"Technology in Architecture Lecture 18 Noise Reduction by Absorption Sound Paths Sound Isolation Noise Reduction by Absorption Noise Reduction by Absorption Incr"
Technology in Architecture Lecture 18 Noise Reduction by Absorption Sound Paths Sound Isolation Noise Reduction by Absorption Noise Reduction by Absorption Increased absorption reduces ambient noise S: p. 771, F.18.2 Noise Reduction 69 db by Absorption Reverberation increases ambient sound levels S: p. 798 F.19.1 Sound Paths Sound Paths Air-Borne Sound Structure-Borne Sound S: p. 806, F.19.10 Sound Transmission Barriers reduce sound transmission to reduce noise intrusion S: p. 807, F.19.11 Air-Borne Sound Transmission Loss (TL): sound energy lost through a construction assembly S: 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) S: 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 S: 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 Isolation 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 S: 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. S: p.1712, Index K.1 Sound Transmission Class Wall assembly description 2x4 stud with gyp. bd. S: p. 1716, Table K.3 Sound Transmission Class Wall assembly selection TL data 2x4 stud with gyp. bd. S: p. 1713, Index K.2 Sound Transmission Class Floor assembly follows same process S: 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. S: p. 759, F.17.17 Noise Criteria Noise Criteria for various applications S: p.831, T.19.8 Room Criteria Room Criteria (RC(x)): accepted noise level for a given space. Defined for NC frequencies plus extremely low frequencies (~16 and 31.5 hz) Beginning to replace NC curves in practice Room Criteria Curves Room Criteria accepted noise level for a given space. S: p. 761, F.17.18