of the measurements discussed in the later 

 chapters. 



The conditions under which air bubbles may exist in 

 the ocean are discussed in a number of references. 36-38 



10 



