Fujitsu UTZ-BD035B Technical Manual page 33

 CONTROLLING NOISE
GENERATED FROM EQUIPMENT
AND AIR COURSES ABOVE
CEILING AND UNDER ROOF
1. If noise control is deemed necessary as the unit is
utilized in a quiet place, the following points should be
carefully considered. (Otherwise, noise levels may rise.)
(1) Do not downgrade the duct diameters extremely.
(E.g., ø250 -> ø150, ø200 -> ø100)
(2) Do not bend aluminum flexible ducts extremely.
(Particularly, the bending immediately after the exit
opening of the unit body)
(3) Do not make unnecessary openings on the ceilings.
(4) Do not suspend the unit under members with insufficient
strength.
2. The following control measures may be taken.
(1) Ceiling materials should be of high sound insulation
quality (with large transmission losses)
<Note>
Specifically, low-frequency noises cannot be
significantly absorbed by certain ceiling materials.
(2) Apply additional sound-absorbing materials immediately
below the sound source.
(3) Cover the unit body entirely with sound insulation sheets.
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