SIST EN ISO 3743-1:2010

SLOVENSKI STANDARD
01-december-2010
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Acoustics - Determination of sound power levels and sound energy levels of noise
sources using sound pressure - Engineering methods for small movable sources in
reverberant fields - Part 1: Comparison method for a hard-walled test room (ISO 3743-
1:2010)
Akustik - Bestimmung der Schallleistungs- und der Schallenergiepegel von
Geräuschquellen aus Schalldruckmessengen - Verfahren der Genauigkeitsklasse 2 für
kleine, transportable Quellen in Hallfeldern - Teil 1: Vergleichsverfahren in Prüfräumen
mit schallharten Wänden (ISO 3743-1:2010)
Acoustique - Détermination des niveaux de puissance acoustique et des niveaux
d'énergie acoustique émis par les sources de bruit a partir de la pression acoustique -
Méthode d'expertise en champ réverbéré applicable aux petites sources transportables -
Partie 1: Méthode par comparaison (ISO 3743-1:2010)
Ta slovenski standard je istoveten z: EN ISO 3743-1:2010
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 3743-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2010
ICS 17.140.01 Supersedes EN ISO 3743-1:2009
English Version
Acoustics - Determination of sound power levels and sound
energy levels of noise sources using sound pressure -
Engineering methods for small movable sources in reverberant
fields - Part 1: Comparison method for a hard-walled test room
(ISO 3743-1:2010)
Acoustique - Détermination des niveaux de puissance et Akustik - Bestimmung der Schallleistungs- und
d'énergie acoustiques émis par les sources de bruit à partir
Schallenergiepegel von Geräuschquellen aus
de la pression acoustique - Méthodes d'expertise en champ Schalldruckmessungen - Verfahren der Genauigkeitsklasse
réverbéré applicables aux petites sources transportables - 2 für kleine, transportable Quellen in Hallfeldern - Teil 1:
Partie 1: Méthode par comparaison en salle d'essai à Vergleichsverfahren in einem Prüfraum mit schallharten
parois dures (ISO 3743-1:2010) Wänden (ISO 3743-1:2010)
This European Standard was approved by CEN on 14 August 2010.

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, Croatia, 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
© 2010 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 3743-1:2010: E
worldwide for CEN national Members.

Contents Page
Foreword .3
Annex ZA .4

Foreword
The text of ISO 3743-1:2010 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 3743-1:2010 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 April 2011, and conflicting national standards shall be withdrawn at the
latest by April 2011.
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 3743-1:2009.
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 EU Directive.
For relationship with EU Directive, see informative Annex ZA, which is an integral part 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, Croatia, 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 3743-1:2010 has been approved by CEN as a EN ISO 3743-1:2010 without any modification.
Annex ZA
(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 one 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 products falling
within the scope of this standard.

INTERNATIONAL ISO
STANDARD 3743-1
Second edition
2010-10-01
Acoustics — Determination of sound
power levels and sound energy levels of
noise sources using sound pressure —
Engineering methods for small movable
sources in reverberant fields
Part 1:
Comparison method for a hard-walled
test room
Acoustique — Détermination des niveaux de puissance et d'énergie
acoustiques émis par les sources de bruit à partir de la pression
acoustique — Méthodes d'expertise en champ réverbéré applicables
aux petites sources transportables
Partie 1: Méthode par comparaison en salle d'essai à parois dures

Reference number
ISO 3743-1:2010(E)
©
ISO 2010
ISO 3743-1:2010(E)
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ii © ISO 2010 – All rights reserved

ISO 3743-1:2010(E)
Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.1
3 Terms and definitions .2
4 Test room and size of noise source under test.6
5 Instrumentation and measurement equipment .7
6 Definition, location, installation, and operation of noise source under test.8
7 Measurement procedure.10
8 Determination of sound power levels and sound energy levels .12
9 Measurement uncertainty.16
10 Information to be recorded.19
11 Test report.21
Annex A (normative) Sound power level and sound energy level under reference meteorological
conditions.22
Annex B (normative) Calculation of A-weighted sound power levels and A-weighted sound
energy levels from octave band levels.24
Annex C (informative) Guidelines on the development of information on measurement uncertainty .26
Bibliography.35

ISO 3743-1:2010(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 2.
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 document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 3743-1 was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 1, Noise.
This second edition cancels and replaces the first edition (ISO 3743-1:1994), which has been technically
revised.
ISO 3743 consists of the following parts, under the general title Acoustics — Determination of sound power
levels and sound energy levels of noise sources using sound pressure — Engineering methods for small
movable sources in reverberant fields:
⎯ Part 1: Comparison method for a hard-walled test room
⎯ Part 2: Methods for special reverberation test rooms

iv © ISO 2010 – All rights reserved

ISO 3743-1:2010(E)
Introduction
[1] [7]
This part of ISO 3743 is an element of the series ISO 3740 to ISO 3747 , which specify various methods
for determining the sound power levels and sound energy levels of noise sources including machinery,
equipment and their sub-assemblies. The selection of one of the methods from the series for use in a
particular application depends on the purpose of the test to determine the sound power level or sound energy
[1]
level and on the facilities available. General guidelines to assist in the selection are provided in ISO 3740 .
[1] [7]
ISO 3740 to ISO 3747 give only general principles regarding the operating and mounting conditions of the
machinery or equipment for the purposes of the test. It is important that test codes be established for
individual kinds of noise source, in order to give detailed requirements for mounting, loading, and operating
conditions under which the sound power levels or sound energy levels are to be obtained.
The method given in this part of ISO 3743 is based on a comparison of the sound pressure levels in octave
frequency bands of a noise source under test with those of a calibrated reference sound source; A-weighted
sound power levels or sound energy levels may be calculated from the octave-band levels. The method is
applied in a hard-walled test room with prescribed acoustical characteristics, where it can be used for small
items of portable equipment. Such a room allows either the sound power levels or the sound energy levels of
the noise source under test to be determined, depending on the character of the noise emitted by the source.
However, this kind of test room is not suitable for larger pieces of stationary equipment which, due to their
manner of operation or installation, cannot readily be moved. The application of the method for use where the
[7]
equipment or machinery is found in situ is described in ISO 3747 .
The methods specified in this part of ISO 3743 permit the determination of the sound power level and the
sound energy level in frequency bands and/or with frequency A-weighting applied.
This part of ISO 3743 describes a method of accuracy grade 2 (engineering grade) as defined in ISO 12001.
[2]
For applications where greater accuracy is required, reference can be made to ISO 3741 or an appropriate
[15][17]
part of ISO 9614 . If the relevant criteria for the measurement environment specified in this part of
ISO 3743 are not met, it might be possible to refer to another standard from this series, or to an appropriate
[15][17]
part of ISO 9614 .
INTERNATIONAL STANDARD ISO 3743-1:2010(E)

Acoustics — Determination of sound power levels and sound
energy levels of noise sources using sound pressure —
Engineering methods for small movable sources in reverberant
fields
Part 1:
Comparison method for a hard-walled test room
1 Scope
1.1 General
This part of ISO 3743 specifies methods for determining the sound power level or sound energy level of a
noise source by comparing measured sound pressure levels emitted by this source (machinery or equipment)
mounted in a hard-walled test room, the characteristics of which are specified, with those from a calibrated
reference sound source. The sound power level (or, in the case of noise bursts or transient noise emission,
the sound energy level) produced by the noise source, in frequency bands of width one octave, is calculated
using those measurements. The sound power level or sound energy level with A-weighting applied is
calculated using the octave-band levels.
1.2 Types of noise and noise sources
The method specified in this part of ISO 3743 is suitable for all types of noise (steady, non-steady, fluctuating,
isolated bursts of sound energy, etc.) defined in ISO 12001.
The noise source under test may be a device, machine, component or sub-assembly. The maximum size of
the source depends upon the size of the room used for the acoustical measurements (see 4.2).
1.3 Test environment
The test environment that is applicable for measurements made in accordance with this part of ISO 3743 is a
hard-walled test room with prescribed acoustical characteristics.
1.4 Measurement uncertainty
Information is given on the uncertainty of the sound power levels and sound energy levels determined in
accordance with this part of ISO 3743, for measurements made in frequency octave bands and for A-weighted
frequency calculations performed on them. The uncertainty conforms to ISO 12001:1996, accuracy grade 2
(engineering grade).
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 5725 (all parts), Accuracy (trueness and precision) of measurement methods and results
ISO 3743-1:2010(E)
ISO 6926, Acoustics — Requirements for the performance and calibration of reference sound sources for the
determination of sound power levels
ISO 12001:1996, Acoustics — Noise emitted by machinery and equipment — Rules for the drafting and
presentation of a noise test code
ISO/IEC Guide 98-3, Uncertainty in measurement — Part 3: Guide to the expression of uncertainty in
measurement (GUM:1995)
IEC 60942:2003, Electroacoustics — Sound calibrators
IEC 61260:1995, Electroacoustics — Octave-band and fractional-octave-band filters
IEC 61672-1:2002, Electroacoustics — Sound level meters — Part 1: Specifications
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
sound pressure
p
difference between instantaneous pressure and static pressure
[19]
NOTE 1 Adapted from ISO 80000-8:2007 , 8-9.2.
NOTE 2 Sound pressure is expressed in pascals.
3.2
sound pressure level
L
p
ten times the logarithm to the base 10 of the ratio of the square of the sound pressure, p, to the square of a
reference value, p , expressed in decibels
p
L = 10lg dB (1)
p
p
where the reference value, p , is 20 µPa
[18]
[ISO/TR 25417:2007 , 2.2]
NOTE 1 If specific frequency and time weightings as specified in IEC 61672-1 and/or specific frequency bands are
applied, this is indicated by appropriate subscripts; e.g. L denotes the A-weighted sound pressure level.
pA
[19]
NOTE 2 This definition is technically in accordance with ISO 80000-8:2007 , 8-22.
3.3
time-averaged sound pressure level
L
p,T
ten times the logarithm to the base 10 of the ratio of the time average of the square of the sound pressure, p,
during a stated time interval of duration, T (starting at t and ending at t ), to the square of a reference value,
1 2
p , expressed in decibels
2 © ISO 2010 – All rights reserved

ISO 3743-1:2010(E)
t
⎡⎤2
⎢⎥
pt()dt
∫
⎢⎥T
t
⎢⎥1
L = 10 lg dB (2)
pT,
⎢⎥
p
⎢⎥
⎢⎥
⎢⎥
⎣⎦
where the reference value, p , is 20 µPa
NOTE 1 In general, the subscript “T” is omitted since time-averaged sound pressure levels are necessarily determined
over a certain measurement time interval.
NOTE 2 Time-averaged sound pressure levels are often A-weighted, in which case they are denoted by L , which is
pA,T
usually abbreviated to L .
pA
[18]
NOTE 3 Adapted from ISO/TR 25417:2007 , 2.3.
3.4
single event time-integrated sound pressure level
L
E
ten times the logarithm to the base 10 of the ratio of the integral of the square of the sound pressure, p, of an
isolated single sound event (burst of sound or transient sound) over a stated time interval T (starting at t and
ending at t ) to a reference value, E , expressed in decibels
2 0
t
⎡⎤2
⎢⎥
pt()dt
∫
⎢⎥
t
⎢⎥
L = 10 lg dB (3)
E
⎢⎥
E
⎢⎥
⎢⎥
⎢⎥
⎣⎦
2 −10 2
where the reference value, E , is (20 µPa) s = 4 × 10 Pa s
T
NOTE 1 This quantity can be obtained by L +10 lg dB , where T = 1 s
pT, 0
T
NOTE 2 When used to measure sound immission, this quantity is usually called “sound exposure level”
[18]
(see ISO/TR 25417:2007 ).
3.5
measurement time interval
T
portion or a multiple of an operational period or operational cycle of the noise source under test for which the
time-averaged sound pressure level is determined
NOTE Measurement time interval is expressed in seconds.
3.6
comparison method
method by which the sound power level or sound energy level of a noise source under test is determined from
a comparison of the sound pressure levels produced by the source under test with those of a reference sound
source of known sound power output, when both sources are operated in the same environment
ISO 3743-1:2010(E)
3.7
hard-walled test room
room in which the acoustical reflectivity of all room surfaces (including the floor and ceiling) is high over the
frequency range of interest
3.8
reverberant sound field
that portion of the sound field in the test room over which the influence of sound received directly from the
source is negligible
3.9
sound absorption coefficient
α
at a given frequency and for specified conditions, the relative fraction of sound power incident upon a surface
which is not reflected
3.10
reference sound source
sound source meeting specified requirements
NOTE For the purposes of this International Standard, the requirements are those specified in ISO 6926:1999,
Clause 5.
3.11
frequency range of interest
for general purposes, the frequency range of octave bands with nominal mid-band frequencies from 125 Hz to
8 000 Hz
NOTE For special purposes, the frequency range can be reduced, provided that the test environment, reference
sound source, and instrument specifications are satisfactory for use over the modified frequency range. The frequency
range can be extended downwards as far as the 63 Hz octave band, but cannot be extended upwards beyond the
8 000 Hz band. Any reduced or extended frequency range is clearly indicated as such in the report.
3.12
reference box
hypothetical right parallelepiped terminating on the floor of the test room on which the noise source under test
is located, that just encloses the source including all the significant sound radiating components and any test
table on which the source is mounted
NOTE If required, the smallest possible test table can be used for compatibility with emission sound pressure
measurements at bystander positions in accordance with the ISO 11200 to ISO 11204 series.
3.13
background noise
noise from all sources other than the noise source under test
NOTE Background noise includes contributions from airborne sound, noise from structure-borne vibration, and
electrical noise in the instrumentation.
3.14
background noise correction
K
correction applied to the measured sound pressure levels to account for the influence of background noise
NOTE 1 Background noise correction is expressed in decibels.
NOTE 2 The background noise correction is frequency dependent; the correction in the case of a frequency band is
denoted K , where f denotes the relevant mid-band frequency, and that in the case of A-weighting is denoted K .
1f 1A
4 © ISO 2010 – All rights reserved

ISO 3743-1:2010(E)
3.15
sound power
P
through a surface, product of the sound pressure, p, and the component of the particle velocity, u , at a point
n
on the surface in the direction normal to the surface, integrated over that surface
[19]
[ISO 80000-8:2007 , 8-16]
NOTE 1 Sound power is expressed in watts.
NOTE 2 The quantity relates to the rate per time at which airborne sound energy is radiated by a source.
3.16
sound power level
L
W
ten times the logarithm to the base 10 of the ratio of the sound power of a source, P, to a reference value, P ,
expressed in decibels
P
L = 10lg dB (4)
W
P
where the reference value, P , is 1 pW
NOTE 1 If a specific frequency weighting as specified in IEC 61672-1 and/or specific frequency bands are applied, this
should be indicated by appropriate subscripts; e.g. L denotes the A-weighted sound power level.
WA
[19]
NOTE 2 This definition is technically in accordance with ISO 80000-8:2007 , 8-23.
[18]
[ISO/TR 25417:2007 , 2.9]
3.17
sound energy
J
integral of the sound power, P, over a stated time interval of duration T (starting at t and ending at t )
1 2
t
J = Pt()dt (5)
∫
t
NOTE 1 Sound energy is expressed in joules.
NOTE 2 The quantity is particularly relevant for non-stationary, intermittent sound events.
[18]
[ISO/TR 25417:2007 , 2.10]
3.18
sound energy level
L
J
ten times the logarithm to the base 10 of the ratio of the sound energy, J, to a reference value, J , expressed
in decibels
J
L = 10 lg dB (6)
J
J
where the reference value, J , is 1 pJ
ISO 3743-1:2010(E)
NOTE If a specific frequency weighting as specified in IEC 61672-1 and/or specific frequency bands are applied, this
should be indicated by appropriate subscripts; e.g. L denotes the A-weighted sound energy level.
JA
[18]
[ISO/TR 25417:2007 , 2.11]
4 Test room and size of noise source under test
4.1 Reference box
In order to assist in specification of the size of the test room, the reference box shall first be delineated. The
reference box is a hypothetical surface defined by the smallest right parallelepiped that just encloses the noise
source under test. The noise source under test shall be taken to include all significant sources of sound
emission, including auxiliary equipment which cannot either be removed or adequately quietened, and the
reference box shall be extended appropriately. When defining the dimensions of the reference box, elements
protruding from the source which are not significant radiators of sound may be disregarded.
4.2 Volume of test room and size of noise source under test
The volume of the test room shall be at least 40 m , and at least 40 times the volume of the reference box.
3 3
In rooms with volumes between 40 m and 100 m , the largest dimension of the reference box shall not
exceed 1,0 m. In rooms with volumes greater than 100 m , the largest dimension of the reference box shall
not exceed 2,0 m.
4.3 Acoustical properties of test room
A hard-walled room shall be used. This means that the sound absorption coefficient of any portion of any
boundary surface shall not exceed 0,20 at all frequencies within the frequency range of interest. Most ordinary,
unfurnished rooms without special acoustical treatment (e.g. acoustical ceilings and/or absorptive wall
coverings) comply with this requirement. Table 1 gives guidelines.
Table 1 — Acceptable and unacceptable rooms
Acceptable rooms Unacceptable rooms
Nearly empty rooms with smooth hard walls and ceiling Rooms with upholstered furniture, machinery or industrial
made of concrete, brick, plaster or tile rooms with a small amount of sound absorptive material on
ceiling or walls (e.g. partially absorptive ceiling)
Partly empty rooms, rooms with smooth hard walls Rooms with some sound absorptive materials on both
ceiling and walls
Rooms without upholstered furniture, right cuboid Rooms with large amounts of sound absorptive materials
machinery rooms or industrial rooms, no sound absorptive on either ceiling or walls
materials on surfaces
Irregularly shaped rooms without upholstered furniture,
irregularly shaped machinery rooms or industrial rooms, no
sound absorptive materials on surfaces

4.4 Criterion for acoustic adequacy of test room
The suitability of a test room can differ from one noise source under test to another. The requirements for the
room are most critical when a highly directional sound source is to be evaluated. When testing the general
suitability of a test room, the procedure described hereafter shall be followed.
6 © ISO 2010 – All rights reserved

ISO 3743-1:2010(E)
[4] [5]
A highly directional, broad-band sound source, having a directivity index (see ISO 3744 or ISO 3745 ) of at
least 5 dB at all frequencies of interest above 500 Hz, is located in the test room as given in 6.3, so that the
strongest component of sound energy is within 45° of the horizontal plane and is reflected at least once from a
boundary with a minimum of loss before reaching any of the microphone positions. Microphone positions are
chosen in accordance with 7.3 and the mean background noise corrected octave band time-averaged sound
pressure level, L , is determined [see Equation (14) omitting RSS terms, i.e.
p1
′
LL≡≡K ≡ 0
Wp(RSS) (RSS) 1(RSS)
and substituting L for L ]. The sound source is then turned 45° to 135° in compliance with the requirement
p1 W
of 6.3 and the corresponding octave-band time-averaged sound pressure level, L , is determined. This
p2
procedure is repeated twice more to determine L and L . The fourth position shall be within 45° to 90°
p3 p4
of the first position. This whole procedure is then repeated four more times with the sound source turned
upwards so that the strongest component of sound energy is within 45° of the vertical, and four more mean
octave band time-averaged sound pressure levels are determined. The test room is considered to be suitable
for the purposes of this part of ISO 3743 if the maximum difference between the octave band sound pressure
levels of any two source positions for the frequency bands with mid-band frequencies between 125 Hz and
8 000 Hz does not exceed the standard deviations of reproducibility of Table 3.
NOTE As an alternative to the highly directional sound source, a sound source of the same type as the noise source
to be tested can be used. However, if this alternative procedure is used, the suitability of the room can be taken as proven
only for testing this type of noise source.
4.5 Criterion for background noise
The mean octave-band time-averaged sound pressure level of the background noise measured and averaged
over the microphone positions or traverses (see 8.1.2), shall be at least 6 dB, and preferably more than 15 dB,
below the corresponding mean uncorrected octave-band sound pressure levels (time averaged or single
event) from the noise source under test (see 8.1.2 and 8.2.2) and from the reference sound source.
NOTE If it is necessary to make measurements where the difference between the sound pressure levels of the
[15] [16]
background noise and the sources is less than 6 dB, ISO 9614-1 or ISO 9614-2 can be used.
4.6 Ambient temperature and humidity
The ambient temperature and relative humidity in the test room shall be monitored and maintained at as
nearly constant values as practicable during measurements.
5 Instrumentation and measurement equipment
5.1 General
The instrumentation system, including the microphones and cables, shall meet the requirements of
IEC 61672-1:2002, class 1, and the filters shall meet the requirements of IEC 61260:1995, class 1. The
reference sound source shall meet the requirements given in ISO 6926.
5.2 Calibration
Before and after each series of measurements, a sound calibrator meeting the requirements of
IEC 60942:2003, class 1 shall be applied to each microphone to verify the calibration of the entire measuring
system at one or more frequencies within the frequency range of interest. Without any further adjustment, the
difference between the readings made before and after each series of measurements shall be less than or
equal to 0,5 dB. If this value is exceeded, the results of the series of measurements shall be discarded.
ISO 3743-1:2010(E)
The calibration of the sound calibrator, the compliance of the instrumentation system with the requirements of
IEC 61672-1, the compliance of the filter set with the requirements of IEC 61260, and the compliance of the
reference sound source with the requirements of ISO 6926, shall be verified, at intervals in a laboratory
making calibrations traceable to appropriate standards.
Unless national regulations dictate otherwise, it is recommended that the sound calibrator should be calibrated
at intervals not exceeding 1 year, the reference sound source should be calibrated at intervals not exceeding
2 years, the compliance of the instrumentation system with the requirements of IEC 61672-1 should be
verified at intervals not exceeding 2 years, and the compliance of the filter set with the requirements of
IEC 61260 should be verified at intervals not exceeding 2 years.
6 Definition, location, installation, and operation of noise source under test
6.1 General
It is important to decide which components, sub-assemblies, auxiliary equipment, power sources, etc.,
constitute integral parts of the noise source whose sound power level or sound energy level is to be
determined. It is important also to define the manner in which the noise source is installed and operated for
the test, since both these factors can have a significant influence on the sound power or sound energy emitted.
This clause describes the approach to be adopted in setting up the noise source for testing and in defining the
conditions, so as to achieve an arrangement which is reproducible and which can be related clearly to the
results obtained.
This part of ISO 3743 gives general specifications relating to noise source definition, installation and operation,
but these are overridden by the instructions and specifications of a noise test code, if any exists, for the
particular type of source.
6.2 Auxiliary equipment
Care shall be taken to ensure that any electrical conduits, piping or air ducts connected to the noise source
under test do not radiate significant amounts of sound energy into the test environment.
If practicable, all auxiliary equipment necessary for the operation of the noise source under test that is not a
part of it shall be located outside the test room. If this is impractical, care shall be taken to minimize any sound
radiated into the test room from such equipment. The noise source under test shall be taken to include all
significant sources of sound emission, including auxiliary equipment which cannot either be removed or
adequately quietened, and the reference box (see 4.1) shall be extended appropriately.
6.3 Noise source location
The noise source to be tested shall be installed in the test room at one or more locations (see the following) as
if it was being installed for normal use. If there are no contrary requirements, the source shall be placed on the
floor of the test room. If a table or stand is considered essential for normal operation, the source shall be
placed at the centre of the table top, and the source and table shall be regarded as an integral whole for the
purpose of the test. The minimum distance between any wall or the ceiling of the test room and the reference
box shall be 1 m. The sides of the reference box shall not be parallel to the walls of the room. Consideration
shall be given to the placement of the source in relation to the microphone positions used for measurements,
see 7.3. This usually leads to the source being placed near the middle of a large test room so that
microphones can be positioned around all four sides of the source. In a small test room, the source can be
placed nearer to one end of the room so that a reverberant sound field where measurements are made can be
established at the other end.
A preliminary aural examination of the noise emitted by the source shall be made to determine whether it is
noticeably directional. If a source emits more sound energy in one direction than another, it shall be oriented
in such a way that the strongest component of sound energy is reflected at least once from a boundary
surface of the test room, with a minimum of loss, before reaching any of the microphone positions.
8 © ISO 2010 – All rights reserved

ISO 3743-1:2010(E)
The aural examination shall also be used to detect whether the noise emitted by the source contains discrete
tones or strong components in narrow bands of frequency. If this is the case, some preliminary measurements
shall be made (see 7.4) to determine whether it is necessary to use two different source locations in the test
room, or even to repeat the tests in another, different test room, still complying with the requirements of this
part of ISO 3743.
6.4 Installation and mounting conditions
In many cases, the sound power or sound energy emitted by a source is affected by the support or mounting
conditions. Whenever a typical condition of mounting exists for the noise source under test, that condition
shall be used or simulated, if feasible.
Mounting conditions specified or recommended by the manufacturer of the noise source under test shall be
used unless otherwise specified in any relevant noise test code. If a typical mounting condition does not exist,
or cannot be utilized for the test, or if there are several alternative possibilities, care shall be taken to ensure
that the mounting arrangement does not induce a variability in the sound output of the source which is atypical.
Precautions shall be taken to reduce any sound radiated from the structure on which the noise source is
mounted.
Many small sound sources, although themselves poor radiators of low-frequency sound, can, as a result of the
method of mounting, radiate more low-frequency sound when their vibrational energy is transmitted to
surfaces large enough to be efficient radiators. In such cases, resilient mounting shall be interposed, if
possible, between the noise source under test and the supporting structure, so that the transmission of
vibration to the support and the reaction on the source are both minimized. In this case, the mounting base
should be rigid (i.e. having a sufficiently high mechanical impedance) to prevent it from vibrating excessively
and radiating sound. However, resilient mounts shall be used only if the noise source under test is resiliently
mounted in typical field installations.
Coupling conditions, e.g. between prime movers and driven machines, can exert considerable influence on
the sound radiation of the item under test. It may be appropriate to use a flexible coupling, but similar
considerations apply to these as to resilient mounts.
Noise sources that are hand held in normal usage shall either be held by hand for the purpose of the test, or
suspended in such a way that no structure-borne sound is transmitted via any attachment that is not an
integral part of the source itself. If a noise source under test requires a support for its operation during testing,
the support structure shall be small and considered as part of the source itself. Sources normally mounted
through a window, wall or ceiling shall be mounted through a wall or ceiling of the test room.
6.5 Operation of source during test
The sound power or sound energy emitted by a source can be affected by the load applied, the running speed,
and the conditions under which it is operating. The source shall be tested, wherever possible, under
conditions that are reproducible and representative of the noisiest operation in typical usage. The
specifications given in a noise test code, if any exists, shall be followed, but in the absence of a noise test
code one or more of the following modes of operation shall be selected for the test(s):
a) source under specified load and conditions;
b) source under full load [if different from a)];
c) source under no load (idling);
d) source at maximum operating speed under defined conditions;
e) source operating under conditions corresponding to maximum sound generation representative of normal
use;
f) source with simulated loading, under defined conditions;
g) source undergoing a characteristic work cycle under defined conditions.
ISO 3743-1:2010(E)
The source shall be stabilized in the desired operating condition, with any power source or transmission
system running at a stable temperature, prior to the start of measurements for sound power level or sound
energy level determination. The load, speed and operating conditions shall either be held constant during the
test, or varied through a defined cycle in a controlled manner.
If the sound power or sound energy emission depends on secondary operating parameters, e.g. the type of
material being processed or the design of cutting tool, those parameters shall be selected, as far as is
practicable, that give the smallest variations and that are typical of normal use. If simulated loading conditions
are used, they shall be chosen such that the sound power levels or sound energy levels of the source under
test are representative of normal use.
7 Measurement procedure
7.1 General
For determination of either the sound power level of a noise source emitting stationary noise or the sound
energy level of a source which emits bursts of noise, two sets of measurements of sound pressure levels shall
be made in the test room, first with the noise source under test operating and then with the reference sound
source operating. The specifications given in a noise test code, if one exists, shall be followed, but in the
absence of a noise test code the procedures described hereafter shall be followed for the test(s).
7.2 Location of noise source under test and reference sound source
For the first set
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