Introduction to Acoustics

Gypsum board
partition
(as scheduled)
Duct
Minimum 10cm
Short duct
section
Duct
Before the final ducts
are connected, fill gap
between the gypsum
board and duct with
fibrous material and
seal with caulk
During the erection
of the wall, install
short sections of duct
to use for sealing the
partition. After the
partition is sealed
and finished, connect
the final ductwork
Duct
Duct
Short duct
section
During the
partition
construction,
close smaller
gaps between
the short duct
sections with
two layers of
GWB on each
side of the
wall with
insulation
in the cavity
Fig. 11.52 Cross section of sealed multiple duct penetrations
in a partition
shows an effective design to reduce the transfer of
vibrations between the piping and the floor using neoprene
pads and spring hangers. Note that any spring
hangers must be appropriately sized for each situation.
When lateral restraints are required for large equipment,
Fig. 11.59 offers a general design for effective
vibration isolation.
Enclosures for Floor-Based Equipment
When barriers and source treatments do not provide
enough noise control, the only practical noise control
option for many floor-based units may be a full enclosure.
Key issues for enclosures of HVAC equipment are
access (for maintenance) and ventilation. A practical
design for indoor environments is shown in Fig. 11.60,
in which a heavy curtain system (which can be drawn
along tracks for access) surrounds the equipment. There
are hoods built into the sliding curtains to provide the
necessary ventilation for the equipment.
Exterior enclosures are discussed in Sect. 11.5.5 below.
Building Acoustics 11.5 Noise Control Methods for Building Systems 415
a)
b)
5cm glass
fiber
insulation
cover with
2.5cm thick
dense plaster
or 2 layers of
1.58 cm thick
gypsum
board with
all joints
staggered
and sealed
air tight
(2/3)L
min.
Silencer Duct
Angled channel as needed
to support enclosure material
1.2cm space all around, packed with
fibrous material. Seal at least one side
with permanently resilient sealant
Silencer
L
Duct
1.2cm space all around,
packed with fibrous material.
Seal at least one side with
permanently resilient sealant
Fig. 11.53a,b Cross section of a duct penetration with
appropriate silencer locations. (a) preferred location; (b) alternate
location
Fig. 11.54 A properly mounted spring isolator
11.5.3 Plumbing Systems
As for HVAC systems, the most common plumbingsystem
noise issues are related to reducing flow
turbulence and vibration isolation. For plumbing sys-
Part C 11.5