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Technology in ArchitectureTechnology in ArchitectureTechnology in ArchitectureTechnology in Architecture
Lecture 17Noise Reduction by Absorption
Sound PathsSound IsolationSound Privacy
Structure Borne Sound
Lecture 17Noise Reduction by Absorption
Sound PathsSound IsolationSound Privacy
Structure Borne Sound
Noise Reduction by Noise Reduction by AbsorptionAbsorption
Increased absorption reduces ambient noise
S: p. 771, F.18.2
Noise Reduction Noise Reduction by Absorptionby Absorption
Reverberation increases ambient sound levels
S: p. 798 F.19.1
69 db
Sound TransmissionSound Transmission
Barriers reduce sound transmission to reduce noise intrusion
S: p. 807, F.19.11
Air-Borne SoundAir-Borne Sound
Transmission Loss (TL): sound energy lost through a construction assembly
S: p. 813, F.19.17
Noise ReductionNoise Reduction
Combined effect of TL and absorption
NR=TL-10 Log (S/AR)
NR: noise reduction (db)TL: transmission loss (db)S: area of barrier wall (ft2)AR: total absorption of receiving room
(sabins, ft2)
Noise Reduction ExampleNoise Reduction Example
What is the noise reduction at 500 hz between two rooms separated by a 2x4 stud wall with ½” gyp. bd. on each side.
Receiving room absorption: 450 sabins, ft2
Separation wall: 10’ x 20’
Noise Reduction ExampleNoise Reduction Example
Find NR500
NR500=TL500-10 Log (S/AR)
=35-10 Log (200/450) =35-10 Log (0.444) =35-10(-0.35) =35+3.5=38.5 say 39db
Sound Transmission ClassSound Transmission Class
Sound Transmission Class (STC): defines overall transmission loss across center band frequencies
Barrier STC Descriptor/ ApplicationRanking
25 Poor/1 Space divider30 Fair/2 Room divider35 Very Good/4 Offices near quiet space42-45 Excellent/5 Party walls46-50 Total Privacy/6 Quiet next to noisy
from S: p. 828. T.19.6
Sound Transmission ClassSound Transmission Class
STC can be compromised by:
Combination with lesser sound barriers
Gaps in construction
“An air path is a good sound path”
Sound Transmission ClassSound Transmission Class
STC of a wall assembly
2x4 stud with gyp. Bd.
S: p.1712, Index K.1
Sound Sound Transmission Transmission ClassClass
Wall assembly description
2x4 stud with gyp. bd.
S: p. 1716, Table K.3
Sound Transmission ClassSound Transmission Class
Wall assembly selection TL data
2x4 stud with gyp. bd.
S: p. 1713, Index K.2
Sound Transmission ClassSound Transmission Class
Floor assembly follows same process
S: p. 1724, Index L.1
Noise CriteriaNoise Criteria
Noise Criteria (NC): accepted noise level for a given space.
Defined for center band frequencies
62.5 125 250 500 1000 2000 4000
Noise Criteria CurvesNoise Criteria Curves
Accepted noise level for a given space.
S: p. 759, F.17.17
Sound PrivacySound PrivacyPrivacy is affected by initial sound source, TL, NC and absorbtion
Privacy Maintained Privacy Violated
NC2
SPL
NC1
TL TL
Room A Room B
Sectional View
Sound Privacy—Example 1Sound Privacy—Example 1
Room A: NC500=35
Room B: NC500=25
Privacy Maintained Privacy Violated
NC2=25
SPL=70
NC1=35
TL=30 TL=30
Room A Room B
Sectional View
SPL=40SPL=40
Noise Criteria CurvesNoise Criteria Curves
Privacy is affected by background noise level
NC 35 @ 500 hz
Max SPL500=40 db
S: p. 759, F.17.17
Sound Privacy—Example 1Sound Privacy—Example 1
Room A: NC500=35, SPL500 ≤ 40 db
Room B: NC500=25, SPL500 ≤ 31 db
Initial check based on TL alone
Privacy Maintained Privacy Violated
NC2=25
SPL=70
NC1=35
TL=30 TL=30
Room A Room B
Sectional View
SPL=40SPL=40
Sound Privacy—Example 1Sound Privacy—Example 1
Combine effect of TL and absorption for final analysis
NR=TL-10 Log (S/AR)
NR: noise reduction (db)TL: transmission loss (db)S: area of barrier wall (ft2)AR: total absorption of receiving room (sabins, ft2)
Sound Privacy—Example 1Sound Privacy—Example 1
For each frequency:
If SPL-NR ≤ NCmax privacy achieved
If SPL-NR > NCmax privacy violated
Sound Privacy EnhancementSound Privacy EnhancementTL data can be enhanced by standard enhancements
Wood stud wall (STC 35) Add gyp bd to one side +2 db Add gyp bd to both sides +4 db Double thickness insulation +6 db Staggered studs +9 db Double studs +13 db
from S: p. 816, T.19.1
Sound Privacy ReductionSound Privacy Reduction
Privacy is diminished by flanking noise, weaker STC constructions and/or gaps
S: p. 825, F.19.34
Sound Privacy—Example 1Sound Privacy—Example 1
A 100 ft2 wall assembly has TL=50 [excellent]
What is the overall TL if a 20 ft2 door with TL=20 is part of the wall?
S: p. 817, F.19.22
Sound Privacy—Example 1Sound Privacy—Example 1
S1= 100 ft2 S2= 20 ft2
S2/S1=20/100=20%
TL1-TL2=50-20=30 db
TL1-TLC=23
TLC=TL1-23=27 db
[fair-poor] S: p. 817, F.19.22
Sound Privacy—Example 2Sound Privacy—Example 2
A 10x10 (100 ft2) wall assembly has TL=35[very good]
What is the overall TL if a 1/16” gap exists along each vertical edge?
S: p. 817, F.19.23
Sound Privacy—Example 2Sound Privacy—Example 2
S1= 14400 in2 S2= 15 in2
S2/S1=15/14400=0.1%
TL1=35 db
TLC=29 db
[fair-poor] S: p. 817, F.19.23
Sound Transmission Sound Transmission ReductionReduction
Impact Isolation
Structural isolation
Flexible connections
Spring mounts
Inertial dampening
S: p. 845, F.19.47
Sound TransmissionSound TransmissionReduction– Floors Reduction– Floors Sound Transmission Class (STC)
Impact Isolation Class (IIC)
S: p.1726, Index L.3
Impact Isolation Class—Impact Isolation Class—Enhancements Enhancements
Construction Tectonics
S: p. 842, F.19.43
Impact Isolation Class—Impact Isolation Class—Enhancements Enhancements
Resilient Floor Finishes: 1/16” vinyl tile 0 db 1/8” linoleum or rubber tile 4 +/- 1 db ¼” cork tile 10 +/- 2 db Low pile carpet on fiber pad 12 +/- 2 db Low pile carpet on fiber pad 18 +/- 3 db High pile carpet on foam pad 24 +/- 3 db
from S: p. 843
Mechanical IsolationMechanical Isolation
Moving parts (vibration sources) eliminated by mechanical isolation
S: p. 851, F.19.54