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Engine noise is reduced by
restricting it to the engine compartment. To do that, the
engine compartment itself is turned into an efficient acoustic
enclosure. If necessary, a separate enclosure can be built
around the engine for maximum results. An effective acoustic
enclosure must provide sound absorption and sound transmission
loss. DECI-FLEX noise absorption and barrier materials
are specifically designed for this purpose - to maximise
sound reduction.
To achieve optimum results you have to literally batten
down the hatches. All gaps must be plugged; access hatches,
doors, cable and pipe penetrations must be thoroughly gasketed
and sealed
Ventilation openings must also be acoustically treated,
typically as shown :
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Resonac noise barrier
are used on deckheads, over engine rooms and on bulkheads
beside the engine room
DECI-FOAM sound absorption materials soak up sound
when used as ceiling and wall linings
Resonac vibration-damping materials inhabit radiation
of structure-borne noise
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Vibration transmitted through
the boat structure is radiated by the hull, the deckheads
and bulkheads. This is known as 'structure-borne vibration'.
It causes radiation of mechanical noise usually well away
from the vibration source itself
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Resonac treatments on
the hull and bulkheads reduce vibration due to:
- engine vibration
- mechanical equipment
- propeller turbulence and cavitation (surprisingly this can
be a major noise source)
- wave-slap, and
- foot fall on decks and stairs
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Resonac is particularly
effective in vibration-sensitive aluminium boats but is also
effective for other construction materials
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Engines should be mounted on flexible anti-vibration
mounts and any connecting pipework (i.e. intake, exhaust,
cooling water etc.) should have flexible anti-vibration couplings,
For best results, a flexible coupling is required in the propeller
shaft.
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