Specifications
Sonartheory
•Reverberationonpage107
•Blockingonpage108
•Checkthenoiseyourself!onpage108
Cavitation
Asthepropellerbladesmovethroughthewater,lowpressureareasareformedasthe
wateracceleratesaroundandmovespasttheblades.Thefasterthebladesmove,the
lowerthepressurearounditwillbecome.Asitreachesvapourpressure,thewater
vaporizesandformssmallbubblesofgas.Thisiscavitation.
Figure7Cavitation
[1]
Whenthebubblescollapse,theycauseverystronglocalshock-wavesinthewater.
Thesemaybeaudibleandcanalsodamagethepropellerblades.Inadditiontothis,the
cavitationwillgenerateverystrongreverberation,commonlyseenasaredstripeof
echoesbehindthevessel.
Ifyouhavebigproblemswithcavitation,trytoadjustthepropellerpitchand/orthe
numberofrevolutions.
Reverberation
Reverberationisgeneratedwhentheechoesfromyoursonartransmissionarereected
notonlybyshandobjectsinthewater,butalsofromthebottomandtheseasurface.
1.PhotofromUSNavy/Wikipediainthepublicdomain.
372739/D
107