INTERNATIONAL IS0
STANDARD 11654
First edition
1997-04-O 1
Acoustics - Sound absorbers for use in
buildings - Rating of sound absorption
Acousticye - Absorban ts pour I utilisation dans /es 62 timen ts -
evaluation de /‘absorption acoustique
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ISO 11654:1997
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Reference number
IS0 11654: 1997(E)
IS0 11654: 1997(E)
Contents Page
1 Scope . .. .. .. ... .. .. .. .. .. .. .. . .. .. . ... . ... .. .... . ... .. .. .. .. .. .. .. .. .. .. .. ... .. .. ... .. .. .. .. . 1
2 Normative references . .. . .. .. .. .. .. ... ... .. .. .. .. .. ... . ... .. . ... . ... .. .. ... .. .. ... . .. 1
3 Definitions . .. .. .. .. .. .. .. .. . .. .. .. . .. .. .. ... .. ... .. ... . ... . ... .. .. .. .. .. .. .. ... .. .. ... .. .. .. 2
4 Calculation .. .. .. .. .. .. . ... . .. . .. ...~....................................................... 2
5 Presentation of results .. .. . .. .. .. .. ... ... .. .. ... . .. .. .. ... . ... .. .. .. .. .. ... .. ... . ... . 3
Annexes
A Examples of calculations of a, with and without a shape
indicator .. .. .. .. .. .. .. . .. .. .. . .. .. . .. .. .. ... .. ... .. .. ... .. .. .. .. .. .. . ... .. .. .. .. ... .. .. .. ... . 5
B Classification of sound absorbers . ... . ... .. .. .. .. .. ... . .. .. .. ... .. .. ... .. .. .. .. 6
C Example of a standardized diagram for as values . ... .. ... .. .. .. .. .. . 7
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0 IS0 1997
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@ IS0 IS0 11654:1997(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide
federation of national standards bodies (IS0 member bodies). The work of
preparing International Standards is normally carried out through IS0
technical committees. Each member body interested in a subject for which
a technical committee has been established has the right to be represented
on that committee. International organizations, governmental and non-
governmental, in liaison with ISO, also take part in the work. IS0
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
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International Standard IS0 11654 was prepared by Technical Committee
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ISO/TC 43, Acoustics, Subcommittee SC 2, Building acoustics.
Annexes A,
ISOB 11654:1997
and C of this International Standard are for information only.
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INTERNATIONAL STANDARD @Iso IS0 11654: 1997(E)
Acoustics - Sound absorbers for use in buildings -
Rating of sound absorption
1 Scope
1.1 This International Standard specifies a method by which the frequency-dependent values of the sound
absorption coefficient can be converted into a single number. Before this is done, the one-third-octave band values
of the sound absorption coefficient measured in accordance with IS0 354 are converted into octave bands.
In annex B a classification method, based on these single numbers, is given for information.
1.2 The single-number rating specified in this International Standard can be used to formulate requirements and to
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describe acoustical properties of sound-absorbing products to be used for routine applications in normal offices,
corridors, class rooms, hospitals, etc. The rating is not appropriate when the products are to be used in qualified
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environments requiring careful acoustical design by expertise. In such cases, only complete sound absorption data
as a function of frequency are satisfactory.
This International Standard is not applicable unless ISO 11654:1997
the applications cover the whole frequency range of the
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reference curve. If only a part of this range is of interest, it may be more appropriate to look for products with a good
sound absorption within this range only. The137a53bc0f33/iso-11654-1997
shape indicators described in this International Standard give some
guidance in identifying such products which may have a relatively low single number but a much higher potential if a
more restricted frequency range is considered. Such products should be judged from the complete sound
absorption curve.
As the rating curve in this International Standard has as a lower limit the 250 Hz octave band, the rating is not
appropriate below this frequency. If such low frequencies are of interest, reference must be made to the complete
sound absorption curve.
This International Standard is, in principle, applicable to all building products for which the sound absorption
coefficient has been determined in accordance with IS0 354. It is, however, often not suitable for application to
single items, such as chairs, baffles, etc., nor is it applicable to road barriers and road surfaces.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this
International Standard. At the time of publication, the editions indicated were valid. All standards are subject to
revision, and parties to agreements based on this International Standard are encouraged to investigate the
possibility of applying the most recent editions of the standards indicated below. Members of IEC and IS0 maintain
registers of currently valid International Standards.
IS0 354:1985, Acoustics - Measurement of sound absorption in a reverberation room.
IS0 354:1985/Amd. 1:--I), Annex D: Test specimen mountings for sound absorption tests.
1) To be published.
IS0 11654: 1997(E) @ IS0
3 Definitions
For the purposes of this International Standard, the following definitions apply.
3.1 practical sound absorption coefficient, aP: Frequency-dependent value of the sound absorption coefficient
which is based on measurements on one-third-octave bands in accordance with IS0 354 and which is calculated in
octave bands in accordance with this International Standard.
NOTE - For the value in the jth octave band, the notation api is used.
3.2 weighted sound absorption coefficient, a,: Single-number frequency-independent value which equals the
value of the reference curve at 500 Hz after shifting it as specified in this International Standard.
3.3 shape indicators, L, M, H: Indication showing practical sound absorption coefficients exceeding those of the
shifted reference curve by 0,25 or more in different frequency ranges as specified in this International Standard.
NOTE - Negative deviations (values curve) are not considered as they are already maximized to 0,l in
the curve-shifting procedure.
4 Calculation
4.1 Practical sound absorption coefficient
Calculate the practical sound absorption coefficient, api, for each octave band i from the arithmetic mean value of
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the three one-third-octave sound absorption coefficients, ail, ai2, and ais within the octave:
Ccpi =
(%l + ai + %3) (standards.iteh.ai)
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ISO 11654:1997
The mean value is calculatedhttps://standards.iteh.ai/catalog/standards/sist/cf38f5fe-b915-452e-9a09-
to the second decimal and rounded in steps of 0,05 and maximized to aPi = 1 ,OO for
rounded mean values > 1 ,OO. 137a53bc0f33/iso-11654-1997
NOTE - X,Y~ is rounded to XJO and ~,y3 is rounded to x,y5. x,y7 is rounded to ~,y5 and X,Y~ is rounded to x,y + 0,l .
EXAMPLE
0,92 is rounded to 0,90.
4.2 Weighted sound absorption coefficient
Use the api values to calculate the weighted sound absorption coefficient a, from the reference curve shown in
figure 1. Shift the reference curve in steps of 0,05 towards the measured value until the sum of the unfavourable
deviations is less than or equal to 0,lO. An unfavourable deviation occurs at a particular frequency when the
measured value is less than the value of the reference curve. Only deviations in the unfavourable direction shall be
counted. The weighted sound absorption a, is defined as the value of the shifted reference curve at 500 Hz.
Examples of calculations of a, are given in annex A.
4.3 Shape indicators
Whenever a practi cal sound absorption coefficient api exceeds the value of the shi fted refe rence curve by 0,25 or
more, one or more shape indicators shal I be added in parentheses, to the a, value.
If the excess absorption occurs at 250 Hz, use the notation L. If the excess absorption occurs at 500 Hz or
1 000 Hz, use the notation M. If the excess absorption occurs at 2 000 Hz or 4 000 Hz, use the notation H.
2
@ IS0 IS0 11654: 1997(E)
NOTE - A shape indicator means that the sound absorption coefficient at one or more frequencies is considerably higher
than the values of the shifted reference curve and that the interested parties are encouraged to look at the complete sound
absorption coefficient curve.
.-lJ
.-
u-
u-
u 03
iki
t0
.-
t
0,
b 0~5
2m
-Cl
5 0,4
0
m
02
0
125 2000 4000
Frequency,Hz
500Hz 1 OOOHz 2000 Hz 4000Hz
/ ~~::encY I 2;*:z I,00 l,oo I,00 0,90 I
Figure 1 - Reference curve for evaluation of weighted sound absorption coefficient, a,,,,
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5 Presentation of results ISO 11654:1997
Results shall be given in the https://standards.iteh.ai/catalog/standards/sist/cf38f5fe-b915-452e-9a09-
formats specified in 5.1 to 5.3. Depending on the purpose of the presentation, one or
more of the descriptors can be omitted, unless137a53bc0f33/iso-11654-1997
otherwise specified.
5.1 as values
Plot the values of the one-third-octave band sound absorption coefficients as, measured in accordance with
IS0 354, on a diagram. Set out the frequency along the x-axis to a logarithmic scale and the values of as along the
y-axis to a linear scale. The distance for an octave on the frequency scale shall be 15 mm; the distance for a range
of 0,30 in absorption coefficient shall also be 15 mm. (See annex C.)
Optionally, the diagram may be replaced or supplemented by a table. In that case, the values shall be given to two
decimal places.
5.2 ap values
Plot the values of the practical sound absorption coefficient ap on a diagram. Set out the frequency along the x-axis
to a logarithmic scale and the values of ap along the y-axis to a linear scale. The distance for an octave on the
frequency scale shall be 15 mm; the distance for a range of 0,30 in absorption coefficient shall also be 15 mm.
Scale the y-axis from ap = 0 to ap = I,0 and the x-axis in octave bands from 125 Hz to 4 000 Hz. (See annex A.)
Optionally, the diagram may be replaced or supplemented by a table. In that case, the values shall be given to two
decimal places.
IS0 11654: 1997(E) @ IS0
5.3 h val ues and shape indicators
Express the weighted sound absorption coefficient a,,,,to two decimal places. Express the shape indicators, without
commas, in parentheses, after the a, value.
EXAMPLE
a, = 0,70(MH)
NOTE - Whenever a shape indicator is given, the following sentence should be added: “It is strongly recommended to use
this single-number rating in combination with the complete sound absorption coefficient curve that can be obtained on request.”
5.4 Other information
For each ap curve and a,,,,value, specify the following.
For all products for which the test specimen was mounted with an air space behind it, specify the depth of
construction. (See figure 2.)
NOTE - In Europe it is recommended to use at least a construction depth of 200 mm. In Japan it is recommended to use at
least a construction depth of 300 mm. In North America it is recommended to use at least a construction depth of 400 mm.
Room surface
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i Soundabsorber
Figure 2 - Specification of depth of construction
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IS0 11654: 1997(E)
Annex A
(informative)
Examples of calculations of aw, with a,nd without a shape indicator
Figure A.1 shows an example of how to calculate u,,,,. Shift the reference curve in steps of 0,05 towards the
measured value until the sum of the unfavourable deviations G 0,lO. In the example, an unfavourable deviation
occurs at 250 Hz and the result is a, = 0,60. No shape indicators need be given.
Figure A.2 gives an example with a shape indicator. The unfavourable deviation is equal to that of figure A.1 and
thus the same a, value is obtained. However, as the practical sound absorption coefficient of the absorber exceeds
that of the shifted reference curve by more than 0,25 at 500 Hz, the mid-frequency (M) shape indicator is added.
.-
.-U
rc
i 0,8 Freq. Ref. curve Absorber
U I I
tE
.- 125 0,20
?- 0,6 250 0,40 0,35
:
n
m 500 0,60 0,70
-u
2 0,4 II 000 0,60 0,65
v1 n Ref.curve
A
fu
.-
; 0,2
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A Absorber 2000
4000
0,60
0,50
0,60
0,55
lk (standards.iteh.ai)
0
125 2000 4000
ISO 11654:1997
Frequency,Hz
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Figure A.1 - Example of a calculation of a,,,,(a~ = 0,60)
ua t
f 1
.-aJ
U
;;I
: 0,8 Freq. Ref. curve Absorber
U
c
0
.-
t
125 0,20
; 0,6 250 0,40 0,35
l!i
lw 500 0,60 I,00
-cl
; 0,4 1000 0,60 0,65
-
m 2000 0,60 0,60
.-
; 0,2 4000 0,50 0,55
b
0
2000 4000
Frequency,Hz
Figure A.2 - Example of a calculation of a,,,,[aw = 0,60(M)]
