Sound Transmission Loss Revisited: Insulation, Privacy, and Wall Construction

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Sound Transmission Loss Revisited Insulation,
Privacy, and Wall Construction

• Architectural Acoustics II
• January 24, 2008

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Transmission Loss

• Transmission loss is a measure of the reduction
  in energy experienced by sound as it passes
  through a barrier or partition
• t Sound (Energy) Transmission Coefficient
• Transmission loss
• What happens to TL when t 0? t 1?

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Factors Affecting Transmission Loss

• Frequency
• TL typically increases as frequency increases
• Mass
• TL typically increases as the mass of the
  partition increases
• Stiffness
• TL typically decreases as the stiffness of the
  partition increases
• Damping
• TL typically increases as the damping in the
  partition increases
• Other
• If the partition has multiple layers (leaves),
  the properties of the cavities between the layers
  affect TL. More shortly.

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Typical TL Measurement Setup
Source and receiving rooms are typically
reverberation chambers to insure random incidence
on the test panel, and to prevent
position-dependent measurement results.
Mic. on a rotating boom
TL SPLSrc. Room SPLRec. Room
10log10(S/A) S surface area of panel, A
absorption in rec. room
MJR Figure 5.15, p. 101, modified
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Sound Transmission Class (STC)

• Measure TL in 1/3-octave bands
• Compare to reference contour
• Look at the deficiencies bands for which TL is
  less than the reference contour
• Move the reference contour up until sum of def.
  32 or max. def gt 8
• STC value of the reference contour at 500 Hz
• Not always a useful quantifier
• No info about frequency or size of deficiencies
• Limited to 125 4k Hz

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Sound Transmission Class (STC)

• Variations
• FSTC Field STC
• Noise Isolation Class (NIC)
• Less stringent, good for field measurements where
  rules about flanking, absorption, RT, etc. cannot
  be met or cannot be confirmed

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Sound Transmission Class
Matlab Demo
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Subjective Perception of STC Values
STC FSTC Effect/Result
30 22 25 Most sentences clearly understood.
40 32 35 Speech can be heard with some effort. Individual words and occasional phrases heard.
50 42 45 Loud speech can be heard with some effort. Music easily heard.
60 52 55 Loud speech essentially inaudible. Music heard faintly bass disturbing.
70 62 65 Loud music heard faintly.
75 67 Most sounds effectively inaudible.
MJR Table 6.1 p. 116.
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Subjective Perception of STC Values
STC FSTC Effect/Result

45 40 Raised voice plainly audible, normal voice not audible
50 45 Raised voice not audible
60 55 Shouting plainly audible, loud voice audible
70 65 Very loud music understandable, no unamplified voice audible.
80 75 Very loud music audible.
Long, Table 15.2 p. 512
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TL/STC Data

• Books
• MJR Appendix J
• Architectural Acoustics by Egan, pp. 204 205
• Manufacturers
• US Gypsum (various GWB wall constructions)
• http//www.usg.com/USG_Marketing_Content/usg.com/w
  eb_files/Documents/System_Catalogs/SA200.pdf
• Saflex (windows)
• http//www.saflex.com/pdf/en/archi/Saflex_Acoustic
  al_Guide.pdf
• Canadian National Research Council
• Gypsum Board Walls Transmission Loss Data
  http//irc.nrc-cnrc.gc.ca/pubs/fulltext
  /ir761/ir761.pdf
• Laboratory Measurements of the Sound Insulation
  of Building Façade Elements
  http//irc.nrc-cnrc.gc.ca/pubs/i
  r/ir818/ir818.pdf

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TL/STC Data

• Articles
• Kurra, S., Arditi, D., Determination of Sound
  Transmission Loss of Multilayered Elements Part
  1 Predicted and measured results,Acta Acustica
  united with Acustica, Volume 87, Number 5,
  September/October 2001 , pp. 582-591.
• Kurra, S., Arditi, D., Determination of Sound
  Transmission Loss of Multilayered Elements Part
  2 An experimental study,Acta Acustica united
  with Acustica, Volume 87, Number 5,
  September/October 2001 , pp. 592-603.
• See also JASA, Applied Acoustics, etc.

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Measurement Repeatability
Halliwell, R.E. Nightingale, T.R.T. Warnock,
A.C.C. Birta, J.A. Gypsum Board Walls
Transmission Loss Data, Internal Report,
Institute for Research in Construction, National
Research Council Canada, 761, pp. 368, March 01,
1998
13
Measurement Repeatability
Halliwell, R.E. Nightingale, T.R.T. Warnock,
A.C.C. Birta, J.A. Gypsum Board Walls
Transmission Loss Data, Internal Report,
Institute for Research in Construction, National
Research Council Canada, 761, pp. 368, March 01,
1998
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The Devil is in the Details
Halliwell, R.E. Nightingale, T.R.T. Warnock,
A.C.C. Birta, J.A. Gypsum Board Walls
Transmission Loss Data, Internal Report,
Institute for Research in Construction, National
Research Council Canada, 761, pp. 368, March 01,
1998
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Prediction

• Various computational methods
• Software WinFLAG
• Free trial version downloadable from
  http//www.winflag.com/

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Leaks and Flanking Paths

• Typical examples
• Under and around doors
• Above non-full-height partitions
• Through HVAC vents/ducts
• Remedies
• Doors should have seals on all four sides
• Partitions should be build up to the structural
  deck
• Ducts should be lined with absorption, should
  serve rooms in parallel not in series

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Flanking Paths
MJR Figure 5.22, p. 107
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Flanking Paths
MJR Figures 6.16 and 6.17, p. 131
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(No Transcript)
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Gypsum Board/Sheetrock Walls
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MJRs Gyp. Wall Details
MJR Fig. 6.11, p. 126
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Resilient Channel
MJR Fig. 6.10 p. 125
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Gyp. Partition
EMPAC Drawings
24
Gyp. Partition Detail at Floor
EMPAC Drawings
25
Gyp. Wall 1 Layer
EMPAC Drawings
26
Gyp. Wall 2 Layers
EMPAC Drawings
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Gyp. Wall 3 Layers
EMPAC Drawings
28
Gyp. Wall 4 Layers
EMPAC Drawings
29
Gyp. Wall 5 Layers
EMPAC Drawings
30
Cement Board Plus Rigid Insulation
EMPAC Drawings
31
Isolated Acoustical Partition
EMPAC Drawings
32
Typical Gyp. Head Detail
EMPAC Drawings
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Resilient Head Detail
EMPAC Drawings
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Resilient Base Detail
EMPAC Drawings
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Acoustical Partition at Floor
EMPAC Drawings
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Acoustical Partition at Ceiling
EMPAC Drawings
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Acoustical Partition at Ceiling
EMPAC Drawings
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Masonry (CMU) Walls
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Typical Solid Masonry Wall Constructions
EMPAC Drawings
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Hollow CMU Walls
EMPAC Drawings
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Masonry Cavity Wall
MJR Fig. 6.5 p. 121
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Typical CMU Head Detail
EMPAC Drawings
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Acoustical CMU Head Detail
EMPAC Drawings
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Combination Walls
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High STC CMU/Gyp. Wall
EMPAC Drawings
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STC Ratings for Various Walls
MJR Fig. 6.7 p. 123
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STC Ratings for Various Walls
MJR Fig. 6.7 p. 123
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Doors and Windows
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Door Seals
MJR Fig. 6.22, p 137
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Door Seals
MJR Fig. 6.22, p 137
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Door Frames
MJR Fig. 6.22, p 137
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High STC Window
MJR Fig. 6.22, p 137
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EMPAC Control-Room Window
EMPAC Drawings
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Box-in-Box Construction
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EMPAC Dimmer Room Construction
EMPAC Drawings
56
EMPAC B-in-B Examples
EMPAC Drawings
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EMPAC B-in-B Examples
EMPAC Drawings