471 



Tunnel No 1 Test section 700 ^ 700 mm 



-3^ ^ 



Bel lows 

 5 



-^^ 



Hydrophone box 1 ( 2mm sleel ) 

 connected to plexiglass 



nndow by rubber bellows 



Free water surface 



"-Hydrophone 



Plexiglc ss 



FIGURE 1. First arrangement for 

 noise measurement. (Tunnel No. 1) 



K 



pressure 



blade frequency period 



H 



\A 



„.«,«*-««-*""^' --Mw^' 







\/ 



Hydrophone near propeller 



v,,,^,i^|fPif^^Hmi^m 





I ^(' ! 





^ time 

 Hydrophone in external box 



FIGURE 2. Pressure signals at different 

 hydrophone positions. 



