NOISE PATHS IN OFFICES

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NOISE PATHS IN OFFICES
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ACOUSTIC DESIGN CRITERIA
Permissible Background Noise Levels
Optimum Reverberation Time
Permissible Levels of Structural Vibration
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Permissible Background Noise Levels
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Permissible Background Noise Levels
External Background Noise Level Determinants
1. Design location i.e. airports proximity,
highways, light/heavy industries. 2. Plant
room reflections. 3. Existing plant and equipment
noise. 4. Future planned projects.
Internal Background Noise Level Determinants
1. M E Services 2. Office Equipment 3.
People 4. Lifts 5. Plant Equipment
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Background Noise Criteria
NR Curves and Table
Recommended Levels
Boardroom, Large Conference Room
NR 25 - 30 Small Conference Room, Executive
Office, Reception Room NR
30 - 35 Open Plan Office
NR 35 Drawing Office, Computer Suite
NR 35 - 45
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DUCTWORK LAYOUTS TO REDUCE CROSSTALK
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MAXIMUM DUCT VELOCITIES TO ACHIEVE NC DESIGN
LEVELS
These figures are only intended as a guide. The
position of the duct relative to the conditioned
space, and the geometry of fittings etc will
determine whether the velocity can be increase or
reduced.
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DUCT LINING SOUND ATTENUATION PER 10FT A
Typical high density foam and medium density
fibreglass duct lining
Frequency Hz
Product 108Kg/m3 Foam 24Kg/m3 Fibreglass 108Kg/m3
Foam 108Kg/m3 Foam 24Kg/m3 Fibreglass
Duct Size 900 x 600 610 x 610 450 x 600 300 x
600 203 x 305
Thickness 25mm 25mm 25mm 25mm 25mm
125 1 3 1 2 8
250 3 5 3 4 10
500 9 12 10 12 19
1000 33 24 43 46 32
2000 21 21 25 37 53
4000 22 17 27 35 37
Frequency Hz
Product 108Kg/m3 Foam 32Kg/m3 Fibreglass 32Kg/m3
Fibreglass
Duct Size 900 x 600 610 x 610 203 x 305
Thickness 12mm 12mm 12mm
125 1 1 4
250 2 2 5
500 5 6 10
1000 11 12 18
2000 16 20 42
4000 14 18 46
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MEASUREMENT OF SOUND REDUCTION INDEX (Rw) IN THE
LABORATORY
Vibration break
Receiving room
2
Source room
Test partition
1
3
Loud speakers
Microphones
4
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HIGH PERFORMANCE LIGHT WEIGHT PARTITION SYSTEMS
Studs 70mm width _at_ 600mm centres. Facings One
layer 12.5mm Lafarge Standard Wallboard both
sides No insulation
As above with 67mm Wilhams Mineral Bonded Slabs
Type MF 100
Studs 70mm width _at_ 600mm centres. Facings Two
layer of 15mm Lafarge sound resisting Wallboard
both sides Insulation 67mm Wilhams Mineral Bonded
Slabs Type MF 100
Studs 70mm width _at_ 600mm centres. Facings Two
layer of 15mm Lafarge sound resisting Wallboard
one side. Other side two layers of 15mm sound
resisting Wallboard fixed to resilient
bar Insulation 67mm Wilhams Mineral Bonded Slabs
Type MF 100
Studs 146mm width _at_ 600mm centres. Facings One
layer of 15mm Lafarge Firecheck Wallboard both
sides Insulation 2 layers of 67mm Wilhams Mineral
Bonded Slabs Type MF 100
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TYPICAL CEILING VOID BARRIER
Concrete buildings floor section
Service pipe
H V duct
Material clamping strip
Suspended ceiling system
Service pipe
Office partition system
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TYPICAL ACOUSTIC DOOR TECHNICAL SPECIFICATION
Rw 48(dB) Steel Side Hung Hinged Single Leaf
Door Set Sound Insulation Values
1/3 Oct Band Frequency Hz 100 125 160 200 250 315
400 500 630 800 1000 1250 1600 2000 2500 3150
SRI dB 35.8 39.8 42 42.9 39.6 42.1 42.8 44.1 47.
2 48.3 48.8 48.6 49 51.4 52.4 51.7
60
50
40
Sound Reduction Index dB
30
20
10
0
250
100
125
160
200
315
400
500
630
800
1000
1600
1250
2500
3150
2000
1/3 Octave Band Centre Frequency Hz
RM. Mean value of the reduction figure over
frequency spectra tested Ia. laboratory
45 48
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SOUND POWER LEVELS OF SPEECH AND OFFICE EQUIPMENT
90
A - 2 tabulators or 4 teletype machines
80
70
B 4 typewriters
Sound power level Lw, (re dB 10 -12w)
60
C Loud as possible without strain
50
D Raised
Male voice
E Normal
40
63
125
250
500
1000
2000
4000
8000
Frequency Hz
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TYPICAL ACOUSTICS SOLUTIONS
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TYPICAL ACOUSTICS SOLUTIONS
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TYPICAL ACOUSTICS SOLUTIONS
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PARTITION SRI LOSS EXAMPLE - ROOM WALL
A 1mm door gap creates 13dB loss of insulation
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Optimum Reverberation Time
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Optimum Reverberation Time
Reverberation time within an office governs the
clarity of speech. An ideal design level should
have an average reverberation time of 0.3 - 0.5
seconds for an open plan office.
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REVERBERATION TIMES
1.0
0.8
Standard office
0.6
Mid-frequency reverberation time (s)
Open plan offices
0.4
Conference rooms Lecture theatres Executive
offices
0.2
0
50
100
500
10000
1000
5000
Room volume( m3 )
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TYPICAL REVERBERATION SOLUTIONS
Sound Absorptive Ceilings
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TYPICAL REVERBERATION SOLUTIONS
Sound Absorptive Walls
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Permissible Levels of Structural Vibration
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Permissible Levels of Structural Vibration
Any vibration in the range of 5Hz should be below
0.1mm and 0.001mm at 50Hz to be imperceptible.
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HUMAN SENSITIVITY TO VIBRATION
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TYPICAL VIBRATION SOLUTIONS
Floating Floor
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TYPICAL VIBRATION SOLUTIONS
Floating Wall
Floating Ceiling
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FLANKING PATHS BETWEEN ROOMS