EN ISO 11820:1996
(Main)Acoustics - Measurements on silencers in situ (ISO 11820:1996)
Acoustics - Measurements on silencers in situ (ISO 11820:1996)
Applies to measurements on silencers in practical applications for acoustic analysis, acceptance tests and similar evaluations. Depending on the method used, the measurement is either of insertion loss or transmission loss.
Akustik - Messungen an Schalldämpfern im Einsatzfall (ISO 11820:1996)
Diese Internationale Norm trifft Festlegungen für Messungen an Schalldämpfern im Einsatzfall. Sie ist anwendbar für Messungen an Schalldämpfern in praktischen Anwendungsfällen zum Zweck schalltechnischer Analyse, für Abnahmeprüfungen und ähnliche Beurteilungen. Gemäss dieser Internationalen Norm erzielte Ergebnisse können nicht mit Leistsungsdaten verglichen werden, die bei gemäss ISO 7235 an Kanalschalldämpfern durchgeführten Labormessungen gewonnen wurden, teils wegen der unterschiedlichen Testbedingungenl, wie z.B. Schallfeldverteilung, Strömung, Temperatur.
Acoustique - Mesurage sur silencieux in situ (ISO 11820:1996)
1.1 La présente Norme internationale spécifie des mesurages sur silencieux in situ. Elle est applicable aux mesurages sur des silencieux dans des applications pratiques pour l'analyse acoustique, les essais de réception et des évaluations similaires. Les résultats obtenus conformément à la présente Norme internationale ne peuvent pas être comparés aux performances obtenues à partir des mesurages en laboratoire sur des silencieux en conduit effectués conformément à l'ISO 7235, en partie en raison de conditions d'essai différentes (comme la répartition du champ acoustique, l'écoulement, la température et les conditions de montage) et en partie en raison de définitions différentes. Selon la méthode utilisée, il s'agit du mesurage -- de la perte d'insertion Dis, ou -- de la perte par transmission Dts. La méthode de mesurage dépend du type de silencieux et des conditions d'installation (par exemple, des mesurages de perte d'insertion doivent être effectués pour des silencieux de type «blowdown»).
NOTE 1 Les indices indiquent l'application pratique du silencieux et les conditions particulières d'installation et de fonctionnement; «s» signifie in situ, «t» transmission et «i» insertion. Des grandeurs caractéristiques supplémentaires, qui pourraient comprendre les mesurages effectués en utilisant des sources sonores ar 1786tificielles ou des mesurages effectués pour déterminer la directivité de la propagation du son depuis le silencieux, peuvent être convenues conformément à la présente Norme internationale. 1.2 La présente Norme internationale s'applique a) aux silencieux installés soit sous forme d'un tout, soit sous forme de chicanes individuelles sur le trajet de propagation du son (par exemple, ouvertures de conduites) provenant d'une source sonore (machine, bâtiment, installations telles qu'un générateur de turbine à gaz, une installation de lavage, une tour de refroidissement, une installation de chauffage, ve
Akustika – Merjenje dušilnikov na mestu delovanja (ISO 11820:1996)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-november-1999
Akustika – Merjenje dušilnikov na mestu delovanja (ISO 11820:1996)
Acoustics - Measurements on silencers in situ (ISO 11820:1996)
Akustik - Messungen an Schalldämpfern im Einsatzfall (ISO 11820:1996)
Acoustique - Mesurage sur silencieux in situ (ISO 11820:1996)
Ta slovenski standard je istoveten z: EN ISO 11820:1996
ICS:
17.140.01 $NXVWLþQDPHUMHQMDLQ Acoustic measurements and
EODåHQMHKUXSDQDVSORãQR noise abatement in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
Is0
INTERNATIONAL
STANDARD 11820
First edition
1996-l 2-I 5
Acoustics - Measurements on silencers
in situ
Acoustique - Mesurages sur silencieux in situ
Reference number
IS0 11820: 1996(E)
IS0 11820: 1996(E)
Page
Contents
1 Scope .
..................................................................
2 Normative references
3 Definitions .
................................................
4 Corrections for background noise
4.1 Transmission sound pressure level difference. .
4.2 Insertion sound pressure level difference .
..................................................................
5 Installation conditions
6 Measuring instruments .
..........................................................
6.1 Acoustic instruments
6.2 Air flow, static pressure and temperature measuring
devices .
7 Test object and measuring conditions .
8 Measurement procedures .
............................................................................... 7
8.1 General
8.2 Acoustic measurements .
.............. 9
8.3 Flow, pressure and temperature measurements.
9 Evaluation . 10
.................. 10
9.1 Evaluation of sound pressure measurements.
Evaluation of flow measurements . 12
9.2
10 Information to be recorded . 13
11 Information to be reported .
Annexes
A Field corrections . 15
B Calibration of directional microphones and microphones
...................................... 17
equipped with a turbulence windscreen
C Bibliography . 18
0 IS0 1996
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
Printed in Switzerland
ii
IS0 11820: 1996(E)
0 IS0
Foreword
IS0 (the International Organization for Standardization) is a worldwide fed-
eration 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 collab-
orates closely with the International Electrotechnical Commission (IEC) on
all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are cir-
culated to the member bodies for voting. Publication as an International
75 % of the member bodies casting
Standard requires approval by at least
a vote.
International Standard IS0 11820 was prepared by Technical Committee
lSO/TC 43, Acoustics, Subcommittee SC 1, Noise.
Annexes A to C of this International Standard are for information only.
IS0 11820:1996(E) @ IS0
Introduction
This International Standard gives a method for evaluating the acoustic
performance of silencers under plant-operating conditions. The attenuation
losses determined express the extent to which the level of sound power
passing through a duct, or across the internal cross-section of an aperture
or opening (e.g. in an enclosure or a building) is reduced by the use of a
silencer. Sound transmission via flanking elements is attributed to the
silencer performance unless the flanking element is not a part of the
silencer or of the related duct walls. The influences of flow noise and of
alterations to the operating conditions with and without a silencer are
included.
In laboratory measurements on ducted silencers in accordance with
IS0 7235, insertion losses, static pressure losses and regenerated sound
(flow noise) are determined under well-defined conditions. In practical ap-
plications both the sound field and flow field are less uniformly distributed.
This can lead to different attenuations and greater pressure losses. In ad-
dition, sound levels and rates of flow are mutually dependent. Therefore, in
this International Standard the regenerated sound is not measured separ-
ately but is treated as a property of the silencer in its operating installation
which limits the degree of attenuation in the particular application.
IS0 11820:1996(E)
INTERNATIONAL STANDARD 0 IS0
Measurements on silencers in sifu
Acoustics -
such as a gas turbine generator, scrubbing plant,
1 Scope
cooling tower, heating ventilation and air con-
ditioning (HVAC) plant, exhaust stack, air intake
1 .l This International Standard specifies measure-
duct, weapon, internal combustion engine, com-
ments on silencers in situ. It is applicable to measure-
pressor, etc.);
ments on silencers in practical applications for
acoustic analysis, acceptance tests and similar
b) all types of passive silencers (absorptive, reac-
evaluations. Results obtained in accordance with this
tive, reflection and blowdown silencer);
International Standard cannot be compared to per-
c) active silencers (involving amplifiers and loud-
formance data obtained from laboratory measure-
speakers) as far as the insertion loss of passive
ments on ducted silencers in accordance with
silencers is equivalent to the off/on conditions of
IS0 7235, partly because of different test conditions
active devices; and
(such as sound field distribution, flow, temperature and
mounting conditions) and partly because of different
d) other measures or means of effecting acoustic
definitions.
attenuation in air or other gases (e.g. components
installed in ducting, louvres, grilles and deflector
Depending on the method used, the measurement is
hoods).
either of
Additionally, this International Standard is applicable to
the determination of the effect of cleaning or refurbish-
- insertion loss Dis, or
ing silencers.
- transmission loss Dt,.
This International Standard is not applicable to closed
high-pressure systems (e.g. silencers in closed pipes)
The measurement method depends upon the type of
since measurements of structure-borne sound are not
silencer and the installation conditions (e.g. insertion
anticipated.
loss measurements must be carried out for blowdown
silencers).
1.3 Quantities to be measured include the following:
The subscripts denote the practical application of
NOTE 1
a) sound pressure levels in octave bands with centre
the silencer and the particular installation and operating
frequencies at least from 63 Hz to 4 kHz and, if
conditions: “s” stands for ‘%I situ”, “t” for transmission, and
“i” for insertion. possible and required, from 31,5 Hz to 8 kHz or in
one-third-octave bands with centre frequencies
Additional characteristic quantities, which could in-
from 50 Hz to 5 kHz and, if possible and required,
clude measurements taken using artificial sound
from 25 Hz to 10 kHz
sources or measurements taken to determine the di-
- at a point or points on the source side of a
rectivity of sound propagation from the silencer, may
silencer,
be agreed upon in accordance with this International
- at a point or points on the receiver side of a
Standard.
silencer;
1.2 This International Standard is applicable to
b) static and dynamic pressures, flow velocities and
temperatures at selected positions.
a) silencers which are installed either as a whole or
Operating data to be determined include flow rate,
in the form of individual baffles in the propagation
pressure and speed, which define the operating con-
path of sound (e.g. openings of ducts) originating
ditions of the machine or plant to be silenced.
from a sound source (machine, building, plant
@ IS0
IS0 11820: 1996(E)
Lp2 is the mean sound pressure level (ref.
2 Normative references
20 PPa), in decibels (in one-third-octave or
octave bands), on the source side of the
The following standards contain provisions which,
silencer, for all measuring points used to de-
through reference in this text, constitute provisions of
termine the airborne sound reaching the
this International Standard. At the time of publication,
silencer.
the editions indicated were valid. All standards are
subject to revision, and parties to agreements based
NOTE 2 Dtl,, is not self-standing but is an intermedi-
on this International Standard are encouraged to in-
ate step towards determining the transmission Boss
vestigate the possibility of applying the most recent
(see 9.1.3).
editions of the standards indicated below. Members of
IEC and IS0 maintain registers of currently valid fnter-
Mean sound pressure levels L, are defined by
national Standards.
IS0 374411994, Acoustics - Determination of sound
1 N
power levels of noise sources using sound press-
1 O”J’%j dB . . .
(2)
c
ure - Engineering method in an essentially free field
j=l
i I
over a reflecting plane.
where
IS0 5221 :I 984, Air distribution and air diffusion -
Rules to methods of measuring air flow rate in an air
L pj is the individual level;
handling duct.
N is the number of measuring points.
I EC 651: 1979, Sound level meters.
3.2 insertion sound pressure leve’l difference,
IEC 651:1979/Amd.l:1993, Amendment No. 1.
Difference, in decibels, in sound pressure levels
Dips:
measured at a point or averaged over a small meas-
I EC 804: 1985, Integrating-averaging sound level
urement area before and after installation of a silencer:
meters.
. . .
(3)
IEC 804:1985/Amd.l :I 989, Amendment No. 1.
IEC 804: 1985/Amd.2: 1993, Amendment No. 2.
LPI is the sound pressure level (ref. 20 PPa), in
decibels (in one-third-octave or octave
bands, see IEC 1260), of the sound source(s)
3 Definitions
measured at a point or averaged over a small
measurement area, after installation of the
For the purposes of this International Standard, the
silencer;
following definitions apply.
Lpll is the sound pressure level (ref. 20 PPa), in
decibels (in one-third-octave or octave
3.1 transmission sound pressure level differ-
bands), occurring at the same measuring
Difference, in decibels, between the mean
ence, Q,,:
point or over a small measurement area due
sound pressure levels on the source and receiver side
to the sound source(s) to which the silencer
of a silencer:
is to be attached, before installation of the
silencer.
P -
. . .
(1)
Dtps = $2 - $1
NOTE 3 As opposed to DtPS, Dips is restricted to a
point or a small area where certain directivity indices of
where
sound radiation with and without the silencer are effec-
tive. The reference to a small area with a diameter of
about half a wavelength rather than a point may be
L,, is the mean sound pressure level (ref.
useful to avoid strong effects of interference between
20 FPa), in decibels (in one-third-octave or
direct and reflected waves which may occur at certain
octave bands, see IEC 1260), on the receiver
points.
side of the silencer, for all measuring points
used to determine the airborne sound within
3.3 transmission loss, Dts: Difference, in decibels,
the duct or propagated from the aperture and
between the levels of the sound power incident upon
external surfaces of the silencer;
and transmitted from the silencer:
IS0 11820:1996(E)
@ IS0
. . . = 1 m2;
(4) SO
Dts = EW2 - LWI
K2 is the correction, in decibels, for the
where
field distribution in the incident and
reflected sound field on the source
Lwl is the level (ref. 1 pW), in decibels (in one-
side of the silencer (see annex A).
third-octave or octave bands), of the sound
NOTE 4 The definitions of the areas SI and S2
power propagated through the silencer into
include basic field corrections so that the correc-
an attached duct, into a room or into free
tions KI and IQ are generally small, typically less
space, to be determined from
than 3 dB in absolute value.
L,, = L,, +I0 Ig ($/so) dB+ K, n . - (5)
3.4 insertion loss, Dis: Difference, in decibels, be-
tween the levels of the transmitted sound power with
in which, depending on the installation con-
and without a silencer:
ditions (see clause 5 and 9.1):
=L,,-L, . . .
is the area of the measurement
Sl (8)
Dis
surface on the receiver side of the
where
silencer corresponding to the mean
sound pressure level LPI , or
Lwr is the sound power level (ref. 1 pW), in deci-
is one-quarter of the absorption A in
Sl
bels (in
...
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