EN ISO 9614-3:2009

Acoustics - Determination of sound power levels of noise sources using sound intensity - Part 3: Precision method for measurement by scanning (ISO 9614-3:2002)

ISO 9614-3:2002 specifies a method for measuring the component of sound intensity normal to a measurement surface which is chosen so as to enclose the sound source(s) of which the sound power level is to be determined.
Surface integration of the intensity component normal to the measurement surface is approximated by subdividing the measurement surface into contiguous partial surfaces, and scanning the intensity probe over each partial surface along a continuous path which covers the extent of the partial surface. The measurement instrument determines the averaged normal intensity component and averaged squared sound pressure over the duration of each scan. The scanning operation can be performed either manually or by means of a mechanical system.
The octave band or band-limited weighted sound power level is calculated from the measured one-third-octave- band values. The method is applicable to any source for which a physically stationary measurement surface can be defined, and on which the sound generated by the source under test and by other significant extraneous sources are stationary in time. The source is defined by the choice of measurement surface. The method is applicable in specific test environments fulfilling all relevant requirements of ISO 9614-3.
ISO 9614-3 specifies certain ancillary procedures, described in annex C, to be followed in conjunction with the sound power determination. The results are used to indicate the quality of the determination, and hence the grade of accuracy. If the quality of the determination does not meet the requirements of ISO 9614-3, the test procedure shall be modified in the manner indicated.
ISO 9614-3 is not applicable to any frequency band in which the sound power of the source is found to be negative on measurement.
It is applicable to sources situated in any environment which is neither so variable over time as to reduce the accuracy of the measurement of sound intensity to an unacceptable degree, nor subjects the intensity measurement probe to gas flows of unacceptable speed or unsteadiness.
In some cases it will be found that the test conditions are too adverse to allow the requirements of ISO 9614-3 to be met. For example, extraneous noise levels can exceed the dynamic capability of the measuring instrument or can vary to an excessive degree during the test. In such cases the method given in ISO 9614-3 is not suitable for the determination of the sound power level of the source.

Akustik - Bestimmung der Schallleistungspegel von Geräuschquellen aus Schallintensitätsmessungen - Teil 3: Scanning-Verfahren der Genauigkeitsklasse 1 (ISO 9614-3:2002)

1.1 Dieser Teil von ISO 9614 legt ein Verfahren fest zur Messung der zu einer Messfläche senkrechten
Komponente der Schallintensität. Dabei wird die Messfläche so gewählt, dass sie die Schallquelle(n), deren
Schallleistungspegel bestimmt werden soll, umschließt.
Die Flächenintegration der zur Messfläche senkrechten Intensitätskomponente wird durch eine Unterteilung
der Messfläche in aneinander angrenzende Teilflächen und das Scannen jeder Teilfläche durch die auf einem
stetigen, die gesamte Teilfläche abdeckenden Messpfad bewegte Intensitätsmesssonde angenähert. Das
Messgerät bestimmt die über den gesamten Scan-Vorgang gemittelte Normalkomponente der Schallintensität
und das gemittelte Schalldruckquadrat. Das Scannen kann manuell oder mechanisiert durchgeführt werden.
Der Oktavband- oder bandbegrenzte bewertete Schallleistungspegel wird aus den gemessenen Terzbandwerten
berechnet. Das Verfahren ist auf jede Quelle anwendbar, für die eine physikalisch konstante Messfläche
festgelegt werden kann und bei der der von der zu untersuchenden Quelle und von anderen
signifikanten Fremdschallquellen abgestrahlte Schall zeitlich stationär ist. Die Quelle ist durch die Wahl der
Messfläche definiert. Das Verfahren kann in speziellen Messumgebungen, die alle der in diesem Teil von
ISO 9614 festgelegten relevanten Anforderungen erfüllen, angewendet werden.
Dieser Teil von ISO 9614 legt bestimmte, in Anhang C beschriebene Zusatzverfahren fest, die in Zusammenhang
mit der Schallleistungsbestimmung durchzuführen sind. Die Ergebnisse werden dazu verwendet, die
Qualität der Schallleistungsbestimmung und somit die Genauigkeitsklasse zu ermitteln. Wenn die Qualität der
Bestimmungen die Anforderungen dieses Teils von ISO 9614 nicht erfüllt, ist das Messverfahren in der hierin
angegebenen Weise zu verändern.
Dieser Teil von ISO 9614 ist nicht in Frequenzbändern anwendbar, in denen die Messung eine negative
Schallleistung der Quelle ausweist.

Acoustique - Détermination par intensimétrie des niveaux de puissance acoustique émis par les sources de bruit - Partie 3: Méthode de précision pour mesurage par balayage (ISO 9614-3:2002)

La présente partie de l'ISO 9614 prescrit une méthode de mesurage de la composante de l'intensité acoustique normale à une surface de mesurage entourant la(les) source(s) de bruit dont le niveau de puissance acoustique est à déterminer.
L'intégration sur la surface de mesurage de la composante de l'intensité normale à la surface est approchée en divisant la surface de mesurage en éléments contigus et en passant la sonde d'intensité sur chaque élément de surface le long d'une trajectoire continue qui couvre l'étendue de l'élément de surface. L'instrument de mesure détermine la composante de l'intensité normale moyenne et la pression acoustique quadratique moyenne sur la durée de chaque balayage. L'opération de balayage peut être effectuée soit manuellement, soit au moyen d'un système mécanique.
Le niveau de puissance acoustique par bandes d'octave, ou le niveau pondéré sur une plage de fréquences limitée est calculé à partir des valeurs mesurées par bandes de tiers d'octave. La méthode est applicable à toute source pour laquelle on peut définir une surface de mesurage physiquement stationnaire et sur laquelle les signaux acoustiques émis par la source en essai et par les sources parasites significatives sont stables dans le temps. La source est définie par le choix de la surface de mesurage. La méthode peut être appliquée dans des environnements d'essai particuliers, satisfaisant aux exigences de la présente partie de l'ISO 9614.
La présente partie de l'ISO 9614 prescrit certaines procédures complémentaires décrites dans l'annexe C, à appliquer lors de la détermination de la puissance acoustique. Les résultats obtenus indiquent la qualité de la détermination et donc la classe de précision de la méthode. Si la qualité de la détermination n'est pas conforme aux exigences de la présente partie de l'ISO 9614, la méthode d'essai doit être modifiée de la façon indiquée.
La présente partie de l'ISO 9614 ne s'applique pas aux bandes de fréquences dans lesquelles la puissance acoustique de la source mesurée est négative.
La présente partie de l'ISO 9614 s'applique aux sources situées dans un environnement quelconque mais dont la variabilité temporelle reste suffisamment faible pour que la précision de la mesure de l'intensité acoustique reste acceptable, et dans lequel la sonde intensimétrique n'est pas soumise à des flux gazeux d'une vitesse ou d'une instabilité inacceptable (voir 5.2.2, 5.3 et 5.4).
Dans certains cas, les conditions d'essai se révéleront trop défavorables pour que les exigences de la présente partie de l'ISO 9614 puissent être respectées. Les niveaux de bruit parasite peuvent dépasser la capacité dynamique de l'instrument de mesure ou peuvent varier de façon excessive pendant l'essai. Dans de tels cas, la méthode donnée dans la présente partie de l'ISO 9614 ne convient pas pour déterminer le niveau de puissance acoustique de la source.

Akustika - Ugotavljanje ravni zvočnih moči virov hrupa z merjenjem jakosti zvoka - 3. del: Precizijska metoda zveznega merjenja po ploskvi (ISO 9614-3:2002)

General Information

• Status: Published
• Publication Date: 04-Aug-2009
• Withdrawal Date: 27-Feb-2010
• ICS: 17.140.01 - Acoustic measurements and noise abatement in general
• ICS: 17.140.20 - Noise emitted by machines and equipment
• Technical Committee: CEN/TC 211 - Acuostics
• Drafting Committee: CEN/TC 211 - Acuostics
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 05-Aug-2009
• Due Date: 25-Sep-2010
• Completion Date: 05-Aug-2009
• Directive: 2006/42/EC - Directive 2006/42/EC of the European Parliament and of the Council of 17 May 2006 on machinery, and amending Directive 95/16/EC (recast)
• Directive: 98/37/EC - Machinery
• Mandate: M/079 - Mandate to CEN and CENELEC for standardization in the field of machines
• Ref Project: SIST EN ISO 9614-3:2009 - Acoustics - Determination of sound power levels of noise sources using sound intensity - Part 3: Precision method for measurement by scanning (ISO 9614-3:2002)

Relations

• Replaces: EN ISO 9614-3:2002 - Acoustics - Determination of sound power levels of noise sources using sound intensity - Part 3: Precision method for measurement by scanning (ISO 9614-3:2002)
• Effective Date: 08-Aug-2009

Standards Content (Sample)

SLOVENSKI STANDARD
01-november-2009
1DGRPHãþD
SIST EN ISO 9614-3:2003
$NXVWLND8JRWDYOMDQMHUDYQL]YRþQLKPRþLYLURYKUXSD]PHUMHQMHPMDNRVWL]YRND
GHO3UHFL]LMVNDPHWRGD]YH]QHJDPHUMHQMDSRSORVNYL,62
Acoustics - Determination of sound power levels of noise sources using sound intensity -
Part 3: Precision method for measurement by scanning (ISO 9614-3:2002)
Akustik - Bestimmung der Schallleistungspegel von Geräuschquellen aus
Schallintensitätsmessungen - Teil 3: Scanning-Verfahren der Genauigkeitsklasse 1 (ISO
9614-3:2002)
Acoustique - Détermination par intensimétrie des niveaux de puissance acoustique émis
par les sources de bruit - Partie 3: Méthode de précision pour mesurage par balayage
(ISO 9614-3:2002)
Ta slovenski standard je istoveten z: EN ISO 9614-3:2009
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.

EUROPEAN STANDARD
EN ISO 9614-3
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2009
ICS 17.140.01 Supersedes EN ISO 9614-3:2002
English Version
Acoustics - Determination of sound power levels of noise
sources using sound intensity - Part 3: Precision method for
measurement by scanning (ISO 9614-3:2002)
Acoustique - Détermination par intensimétrie des niveaux Akustik - Bestimmung der Schallleistungspegel von
de puissance acoustique émis par les sources de bruit - Geräuschquellen aus Schallintensitätsmessungen - Teil 3:
Partie 3: Méthode de précision pour mesurage par Scanning-Verfahren der Genauigkeitsklasse 1 (ISO 9614-
balayage (ISO 9614-3:2002) 3:2002)
This European Standard was approved by CEN on 20 July 2009.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2009 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 9614-3:2009: E
worldwide for CEN national Members.

Contents Page
Foreword .3
Annex ZA (informative) Relationship between this European Standard and the Essential
Requirements of EU Directive 98/37/EC .4
Annex ZB (informative) Relationship between this European Standard and the Essential
Requirements of EU Directive 2006/42/EC .5

Foreword
The text of ISO 9614-3:2002 has been prepared by Technical Committee ISO/TC 43 “Acoustics” of the
International Organization for Standardization (ISO) and has been taken over as EN ISO 9614-3:2009 by
Technical Committee CEN/TC 211 “Acoustics” the secretariat of which is held by DS.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by February 2010, and conflicting national standards shall be withdrawn
at the latest by February 2010.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 9614-3:2002.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association, and supports essential requirements of EC Directives.
For relationship with EC Directives, see informative Annexes ZA and ZB, which are integral parts of this
document.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 9614-3:2002 has been approved by CEN as a EN ISO 9614-3:2009 without any modification.
Annex ZA
(informative)
Relationship between this European Standard and the Essential
Requirements of EU Directive 98/37/EC
This European Standard has been prepared under a mandate given to CEN by the European Commission
and the European Free Trade Association to provide a means of conforming to Essential Requirements of the
New Approach Directive 98/37/EC, amended by 98/79/EC on machinery.
Once this standard is cited in the Official Journal of the European Communities under that Directive and has
been implemented as a national standard in at least one Member State, compliance with the normative
clauses of this standard confers, within the limits of the scope of this standard, a presumption of conformity
with the relevant Essential Requirements of that Directive and associated EFTA regulations.
WARNING - Other requirements and other EU Directives may be applicable to the product(s) falling within the
scope of this standard.
Annex ZB
(informative)
Relationship between this European Standard and the Essential
Requirements of EU Directive 2006/42/EC
This European Standard has been prepared under a mandate given to CEN by the European Commission
and the European Free Trade Association to provide a means of conforming to Essential Requirements of the
New Approach Directive 2006/42/EC on machinery.
Once this standard is cited in the Official Journal of the European Communities under that Directive and has
been implemented as a national standard in at least one Member State, compliance with the normative
clauses of this standard confers, within the limits of the scope of this standard, a presumption of conformity
with the relevant Essential Requirements of that Directive and associated EFTA regulations.
WARNING — Other requirements and other EU Directives may be applicable to the product(s) falling within
the scope of this standard.
INTERNATIONAL ISO
STANDARD 9614-3
First edition
2002-11-01
Acoustics — Determination of sound power
levels of noise sources using sound
intensity —
Part 3:
Precision method for measurement by
scanning
Acoustique — Détermination par intensimétrie des niveaux de puissance
acoustique émis par les sources de bruit —
Partie 3: Méthode de précision pour mesurage par balayage

Reference number
ISO 9614-3:2002(E)
©
ISO 2002
ISO 9614-3:2002(E)
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ii © ISO 2002 – All rights reserved

ISO 9614-3:2002(E)
Contents Page
Foreword . v
Introduction. vi
1 Scope. 1
2 Normative references. 1
3 Terms and definitions. 2
4 General requirements. 7
4.1 Size of sound source under test. 7
4.2 Character of sound radiated by the source. 7
4.3 Measurement uncertainty. 7
5 Acoustic environment. 9
5.1 Criteria for adequacy of the test environment . 9
5.2 Extraneous intensity. 9
5.3 Wind and gas flows. 9
5.4 Temperature. 9
5.5 Configuration of the surroundings. 9
5.6 Atmospheric conditions. 9
6 Instrumentation. 10
6.1 General. 10
6.2 Calibration and field check. 10
6.3 Time-series of sound intensity and sound pressure. 10
7 Installation and operation of the source. 10
7.1 General. 10
7.2 Operating conditions of the source under test. 11
8 Measurement of normal sound intensity component levels . 11
8.1 Determination of measurement surface . 11
8.2 Determination of scanning paths and segments. 11
8.3 Measurements. 12
8.4 Further actions. 14
9 Determination of sound power level . 15
9.1 Calculation of partial sound powers for each partial surface of the measurement surface. 15
9.2 Calculation of normalized sound power level. 15
10 Information to be recorded. 15
Annex A (informative) List of symbols used in this part of ISO 9614 . 17
Annex B (normative) Calculation of field indicators. 19
B.1 General. 19
B.2 Definition of field indicators. 19
B.2.1 Temporal variability indicator, F . 19
T
B.2.2 Unsigned pressure-intensity indicator, F . 19
p I
n
B.2.3 Signed pressure-intensity indicator, F . 20
pI
n
B.2.4 Field non-uniformity indicator, F . 21
S
Annex C (normative) Procedure for achieving the desired accuracy . 22
C.1 Qualification requirements. 22
C.1.1 General. 22
ISO 9614-3:2002(E)
C.1.2 Check for the adequacy of the averaging time . 22
C.1.3 Check for the repeatability of the scan on a partial surface. 22
C.1.4 Check for the adequacy of the measurement equipment .22
C.1.5 Check for the presence of strong extraneous noise . 23
C.1.6 Check for the field non-uniformity. 23
C.2 Action to be taken to increase the grade of accuracy of determination . 23
Annex D (informative) Effects of airflow on measurement of sound intensity. 26
Annex E (informative) Effect of sound absorption within the measurement surface. 27
Annex F (informative) Measurement surface and scanning procedure . 28
Annex G (informative) Procedure for obtaining time-averaged intensities and squared pressures from
a sequence of short-time averaged intensities and squared pressures . 29
Annex H (informative) Normalization of sound power level. 30
H.1 General. 30
H.2 Calculation of normalized sound power level . 30
Annex I (informative) Field indicators used in ISO 9614-1, -2 and -3. 32
Bibliography. 33

iv © ISO 2002 – All rights reserved

ISO 9614-3:2002(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO
member bodies). The work of preparing International Standards is normally carried out through ISO 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. ISO collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
The main task of technical committees is to prepare International Standards. 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.
Attention is drawn to the possibility that some of the elements of this part of ISO 9614 may be the subject of patent
rights other than those identified above. ISO shall not be held responsible for identifying any or all such patent
rights.
ISO 9614-3 was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 1, Noise.
ISO 9614 consists of the following parts, under the general title Acoustics — Determination of sound power levels
of noise sources using sound intensity:
 Part 1: Measurement at discrete points
 Part 2: Measurement by scanning
 Part 3: Precision method for measurement by scanning
Annexes B and C form a normative part of this part of ISO 9614. Annexes A, D, E, F, G, H and I are for information
only.
ISO 9614-3:2002(E)
Introduction
0.1 The sound power radiated by a source is equal in value to the integral of the scalar product of the sound
intensity vector and the associated elemental area vector over any surface totally enclosing the source. Other
International Standards which describe methods of determination of the sound power levels of noise sources,
principally ISO 3740 to ISO 3747, without exception specify sound pressure level as the primary acoustic quantity
to be measured. The relationship between sound intensity level and sound pressure level at any point depends on
the characteristics of the source, the characteristics of the measurement environment, and the disposition of the
measurement positions with respect to the source.
The procedures specified in ISO 3740 to ISO 3747 are not always applicable, for the following reasons.
a) Specific facilities are necessary if high precision is required. It is frequently not possible to install, and operate,
large pieces of equipment in such facilities.
b) They cannot be used in the presence of high levels of extraneous noise generated by sources other than that
under investigation.
0.2 This part of ISO 9614 specifies methods of determining the sound power levels of sources, within specific
ranges of uncertainty, under test conditions which are less restricted than those required by ISO 3740 to ISO 3747.
It is recommended that personnel performing sound intensity measurements according to this part of ISO 9614 are
appropriately trained and experienced.
0.3 This part of ISO 9614 complements ISO 9614-1, ISO 9614-2 and the ISO 3740 to ISO 3747 series, which
specify various methods for the determination of sound power levels of machines and equipment. It differs from the
ISO 3740 to ISO 3747 series principally in three aspects.
a) Measurements are made of sound intensity as well as of sound pressure.
b) The uncertainty of the sound power level determined by the method specified in this part of ISO 9614 is
classified according to the results of specified ancillary tests and calculations performed in association with the
test measurements.
c) Current limitations of intensity measurement equipment which conforms to IEC 61043 restrict measurements
to the one-third octave range 50 Hz to 6,3 kHz. Octave band and band-limited A-weighted values are
determined from the constituent one-third-octave band values.
0.4 The integral over any surface totally enclosing the source of the scalar product of the sound intensity vector
and the associated elemental area vector provides a measure of the sound power radiated directly into the air by
all sources located within the enclosing surface and excludes sound radiated by sources located outside this
surface. In practice, this exclusion is effective only if the source under test and other sources of extraneous
intensity on the measurement surface are stationary over time. In the presence of sound sources operating outside
the measurement surface, any system lying within the surface can absorb a proportion of energy incident upon it.
The total sound power absorbed within the measurement surface will appear as a negative contribution to source
power, and can produce an error in the sound power determination. In order to minimize the associated error, it is
therefore necessary to remove any sound-absorbing material lying within the measurement surface which is not
normally present during the operation of the source under test.
This method is based on sampling of the intensity normal to the measurement surface by moving an intensity probe
continuously along specified paths. The resulting sampling error is a function of the spatial variation of the normal
intensity component over the measurement surface, which depends on the directivity of the source, the chosen
measurement surface, the pattern and speed of the probe scanning, and the proximity of extraneous sources
outside the measurement surface.
vi © ISO 2002 – All rights reserved

ISO 9614-3:2002(E)
The accuracy of measurement of the normal component of sound intensity at a position is sensitive to the
difference between the local sound pressure level and the local normal sound intensity level. A large difference can
occur when the intensity vector at a measurement position is directed at a large angle (approaching 90°) to the

local normal to the measurement surface. Alternatively, the local sound pressure level can contain strong
contributions from sources outside the measurement surface, but can be associated with little net sound energy
flow, as in a reverberant field in an enclosure; or the field can be strongly reactive because of the presence of the
near field and/or standing waves.
The accuracy of determination of sound power level is adversely affected by a flow of sound energy into the
volume enclosed by the measurement surface through a portion of that surface, even though it is, in principle,
compensated by increased flow of the volume out through the remaining portion of the surface. This condition is
caused by the presence of a strong extraneous source outside the measurement surface. This part of ISO 9614
limits such situations by giving relevant criteria.

INTERNATIONAL STANDARD ISO 9614-3:2002(E)

Acoustics — Determination of sound power levels of noise
sources using sound intensity —
Part 3:
Precision method for measurement by scanning
1 Scope
1.1 This part of ISO 9614 specifies a method for measuring the component of sound intensity normal to a
measurement surface which is chosen so as to enclose the sound source(s) of which the sound power level is to
be determined.
Surface integration of the intensity component normal to the measurement surface is approximated by subdividing
the measurement surface into contiguous partial surfaces, and scanning the intensity probe over each partial
surface along a continuous path which covers the extent of the partial surface. The measurement instrument
determines the averaged normal intensity component and averaged squared sound pressure over the duration of
each scan. The scanning operation can be performed either manually or by means of a mechanical system.
The octave band or band-limited weighted sound power level is calculated from the measured one-third-octave-
band values. The method is applicable to any source for which a physically stationary measurement surface can be
defined, and on which the sound generated by the source under test and by other significant extraneous sources
are stationary in time. The source is defined by the choice of measurement surface. The method is applicable in
specific test environments fulfilling all relevant requirements of this part of ISO 9614.
This part of ISO 9614 specifies certain ancillary procedures, described in annex C, to be followed in conjunction
with the sound power determination. The results are used to indicate the quality of the determination, and hence
the grade of accuracy. If the quality of the determination does not meet the requirements of this part of ISO 9614,
the test procedure shall be modified in the manner indicated.
This part of ISO 9614 is not applicable to any frequency band in which the sound power of the source is found to be
negative on measurement.
1.2 This part of ISO 9614 is applicable to sources situated in any environment which is neither so variable over
time as to reduce the accuracy of the measurement of sound intensity to an unacceptable degree, nor subjects the
intensity measurement probe to gas flows of unacceptable speed or unsteadiness (see 5.2.2, 5.3 and 5.4).
In some cases it will be found that the test conditions are too adverse to allow the requirements of this part of
ISO 9614 to be met. For example, extraneous noise levels can exceed the dynamic capability of the measuring
instrument or can vary to an excessive degree during the test. In such cases the method given in this part of
ISO 9614 is not suitable for the determination of the sound power level of the source.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this part of ISO 9614. For dated references, subsequent amendments to, or revisions of, any of these publications
do not apply. However, parties to agreements based on this part of ISO 9614 are encouraged to investigate the
possibility of applying the most recent editions of the normative documents indicated below. For undated
ISO 9614-3:2002(E)
references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain
registers of currently valid International Standards.
IEC 60651, Sound level meters
IEC 60942:1998, Electroacoustics — Sound calibrators
IEC 61260, Electroacoustics — Octave-band and fractional-octave-band filters
IEC 61043:1993, Electroacoustics — Instruments for the measurement of sound intensity — Measurements with
pairs of pressure sensing microphones
GUM:1993, Guide to the expression of uncertainty in measurement. BIPM, IEC, IFCC, ISO, IUPAC, IUPAP, OIML.
3 Terms and definitions
For the purposes of this part of ISO 9614, the following terms and definitions apply.
NOTE Symbols used in this part of ISO 9614 are listed in annex A. Definitions of field indicators are given in annex B.
3.1
sound pressure level
L
p
ten times the logarithm to the base 10 of the ratio of the mean-square sound pressure to the square of the
reference sound pressure
NOTE 1 The reference sound pressure is 20 µPa.
NOTE 2 Sound pressure level is expressed in decibels.
3.2
instantaneous sound intensity
G
I()t
instantaneous flow of sound energy per unit of area and per unit time in the direction of the local instantaneous
acoustic particle velocity
NOTE This is a vectorial quantity which is equal to the product of the instantaneous sound pressure at a point and the
associated particle velocity
G
G
I(tp)=⋅()tu()t (1)
where
p(t) is the instantaneous sound pressure at a point;
G
ut() is the associated instantaneous particle velocity at the same point;
t is time.
3.3
sound intensity
G
I
G
time-averaged value of I (t) in a temporally stationary sound field
GG
T
I = lim It( )dt (2)
∫
T →∞ T
2 © ISO 2002 – All rights reserved

ISO 9614-3:2002(E)
where
T is the integration period
NOTE Also
G
I is the signed magnitude of I ; in this part of ISO 9614, the sign is chosen so that the energy flow going out of the
sound source through the measurement surface is measured positive;
G
I is the unsigned magnitude of I .

3.4
normal sound intensity
I
n
G
component of sound intensity in the direction normal to a measurement surface defined by the unit normal vector n
G
G
I =⋅In (3)
n
G
where n is the unit normal vector directed out of the volume enclosed by the measurement surface

3.5
normal sound intensity level
L
I
n
logarithmic measure of the unsigned value of the normal sound intensity, I , given by
n
I
n
L = 10lg dB (4)
I
n
I
–12 –2
where I is the reference sound intensity (=10 W◊m )
NOTE 1 It is expressed in decibels.
NOTE 2 When I is negative, the level is expressed as (–) XX dB, except when used in the evaluation of δ (see 3.10).
n pI
3.6 Sound powers
3.6.1
partial sound power
P
i
time-averaged flow of sound energy per unit of time through a partial surface of a measurement surface, given by
PI=⋅S (5)
iin i
where
I is the signed magnitude of the partial surface average normal sound intensity measured on the partial
ni
surface i of the measurement surface;
S is the area of the partial surface i.
i
ISO 9614-3:2002(E)
NOTE 1 When the averaged normal sound intensity level L for a partial surface i is expressed as XX dB, the value of I
I ni
n
is calculated from the equation.
XX /10
II= 10 (6)
n0i
NOTE 2 When the averaged normal sound intensity level L for a partial surface i is expressed as (–) XX dB, the value of
I
n
I is calculated from the equation.
ni
XX /10
II=− 10 (7)
n0
i
3.6.2
sound power
P
total sound power generated by a source, as determined using the method given in this part of ISO 9614, given by
N
PP= (8)
i
∑
i=1
where N is the total number of partial surfaces of the measurement surface
3.6.3
sound power level
L
W
logarithmic measure of the sound power generated by a source, as determined using this part of ISO 9614, given
by
P
L = 10 lg dB (9)
W
P
–12
where P is the reference sound power (= 10 W)
NOTE 1 It is expressed in decibels.
NOTE 2 When P is negative, the level is expressed as (–) XX dB for record purposes only.
3.6.4
normalized sound power level
L
W0
sound power level under the reference meteorological condition (temperature θ = 23 °C, barometric pressure
B = 101 325 Pa), given by
B 296,15
LL=−15 lg ×dB (10)
WW0 
101325 273,15 +θ

where
θ is the air temperature, in degrees Celsius, during the actual measurement;
B is the barometric pressure, in pascals, during the actual measurement.
NOTE See annex H.
4 © ISO 2002 – All rights reserved

ISO 9614-3:2002(E)
3.7 Surfaces
3.7.1
measurement surface
hypothetical surface on which intensity measurements are made, and which either completely encloses the sound
source under test or, in conjunction with an acoustically rigid continuous surface, encloses the sound source under
tests
NOTE In cases where the hypothetical surface is penetrated by bodies possessing solid surfaces, the measurement
surface terminates at the lines of intersection between the bodies and the surface.
3.7.2
partial surface
one of a set of smaller surfaces into which a measurement surface is divided and over which a partial sound power
is obtained
See Figure 1.
3.7.3
segment
one of a set of smaller surfaces into which a partial surface is divided
See Figure 2.
NOTE The idea of “segment” is introduced so that the scanning path and time are determined on a partial surface.
3.8
extraneous intensity
contribution to the sound intensity which arises from the operation of sources external to the measurement surface
(source mechanisms operating outside the volume enclosed by the measurement surface)
3.9
probe
that part of the intensity measurement system which incorporates the sensors
3.10
pressure-residual intensity index
δ
pl
difference between the indicated L and indicated L when the intensity probe is placed and oriented in a sound
p Iδ
field such that the sound intensity is zero
δ =−L L (11)
pI p Iδ
where L is the level of residual intensity I given by
Iδ δ
I
δ
L = 10 lg dB (12)
Iδ
I
NOTE 1 It is expressed in decibels.
NOTE 2 Details for determining δ are given in IEC 61043.
pI
3.11
dynamic capability index
L
d
index given by
ISO 9614-3:2002(E)
L=−δ K (13)
d pI
NOTE 1 It is expressed in decibels.
NOTE 2 The value of the bias error factor K is 10 dB for the measurement according to this part of ISO 9614. δ is the
pI
relevant value of the microphone separation used in the actual measurement.
3.12
stationary signal
signal whose time-averaged properties during a measurement on one partial surface of the measurement surface
are equal to those obtained on the same partial surface when the averaging period is extended over the total time
taken to measure on all partial surfaces
3.13 Scanning
3.13.1
scan
continuous movement of an intensity probe along a specified path on a partial surface of a measurement surface
3.13.2
scan-line density
inverse of the average separation of adjacent scanning lines
3.13.3
scanning time
T
s
time spent for one scan of a path defined on a partial surface
3.14 Instrumentation and data acquisition

3.14.1
instantaneous mode
real-time mode of a measuring instrument that continuously measures time-series of intensity and squared sound
pressure and stores one-third-octave band intensity and squared sound pressure components
3.14.2
measurement interval
∆t
time interval of a continuous series of short-time averaged intensity and pressure measurements
NOTE The time interval is limited by the speed of the data processing and storage.
3.14.3
time-series of intensity I and squared pressure p
nq q
sequence of short-time averaged intensity and squared pressure values, sampled at discrete times q∆t, where
q = 1, 2, 3,.Q
See Figure 3.
3.14.4
time-averaged sound intensity I and squared pressure p
n m m
averaged sound intensity and squared pressure over the period [(m – 1)T, mT], m = 1, 2, 3,. M, which are given,
respectively, by
6 © ISO 2002 – All rights reserved

ISO 9614-3:2002(E)
mQ
I = I (14)
nnq
m ∑
Q
qm=−(1)Q+1
and
mQ
p = p (15)
mq∑
Q
qm=−(1)Q+1
where Q is the number of values of I and p that fall within the period [(m – 1)T, mT]
nq q
See Figure 3.
NOTE When evaluating F , the averaging intervals with period T may be separated from each other.
T
4 General requirements
4.1 Size of sound source under test
The size of the sound source under test is unrestricted provided that all criteria specified in annex C are satisfied.
The extent of the source is defined by the choice of the measurement surface.
4.2 Character of sound radiated by the source
The signal shall be stationary over time, as defined in 3.12. Actions should be taken to avoid measurement during
times of operation of non-stationary extraneous noise sources of which the occurrences are predictable (see
Table C.1).
4.3 Measurement uncertainty
The value of the sound power level of a sound source determined by a single application of the procedures of this
part of ISO 9614 is likely to differ from the true value. The actual difference cannot be evaluated accurately, but the
confidence that the value of sound power level determined lies within a certain range around the true value can be
stated, on the assumption that the values determined by numerous applications of the procedure are normally
distributed about the true value. Where repeated applications are made to a source located at a given test site
under nominally identical test conditions, using the same test procedures and instrumentation, the values so
determined constitute the data set which statistically describes the repeatability of the determination. Where the
values are determined from tests conforming to this part of ISO 9614 made on the given source at different test
sites using physically different instruments, the data set so obtained statistically describes the reproducibility of the
determination. Reproducibility is affected by variations in experimental technique and in environmental conditions at
the test sites. The standard deviations do not account for variations of sound power output caused by changes in
operating conditions of a source (e.g. rotational speed, line voltage) or mounting conditions.
Estimated upper values of the standard deviations of reproducibility of sound power levels determined in
accordance with this part of ISO 9614 are given in Table 1. The figures take into account random deviations
associated with the measurement procedure as well as tolerances in the instrument performance specified in
IEC 61043 but exclude the effects of variation in source installation, mounting and operating conditions. Unless
more specific knowledge of relevant sources of uncertainty is available, the expanded measurement uncertainty for
a coverage probability of 95 % as defined in the GUM shall be stated to be two times the standard deviation of
reproducibility given in Table 1.
The uncertainty in determination of the sound power level of a sound source is related to the nature of the sound
field of the source, the nature of the extraneous sound field, the absorption of the source under test, and the form of
the intensity field sampling and measurement procedure employed. For this reason this part of ISO 9614 specifies
initial procedures for the evaluation of indicators of the nature of the sound field which exists in the region of the
ISO 9614-3:2002(E)
proposed measurement surface (see annex B). The results of this initial test are used to select an appropriate
course of action according to Table C.1.
Below 50 Hz there are insufficient data on which to base uncertainty values. For the purposes of this part of
ISO 9614, the normal range for A-weighted data is covered by the one-third-octave bands from 50 Hz to 6,3 kHz.
The A-weighted value which is computed from one-third-octave band levels in the range 50 Hz to 6,3 kHz is correct
if there are no significantly high levels in the bands 31 Hz to 40 Hz and 8 kHz to 10 kHz. For the purposes of this
assessment, significant levels are band levels which after A-weighting are no more than 6 dB below the A-weighted
value computed. If A-weighted measurements and associated sound power level determinations are made in a
more restricted frequency range, this range shall be stated in accordance with 10 b). If only an A-weighted
determination is required, any single A-weighted band level of 10 dB or more below the highest A-weighted band
level may be neglected. If two or more band levels appear insignificant, they may be neglected if the level of the
sum of the A-weighted sound powers in these bands is 10 dB or more below the highest A-weighted band level. If
only an A-weighted overall sound power level is required, the uncertainty of determination of the sound power level
in any band in which it is 10 dB or more below the overall weighted level, is irrelevant.
Table 1 — Estimated upper values of the standard deviations of reproducibility of sound power levels
determined in accordance with this part of ISO 9614
One-third-octave band Upper values of standard deviation of
centre frequencies reproducibility
Hz dB
50 to 160 2,0
200 to 315 1,5
400 to 5 000 1,0
6 300 2,0
a b
A-weighted 1,0
a
Calculated from one-third-octave bands from 50 Hz to 6,3 kHz.

b
Applicable to a source which emits sound with a relatively “flat” spectrum in the frequency range 50 Hz to

6,3 kHz in the one-third-octave band.

NOTE 1 If certain operatives use similar facilities and instrumentation, the results of sound power determinations on a given
source at a given site are likely to exhibit smaller standard deviations than those indicated in Table 1.
NOTE 2 For a particular family of sound sources of similar size with similar sound power spectra operating in similar
environmental conditions, and measured according to a specific test code, the standard deviations of reproducibility are likely to
be less than those indicated in Table 1. Statistical methods for the characterization of batc
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