Noise Control - Fujitsu UTZ-BD035B Technical Manual

4-4-7. NOISE CONTROL

 CONTROLLING NOISE FROM
EXHAUST/INTAKE OPENING
1. The following components are recommended for a
ceiling-mounted unit.
(1) Noise-reduction duct —— Glass-wool duct
(2) Noise-reducing intake/exhaust duct
2. The following option is available for cases in which
the noise reduction measures in "1" above are still
insufficient, or in the case of the ceiling-suspension type.
(1) Highly efficient sound-absorption materials are used
for the interior cover materials.
3. When the airflow sound is generated at the exhaust/
intake opening in the ceiling-mounted type, the following
options are available, as the sound absorption effects
are higher in ducts with smaller diameters.
(1) Branched ducts (the airflow rates at the exhaust/
intake opening are reduced by dividing the flow)
(2) One-rank lower multiple noise-reduction ducts (with
smaller diameters) should be used.
│
└ — Noise-reduction flexible duct
- (01-29) -
 EFFECTS OF NOISE CONTROL
MEASURES
Points
1. The noise-reduction duct (not less than 2m) should
always be used at the exit of the unit on the internal
supply side.
2. Spiral ducts (galvanized steel tubes) and aluminum
flexible ducts should not be connected to the unit exit
opening.
General Comparison of Effects
(1) Noise-reduction duct, installed
for 6m
Unit
Noise-reduct
ion duct
(6m)
Intake/Exhaust
Grill
(3) Noise-reduction duct on the
side of the intake/exhaust grill,
installed for 2m
Unit
Spiral Duct
(4m)
Noise-reduct
ion duct
(2m)
Intake/Exhaust
Grill
Catalog Level
Note: (1) The noise levels were measured at 1.5m below the intake/exhaust
grill.
(2) The noise figures are those converted to the level in an anechoic
chamber. In real settings, the levels will be raised due to echoes
and other effects (by about 5dB).
(1) Great Effects –
(4) Small Effects
(2) Noise-reduction duct on the
side of the unit, installed for 2m
Unit
Noise-reduct
ion duct
(2m)
Spiral Duct
(4m)
Intake/Exhaust
Grill
(4) Spiral duct, installed for 6m (no
noise-reduction measure)
Unit
Spiral Duct
(6m)
Intake/Exhaust
Grill