ASHRAE.HandBook_47-2007 SOUND AND VIBRATION CONTROL.pdf

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CHAPTER 47
SOUND AND VIBRATON CONTROL
Data Reliabiliy
47.1 Health E/lecis o1acoustical Materials
47
SOUND GENLRA1ON AND CONTROL
47.1 IBRATION ISOLATION AND CONIROL
Acoustical Desion OHAC Svstems
Tainment libration
47.38
Basic Acoustical Design Technique
472 Fibration Criteria
47.38
Source Sound Levels
47.3 Snecilication o/ Libration Isolators
47.39
Bath Noise Estimationand.
47.12 temma ersus External olation
47.43
17. 20 Isolation vibrtion and Noise in Pining
Receiver Room Sound Correction
Lor Outdoor Equipment
47. 26 Seismic Protection
..47.46
Lime Hood Duct Design
47.27 Libration Investigations
47.46
Mechanical linment Room Sound solation
47.28 ROUBLLSHOOTNG
47.46
P,.
47.30De
47.46
47.35 Determinin Prblem i
47.46
H
VAC cquipmcnt is onc of thc major sources of noisc in a build
DATA RIEILIABILMTY
ing, and its eflect on the interior ac
Data in this chaptcr comc both from consulting cxpcricncc and
the community. Thercfore, mcchanical cquipmcnt must bc sclcctcd. research Studies. Use caution when appl ying the data, especially
and cquipmcnt spaces designed, with an cmphasis on both thc in
tended uses of the equipment and the goal of providing acceptable
rcscarch. Although spccific unccrtaintics cannot be statcd for cach
sound levels in occupied spaces of the building in which the equip
data sct, thc sound Icvcls or attcnuation data arc probably within
mcnt is located and in thc community. Furthcrmorc, opcration of
HVAC cquipmcnt causcs vibrations that can propagate into occu-
greater variations may occur, especially in low frequency ranges
pied spaces. Vibration can create uncomfortable conditions for o
and particularly in the 63 Hz octave band. Specific data scts may
cupants, and often creates secondary noise sources (e.g, vibrating
havc a widc uncertainty rangc, but cxpcricncc suggests that, i[ donc
walls, floors, piping
corrcctly, systcm cstimates that combine data scts usually comparc
In this chaptcr, sound and noise arc used intcrchangcably, al
within about 5 db of mcasurcd lcvcls
though only unwanted sound is considered to be noise
The system concept of noise control is used throughout thi
SOUND GENERATION AND CONTROL
chaptcr: cach of thc componcnts is thought of as bcing related to thc
Ith-rcccivcr chain. The noisc-gcncrating mcchanism is thc
ACOUSTICAL DESIGN OF HVAC SYSTEMS
source of the sound, which travels from the source via a path, which
can be through the air(airborne )or through the structure(structure- and vibration sources, transmission paths, and rcccivcrs. Sourccs
borne)until il reaches thc car of the listcncr
Noisc propagates from the sources through the air distribution
arc the componcnts that cither gcncratc noise and vibration (c.
fans or pumps )or producc noisc when airflow passes through thcn
systems, through the structure, and through combination
(e.g, dampers or diffusers ). Paths are the routes by which the sound
paths, reaching the occupants. Components of the mechanical sys
through the air, over barriers, or along a ducted
tcm(cg, fans, dampers, diffusers, junctions )all may produce sound Rcccivers are usually t