Technology in Architecture Lecture 17 Noise Reduction by Absorption Sound Paths Sound Isolation Sound Privacy Structure Borne Sound

Noise Reduction by Absorption Increased absorption reduces ambient noise M: p. 771, F.18.2

Noise Reduction by Absorption 69 db Reverberation increases ambient sound levels M: p. 798 F.19.1

Sound Paths Air-Borne Sound Structure-Borne Sound M: p. 806, F.19.10

Sound Transmission Barriers reduce sound transmission to reduce noise intrusion M: p. 807, F.19.11

Air-Borne Sound Transmission Loss (TL): sound energy lost through a construction assembly M: p. 813, F.19.17

Noise Reduction Combined effect of TL and absorption NR=TL-10 Log (S/AR) NR: noise reduction (db) TL: transmission loss (db) M: area of barrier wall (ft2) AR: total absorption of receiving room (sabins, ft2)

Noise 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 Example Find TL500 TL500=35 db M: p. 813, F.19.17

Noise 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 Class Sound Transmission Class (STC): defines overall transmission loss across center band frequencies Barrier STC Descriptor/ Application Ranking 25 Poor/1 Space divider 30 Fair/2 Room divider 35 Very Good/4 Offices near quiet space 42-45 Excellent/5 Party walls 46-50 Total Privacy/6 Quiet next to noisy from M: p. 828. T.19.6

Sound 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 Class STC of a wall assembly 2x4 stud with gyp. Bd. M: p.1712, Index K.1

Sound Transmission Class Wall assembly description 2x4 stud with gyp. bd. M: p. 1716, Table K.3

Sound Transmission Class Wall assembly selection TL data 2x4 stud with gyp. bd. M: p. 1713, Index K.2

Sound Transmission Class Floor assembly follows same process M: p. 1724, Index L.1

Noise 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 Curves Accepted noise level for a given space. M: p. 759, F.17.17

Noise Criteria Noise Criteria for various applications M: p.831, T.19.8

Sound Privacy Privacy is affected by initial sound source, TL, NC and absorbtion Room A Room B SPL NC1 NC2 Privacy Maintained TL TL Privacy Violated Sectional View

Sound Privacy—Example 1 Room A: NC500=35 Room B: NC500=25 Room A Room B SPL=70 NC1=35 SPL=40 SPL=40 NC2=25 Privacy Maintained TL=30 TL=30 Privacy Violated Sectional View

Noise Criteria Curves Privacy is affected by background noise level NC 35 @ 500 hz Max SPL500=40 db M: p. 759, F.17.17

Sound Privacy—Example 1 Room A: NC500=35, SPL500 ≤ 40 db Room B: NC500=25, SPL500 ≤ 31 db Initial check based on TL alone Room A Room B SPL=70 NC1=35 SPL=40 SPL=40 NC2=25 Privacy Maintained TL=30 TL=30 Privacy Violated Sectional View

Sound 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) M: area of barrier wall (ft2) AR: total absorption of receiving room (sabins, ft2)

Sound Privacy—Example 1 For each frequency: If SPL-NR ≤ NCmax privacy achieved If SPL-NR > NCmax privacy violated

Sound Privacy Enhancement TL 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 M: p. 816, T.19.1

Sound Privacy Reduction Privacy is diminished by flanking noise, weaker STC constructions and/or gaps M: p. 825, F.19.34

Sound Privacy Privacy diminished by weaker STC constructions M: p. 817, F.19.22

Sound 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? M: p. 817, F.19.22

Sound 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] M: p. 817, F.19.22

Sound Privacy Privacy diminished by construction gaps M: p. 817, F.19.23

Sound 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? M: p. 817, F.19.23

Sound Privacy—Example 2 S1= 14400 in2 S2= 15 in2 S2/S1=15/14400=0.1% TL1=35 db TLC=29 db [fair-poor] M: p. 817, F.19.23

Sound Paths Structure-Borne Sound M: p. 806, F.19.10

Sound Transmission Reduction Impact Isolation Structural isolation Flexible connections Spring mounts Inertial dampening M: p. 845, F.19.47

Sound Transmission Reduction– Floors Sound Transmission Class (STC) Impact Isolation Class (IIC) M: p.1726, Index L.3

Impact Isolation Class—Enhancements Construction Tectonics M: p. 842, F.19.43

Impact Isolation Class—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 M: p. 843

Mechanical Isolation Moving parts (vibration sources) eliminated by mechanical isolation M: p. 851, F.19.54