EN ISO 9614-1:2009

SLOVENSKI STANDARD
01-november-2009
1DGRPHãþD
SIST EN ISO 9614-1:1997
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Acoustics - Determination of sound power levels of noise sources using sound intensity -
Part 1: Measurement at discrete points (ISO 9614-1:1993)
Akustik - Bestimmung der Schalleistungspegel von Schallquellen aus
Schallintensitätsmessungen - Teil 1: Messungen an diskreten Punkten (ISO 9614-
1:1993)
Acoustique - Détermination par intensimétrie des niveaux de puissance acoustique émis
par les sources de bruit - Partie 1: Mesurages par points (ISO 9614-1:1993)
Ta slovenski standard je istoveten z: EN ISO 9614-1:2009
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 9614-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2009
ICS 17.140.01 Supersedes EN ISO 9614-1:1995
English Version
Acoustics - Determination of sound power levels of noise
sources using sound intensity - Part 1: Measurement at discrete
points (ISO 9614-1:1993)
Acoustique - Détermination par intensimétrie des niveaux Akustik - Bestimmung der Schalleistungspegel von
de puissance acoustique émis par les sources de bruit - Schallquellen aus Schallintensitätsmessungen - Teil 1:
Partie 1: Mesurages par points (ISO 9614-1:1993) Messungen an diskreten Punkten (ISO 9614-1:1993)
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 9614-1:2009: 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 9614-1:1993 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 9614-1:2009 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 9614-1:1995.
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 9614-1:1993 has been approved by CEN as a EN ISO 9614-1:2009 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
IS0
STANDARD
9614-1
First edition
1993-06-01
Acoustics - Determination of sound
.
power levels of noise sources using sound
intensity -
Part 1:
Measurement at discrete points
Acoustique - Dgtermination par intensimhrie des niveaux de puissance
acoustique 6mis par /es sources de bruit -
Partie 1: Mesurages par points
Reference number
IS0 9614-l :1993(E)
IS0 9614=1:1993(E)
Contents
Page
1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 Normative references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3 Definitions
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4 General requirements
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5 Acoustic environment
6 Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . .I. 5
7 Installation and operation of the source
. . . . 6
8 Measurement of normal sound intensity component levels
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9 Calculation of sound power level
,.
10 Information to be reported
Annexes
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A Calculation of field indicators
........... 12
B Procedure for achieving a desired grade of accuracy
......... 16
C Effects of airflow on measurement of sound intensity
D Effect of sound absorption within the measurement surface
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
E Bibliography
0 IS0 1993
All rights resewed. 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 per-
mission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
ii
IS0 9614=1:1993(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.
International Standard IS0 9614-1 was prepared by Technical Committee
lSO/lC 43, Acoustics, Sub-Committee SC 1, Noise.
IS0 9614 consists of the following parts, under the general title
Acoustics - Determination of sound power levels of noise sources using
sound intensity:
- Part I: Measurement at discrete points
- Part 2: Measurement by scanning
Annexes A and B form an integral part of this part of IS0 9614. Annexes
C, D and E are for information only.

IS0 9614=1:1993(E)
Introduction
0.1 The sound power radiated by a source is equal in value to the inte-
gral of the scalar product of the sound intensity vector and the associated
elemental area vector over any surface totally enclosing the source. Pre-
vious International Standards which describe methods of determination
of sound power levels of noise sources, principally IS0 3740 to IS0 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.
Therefore IS0 3740 to IS0 3747 necessarily specify the source charac-
teristics, the test environment characteristics and qualification procedures,
together with measurement methods which are expected to restrict the
uncertainty of the sound power level determination to within acceptable
limits.
The procedures specified in IS0 3740 to IS0 3747 are not always appro-
priate, for the following reasons.
a) Costly facilities are necessary if high precision is required. It is fre-
quently not possible to install and operate large pieces of equipment
in such facilities.
b) They cann ot be used in the prese nce of high levels of extraneo us noise
gene rated by sources other than that under investigation.
The purpose of IS0 9614 is to specify methods whereby the sound power
levels of sources may be determined, within specific ranges of uncer-
tainty, under test conditions which are less restricted than those required
by the series IS0 3740 to IS0 3747. The sound power is the in situ sound
power as determined by the procedure of this part of IS0 9614; it is
physically a function of the environment, and may in some cases differ
from the sound power of the same source determined under other con-
ditions.
This part of IS0 9614 complements the series IS0 3740 to IS0 3747
0.2
which specify various methods for the determination of sound power lev-
els of machines and equipment. It differs from these International Stan-
dards 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 IS0 9614 is classified according to the results
of specified ancillary tests and calculations performed in association
with the test measurements.
IS0 9614=1:1993(E)
c) Current limitations of intensity measurement equipment restrict
measurements to the one-third-octave range 50 Hz to 6,3 kHz. Band-
limited A-weighted values are determined from the constituent one-
octave or one-third-octave band values and not by direct A-weighted
measurements.
0.3 This part of IS0 9614 gives a method for determining the sound
power level of a source of stationary noise from measurements of sound
intensity on a surface enclosing the source. In principle, 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 the presence of sound sources
operating outside the measurement surface, any system lying within the
surface may 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 may 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 part of IS0 9614 is based on discrete-point sampling of the intensity
field normal to the measurement surface. 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 sampling surface, the distribution of sample positions, and the
proximity of extraneous sources outside the measurement surface.
The precision of measurement of the normal component of sound inten-
sity at a position is sensitive to the difference between the local sound
pressure level and the local normal sound intensity level. A large difference
may 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 may contain strong
contributions from sources outside the measurement surface, but may be
associated with little net sound energy flow, as in a reverberant field in
an enclosure; or the field may be strongly reactive because of the pres-
ence of the near-field and/or standing waves.

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IS0 9614=1:1993(E)
INTERNATIONAL STANDARD
Acoustics - Determination of sound power levels of
noise sources using sound intensity -
Part 1:
Measurement at discrete points
mination, and hence the grade of accuracy. If the in-
1 Scope
dicated quality of the determination does not meet
the requirements of this part of IS0 9614, the test
1.1 This part of IS0 9614 specifies a method for
procedure should be modified in the manner indi-
measuring the component of sound intensity normal
cated.
to a measurement surface which is chosen so as to
enclose the noise source(s) of which the sound power
level is to be determined. The one-octave, one-third-
2 Normative references
octave or band-limited weighted sound power level is
calculated from the measured values. The method is
The following standards contain provisions which,
applicable to any source for which a physically sta-
through reference in this text, constitute provisions
tionary measurement surface can be defined, and on
of this part of IS0 9614. At the time of publication, the
which the noise generated by the source is stationary
editions indicated were valid. All standards are subject
in time (as defined in 3.13). The source is defined by
to revision, and parties to agreements based on this
the choice of measurement surface. The method is
part of IS0 9614 are encouraged to investigate the
applicable in situ, or in special purpose test environ-
possibility of applying the most recent editions of the
ments.
standards indicated below. Members, of IEC and IS0
maintain registers of currently valid International
I.2 This part of IS0 9614 is applicable to sources
Standards.
situated in any environment which is neither so vari-
able in time as to reduce the accuracy of the meas-
IS0 5725:1986, Precision of test methods - Deter-
urement of sound intensity to an unacceptable
mination of repeatability and reproducibility for a
degree, nor subjects the intensity measurement
standard test method by inter-laboratory tests.
probe to gas flows of unacceptable speed or un-
steadiness (see 5.3 and 5.4).
I EC 942: 1988, Sound calibrators.
In some cases, it will be found that the test conditions
I EC 1043:-, l) Instruments for the measurement of
are too adverse to allow the requirements of this part
sound intensity.
of IS0 9614 to be met. In particular, extraneous noise
levels may vary to an excessive degree during the
test. In such cases, the method given in this part of
IS0 9614 is not suitable for the determination of the
3 Definitions
sound power level of the source.
For the purposes of this part of IS0 9614, the follow-
NOTE 1 Other methods, e.g. determination of sound
ing definitions apply.
power levels from surface vibration levels as described in
lSO/TR 7849, may be more suitable.
3.1 sound pressure level, Lp: Ten times the logar-
ithm to the base 10 of the ratio of the mean-square
I.3 This part of IS0 9614 specifies certain ancillary
sound pressure to the square of the reference sound
procedures, described in annex B, to be followed in
pressure. The reference sound pressure is 20 PPa.
conjunction with the sound power determination. The
results are used to indicate the quality of the deter-
Sound pressure level is measured in decibels.
1) To be published.
IS0 9614=1:1993(E)
3.2 instantaneous sound ‘intensity, 7(t): Instan-
36 . sound power
taneous rate of flow of sound energy per unit of sur-
face area in the direction of the local instantaneous
3.6.1 partial sound power, Pi: Time-averaged rate
acoustic particle velocity.
of flow of sound energy through an element (seg-
ment) of a measurement surface, given by:
This is a vectorial quantity which is equal to the prod-
uct of the instantaneous sound pressure at a point
pi = z*c = J”i$
. . .
(5)
and the associated particle velocity:
where
. . .
F(t) = p(t)Gi(t)
(1)
z is the signed magnitude of the normal
ni
sound intensity component measured at
position i on the measurement surface;
is the instantaneous sound pressure at a
PM
point;
s is the area of the segment of surface as-
i
sociated with point i.
is the associated i nstantan eous particle
velocity at the same point;
3.6.2 sound power, P: Total sound power gener-
t is the time, in seconds.
ated by a source as determined using the method
given in this part of IS0 9614, given by:
N
33 sound intensity, 7’: Time-avera ged value of 7’(t)
P=cP, . . .
(6)
ina temporally stationary sound field
i=l
. . .
and
(2)
N
=
. . .
IPI (7)
where T is the integration period. pi
c
i=l
I I
Also
where N is the total number of segments of the
z is the signed magnitude of 7’; the
sign is measurement surface.
an indication of directional sense, and is
i
dictated by the choice of positive d rection
3.6.3 sound power level, l;w: Logarithmic measure
of energy flow;
of the sound power generated by a source, as deter-
mined using the method given in this part of
is the unsigned magnitude 0f i.
IS0 9614, given by:
Lw= 10 Ig[lPl/Po] dB . . .
(8)
3.4 normal sound intensity, In: Component of the
sound intensity in the direction normal to a measure-
ment surface defined by the unit normal vector n’.
is the magnitude of the sound power of
IPI
Zn = hi
. . . the source;
(3)
is the reference sound power
where z is the unit normal vector directed out of the PO
(=lo-‘*w).
volume enclosed by the measurement surface.
Sound power level is expressed in decibels.
3.5 normal sound intensity level, L,: Logarithmic
When P is negative, the level is expressed as
measure of the unsigned value of the “normal sound
(-) XX dB for record purposes only.
intensity IIn I, given by:
NOTE 2 This part of IS0 9614 is not applicable if the
. . .
LI = lo IscII,I/lOl dB (4)
n
value of P of the source is found to be negative.
is the reference sound
where I, intensity
3.7 measurement surface: Hypothetical surface on
( = 1 O-l* W/m*).
which intensity measurements are made, and which
either completely encloses the noise source under
It is expressed in decibels.
test or, in conjunction with an acoustically rigid, con-
When Zn is negative, the level is expressed as tinuous surface, encloses the noise source under test.
(-) XX dB, except when used in the evaluation of bpr, In cases where the hypothetical surface is penetrated
(see 3.11) . by bodies possessing solid surfaces, the measure-
IS0 9614=1:1993(E)
ment surface terminates at the lines of intersection
4 General requirements
between the bodies and the surface.
3.8 segment: Portion of the measurement surface
associated with one measurement position. 4.1 Size of noise source
3.9 extraneous intensity: Contribution to the sound
The size of the noise source is unrestricted. The ex-
intensity which arises from the operation of sources
tent of the source is defined by the choice of the
external to the measurement surface (source mech-
measurement surface.
anisms operating outside the volume enclosed by the
measurement surface).
3.10 probe: That part of the intensity measurement
4.2 Character of noise radiated by the
system which incorporates the sensors.
source
3.11 pressure-residual intensity index, Q: The
The signal shall be stationary in time, as defined in
difference between the indicated Lp and the indicated
3.13. If a source operates according to a duty cycle,
LI when the intensity probe is placed and oriented in
within which there are distinct continuous periods of
a “sound field such that the sound intensity is zero. It
steady operation, for the purposes of this part of
is expressed in decibels.
IS0 9614, an individual sound power level is deter-
mined and reported for each distinct period. Action
Details for determining $,b are given in IEC 1043. In
shall be taken to avoid measurement during times of
this case only, the subscnpt “n” indicates the direc-
operation of non-stationary extraneous noise sources
tion of the probe axis.
of which the occurrences are predictable (see
. . .
6 table B.3 in annex B).
(9)
PI0 = wp -r/l,,
3.12 dynamic capability index, Ld: Given by:
. . . 4.3 Measurement uncertainty
Ld = 6pr, - K (10)
For the purposes of this part of IS0 9614, three
It is expressed in decibels.
grades of accuracy are defined in table 2. The stated
The value of K is selected according to the grade of
uncertainties account for random errors associated
accuracy required (see table 1).
with the measurement procedure, together with the
maximum measurement bias error which is limited
by the selection of the bias error factor K appropriate
- Bias error factor, K
Table 1
to the required grade of accuracy (see table 1). They
I I
Bias error factor
do not account for tolerances in nominal instrument
Grade of accuracy
performance which are specified in IEC 1043, nor do
dB
they account for the effects of variation in source in-
stallation, mounting and operating conditions.
Precision (grade I )
Engineering (grade 2)
Below 50 Hz there are insufficient data on which to
7 base uncertainty values. For the purposes of this part
Survey (grade 3)
/
of IS0 9614, the normal range for A-weighted data is
covered by the one-octave bands from 63 Hz to
4 kHz, and the one-third-octave bands from 50 Hz to
3.13 stationary signal: For the purposes of this part
6,3 kHz. The A-weighted value which is computed
of IS0 9614, a signal is considered stationary in time
if, for each measurement position, its time-averaged from one-octave band levels in the range 63 Hz to
properties during each individual measurement period 4 kHz, and one-third-octave band levels in the range
are equal to those obtained at the same position 50 Hz to 6,3 kHz is correct if there are no significantly
high levels in the bands below 50 Hz and above
when the averaging period is extended over the total
time taken to measure at all positions on the meas- 6,3 kHz. For the purposes of this assessment, signif-
icant levels are band levels which after A-weighting
urement surface. Cyclic, or periodic, signals are, by
this definition, stationary if at each individual position are no more than 6 dB below the A-weighted value
computed. If A-weighted measurements and associ-
the measurement period extends over at least ten
ated sound power level determinations are made in a
cycles.
more restricted frequency range, this range shall be
3.14 field indicators, F, to &: See annex A. stated in accordance with 10.5 b).

IS0 9614+1993(E)
Table 2 - Uncertainty in the determination of sound power levels
Standard deviations, s 1)
Octave band One-third-octave
centre band centre ’
Precision Engineering Survey
frequencies frequencies
(grade 1) (grade 2) (grade 3)
Hz Hz dB dB dB
63 to 125 50 to 160 2 3
250 to 500 200 to 630 1,5 2
1 000 to 4 000 800 to 5 000 1 L5
6 300 2 23
A-weighted21 43)
1) The true value of the sound power level is to be expected with a certainty of 95 %
in the range of f 2s about the measured value.
2) 63 Hz to 4 kHz or 50 Hz to 6,3 kHz.
3) In view of the wide variation of equipment for which the standards may be applied,
the value given is only tentative.
I ne uncertainty in the determination of the sound
5.2 Extraneous intensity
power level of a noise source is related to the nature
of the sound field of the source, to the nature of the
5.2.1 Level of extraneous intensity
extraneous sound field, to the absorption of the
source under test, and to the type of intensity-field
Make every effort to minimize the level of extraneous
sampling and measurement procedure employed. For
intensity, which shall not be such as to reduce unac-
this reason this part of IS0 9614 specifies initial pro-
ceptably the measurement accuracy (see annex B
cedures for the evaluation of indicators of the nature
and A.2.2 of annex A).
of the sound field which exists in the region of the
proposed measurement surface (see annex A). The
NOTE 3 If substantial quantities of absorbing material are
results of this initial test are used to select an appro-
part of the source under test, high levels of extraneous in-
priate course of action according to tables B.2 and B.3
tensity may lead to an erroneous estimate of the sound
(see annex B).
power. Annex D gives indications of how to evaluate the
resulting error in the special case where the source under
If only an A-weighted determination is required, any
test can be switched off.
single A-weighted band level of 10 dB or more below
the highest A-weighted band level shall be neglected.
If more than one band levels appear insignificant, they
5.2.2 Variability of extraneous noise
may be neglected if the level of the sum of the A-
weighted sound powers in these bands is 10 dB or
Ensure that the variability of the extraneous noise in-
more below the highest A-weighted band level. If only
tensity is not such that the specified limit on the
a frequency-weighted overall sound power level is
sound field temporal variability indicator, F,, is ex-
required, the uncertainty of determination of the
ceeded. See table B.3.
sound power level in any band in which its weighted
value is 10 dB or more below the overall weighted
level, is irrelevant.
5.3 Wind, gas flow, vibration and
temperature
5 Acoustic environment
Do not make measurements when air flow conditions
in the vicinity of the intensity probe contravene the
5.1 Criterion for adequacy of the test
limits for satisfactory performance of the measure-
environment ment system, as specified by the manufacturer. In the
absence of such information, do not make measure-
The test environment shall be such that the principle
ments if the mean air speed exceeds 2 m/s (see an-
upon which sound intensity is measured by the par-
nex C). Always use a probe windscreen during
ticular instrument employed, as given in IEC 1043, is
outdoor measurements (refer to IEC 1043 for guid-
not invalidated. In addition, it shall satisfy the require-
ance). Do not place the probe in, or very close to, any
ments stated in 5.2 to 5.4.
stream of flowing gas of which the mean speed ex-
IS0 9614=1:1993(E)
If no field check is specified, carry out the procedures
ceeds 2 m/s, and mount it so that it is not subject to
given in 6.2.1 and 6.2.2 to indicate anomalies within
significant vibration.
the measuring system that may have occurred during
NOTES
transportation, etc.
4 Because wind speed fluctuates about a mean, the sound
power level determined may be an overestimate in cases
6.2.1 Sound pressure level
where the mean wind speed is close to the maximum al-
lowed.
Check each pressure microphone of the intensity
probe for sound pressure level using a class 0 or 1 or
5 The probe should not be placed closer than 20 mm to
1 L calibrator in accordance with IEC 942.
bodies having a temperature significantly different from that
of the ambient air. The use of a probe in temperatures much
higher than ambient, especially if there is a high tempera-
6.2.2 Intensity
ture gradient across the probe, should be avoided.
Place the intensity probe on the measurement sur-
6 Air pressure and temperature affect air density and the
face, with the axis oriented normal to the surface, at
speed of sound. The effects of these quantities on instru-
a position with intensity higher than the surface aver-
ment calibration should be ascertained and appropriate cor-
rections should be made to indicate intensities (see age intensity. Measure the normal sound intensity
IEC 1043).
level (see 3.5). Rotate the intensity probe through
180” about an axis normal to the measurement axis
and place it with its acoustic centre in the same pos-
5.4 Configuration of the surroundings
ition as the first measurement. Measure the intensity
again. Mount the intensity probe on a stand to retain
The configuration of the test surroundings shall, as far
the same position while rotating the probe. For the
as possible, remain unchanged during the perform-
maximum band level measured in one-octave or one-
ance of a test; this is particularly important if the
third-octave bands, the two values of &, shall have
source emits sound of a tonal nature. Examine the
opposite signs and the difference between the two
repeatability of the results (as defined in IS0 5725)
sound intensity levels shall be less than 1,5 dB in or-
and record cases where variation in the test sur-
der for the measuring equipment to be acceptable.
roundings during a test is unavoidable. Ensure, as far
as is possible, that the operator does not stand in a
position on, or close to, the axis of the probe during
the period of measurement at any position. If practi-
7 Installation and operation of the
cable, remove any extraneous objects from the vicin-
source
ity of the source.
7.1 General
6 Instrumentation
Mount the source or place it in a proper way rep-
6.1 General
resentative of normal use or the way stated in a spe-
cial test code for the particular type of machinery or
A sound intensity measurement instrument and probe
equipment.
that meet the requirements of IEC 1043 shall be
used. Class 1 instruments shall be used for grade 1
and grade 2 determinations. Adjust the intensity
7.2 Operating and mounting conditions of
measurement instrument to allow for ambient air
the source under test
pressure and temperature according to IEC 1043. Re-
cord the pressure-residual intensity index of the in-
Use the operating and mounting conditions specified
strument used for measurements according to this
in a test code, if any, for the particular type of ma-
part of IS0 9614 for each frequency band of meas-
chinery or equipment. If there is no test code, operate
urement.
the source heavily loaded in a steady condition rep-
resentative of normal use.
6.2 Calibration and field check
The following operational conditions may be appropri-
ate:
The instrument, including the probe, shall comply with
IEC 1043. Verify compliance with IEC 1043 at least
under the load of maximum sound generation
a)
once a year in a laboratory making calibrations in ac-
representative of normal use (probability of such
cordance with national standards. Record the results
use being more than 10 %);
in accordance with 10.3.
To check the instrumentation for proper operation under full load;
b)
prior to each series of measurements, apply the
field-check procedure specified by the manufacturer. under no load (idling);
c)
IS0 9614=1:1993(E)
d) under simulated load (the load is not represen- The average distance between the measurement
tative of normal use but simulating it, preferably surface and the surface of the source under test shall
being the load of maximum sound generation); be greater than 0,5 m, unless that position is on a
component which can be shown, by test, to radiate
e) under other specified load and operating con- an insignificant proportion of the sound power of the
ditions. source under test. The chosen surface may incorpor-
ate areas which are non-absorbent (diffuse-field ab-
One of the alternatives a) or b) is recommended in
sorption coefficient less than 0,06), such as a
this order to be applied as the main operating con-
concrete floor or masonry wall, where convenient.
dition. One or more of the others can be chosen as
Intensity measurements shall not be made on such
additional operating conditions.
surfaces, and the areas of such surfaces shall not be
included in the evaluation of source sound power ac-
cording to equation (6) (see 3.6.2).
8 Measurement of normal sound
intensity component levels
Choose a “typical” measurement position on the in-
itial measurement surface for the assessment of
whether the sound field is stationary. Calculate indi-
8.1 Averaging time
cator F, for all frequency bands of measurement ac-
cording to A.2.1 of annex A. If the temporal variability
For a 95 % confidence level of a maximum error of
of the sound field exceeds that specified in table B.3
5 % in measured intensity, the averaging time re-
in annex B, take appropriate action according to
quirement for instruments using filters for white noise
table 8.3 to reduce this variability.
with Gaussian distribution is given by
BT >, 400
If it is possible to turn off the source under test, ex-
traneous noise is insignificant if A-weighted sound
where
pressure levels measured at five positions (distributed
reasonably uniformly over the measurement surface)
B is the filter bandwidth;
fall by at least 10 dB when the source is turned off.
T is the averaging time.
NOTE 8 This condition does not apply in cases where the
source under test drives sources of significant extraneous
For instruments which synthesize one- or one-third-
noise external to the measurement surface.
octave bands from narrow-band analyses, reference
shall be made to IEC 1043 for guidance on the equiv-
Make measurements of normal sound intensity levels
alent averaging time/number of averages. Special care
and sound pressure levels in those frequency bands
shall be taken in cases of cyclic signals.
in which the sound power determination is to be
made, at a minimum of one position per square me-
8.2 Initial test
tre, and a minimum of 10 positions distributed as
uniformly as possible (according to segment area)
Make measurements of normal sound intensity on an
over the measurement surface. In cases where the
initial measurement surface. If this initial surface
extraneous noise is not insignificant, and where this
proves to be unsatisfactory, modify it according to the
would require more than 50 measurement positions,
actions specified in annex B.
a reduction to one position per 2 m2 is permissible,
provided that the total number is not less than 50. In
The initial measurement surface shall be defined
cases where the extraneous noise is insignificant, and
around the source under test.
for measurement surface areas greater than 50 m2,
distribute 50 positions as uniformly as possible (ac-
NOTE 7 This should preferably take one of the geo-
cording to segment area) over the entire measure-
metrically simple and quantifiable forms indicated in
figure 1. ment surface.
-----a
-N
Parallelepiped Hemisphere Cylinder
Figure 1 - Preferred initial measurement surfaces

IS0 9614-1:1993(E)
Selective increase of the number of measurement
Calculate the field indicators F2, F3 and I$ for all fre-
quency bands of measurement according to positions in such segments will normally improve the
annex A, and introduce them into the formulae given accuracy of determination of sound power. The
for the qualification procedure of B.l .l of annex B. If possibility is assessed according to the calculation
this check is fulfilled for each frequency band, the in- procedure given in B.1.3.
itial sound power determination is qualified as a final
If confirmation of the existence of partial sound power
result within the range of uncertainty given by
concentrations is obtained, evaluate the necessary
table 2.
number of additional positions on the subset of seg-
If criterion 1 of B.l .l is not satisfied for all frequency ments passing the major part of the sound power ac-
bands of measurement, then take one of the follow- cording to the calculation procedure specified in
ing alternative courses of action: B.1.3, and distribute the number uniformly (according
to segment area) over that subset. Measure normal
make a statement in the report according to 10.5 sound intensity levels only at the new measurement
to the effect that the uncertainty of the sound positions. Calculate the partial sound powers and
power level determination in these frequency source sound power level from equations (11) and
bands exceeds that stated in table2 for the de- (12), and qualify the sound power determination as a
sired grade of accuracy; or final result within the range of uncertainty given by
table 2.
take action according to table B.3, to increase the
If this selective modification procedure cannot be im-
accuracy of the determination.
plemented, take alternative appropriate action ac-
cording to B.2 and table B.3.
If criterion 2 of B.l.2 is not satisfied in all frequency
bands of measurement, take alternative action in ac-
cordance with either 8.3 or 8.4.
8.4 Further tests
8.3 Optional procedure designed to If the checks given in B.l indicate that neither the in-
itial choice of measurement array nor, if the procedure
minimize the number of additional
in 8.3.2 is implemented, the modified measurement
measurement positions on an initial
array meets the desired grade of accuracy, take ap-
measurement surface
propriate action according to B.2. Measure the normal
sound intensity component levels and associated
8.3.1 Identification of concentrations of partial
sound pressure levels using the modified measure-
sound power
ment surface and/or array. Recalculate the field indi-
cators F2, F3 and F4 and assess them according to
If the check given in B.1.2 (criterion 2) indicates that,
I
B.l. Take action according to B.2.
for any frequency band (or bands), the normalized
standard deviation of the measured values of normal
Repeat this procedure until the required grade of ac-
sound intensity indicated by F’ on the initial meas-
curacy, as indicated by B.1, is attained. In cases
urement surface exceeds that necessary to ensure a
where repeated action fails to satisfy the specified
sampling error within the range corresponding to the
criteria, record a null test result and state the associ-
desired class of accuracy, it may be possible to mini-
ated reasons.
mize the additional measurement effort required to
qualify the initial measurement surface by selectively
modifying the array of measurement positions in a 9 Calculation of sound power level
manner which optimizes the normal sound intensity
sampling process. The possibility of such optimization
9.1 Calculation of partial sound powers for
may be checked by implementing the procedure
each segment of the measurement surface(s)
given in 8.3.2.
Calculate a partial sound power in each frequency
8.3.2 Positive partial sound power concentration
band for each segment of the measurement surface
from the equation:
This procedure determines whether or not it is poss-
Pi = I&Si
. . .
ible to optimize the normal sound intensity sampling (11)
process by selectively modifying the array of meas-
where
urement positions. If criterion 1 of B.l .l is satisfied
but criterion 2 of B.1.2 is not satisfied, and if
P is the partial sound powe
...