Handbook of air conditioning and refrigeration / Shan K

Types of Silencer
SOUND CONTROL 19.13
Silencers can be classified into rectanguar, cylindrical, and sound-attenuating plenum according to
their configuration. A typical rectangular splitter silencer is shown in Fig. 19.2a. Inside the retangular
casing are a number of flat splitters, depending on the width of the silencer. These splitters direct
the airflow into small sound-attenuating passages. The splitter is made from an envelope containing
sound-attenuating material, such as fiberglass or mineral wool, with protected noneroding facing.
The thickness of a splitter is often between 1 and 4 in. (25 and 100 mm). Splitters often have a
round instead of a flat nose, to reduce their airflow resistance. A rectangular silencer is often connected
with retangular ducts or sometimes with rectangular fan intakes and discharges.
A cylindrical silencer has an outer cylindrical jacket and an inner concentric center body, as
shown in Fig. 19.2b. Both the cylindrical jacket and the center body contain sound-attenuating material
and noneroding facing. A cylindrical silencer is often used in conjunction with vane-axial fans
and in round duct systems.
A sound-attenuating plenum consists of several splitters in the form of two, three, or four
successive square elbows, shown in Fig. 19.3, filled with sound-absorbing material with noneroding
FIGURE 19.3 Sound-attenuating plenum.