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Authors' Reply 



GORAN BARK and WILLEM B. van BERLEKOM 



It is very interesting to hear of this hypoth- 

 esis concerning generation of noise by tip vortex 

 cavitation. We have perfoirmed experiments with tip 

 vortex cavitation at propellers and hydrofoils and 

 found that intermittant tip vortex cavities were 

 noisiest. However, we have not performed high speed 

 filming or other more advanced attempts to study 

 the real mechanisms involved in the volume fluctu- 

 ations of the tip vortex cavity. In the case of 



bubble cavitation and unsteady sheet cavitation, 

 which we have studied in more detail, we are of 

 the opinion that the highest pulses are generated 

 during the final part of a collapse, which often 

 is rather symmetrical, and that filling the cavities 

 with gas is of minor importance as a primary gen- 

 eration mechanism. However, some results indicate 

 that this gas decreases the violence of the collapse. 



