HomeMy WebLinkAboutAVAGO TECHNOLOGIES BLDG. 4 WEST EXPANSION - MJA/FDP - FDP130006 - REPORTS - MAPS/GRAPHICS (3)Companies with noise mitigating barriers
Noise Barriers - Chillers
http://www.enoisecontrol.com/AiT Cooled Chiller Noise Control Case Studv.html
hHPI/www_acousbcalsolulions_m /silent-acreen-noise-system
http://www_atcosl corrVen-ca/Products-and-ServicesAndustrial-Noise-ControlMase-Barriers
3-Sided Barrier
Structural Bracing
Case Studies
General Design Guidelines
• The "line of sight" between the
source and receiver must be cut
off completely by the barrier.
• A barrier should be at least
5 times wider than it is high.
• The barrier should be built as
close as possible to either the
source or receiver.
Sound Absorption
• Sound absorbing material is
often used on the source side of
the barrier to reduce the buildup
of sound pressure level.
• Prevents sound reflection from
barrier surface.
• Improves overall acoustic
performance of barrier system.
Materials
• Useful materials include steel,
pre -cast concrete, wood and
composition boards.
• Steel panels are particularly
suitable for mechanical
equipment noise barriers (easy
to cut holes and openings for
pipes and duct penetrations).
Materials
• Barriers should be constructed
of solid, non -porous material.
• Minimum density of material
should be 20 kg/m2 (4 Ib/ft2).
• Sound transmission loss of
barrier material must be at least
10 dB higher than the barrier
attenuation.
Design Issues
• Materials to be Used
• Sound Absorption
• Equipment Accessibility
• Equipment Ventilation
• Structural Issues
• General Design Guidelines
Reflecting Surfaces
BUILDING
SOURC�
d
BARRIER TO RECEIVER
REFLECTIONS AROUND ENDS OF BARRIER
Reflecting Surfaces
TO RECEIVER
BARRIER TREES
REFLECTION FROM TREES OVER TOP OF BARRIER
Reflecting Surfaces
BUILDING
SOURCE TO RECEIVER
AIL
BARRIER
REFLECTION FROM WALL BEHIND BARRIER
Practical limitations
• Barrier attenuation is generally
limited to 10 to 15 d BA.
• There are usually practical limits
on barrier height and width.
• Sound flanking around barrier
edges.
• Reflections from near -by objects.
Attenuation Worksheet
Sound Barrier Attenuation Worksheet
Source: Return air intake louvre'
Receiver: Second floor bedroom window at 100 feet distance (30 m)
S/R distance - d (m)
106
S/Bdistance-Dsb rn
6
B/R distance - Dbr (m)_
100
Source height - Hs (m)
1 33
Receiver height - Hr (m)
_ 15
Barrier height - h (m)
36
PLD (m)
.. 2.9
Return fan discharge PWL (di) _ (
94
Adjustment for 2 similar fans (dBj _
3
Plenum attenuation (dB)
3
Directivity index on axis (dB) _
8
Distance attenuation (dB)
41
Receiver noise level -no barrier (dB)
61
Fresnel Number - N 1.058
Barrier attenuation (dB) 8
Receiver noise level - wlth farrier (d6),__ _ 53
125
250
500
1000
2000
4000
S000 dBA
94
92
92
94
94
90
86 99
3
3
3
3
3
3
3
3
3
3
3
3
3_
3
6
8
_ 8
8
8
8 8
41
41
41
41
41
41 41
61
59
_59
61
61
_ 57 53 66'
2.100
4.200
8.399
16.799
33.598
67.196 134.391
10
12
15
18
20
22 23
1511
471
44
43
41
35' 30 48]
Barrier Attenuation
• High frequencies are attenuated
more effectively than low
frequencies.
• The maximum theoretical limit
for barrier attenuation is 24 dB.
• The actual attenuation will
always be less due to practical
limitations.
RTION LOSS VALUES
FOR AN
IDEAL SOLID BARRIER
Insertion
Loss, dB
Path -Length
Octave Band Center Frequency, Hz
Difference, ft
31
63
125
250
500
1000 2000
4000
0.01
5
5
5
5
5
6 7
8
0.02
5
5
5
5
5
6 8
9
0.05
5
5
5
5
6
7 9
10
0.1
5
5
5
6
7
9 11
13
0.2
5
5
6
8
9
11 13
16
0.5
6
7
9
10
12
15 18
20
1.0
7
8
10
12
14
17 20
22
2.0
8
10
12
14
17
20 22
23
5.0
10
12
14
17
20
22 23
24
10.0
12
15
17
20
22
23 24
24
20.0
15
18
20
22
23
24 24
24
50.0
18
20
23
24
24
24 24
24
Path length Difference
B;g.1ft
SOITRCE
��1 ft.
9ft
pv104it
POSITION 2: PLD = A + - D = 2.8 ft
RECEIVER
Path length Difference
POSITION 1: PLD = A + - D = 1.1 ft
Path length Difference
• PLD is determined from basic
geometry.
• Affected by barrier height and
location.
• Also affected by source and
receiver heights.
• A larger PLD will result in higher
attenuation.
BarrierAttennation
• Based on mathematics involving
Fresnel integrals (borrowed from
optical diffraction theory).
• The theory agrees well with
measurements.
• Tables and graphs are available
for practical use.
Fundamental Issues
• How high does the barrier have
to be?
• How close should the barrier be
to the equipment?
• How much sound attenuation
will we get from the barrier?
Typical Noise Barrier Wall
Barrier Fundamentals
THE EFFECT OF A BARRIER ON SOUND WAVES
Barrier Fundamentals
• A sound barrier is a solid
structure that intercepts the
direct sound path from a
sound source to a receiver.
• It reduces the sound pressure
level within its shadow zone.
Topics
• Barrier Fundamentals
• Attenuation Calculations
• Practical Limitations
• Design Considerations
• Structural Issues
• Case Studies
Return to www.enoisecontrol.com
Noise Barriers
Outdoor Noise Barriers:
Design and Applications
Tom Paige, P.Eng.
Products Application Engineer
Kinetics Noise Control, Inc.
Mississauga, Ontario
tpaige@vibron.com