EN ISO 3743-2:2019

SLOVENSKI STANDARD
01-december-2019
Nadomešča:
SIST EN ISO 3743-2:2009
Akustika - Ugotavljanje ravni zvočnih moči virov hrupa z merjenjem zvočnega
tlaka - Inženirske metode za majhne premične vire v odmevnih poljih - 2. del:
Metode za posebne odmevnice (ISO 3743-2:2018)
Acoustics - Determination of sound power levels of noise sources using sound pressure -
Engineering methods for small, movable sources in reverberant fields - Part 2: Methods
for special reverberation test rooms (ISO 3743-2:2018)
Akustik - Bestimmung der Schallleistungspegel von Geräuschquellen aus
Schalldruckmessungen - Verfahren der Genauigkeitsklasse 2 für kleine, transportable
Quellen in Hallfeldern - Teil 2: Verfahren für Sonder-Hallräume (ISO 3743-2:2018)
Acoustique - Détermination des niveaux de puissance acoustique émis par les sources
de bruit à partir de la pression acoustique - Méthodes d'expertise en champ réverbéré
applicables aux petites sources transportables - Partie 2: Méthodes en salle d'essai
réverbérante spéciale (ISO 3743-2:2018)
Ta slovenski standard je istoveten z: EN ISO 3743-2:2019
ICS:
17.140.01 Akustična merjenja in Acoustic measurements and
blaženje hrupa na splošno noise abatement in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 3743-2
EUROPEAN STANDARD
NORME EUROPÉENNE
September 2019
EUROPÄISCHE NORM
ICS 17.140.01 Supersedes EN ISO 3743-2:2009
English Version
Acoustics - Determination of sound power levels of noise
sources using sound pressure - Engineering methods for
small, movable sources in reverberant fields - Part 2:
Methods for special reverberation test rooms (ISO 3743-
2:2018)
Acoustique - Détermination des niveaux de puissance Akustik - Bestimmung der Schallleistungspegel von
acoustique émis par les sources de bruit à partir de la Geräuschquellen aus Schalldruckmessungen -
pression acoustique - Méthodes d'expertise en champ Verfahren der Genauigkeitsklasse 2 für kleine,
réverbéré applicables aux petites sources transportable Quellen in Hallfeldern - Teil 2: Verfahren
transportables - Partie 2: Méthodes en salle d'essai für Sonder-Hallräume (ISO 3743-2:2018)
réverbérante spéciale (ISO 3743-2:2018)
This European Standard was approved by CEN on 29 January 2018.

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-CENELEC 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-CENELEC 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, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 3743-2:2019 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
Annex ZA (informative) Relationship between this European Standard and the essential
requirements of Directive 2006/42/EC aimed to be covered . 4

European foreword
This document (EN ISO 3743-2:2019) has been prepared by Technical Committee ISO/TC 43
"Acoustics" in collaboration with Technical Committee CEN/TC 211 “Acoustics” the secretariat of which
is held by DIN.
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 March 2020, and conflicting national standards shall
be withdrawn at the latest by March 2020.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 3743-2:2009.
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(s).
For the relationship with EU Directive(s) 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, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 3743-2:2018 has been approved by CEN as EN ISO 3743-2:2019 without any
modification.
Annex ZA
(informative)
Relationship between this European Standard and the essential
requirements of Directive 2006/42/EC aimed to be covered
This European Standard has been prepared under a Commission’s standardization request M/396
(Machinery) to provide one voluntary means of conforming to essential requirements of 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).
Once this standard is cited in the Official Journal of the European Union under that Directive,
compliance with the normative clauses of this standard given in Table ZA.1 confers, within the limits of
the scope of this standard, a presumption of conformity with the corresponding essential requirements
of that Directive, and associated EFTA regulations.
Table ZA.1 — Correspondence between this European Standard and Directive 2006/42/EC
Essential Requirements of Clause(s)/sub-clause(s) of this EN Remarks/Notes
Directive
1.7.4.2 u) Clauses 5 to 13, Annexes A, E and F
WARNING 1 — Presumption of conformity stays valid only as long as a reference to this European
Standard is maintained in the list published in the Official Journal of the European Union. Users of this
standard should consult frequently the latest list published in the Official Journal of the European
Union.
WARNING 2 — Other Union legislation may be applicable to the product(s) falling within the scope of
this standard.
INTERNATIONAL ISO
STANDARD 3743-2
Second edition
2018-02
Acoustics — Determination of sound
power levels of noise sources using
sound pressure — Engineering
methods for small, movable sources in
reverberant fields —
Part 2:
Methods for special reverberation
test rooms
Acoustique — Détermination des niveaux de puissance acoustique
émis par les sources de bruit à partir de la pression acoustique —
Méthodes d'expertise en champ réverbéré applicables aux petites
sources transportables —
Partie 2: Méthodes en salle d'essai réverbérante spéciale
Reference number
ISO 3743-2:2018(E)
©
ISO 2018
ISO 3743-2:2018(E)
© ISO 2018
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
ii © ISO 2018 – All rights reserved

ISO 3743-2:2018(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Noise source . 2
6 Requirements for special reverberation test room . 2
6.1 General . 2
6.2 Volume of test room. 2
6.3 Reverberation time of test room. 3
6.4 Surface treatment . 3
6.5 Criterion for background noise. 3
6.6 Criteria for temperature and humidity . 4
6.7 Evaluation of suitability of test room . 4
7 Instrumentation . 5
7.1 General . 5
7.2 Microphone and its associated cable . 5
7.3 Amplifier and weighting network . 5
7.4 Octave-band filters . 6
7.5 Squaring and averaging circuits and indicating device . 6
7.6 Frequency response of the instrumentation system . 6
7.7 Calibration . 6
8 Installation and operation of source under test . 6
8.1 General . 6
8.2 Source location . 6
8.3 Source mounting . 7
8.4 Auxiliary equipment . 7
8.5 Operation of source during the test . 7
9 Measurements in test room . 8
9.1 General . 8
9.2 Period of observation . 8
9.3 Microphone positions . 8
9.4 Number of microphones and source positions . 8
9.5 Criteria for the presence of spectral irregularities .10
9.6 Averaging technique with moving microphones .10
9.6.1 General.10
9.6.2 Path length for continuous averaging .10
9.6.3 Location of path within test room .10
9.6.4 Speed of traverse .10
9.7 Array of fixed microphones .11
9.8 Correction for background sound pressure levels .11
10 Calculation of sound power levels .11
10.1 Calculation of mean band pressure levels .11
10.2 Direct method for determining sound power levels .12
10.3 Comparison method for determining band power levels .12
10.4 A-weighted sound power levels determined by the comparison method .13
11 Measurement uncertainty .13
11.1 Methodology .13
11.2 Determination of σ .14
omc
ISO 3743-2:2018(E)
11.3 Determination of σ .14
R0
11.3.1 General.14
11.3.2 Round robin test .14
11.3.3 Modelling approach for σ .15
R0
11.4 Typical upper bound values of σ .15
R0
11.5 Total standard deviation σ and expanded uncertainty U .16
tot
12 Information to be recorded .16
12.1 General .16
12.2 Sound source under test .16
12.3 Acoustical environment .17
12.4 Instrumentation .17
12.5 Acoustical data .17
13 Information to be reported .17
Annex A (normative) Characteristics and calibration of reference sound source .18
Annex B (informative) Guidelines for the design of special reverberation test rooms .19
Annex C (informative) Examples of suitable instrumentation systems .24
Annex D (informative) Guidance on the development of information on
measurement uncertainty .26
Annex E (normative) Sound power level under reference meteorological conditions .36
Annex F (normative) Calculation of A-weighted sound power levels from octave band levels .37
Bibliography .38
iv © ISO 2018 – All rights reserved

ISO 3743-2:2018(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 1, Noise.
This second edition cancels and replaces the first edition (ISO 3743-2:1994), of which it constitutes a
minor revision. The main changes are the following:
— Table 0.1 in the Introduction deleted;
— restructuring of the content of Clause 1;
— references updated;
— clause on measurement uncertainty revised to be in-line with the other standards of the ISO 3740
series (now Clause 11);
— new Annexes D, E, and F added;
— new entries in Bibliography added.
A list of all the parts in the ISO 3743 series can be found on the ISO website.
ISO 3743-2:2018(E)
Introduction
ISO 3743 is one standard of the series ISO 3741 to ISO 3747 series, which specifies various methods for
determining the sound power levels of machines, equipment and sub-assemblies. These basic standards
specify the acoustical requirements for measurements appropriate for different test environments.
When selecting one of the methods of the series ISO 3741 to ISO 3747, it is necessary to select the most
appropriate for the conditions and purposes of the noise test. General guidelines to assist in the selection
are provided in ISO 3740. The series ISO 3741 to ISO 3747 gives only general principles regarding the
operating and mounting conditions of the machine or equipment under test. Reference should be made
to the noise test code for a specific type of machine or equipment, if available, for specifications on
mounting and operating conditions.
The method given in this document enables measurement of sound pressure levels with A-weighting
and in octave bands at pre-scribed fixed microphone positions or along prescribed paths. It allows
determination of A-weighted sound power levels or sound power levels with other weighting and octave-
band sound power levels. Quantities which cannot be determined are the directivity characteristics of
the source and the temporal pattern of noise radiated by sources emitting non-steady noise.
ISO 3743-1 and this document specify engineering methods for determining the A-weighted and octave-
band sound power levels of small noise sources. The methods are applicable to small machines, devices,
components and sub-assemblies which can be installed in a special reverberation test room or in a hard-
walled test room with prescribed acoustical characteristics. The methods are particularly suitable for
small items of portable equipment; they are not intended for larger pieces of stationary equipment
which, due to their manner of operation or installation, cannot readily be moved into the test room and
operated as in normal usage. The procedures are intended to be used when an engineering grade of
accuracy is desired without requiring the use of laboratory facilities.
In ISO 3743-1, a comparison method is used to determine the octave-band sound power levels of the
source. The spatial average (octave-band) sound pressure levels produced by the source under test are
compared to the spatial average (octave-band) sound pressure levels produced by a reference sound
source of known sound power output. The difference in sound pressure levels is equal to the difference
in sound power levels if conditions are the same for both sets of measurements. The A-weighted sound
power level is then calculated from the octave-band sound power levels.
The requirements to be fulfilled by the special reverberation test room for measurements in accordance
with this document are significantly more restrictive than those placed on the hard-walled test room
by the comparison method of ISO 3743-1.
vi © ISO 2018 – All rights reserved

INTERNATIONAL STANDARD ISO 3743-2:2018(E)
Acoustics — Determination of sound power levels of noise
sources using sound pressure — Engineering methods for
small, movable sources in reverberant fields —
Part 2:
Methods for special reverberation test rooms
1 Scope
This document specifies a relatively simple engineering method for determining the sound power levels
of small, movable noise sources. The methods specified in this document are suitable for measurements
of all types of noise within a specified frequency range, except impulsive noise consisting of isolated
bursts of sound energy which are covered by ISO 3744 and ISO 3745.
NOTE A classification of different types of noise is given in ISO 12001.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 3741, Acoustics — Determination of sound power levels and sound energy levels of noise sources using
sound pressure — Precision methods for reverberation test rooms
ISO 3743-1, 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 3745, Acoustics — Determination of sound power levels and sound energy levels of noise sources using
sound pressure — Precision methods for anechoic rooms and hemi-anechoic rooms
ISO 5725 (all parts), Accuracy (trueness and precision) of measurement methods and results
ISO 6926, Acoustics — Requirements for the performance and calibration of reference sound sources used
for the determination of sound power levels
ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
measurement (GUM: 1995)
IEC 60942, Electroacoustics — Sound calibrators
IEC 61260 (all parts), Electroacoustics — Octave-band and fractional-octave-band filters
IEC 61672-1, Electroacoustics — Sound level meters — Part 1: Specifications
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 3743-1 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
ISO 3743-2:2018(E)
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
special reverberation test room
room which meets the requirements of Clause 6 of ISO ISO 3743-2
Note 1 to entry: The requirements for a test room according to this document are significantly more restrictive
than those placed on the hard-walled test room by the comparison method of ISO 3743-1.
4 Principle
The measurements are carried out when the source is installed in a specially designed room having a
specified reverberation time over the frequency range of interest. The A-weighted sound power level
of the source under test is determined from a single A-weighted sound pressure level measurement
at each microphone position, rather than from a summation of octave-band levels. This direct method
eliminates the need for a reference sound source, but requires the use of a special reverberation test
room. The direct method is based on the premise that the sound pressure level, averaged in space
and time in the test room, can be used to determine the sound power level emitted by the source. The
properties of the special reverberation test room are chosen so that the room's influence on the sound
power output of the equipment under test is small. The number of microphone positions and source
locations required in the test room are specified. Guidelines for the design of special reverberation
rooms are given in Annex B.
In addition to the direct method, a comparison method is also described (see 10.3). However, since the
requirements on the test room for the comparison method of ISO 3743-1 are considerably less restrictive,
it is recommended that the comparison method of ISO 3743-1 be used if a special reverberation test
room is not available.
NOTE Precision methods for the determination of the sound power levels of small noise sources are specified
in ISO 3741 and ISO 3745.
5 Noise source
The noise source may be a device, machine, component or sub-assembly.
The maximum size of the source under test and the lower limit of the frequency range for which the
methods are applicable depend upon the size of the room used for the acoustical measurements. The
volume of the noise sources should not exceed 1 % of the volume of the special reverberation test room.
3 3
For the minimum test room volume of 70 m , the recommended maximum size of the source is 0,7 m .
Measurements on sources emitting discrete-frequency components below 200 Hz are frequently
difficult to make in such small rooms.
6 Requirements for special reverberation test room
6.1 General
Guidelines for the design of a suitable test room and an example of the determination of the nominal
reverberation time of the room are given in Annex B. Methods of measurement of reverberation time
are given in ISO 354.
6.2 Volume of test room
The volume of the test room shall be at least 70 m and preferably greater if the 125 Hz octave band is
within the frequency range of interest. If the 4 kHz and 8 kHz octave bands are within the frequency
range of interest, the volume shall not exceed 300 m .
NOTE When using the comparison method, the use of larger room volumes is acceptable.
2 © ISO 2018 – All rights reserved

ISO 3743-2:2018(E)
6.3 Reverberation time of test room
The calculation of sound power levels from measured values of the sound pressure levels requires
a compensation for the frequency-dependent concentration of sound energy near the walls of the
test room. To facilitate this compensation, the reverberation time should be slightly higher at low
frequencies. The reverberation time of the test room shall fall within the limiting curves defined by
T = 0,9 RT and 1,1 RT where the reverberation parameter, R, is given by
nom nom
R=+1 (1)
13/
fV
where
f is the frequency, in hertz;
V is the volume, in cubic metres.
NOTE The following is a more robust formula for R and is not limited to rooms that are nearly cubical:
cS⋅
R=+1
fV⋅8
where
c is the sound velocity, in metres per second;
S is the surface area of the test room, in square metres.
For frequencies above 6,3 kHz, constants 0,9 and 1,1 shall be replaced by 0,8 and 1,2 respectively. The
nominal reverberation time of the room, T is determined by centring the measured values of T
nom
(normalized to the reverberation time at 1 000 Hz) within the limiting curves specified above, and shall
be between 0,5 s and 1,0 s (see Annex B for an example). For a room volume V of 70 m , the value of R is
determined from Figure 1.
If, during the acoustical measurements, sound-absorptive structures support the source or if the source
has absorptive surfaces, the reverberation time T shall be measured with these items present.
6.4 Surface treatment
The floor of the test room shall be reflective with an absorption coefficient less than 0,06. Except for the
floor, none of the surfaces shall have absorptive properties significantly deviating from each other. For
each octave band within the frequency range of interest, the mean value of the absorption coefficient of
each wall and of the ceiling shall be within 0,5 and 1,5 times the mean value of the absorption coefficient
of the walls and ceiling.
6.5 Criterion for background noise
At each microphone position, the sound pressure levels due to background noise shall be at least 4 dB
and preferably more than 10 dB below the A-weighted sound pressure level or the band pressure levels
produced by the source.
ISO 3743-2:2018(E)
Key
f one-third-octave-band centre frequency, in hertz
R reverberation parameter
Figure 1 — Values of R at the one-third-octave-band centre frequencies for V = 70 m
6.6 Criteria for temperature and humidity
The air absorption in the reverberation room varies with temperature and humidity, particularly
at frequencies above 1 000 Hz. The temperature θ, in degrees Celsius, and the relative humidity (H),
expressed as a percentage, shall be controlled during the sound pressure level measurements. The product
H· θ +°5C (2)
()
shall not differ by more than ±10 % from the value of the product which prevailed during the
measurement of the reverberation time of the test room.
NOTE To keep the reverberation time within the specified limits at the highest frequencies, a reduction of
the air absorption is sometimes necessary. An increase in the humidity (for example by using a small humidifier)
may be beneficial.
6.7 Evaluation of suitability of test room
Before a test room is used for sound power level determinations, its suitability shall be evaluated using
the following procedure.
a) Step 1
Obtain a small broad-band reference sound source which has been calibrated in accordance with
ISO 3741, or by following the procedures specified in ISO 6926 and ISO 3745.
b) Step 2
In the special reverberation test room, determine the octave-band power levels of the same
reference sound source under identical operating conditions in accordance with the procedure
given in this document.
4 © ISO 2018 – All rights reserved

ISO 3743-2:2018(E)
c) Step 3
For each octave band within the frequency range of interest, calculate the difference between the
sound power levels obtained in this way.
d) Step 4
Compare these differences with the values given in Table 1.
If the differences in octave-band power levels do not exceed those specified in Table 1, the room
is suitable for sound power determinations of broad-band noise sources in accordance with the
procedures of this document.
Table 1 — Maximum permitted differences between octave-band power levels of broad-band
noise sources measured in accordance with 6.7 a)
Octave-band centre frequency Difference in band power levels
Hz dB
125 ±5
250 to 4 000 ±3
8 000 ±4
7 Instrumentation
7.1 General
The basic instrumentation consists of a microphone, an amplifier with A-weighting network, a squaring
and averaging circuit and an indicating device. A set of octave-band filters is also required. These
elements may be separate instruments or they may be integrated into a complete unit, for example, a
suitable sound level meter. For requirements on sound level meters, see IEC 61672-1.
The microphone shall, whenever possible, be physically separated from the rest of the instrumentation
with which it is connected by means of a cable. Examples of suitable instrumentation systems are given
in Annex C.
7.2 Microphone and its associated cable
The microphone shall have a flat frequency response for randomly incident sound over the frequency
range of interest, as determined by the procedure given in 7.6.
NOTE 1 This requirement is not normally met by the microphone of a sound level meter which is calibrated for
free field measurements.
NOTE 2 If several microphones are used, it is desirable to avoid the axis of each microphone being oriented in
the same direction in space.
The frequency response and stability of the microphone system shall not be adversely affected by the
cable connecting the microphone to the rest of the instrumentation system. If the microphone is moved,
care shall be exercised to avoid introducing acoustical or electrical noise that could interfere with the
measurements.
7.3 Amplifier and weighting network
The properties of the amplifier and the A-weighting network shall comply with the requirements of
IEC 61672-1.
ISO 3743-2:2018(E)
7.4 Octave-band filters
The octave-band filters shall comply with the requirements of IEC 61260 (all parts).
7.5 Squaring and averaging circuits and indicating device
Squaring and averaging the microphone output voltage may be performed by analogue or digital
equipment as described in Annex C. In analogue systems, continuous averaging is generally performed
by an RC-smoothing network with a time constant τ . For these systems, the time constant shall be at
A
least 0,5 s and such that the indicated fluctuations are less than ±5 dB.
In digital systems and in some analogue systems, true integration over a fixed time/interval (integration
time τ ) is employed. The integration time shall be at least 1 s. The indication of the squaring and
D
averaging (integrating) circuits and indicating device shall be within 3 % of the values.
7.6 Frequency response of the instrumentation system
The frequency response of the instrumentation calibrated for randomly incident sound shall be
determined in accordance with the procedure in IEC 61672 with the acceptance limits given in Table 2.
Table 2 — Acceptance limits for the instrumentation system
Frequency Acceptance limits
Hz dB
100 to 4 000 ±1
5 000 ±1,5
6 300
+15,
−2
8 000
+15,
−3
10 000
+2
−4
NOTE Adapted from IEC 61672-1.
7.7 Calibration
During each series of measurements, a sound calibrator with an accuracy of ±0,3 dB (class 1 as specified
in IEC 60942) shall be applied to the microphone to verify the calibration of the entire measuring
system at one or more frequencies over the frequency range of interest.
The calibrator shall be checked annually to verify that its output has not changed. In addition, an
electrical calibration of the instrumentation system over the entire frequency range of interest shall be
carried out periodically, at intervals not exceeding 2 years.
8 Installation and operation of source under test
8.1 General
The acoustical properties of the special reverberation test room and the manner in which the source is
operated may have a significant influence on the sound power emitted by the source.
8.2 Source location
Install the source in the test room in one or more locations as if it were being installed for normal usage.
If no such location(s) can be defined, place the source on the floor of the test room with a minimum
distance of 1 m between any surface of the source and the nearest wall.
6 © ISO 2018 – All rights reserved

ISO 3743-2:2018(E)
The location(s) of the source in the test room shall be described in the test report.
NOTE The influence of the acoustical properties of the room on the sound power emitted by the source
depends to some extent on the position of the source within the room. The requirements on the test room (see
Clause 6) tend to decrease this influence. However, in some cases it may be necessary or desirable to determine
the sound power level of a source in several locations in the test room (see 9.4).
8.3 Source mounting
In many cases, the sound power emitted will depend upon the support or mounting conditions of the
source under test. Whenever a typical condition of mounting exists for the equipment under test, that
condition shall be used or simulated, if feasible.
If a typical condition of mounting does not exist or cannot be utilized for the test, take care to avoid
changes in the sound output of the source caused by the mounting system employed for the test. Take
steps to reduce any sound radiation from the structure on which the equipment may be mounted.
Sources normally mounted through a window, wall or ceiling shall be mounted through a wall or the
ceiling of the test room.
The mounting conditions of the source and its associated equipment shall be described in the test report.
NOTE The use of resilient mounts or vibration-damping material on large surfaces used to support the
equipment under test may be appropriate.
8.4 Auxiliary equipment
Take care to ensure that any electrical conduits, piping or air ducts connected to the source under test
do not radiate significant amounts of sound energy into the test roo
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