SIST EN ISO 11821:1999

SLOVENSKI STANDARD
SIST EN ISO 11821:1999
01-november-1999
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,62
Acoustics - Measurement of the in situ sound attenuation of a removable screen (ISO
11821:1997)
Akustik - Messung der Schalldämpfung von versetzbaren Schallschirmen im Einsatzfall
(ISO 11821:1997)
Acoustique - Mesurage d l'atténuation acoustique in situ d'un écran amovible (ISO
11821:1997)
Ta slovenski standard je istoveten z: EN ISO 11821:1997
ICS:
17.140.01 $NXVWLþQDPHUMHQMDLQ Acoustic measurements and
EODåHQMHKUXSDQDVSORãQR noise abatement in general
SIST EN ISO 11821:1999 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 11821:1999

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SIST EN ISO 11821:1999

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SIST EN ISO 11821:1999

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SIST EN ISO 11821:1999
INTERNATIONAL Is0
11821
STANDARD
First edition
1997-04-O 1
Acoustics - Measurement of the in sifu
sound attenuation of a removable screen
Acoustique - Mesurage de I’atthuation acoustique in situ d’un &ran
amovible
Reference number
IS0 11821:1997(E)

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SIST EN ISO 11821:1999
IS0 11821: 1997(E)
Page
Contents
Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~.
Normative references
Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*.
Instrumentation . . . . . . . . . .*.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Determination of in situ sound attenuation
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Uncertainty
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Information to be recorded
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Information to be reported
Annex
10
..,.....,......................................................................
A Bibliography
0 is0 1997
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 l CH-1211 Geneve 20 l Switzerland
Internet central @ iso.ch
x.400 c=ch; a=400net; p=iso; o=isocs; s=central
Printed in Switzerland
ii

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SIST EN ISO 11821:1999
IS0 11821:1997(E)
@ IS0
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.
International Standard IS0 11821 was prepared by Technical Committee
lSO/TC 43, Acoustics, Subcommittee SC 1, Noise.
Annex A of this International Standard is for information only.

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SIST EN ISO 11821:1999
IS0 11821 :1997(E) @ IS0
Introduction
This International Standard specifies in situ methods for the determination
of the sound attenuation performance of removable sound-protecting
screens for industrial purposes A screen is any object (e.g. panels, flexible
curtains, etc.) breaking the line of sight between source and receiver; such
a screen may be flat or curved. A removable screen is a screen that can be
dismantled without the other environmental conditions being changed. The
purpose of such a screen is to shield a work station or a complete work
area from the noise emitted by sound source(s). Such an area can be a
zone where one operator is located or a zone occupied by several
operators at no fixed positions. For example, screens can be used by a
maintenance unit to reduce the effect of noise at a given location, from
repair work, and to reduce the noise at a work station located close to a
machine or process.
Related standards concern noise attenuation measurements of enclosures
under in situ conditions (IS0 1154602), and sound insulation measure-
ments of cabins under in situ conditions (IS0 II 957).
Other International Standards dealing with screens in other situations are
IS0 10053 (sound attenuation of screens for open plan offices) and
IS0 10847 (sound attenuation of outdoors screens).
Technical information about noise reduction in workrooms can be found in
IS0 11690-2.
IV

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SIST EN ISO 11821:1999
INTERNATIONAL STANDARD o Iso
IS0 11821 :1997(E)
Acoustics - Measurement of the in sifu sound attenuation
of a removable screen
1 Scope
This International Standard specifies methods for evaluating the in situ sound attenuation performance of a
removable screen, either indoors or outdoors. This engineering grade method is based on an insertion loss
measurement that can be carried out either with shielding of the actual sound source(s) or using an artificial sound
source.
The sound attenuation performance achieved by such a screen, as evaluated by the present International Standard,
depends on:
- diffraction around the edges of the screen;
- transmission through the components of the screen;
absorption of the panels of the screen, as well as in its surroundings;
-
- the room in which the screen stands if indoors.
When a specific work station is to be shielded, the in situ sound attenuation value describes the effect of the screen.
However, when a complete area is to be shielded, the performance of the screen will vary depending on the
positions used for measurement. Therefore, it is recommended that the maximum and minimum values of sound
attenuation are given. The sound attenuation performance is determined in terms of insertion loss.
When assessing the performance of a screen located indoors, the room geometry and reflections from walls,
ceilings and room fittings will influence the performance. As a consequence, the comparison of screen performance
can only be made if the test conditions are identical.
This International Standard is applicable to screens with height and length greater than 1,5 m. However, it may also
be used for smaller screens provided that the interested parties come to an agreement on this.
As environmental conditions can affect the measurements outdoors, it is recommended that measurements should
be restricted to within 25 m of the screen. However, measurements may also cover a greater distance provided that
the interested parties come to an agreement on this.
Differences can occur between in situ test results Therefore, comparison of the performance of different screens
can be made only on the basis of data based on the same measurement method performed at the same location.
This International Standard applies to a complete screen only and not to individual components from which it is
made. Sound insulation and sound absorption for screen components (such as panel elements, doors, windows)
should be measured according to other relevant standards.
This International Standard is not applicable to open plan offices screens nor to outdoor barriers dealing with
community noise. It is also not intended for qualification purposes

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SIST EN ISO 11821:1999
@ IS0
IS0 11821:1997(E)
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.
IEC 651 :I 979, Sound /eve/ meters.
IEC 804:1985, Integrating-averaging sound level meters.
I EC 942: 1988, Sound calibrators.
I EC 1260: 1995, Hectroacoustics - Octave-band and fractional-octave-band filters.
3 Definitions
For the purposes of this International Standard, the following definitions apply.
3.1 screen: Any object that is specially designed to shield one or more specified positions in a given area from the
noise of specific sound s ource(s).
NOTE - Examples are panels and flexible curtains.
3.2 removable screen: A screen that can be dismantled without the other environmental conditions being
changed.
3.3 actual sound source(s): The sound source(s) to be shielded.
3.4 sound pressure level, Lp: Ten times the logarithm to the base 10 of the ratio of the mean-square sound
pressure of a sound to the square of the reference sound pressure 20 FPa. The sound pressure level is expressed
in decibels.
3.5 A-weighted sound pressure level, Lp~: Sound pressure level weighted in accordance with IEC 651. The A-
weighted sound pressure level is expressed in decibels.
3.6 unscreened sound pressure level, Lpj: Sound pressure level measured at one position not screened from
the sound source(s) without the screen in its intended position. The unscreened sound pressure level is expressed
in decibels.
3.7 screened sound pressure level, Lp2: Sound pressure level measured at the same position as in 3.6 but
screened from the sound source(s) by the screen in its intended position. the screened sound pressure level is
expressed in decibels.
3.8 in situ sound attenuation, Dp: Difference, in decibels, between Lpl and L+ at the particular position defined
in 3.6, LIP1 and LIP2 being determined in either one-third-octave or octave bands.
3.9 A-weighted in situ sound attenuation, Dp~: Difference, in decibels, between L+l and L@ at the position
defined in 3.6 when using the actual sound source(s).
3.10 directivity index, Dli: Difference, in decibels, between L360 (the logarithmic mean value of the sound
pressure level in 12 positions evenly distributed on a horizontal circle surrounding the sound source) and ~~~ i (the
I
sound pressure level in position i of the twelve positions).
The radius of the circle shall be approximately I,5 m.
DI
i = L360 - L30,i
NOTE - The definition of the directivity index stated in this International Standard is in principle equivalent to the definition
given in IS0 140-3. However, the procedure in this International Standard is somewhat simplified by allowing the directivity
2

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SIST EN ISO 11821:1999
@ IS0
IS0 11821 :1997(E)
index to be determined in 12 discrete positions in the horizontal plane instead of using “gliding averaging” in different planes as
described in IS0 140-3.
4 Instrumentation
The instrumentation system, including the microphones and cables, shall meet the requirements for a type 1
instrument as specified in IEC 651 or, in the case of integrating-averaging sound level meters, the requirements for
a type 1 instrument as specified in IEC 804.
For measurements in octave or one-third-octave bands, the instrumentation system shall meet the requirements for
a class 1 filter as specified in IEC 1260.
Before and after each series of measurements, the calibration of the entire measuring system shall be verified at
one or more frequencies over the frequency range of interest, using a sound calibrator with an accuracy of + 0,3 dB
(class 1 as specified in IEC 942).
methods are permissible, provided
NOTE - Other calibration that it is shown tha t the instrume ntation system is stable during
the measu rements and that measurements with and without the scree n are carried out using the same measurement system.
When measuring outdoors, a microphone windscreen with negligible influence on the frequency response of the
microphone shall be used during the measurements.
5 Determination of in situ sound attenuation
5.1 General
The unscreened acoustic field can be generated using the actual sound source(s) to be shielded, provided the
provisions outlined in 5.2 are met. If needed, an artificial sound source can be used instead. The use of the actual
sound source(s) is the preferred method.
nts, ensure that the same operating conditions are for the screened and
When perfo rming the measureme used
unscre lened situat ions.
5.2 Sound source requirements
5.2.1 Actual sound source(s): Preferred method
The generated sound shall be reproducible and the same sound shall be used for measurements with and without
the screen.
The output shall be sufficiently high to give a sound pressure level behind the screen exceeding the background
noise level by at least 6 dB and preferably more than 10 dB for all frequency bands of interest.
lnditions, all relevant sound sou rce s) at the test site should be listed, together with
NOTE - In order to check the operating co
their operating conditions (such as rotational speed, flow rate, power, etc.).
52.2 Artificial sound source
the measurements shall be carried out in
If the requirements in 52.1 are not met by the actual sound source(s)
octave or one-third-octave bands using an artificial sound source instead of the actual sound source(s).
NOTE 1 The artificial sound source may be a loudspeaker, a pistol shot, a bursting membrane, but it can also be machinery
brought in for the purpose of testing the screen.
The artificial sound source must have at least one axis of symmetry which shall be directed perpendicular to the
floor during operation. The directivity index should not exceed + 8 dB in any of
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