Mitsubishi Electric Lossnay series Technical Manual page 56

2) When supply air diffuser (and return grille) is the source of the
sound
Part 1
(A) If the main unit is separated from the supply air diffuser
(and return grille) as shown in Fig. 6, installing an a)
silencer box, b) silence duct or c) silence grille is
recommended.
(B) If sound is being emitted from the supply air diffuser (and
return grille), a) branch the flow as shown in Fig. 7,
b) add a grille to lower the flow velocity and add a
silencer duct to section b).
(If the length is the same, a silencer duct with a small
diameter is more effective.)
3) When supply air diffuser (and return grille) is the source of the
sound
Part 2
(A) If the main unit and supply air diffuser (and return grille)
are integrated as shown in Fig. 8, or if the measures
t a k e n i n 2 ) ( A ) a n d ( B ) a r e i n a d e q u a t e , a d d
s o u n d p ro o fi n g m a te r i a l t h a t h a s a h i g h s o u n d
absorbency as shown in Fig. 8 a).
This is not, however, very effective with direct sounds.
(B) Installing the sound source in the corner of the room as
shown in Fig. 8 b) is effective with sound emitted from
center of the room, but will be inadequate towards sound
emitted from corner of the room.
CHAPTER 4
Fig. 6 Sound from Supply Air Diffuser
Fig. 7 Countermeasure (Example)
Fig. 8 Additional Countermeasure (Example)
•
Characteristics
a) b) c)
a) b)
a) b)
U-47