Air duct design & noise reduction
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Chapter IX Air duct design & noise reduction
I. Air duct design and its effect on noise
(1) Noise of air conditioning system mainly consists of aerodynamic noise, mechanic noise
and electric current noise. Among them, aerodynamic noise makes main contribution.
(2) Noise reduction measures
Installation of air duct type air conditioner is system engineering. Noise reduction includes
that in indoor unit installation and that in air duct design and installation. Refer to introduction
of indoor unit installation for details of noise reduction in indoor unit installation. Air duct
design and noise reduction methods are described below:
Design air duct and air port air speed according to state codes and standards, “Product
installation and operation manual” and “Chunlan design code for home (commercial)
centralized air conditioning system”. Data in following tables can be referenced for design.
(These data may have slight deviations that do not affect functioning as design reference).
Table 1: Air speed in low speed air duct (m/s)
Permitted indoor noise dB
(
m/s)
Main duct air
speed
Branch duct air
speed
Fresh air entrance
25—35 3—4 ≤2
3
35—50 4—7 2—3
3.5
50—65 6—9 2—5 4—4.5
65—85 8—12 5—8
5
Table 2: Max. air delivery speed at lateral delivery louver port (m/s)
Building Max air delivery speed Building Max air delivery speed
Studio
1.5—2.5
Personal office
2.5—5.0
Residence
2.5—3.8
Personal office (no sound insulation)
4.0—6.3
Hotel room
2.5—3.8
Ordinary office
2.5—3.8
Theatre
2.5—3.8
Cinema
2.5—3.8
Hall
2.5—3.8
Department store 7.5
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