Simrad ST90 - Defining the Athwartships Location of the Hull Unit; Important Considerations Related to Noise

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Deningtheathwartshipslocationofthehullunit
Theathwartshipspositionisnotcritical.ThehullunitmaybelocatedontheCentreLine
(CL)ofthevessel,oralongsideitskeel.
Note
Iftheinstallationisoffsetfromthevessel’ scentreline,makesurethattransducer
transmissionsandreceptionwillnotbeobstructedbythekeel.
Relatedtopics
Choosingthebestlocationforthehullunit,page59
Importantconsiderationsrelatedtonoise
Theoperationalperformanceofallhydroacousticsystemsdependonthenoise
conditions.Itisessentialthatthenoisesignatureisaslowaspossible.Carefulplanning
oftheST90installationmayreducetheacousticnoise.
Theinstallationtrunkmustbemountedsothatitremainsverticalduringnormal
operatingconditions.Thefairingaroundtheinstallationtrunkmustbestreamlined.The
transducermustbeprotrudingfarenoughdowntoreachoutoftheboundarylayer.
Theprimarysourcesofunderwaterdisturbance(otherthanavessel’smainpropellerand
bow/sternthruster)thataffectST90receptionperformanceare:
1Mainorbilgekeels
2Zincanodes
3Coolingelementsprotrudingfromthehull
4Equipmentsuchassonartransducers,echosoundertransducersandpilottubes
5Seachests
6Overboarddischarges
7Dentsinthehull
Important
Allappendagestothehull,indentationsandpipein/outletsarepotentialsourcesof
underwaternoise.Theymayactasresonantcavitiesamplifyingnoiseatcertain
frequencies,createcavitationorturbulence.Transducersshouldnotbelocatedinthe
vicinityofsuchobjectsandespeciallynotimmediatelyaftofthem.
Relatedtopics
Choosingthebestlocationforthehullunit,page59
Preparations