Buenos Aires – 5 to 9 September, 2016
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Acoustics for the 21 Century…
PROCEEDINGS of the 22nd International Congress on Acoustics
Challenges and Solutions in Acoustical Measurements and
Design: Paper ICA2016-50
The simplified method versus the detailed method of
calculating flanking sound transmission through walls
with linings
Jeffrey Mahn(a), Christoph Hoeller(b), David Quirt(c)
(a)
(b)
National Research Council Canada, Canada, jeffrey.mahn@nrc-cnrc.gc.ca
National Research Council Canada, Canada, christoph.hoeller@nrc-cnrc.gc.ca
(c)
JDQ Acoustics, Canada
Abstract
The simplified and detailed methods of calculating the apparent sound reduction index
according to the standard, ISO 15712 have often been claimed to result in similar values for the
weighted apparent sound reduction index. However, in extended studies on walls with linings at
the National Research Council Canada, it has been found that the simplified method to
calculate the flanking transmission through building elements with linings sometimes leads to
misleading results. An alternative method for calculating the flanking sound transmission
through walls with linings was proposed to ensure that the simplified method yields more
conservative results than the detailed method. To achieve the best possible estimate of the
sound insulation performance of buildings systems with linings, the detailed method should be
used.
Keywords: sound transmission; flanking; lining; concrete block
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22 International Congress on Acoustics, ICA 2016
Buenos Aires – 5 to 9 September, 2016
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Acoustics for the 21 Century…
The simplified method versus the detailed method of
calculating flanking sound transmission through walls
with linings
1 Introduction
The acoustic requirements for dwellings in Canada were recently updated with the publication of
the 2105 National Building Code of Canada (NBCC). The new acoustic requirements represent
a shift from the STC rating which is a laboratory based requirement to the Apparent Sound
Transmission Class (ASTC) which is a field based requirement. The 2015 NBCC allows for
three different methods of showing compliance with the acoustic requirements: field testing, the
use of the acceptable solutions found in Part 9 of the 2015 NBCC and the calculation of the
ASTC rating as detailed in the publication RR-331 Guide to Calculating Airborne Sound
Transmission in Buildings: 2nd Edition [1]. The calculation method described in the report, RR331 is based on the standards, ISO 15712 [2] and ISO 10848 [3], but written in terms of ASTM
metrics. The NBCC allows for the use of both the simplified and the detailed method for
calculating the ASTC rating.
The Canadian Concrete Masonry Producers Association (CCMPA) has funded a number of
studies for the calculation of the ASTC rating of constructions using concrete masonry walls.
The findings of the study are available in the report, RR-334 Apparent Sound Insulation in
Concrete Block Buildings [4]. Part 5 of the NBCC states that for a heavyweight wall or floor
assembly of concrete or masonry and connected flanking assemblies of concrete or masonry,
the ASTC rating shall be determined accordance with the simplified or detailed method
presented in ISO 15712-1. This paper details a study to calculate the changes in the STC
rating due to the use of linings on one side and on both sides of concrete block wall which are
required for the calculations using the simplified method.
2 The application of linings to concrete block walls
2.1
Changes due to the use of linings
It is common practice, especially in residential buildings, to add finishing surfaces to the basic
concrete masonry wall assemblies (for example, gypsum board wall and ceiling surfaces that
conceal both the bare concrete surfaces and building services such as electrical wiring, water
pipes and ventilation ducts). The finish commonly comprises gypsum board panels, framing
used to support them, and often sound absorptive material filling the inter-stud cavities between
the gypsum board and the face of the concrete blocks. These elements are described as linings
in this paper.
As part of this study, measurements of the sound transmission loss were made in accordance
with the ASTM E90 [5] and ASTM E413 [6] standards for bare concrete masonry walls, for
concrete masonry walls with linings installed on just one side of the wall and for concrete
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Acoustics for the 21 Century…
masonry walls with linings installed on both sides of the walls. An example of the
measurements using paint as a lining on 140 mm lightweight blocks (134 kg/m2) is shown in
Figure 1.
Figure 1: The transmission loss of a bare concrete block wall, the concrete block wall with paint
on one side and the concrete block wall with paint on both sides.
The figure shows that the addition of paint on one side improved the STC rating of the wall from
35 to 39. Painting the second side of the wall further improved the STC rating by an additional
two points. Of course, the improvements shown in the figure are not due to the paint itself, but
rather due to the paint sealing of sound leaks through the lightweight blocks. That is why
sealing the leaks on one side of the wall improved the STC rating by 4 STC points but painting
the other achieved a further improvement of only 2 STC points since most of the leaks were
sealed by the paint applied to the first side.
Another example is shown in Figure 2 for 140 mm lightweight blocks (134 kg/m2) with 16 mm
gypsum board on 38 mm wood furring installed on one side and on both sides of the wall.
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Acoustics for the 21 Century…
Figure 2: The transmission loss of a bare concrete block wall, the concrete block wall with 16 mm
gypsum board on 38 mm wood furring on one side and the concrete block wall with 16 mm
gypsum board on 38 mm wood furring on both sides.
The figure shows again that a large improvement in the STC rating was achieved by applying a
lining on one side of the concrete block wall. Adding the same lining on the second side
improved the STC further, but the improvement wasn’t as great as was achieved by applying
the lining to one side since adding the lining to one side also sealed the sound leaks.
2.2
Characterization of the changes due to the addition of linings
To characterize the change in the sound transmission loss due to adding a specific lining to a
concrete block wall, a single number rating was needed. Any sort of single number metric to
describe the changes in the STC rating due to the application of linings to the concrete block
walls would need to separate the change in the sound insulation due to sealing the air leaks
from the actual change due to the lining since calculations of the flanking transmission would
not include improvements due to sealing air leaks.
While Annex B of ISO 140-16 [7] defines the change due to the addition of linings as Δ𝑅𝑤 , an
equivalent ASTM rating does not exist. A new metric Δ𝑆𝑇𝐶 was created to describe the change
in the sound transmission loss due to adding a specific lining when using ASTM metrics. A
procedure was developed for the calculation of Δ𝑆𝑇𝐶 as detailed in Report RR-334. The
procedure is based in part on that of ISO 140-16 with the STC calculation substituted for the
ISO single number ratings and using Reference Curve B.1 from ISO 140-16 which is a smooth
sound transmission loss curve typical of a heavy wall of masonry. A schematic showing the
procedure for calculating Δ𝑆𝑇𝐶 is shown in Figure 3.
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Acoustics for the 21 Century…
Figure 3: Procedure for calculating ∆𝑺𝑻𝑪
The figure shows that the data needed for the calculation of the Δ𝑆𝑇𝐶 rating includes the STC
rating of the wall with the lining applied to one and to both sides. The final value is the lowest
value of Δ𝑆𝑇𝐶 due the lining applied on one side or the Δ𝑆𝑇𝐶 of the lining applied on both sides
divided by 1.5.
Examples of the calculation of the Δ𝑆𝑇𝐶 rating are shown in Table 1 for various linings. The
data in the table shows that the method of calculating the Δ𝑆𝑇𝐶 rating correctly shows an
improvement in the STC rating of 0 when the wall is painted. Not all of the linings improve the
STC ratings of the walls. Linings such as 13 mm gypsum board directly fixed to the concrete
block wall are shown negatively affect the STC rating of the wall.
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Acoustics for the 21 Century…
Table 1: ∆𝑺𝑻𝑪 values for different linings
(1-side lined) (2-sides lined)
ΔSTC1-side ΔSTC2-sides
Lining
ΔSTC
Paint/sealer covering the surface of the wall
0
0
0
13 mm gypsum board fastened to surface of blocks
-1
-4
-3
0
-1
-1
3
3
2
13 mm gypsum board fastened to 38x38 mm wood furring
1
-1
-1
2 x 13 mm gypsum board fastened to 38x38 mm wood furring
2
1
1
4
6
4
5
8
5
16 mm gypsum board fastened to 38x38 mm wood furring
1
-3
-2
16 mm gypsum board fastened to 38x38 mm wood furring with 38mm
thick glass fiber batts in cavities
4
3
2
13 mm gypsum board fastened to 41 mm steel studs
4
0
0
13 mm gypsum board fastened to 41 mm steel studs with 38mm
thick glass fiber batts in cavities
9
15
9
13 mm gypsum board fastened to 65 mm steel studs
7
3
2
19
33
19
22
43
22
21
39
21
13 mm gypsum board fastened to 22 mm metal furring channels
(“hat” profile)
13 mm gypsum board fastened to 22 mm metal furring channels with
38mm thick glass fiber batts in compressed in cavities
13 mm gypsum board fastened to 38x38 mm wood furring with 38mm
thick glass fiber batts in cavities
2 x 13 mm gypsum board fastened to 38x38 mm wood furring with
38mm thick glass fiber batts in cavities
13 mm gypsum board fastened to 65 mm steel studs with 65 mm
thick glass fiber batts in cavities
2 x 13 mm gypsum board fastened to 65 mm steel studs with 65 mm
thick glass fiber batts in cavities
16 mm gypsum board fastened to 65 mm steel studs with 65 mm
thick glass fiber batts in cavities
2.3
Calculation of the flanking STC rating
An example is given for the calculation of the flanking STC rating through a junction between
two concrete block walls as shown in Figure 4. The flanking STC ( 𝑆𝑇𝐶𝑖𝑗 ) is calculated
according to:
𝑆𝑇𝐶𝑖𝑗 =
𝑆𝑇𝐶𝑖
2
+
𝑆𝑇𝐶𝑗
2
+ 𝑚𝑎𝑥(Δ𝑆𝑇𝐶𝑖 , Δ𝑆𝑇𝐶𝑗 ) +
𝑚𝑖𝑛(Δ𝑆𝑇𝐶𝑖 ,Δ𝑆𝑇𝐶𝑗 )
2
+ 𝐾𝑖𝑗 + 10 log10 (𝑙
𝑆𝑠
𝑜 𝑙𝑖𝑗
)
(1)
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Acoustics for the 21 Century…
where 𝑆𝑇𝐶𝑖 is the STC rating of element 𝑖, Δ𝑆𝑇𝐶𝑖 is the change in the STC rating due to the
lining on element 𝑖, 𝐾𝑖𝑗 is the vibration reduction index along path 𝑖𝑗 and 𝑙𝑖𝑗 is the length of the
𝑆𝑠
)
𝑙𝑜 𝑙𝑖𝑗
junction between the elements. For this example, 𝐾𝑖𝑗 = 5.7 and 10 log10 (
F
= 7.
f
Figure 4: Example of a T-junction between two bare concrete block walls.
The flanking STC is calculated for paths Ff, Fd and Df in Table 2. For this example, the Δ𝑆𝑇𝐶
values are 0 since there are no linings.
Table 2: Calculation of the flanking STC for the bare concrete block walls
If linings of 13 mm gypsum board supported on 65 mm non-loadbearing steel studs spaced
610 mm on center with no absorptive material filling inter-stud cavities are then added to the
concrete block walls as shown in Figure 5, the flanking STC is calculated as shown in Table 3.
F
f
Figure 5: Example of a T-junction between two concrete block walls with linings.
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Acoustics for the 21 Century…
Table 3: Calculation of the flanking STC for the bare concrete block walls
The ∆𝑆𝑇𝐶 value used for the linings were taken from Table 1. The addition of the linings is
shown to improve the flanking STC of each of the transmission paths from 62 to 65.
2.4
Simplified versus detailed methods
The difference in the flanking transmission loss calculated using the simplified and the detailed
method was calculated according to ∆= 𝑆𝑖𝑚𝑝𝑙𝑓𝑖𝑒𝑑 − 𝐷𝑒𝑡𝑎𝑖𝑙𝑒𝑑 when different linings were
applied to concrete block walls. The value of ∆ was calculated using both the ∆𝑆𝑇𝐶 and the
∆𝑅𝑤 metrics when linings were attached to one side and to both sides of the concrete block
walls shown in Figure 4 and are compared in Figure 6.
10

5
1-sided ISO
2-sided ISO
1-sided NRC
2-sided NRC
0
-5
SS
65
_G
FB
SS
65
92
_2
_G
G1
FB
3
SS
92
_2
65
G1
_G
3
FB
SS
65
65
_G
_G
16
FB
SS
65
92
_G
_G
13
FB
SS
65
92
_
G1
_G
WF
3
FB
UR
92
38
_
G1
_G
3
FB
38
_G
13
BA
SE
SS
PA
41
_G
I NT
FB
38
_G
13
WF
G1
3
FC
UR
25
38
_G
_G
13
FB
SS
38
_2
92
G1
_G
3
FB
FC
38
25
_
G
_G
13
FB
38
WF
_G
UR
13
38
_2
WF
G1
WF
UR
3
UR
38
38
_G
_G
13
FB
38
_G
WF
16
UR
38
_G
16
SS
41
_G
13
SS
92
_G
13
SS
65
_G
13
-10
Figure 6: Difference between simplified and detailed calculation of the flanking STC for linings
applied to one and both sides of a concrete block wall. The figure is from Zeitler, et al. [8].
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Buenos Aires – 5 to 9 September, 2016
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Acoustics for the 21 Century…
The figure shows that in terms of the ∆𝑆𝑇𝐶 metric when the lining is applied on one side of the
wall, the simplified method tends to result in flanking STC values that are the same or up to 4
points lower than the detailed method. When the lining is applied to both sides of the wall, the
simplified method can result in values that are up to 6 points lower than the detailed method for
some linings, but can also over predict the flanking STC rating for other linings. However, the
using the ∆𝑆𝑇𝐶 metric results in significantly less over predictions using the simplified method
than when the ∆𝑅𝑤 metric is used since the ∆𝑅𝑤 metric does not take into account the sealing of
leaks in the walls due to the application of the lining
3 Conclusions
A new single number metric, ∆𝑆𝑇𝐶 has been developed for the calculation of the change in the
transmission loss of walls due to the application of linings. The ∆𝑆𝑇𝐶 metric differentiates
between the changes in the transmission loss of walls due to the blockage of leaks and due to
the improvements due to the linings. The ∆𝑆𝑇𝐶 metric has been shown to result in more
conservative estimates of the flanking STC ratings than the use of the ∆𝑅𝑤 metric as compared
to calculations using the detailed method. However, to achieve the best possible estimate of
the sound insulation performance of buildings systems with linings, the detailed method should
be used.
Acknowledgments
This work was sponsored by Canadian Concrete Masonry Producers Association (CCMPA) and
the National Research Council Canada.
References
[1] Zeitler B, Quirt D, Hoeller C, Mahn J, Schoenwald S, Sabourin I. Guide to Calculating Airborne
Sound Transmission in Buildings: 2nd Edition. Ottawa, Canada: National Research Council Canada;
2016.
[2] ISO 15712-1:2005 -- Building acoustics -- Estimation of acoustic performance of buildings from the
performance of elements -- Part 1: Airborne sound insulation between rooms. Geneva, Switzerland:
International Standards Organization; 2005.
[3] ISO 10848-2:2006 -- Acoustics -- Laboratory measurement of the flanking transmission of airborne
and impact sound between adjoining rooms -- Part 2: Application to light elements when the junction
has a small influence. Geneva, Switzerland: International Standards Organization; 2006.
[4] Zeitler B, Quirt D, Schoenwald S, Mahn J. Apparent Sound Insulation in Concrete Block Buildings.
Ottawa, Canada: National Research Council Canada; 2015.
[5] ASTM E90-09, Standard Test Method for Laboratory Measurement of Airborne Sound Transmission
Loss of Building Partitions and Elements. West Conshohocken, PA: ASTM International; 2009.
[6] ASTM E413 - 10, Classification for Rating Sound Insulation. West Conshohocken, PA: ASTM
International; 2010.
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[7] ISO 140-16:2006 -- Acoustics -- Measurement of sound insulation in buildings and of building
elements -- Part 16: Laboratory measurement of the sound reduction index improvement by
additional lining. Geneva, Switzerland: International Standards Organization; 2006.
[8] Zeitler B, Mahn J, Quirt D. Comparison of the Detailed and Simplified Methods to Calculate the
Apparent Sound Transmission Class for the Proposed 2015 National Building Code of Canada.
Proceedings of InterNoise 2015, San Francisco, USA: 2015.
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