EN 60942:2003

SLOVENSKI SIST EN 60942:2004
STANDARD
julij 2004
Electroacoustics - Sound calibrators (IEC 60942:2003)
ICS 17.140.50 Referenčna številka
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

EUROPEAN STANDARD EN 60942
NORME EUROPÉENNE
EUROPÄISCHE NORM May 2003
ICS 17.140.50 Supersedes EN 60942:1998 + A1:2001

English version
Electroacoustics –
Sound calibrators
(IEC 60942:2003)
Electroacoustique –  Elektroakustik –
Calibreurs acoustiques Schallkalibratoren
(CEI 60942:2003) (IEC 60942:2003)

This European Standard was approved by CENELEC on 2003-04-01. CENELEC 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 Central Secretariat or to any CENELEC 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 CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,
Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta,
Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2003 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 60942:2003 E
Foreword
The text of document 29/528/FDIS, future edition 3 of IEC 60942, prepared by IEC TC 29,
Electroacoustics, in cooperation with the International Organization of Legal Metrology (OIML), was
submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 60942 on
2003-04-01.
This European Standard supersedes EN 60942:1998 + A1:2001.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2004-01-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2006-04-01

Annexes designated "normative" are part of the body of the standard.
In this standard, annexes A, B, C and ZA are normative.
Annex ZA has been added by CENELEC.
The most significant changes from the previous edition are: the inclusion of maximum permitted
uncertainties of measurement within the tolerance limits; the inclusion of a normative annex giving the
format for reporting results of pattern evaluation tests; changes to the class designations; specification
of the type designation of the microphone to be used to determine the class; harmonization of the
range of operating environmental conditions with those for sound level meters. Specifications for
equivalent free-field and diffuse-field levels have been removed.
__________
Endorsement notice
The text of the International Standard IEC 60942:2003 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following note has to be added for the standard
indicated:
IEC 61000-6-2 NOTE Harmonized as EN 61000-6-2:2001 (modified).
__________
- 3 - EN 60942:2003
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of any
of these publications apply to this European Standard only when incorporated in it by amendment or
revision. For undated references the latest edition of the publication referred to applies (including
amendments).
NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
Publication Year Title EN/HD Year
IEC 60050-801 1994 International Electrotechnical - -
Vocabulary (IEV)
Chapter 801: Acoustics and
electroacoustics
IEC 61000-4-2 1995 Electromagnetic compatibility (EMC) EN 61000-4-2 1995
Part 4-2: Testing and measurement
techniques - Electrostatic discharge
immunity test
IEC 61000-4-3 2002 Part 4-3: Testing and measurement EN 61000-4-3 2002
techniques - Radiated, radio-frequency,
electromagnetic field immunity test

IEC 61000-6-1 1997 Part 6-1: Generic standards - Immunity EN 61000-6-1 2001
(mod) for residential, commercial and light-
industrial environments
IEC 61094-1 2000 Measurement microphones EN 61094-1 2000
Part 1: Specifications for laboratory
standard microphones
IEC 61094-2 1992 Part 2: Primary method for pressure EN 61094-2 1993
calibration of laboratory standard
microphones by the reciprocity
technique
IEC 61094-4 1995 Part 4: Specifications for working EN 61094-4 1995
standard microphones
IEC 61094-5 2001 Part 5: Methods for pressure calibration EN 61094-5 2001
of working standard microphones by
comparison
IEC 61672-1 2002 Electroacoustics - Sound level meters EN 61672-1 2003
Part 1: Specifications
CISPR 22 (mod) 1997 Information technology equipment - EN 55022 1998
Radio disturbance characteristics - + corr. July 2001
Limits and methods of measurement

Publication Year Title EN/HD Year
CISPR/IEC 1996 Electromagnetic compatibility (EMC) EN 61000-6-3 2001
61000-6-3 (mod) Part 6-3: Generic standards - Emission
standard for residential, commercial and
light-industrial environments
ISO/IEC Guide 1995 Guide to the expression of uncertainty - -
Expres in measurement
ISO 266 1997 Acoustics - Preferred frequencies - -

ISO Publication 1993 International vocabulary of basic and - -
ISBN 92-67-01075-1
general terms in metrology
OIML R 97 1990 Barometers - -
NORME CEI
INTERNATIONALE IEC
INTERNATIONAL
Troisième édition
STANDARD
Third edition
2003-01
Electroacoustique –
Calibreurs acoustiques
Electroacoustics –
Sound calibrators
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Pour prix, voir catalogue en vigueur
For price, see current catalogue

60942 © IEC:2003 – 3 –
CONTENTS
FOREWORD . 5
INTRODUCTION .9
1 Scope .11
2 Normative references.11
3 Terms and definitions.13
4 Reference environmental conditions .17
5 Requirements .17
5.1 General .17
5.2 Sound pressure level .21
5.3 Frequency.23
5.4 Influence of static pressure, air temperature and humidity .25
5.5 Total distortion.29
5.6 Power supply requirements .29
5.7 Specification and calibration of microphones .29
5.8 Electromagnetic compatibility .31
6 Instrument marking and documentation .33
6.1 Marking of the sound calibrator .33
6.2 Individual calibration chart for a class LS sound calibrator .35
6.3 Instruction manual .35
Annex A (normative) Pattern evaluation tests.39
A.0 Introduction .39
A.1 Submission for test.41
A.2 Principal values .41
A.3 Marking of the sound calibrator and supplied documentation.41
A.4 Performance tests at and around reference environmental conditions .41
A.5 Environmental tests.53
A.6 Electromagnetic compatibility .69
Annex B (normative) Periodic tests .77
B.0 Introduction .77
B.1 Submission for test.77
B.2 Preliminary inspection .79
B.3 Performance tests .79
B.4 Calibration of the sound calibrator with other models of microphone.85
B.5 Documentation .85
Annex C (normative) Format for the pattern evaluation report .89
C.0 Introduction .89
C.1 Marking.89
C.2 Submission for test.89
C.3 Pattern evaluation report .91
Bibliography .177

60942 © IEC:2003 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROACOUSTICS –
SOUND CALIBRATORS
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, the IEC publishes International Standards. Their preparation is
entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. The IEC collaborates closely with the International Organization
for Standardization (ISO) in accordance with conditions determined by agreement between the two
organizations.
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60942 has been prepared by IEC technical committee 29:
Electroacoustics, in cooperation with the International Organization of Legal Metrology (OIML).
This third edition cancels and replaces the second edition published in 1997, and its
amendment 1 (2000), of which it constitutes a technical revision.
The most significant changes from the previous edition are: the inclusion of maximum
permitted uncertainties of measurement within the tolerance limits; the inclusion of a normative
annex giving the format for reporting results of pattern evaluation tests; changes to the class
designations; specification of the type designation of microphone to be used to determine the
class; harmonization of the range of operating environmental conditions with those for sound
level meters. Specifications for equivalent free-field and diffuse-field levels have been
removed.
The text of this standard is based on the following documents:
FDIS Report on voting
29/528/FDIS 29/533/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

60942 © IEC:2003 – 7 –
The committee has decided that the contents of this publication will remain unchanged until
2005. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
60942 © IEC:2003 – 9 –
INTRODUCTION
Sound calibrators are designed to produce one or more known sound pressure levels at one or
more specified frequencies when coupled to specified models of microphone in specified
configurations, for example, with or without protective grid. The sound pressure level generated
by a sound calibrator may depend on environmental conditions such as static pressure, air
temperature and relative humidity.
Sound calibrators have two principal applications:
a) the determination of the electroacoustical pressure sensitivity of specified models of
microphone in specified configurations;
b) checking or adjusting the overall sensitivity of acoustical measuring devices or systems.

60942 © IEC:2003 – 11 –
ELECTROACOUSTICS –
SOUND CALIBRATORS
1 Scope
This International Standard specifies the performance requirements for three classes of sound
calibrator: laboratory standard (class LS), class 1 and class 2. Tolerance limits are smallest for
class LS and greatest for class 2 instruments. Class LS sound calibrators are normally used
only in the laboratory; class 1 and class 2 are considered as sound calibrators for field use.
A class 1 sound calibrator is primarily intended for use with a class 1 sound level meter and a
class 2 sound calibrator primarily with a class 2 sound level meter, as specified in IEC 61672-1.
The tolerance limits for class LS sound calibrators are based on the use of a laboratory
standard microphone, as specified in IEC 61094-1, for demonstrations of conformance to the
requirements of this standard. The tolerance limits for class 1 and class 2 sound calibrators are
based on the use of a working standard microphone, as specified in IEC 61094-4, for
demonstrations of conformance to the requirements of this standard.
A multi-level and multi-frequency sound calibrator has the same class designation for all sound
pressure level and frequency combinations for which the instruction manual states that the
instrument conforms to the requirements of this standard.
This standard does not include requirements for equivalent free-field or random-incidence
sound pressure levels, such as may be used in the overall sensitivity adjustment of a sound
level meter.
A sound calibrator may provide other functions, for example, tonebursts. Requirements for
these other functions are not included in this standard.
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.
IEC 60050(801):1994, International Electrotechnical Vocabulary (IEV) – Chapter 801:
Acoustics and electroacoustics
IEC 61000-4-2:1995, Electromagnetic compatibility (EMC) – Part 4: Testing and measurement
techniques – Section 2: Electrostatic discharge immunity test. Basic EMC Publication
IEC 61000-4-3:2002, Electromagnetic compatibility (EMC) – Part 4-3: Testing and measure-
ment techniques – Radiated, radio-frequency, electromagnetic field immunity test. Basic EMC
Publication
60942 © IEC:2003 – 13 –
IEC 61000-6-1:1997, Electromagnetic compatibility (EMC) – Part 6: Generic standards –
Section 1: Immunity for residential, commercial and light-industrial environments
IEC 61094-1:2000, Measurement microphones – Part 1: Specifications for laboratory standard
microphones
IEC 61094-2:1992, Measurement microphones – Part 2: Primary method for pressure
calibration of laboratory standard microphones by the reciprocity technique
IEC 61094-4:1995, Measurement microphones – Part 4: Specifications for working standard
microphones
IEC 61094-5:2001, Measurement microphones – Part 5: Methods for pressure calibration of
working standard microphones by comparison
IEC 61672-1:2002, Electroacoustics – Sound level meters – Part 1: Specifications
CISPR 22:1997, Information technology equipment – Radio disturbance characteristics – Limits
and methods of measurement
CISPR/IEC 61000-6-3:1996, Electromagnetic compatibility (EMC) – Part 6: Generic standards –
Section 3: Emission standard for residential, commercial and light-industrial environments
ISO/IEC Guide :1995, Guide to the expression of uncertainty in measurement
ISO 266:1997, Acoustics – Preferred frequencies
ISO Publication:1993, ISBN 92-67-01075-1, International vocabulary of basic and general
terms in metrology
OIML International Recommendation R 97:1990, Barometers
3 Terms and definitions
For the purposes of this International Standard, the definitions contained in IEC 60050(801)
and the ISO Publication International Vocabulary of Basic and General Terms in Metrology, as
well as the following definitions, apply. Definitions for other relevant quantities are given in the
documents referenced in Clause 2.
3.1
sound calibrator
device that generates a sinusoidal sound pressure of specified sound pressure level and
frequency when coupled to specified models of microphone in specified configurations
3.2
specified sound pressure level
sound pressure level(s) generated under reference environmental conditions for use with a
particular microphone model and configuration, valid for either an individual sound calibrator (in
the case of a class LS calibrator) or all sound calibrators of the same model (in the case of a
class 1 or class 2 calibrator)

60942 © IEC:2003 – 15 –
3.3
nominal sound pressure level
close approximation to the specified sound pressure level(s), valid for all sound calibrators of
the same model, rounded to the nearest decibel (intended for marking)
3.4
specified frequency
frequency(ies) of the sound generated by the sound calibrator under reference environmental
conditions, valid for either an individual sound calibrator (in the case of a class LS calibrator) or
all sound calibrators of the same model (in the case of a class 1 or class 2 calibrator)
3.5
nominal frequency
close approximation to the specified frequency, often rounded according to ISO 266 (intended
for marking)
3.6
principal sound pressure level
sound pressure level specified in the instruction manual as principal
NOTE Principal sound pressure level is used during demonstration of conformance of the sound calibrator to the
requirements of this standard.
3.7
principal frequency
frequency specified in the instruction manual as principal
NOTE Principal frequency is used during demonstration of conformance of the sound calibrator to the
requirements of this standard.
3.8
replication
repeat of a measurement involving coupling the microphone to the sound calibrator and then
completely removing the microphone from the sound calibrator
3.9
total distortion
ratio in per cent of the root-mean-square of the total distortion components to the root-mean-
square of the entire signal
3.10
reference orientation
orientation of a sound calibrator such that the principal axis of the opening of the cavity (the
axis along which the microphone is inserted into the cavity) coincides with the principal
direction of an emitter or receiver of radiofrequency fields. The opening of the cavity faces
away from the emitter or receiver
3.11
reference plane
plane of contact between the microphone and the sound calibrator
3.12
effective load volume of a microphone
volume of air at reference environmental conditions that has the same acoustic compliance as
the cavity bounded by the reference plane, the microphone diaphragm and the outer cylindrical
surface of the microphone at the reference plane, including the equivalent volume of the
microphone (see IEC 61094-1)
NOTE Effective load volume is generally expressed in cubic millimetres.

60942 © IEC:2003 – 17 –
4 Reference environmental conditions
Reference environmental conditions for specifying the performance of a sound calibrator are:
– air temperature: 23 °C
– static pressure: 101,325 kPa
– relative humidity: 50 %
5 Requirements
5.1 General
5.1.1 A sound calibrator conforming to the requirements of this standard shall have the
characteristics described in this clause. Adaptors may be provided to accommodate more than
one model of microphone. For the purpose of this standard, any such adaptor is an integral
part of the sound calibrator.
5.1.2 The sound calibrator shall conform to the requirements of this standard for one or more
of the sound pressure level and frequency combinations available. All the combinations
conforming to the requirements given in this standard shall conform to the same class
designation. Conformance to the requirements of this standard shall not be stated for sound
pressure level and frequency settings for which this standard provides no tolerance limits.
5.1.3 Class LS sound calibrators shall be supplied with an individual calibration chart
containing the information required by 6.2. For class 1 and class 2 sound calibrators, the
specified sound pressure level(s) and specified frequency(ies) shall be given in the instruction
manual.
5.1.4 Class LS and class 1 sound calibrators that require corrections for the influence of
static pressure to conform to the specifications for the appropriate class shall have the letter
‘C’ added to their class designation. Class LS and class 1 sound calibrators shall not require
corrections for any of the other environmental conditions to achieve the requirements specified
for the appropriate class. Class 2 sound calibrators that require corrections for any of the
environmental conditions to conform to the specified requirements shall have the letter ‘C’
added to their class designation. Where appropriate, the class designation shall be described
as class LS/C, class 1/C, class 2/C. Where corrections are permitted, and are necessary to
conform to the specified requirements as an environmental condition varies, these corrections
shall be stated in the instruction manual.
5.1.5 Class 1 sound calibrators that require a correction for the influence of static pressure to
conform to the specifications of this standard shall be supplied with a barometer. The
barometer shall enable the static pressure to be measured so that the ability of a sound
calibrator to conform to the requirements for the class is not affected. Class 2 sound
calibrators that require a correction for the influence of static pressure to conform to the
specifications of this standard shall be supplied with a barometer (which shall enable the static
pressure to be measured in such a way that the ability of a sound calibrator to conform to the
requirements for the class is not affected), unless the corrections are sufficiently small that for
any change in static pressure of ±6,0 kPa the uncorrected measured sound pressure levels
conform to the specifications of this standard. In this case, the corrections to be applied for the
influence of variations in static pressure shall be stated in the instruction manual, together with
information on how to calculate the relevant correction when operating the sound calibrator at
different heights above sea-level.

60942 © IEC:2003 – 19 –
NOTE 1 A class LS sound calibrator is normally used only in the laboratory where a suitable device should be
available for measuring static pressure if the sound calibrator has a class ‘C’ designation. Hence, there is no
requirement to supply a barometer for this class.
NOTE 2 The barometer may provide the data directly in the form to be used to correct measured sound pressure
levels to the reference static pressure.
5.1.6 Where a class 2 sound calibrator, that requires a correction for the influence of
temperature or relative humidity to conform to the specifications of this standard, is supplied
with the means to measure the relevant environmental condition, the supplied means shall
enable the condition to be measured in such a way that the ability of a sound calibrator to
conform to the requirements for the class is not affected.
NOTE The ‘supplied means’ may provide the data directly in the form to be used to correct measured sound
pressure levels to the reference environmental conditions.
5.1.7 The design of the sound calibrator and the materials used in the construction should be
such as to provide long-term stability for the operation of the sound calibrator.
5.1.8 If a specific orientation of the sound calibrator is to be used to conform to the
requirements of this standard, this orientation shall either be indicated on the sound calibrator,
or the indication on the sound calibrator shall refer to the instruction manual, which shall state
the required orientation.
5.1.9 All performance requirements relate to the operation of the sound calibrator following
stabilizing of the coupling of the microphone and sound calibrator, and after the sound
pressure level and frequency have stabilized. The elapsed time necessary for stabilization of
the sound pressure level and frequency, which begins once the sound calibrator is switched on
with the microphone coupled to it, shall be stated in the instruction manual, and shall not
exceed 30 s for any applicable combination of environmental conditions specified in 5.4. The
sound calibrator and microphone shall be allowed to reach equilibrium with the prevailing
environmental conditions before coupling.
NOTE The stabilization time required following the coupling of the microphone to the sound calibrator may vary
considerably depending on the model of microphone and sound calibrator in use.
5.1.10 Those components of a sound calibrator that are not intended to be accessible to the
user shall be protected by seals or marks.
5.1.11 The tolerance limits in this standard include the associated expanded uncertainty of
measurement calculated for a coverage factor of 2 corresponding to a level of confidence of
approximately 95 %, in accordance with the guidelines given in the ISO/IEC Guide to the
expression of uncertainty in measurement. For testing laboratories the maximum permitted
expanded uncertainties of measurement are stated in Annexes A and B of this document.
Sound calibrator manufacturers may calculate the proportion of the tolerance limits available
for design and manufacturing purposes by subtracting the maximum permitted expanded
uncertainties of measurement from the appropriate tolerance limit.
5.1.12 Conformance to the requirements of this standard is demonstrated when the result of a
measurement or the absolute value of the difference between the result and the design goal,
as appropriate, extended by the actual expanded uncertainty of measurement of the testing
laboratory, lies fully within the specified tolerance limits for the appropriate class. For legal
metrology purposes, the tolerance limits stated in this standard are considered to be the
maximum permissible errors for pattern evaluation, initial verification and subsequent
verification.
5.1.13 If the actual expanded uncertainty of a measurement performed by the test laboratory
exceeds the maximum permitted value given in Annexes A and B, the measurement shall not
be used to demonstrate conformance to the requirements of this standard.

60942 © IEC:2003 – 21 –
5.2 Sound pressure level
5.2.1 General
5.2.1.1 All specified sound pressure level(s) generated shall be stated in the instruction
manual with a resolution better than, or equal to, 0,1 dB.
5.2.1.2 All the requirements and tolerance limits specified in this standard relate to the level
of the sound pressure produced at the diaphragm of the inserted microphone.
5.2.1.3 The principal sound pressure level of the sound calibrator shall be at least 90 dB (re
20 µPa) when the sound calibrator is applied to the models of microphone in the configurations
specified in the instruction manual.
5.2.2 Generated sound pressure level
The sound pressure level generated by the sound calibrator shall be measured as an average
over 20 s of operation. For sound calibrators with letter ‘C’ designation the measured level
shall be corrected, if necessary, to the reference environmental conditions given in Clause 4.
The absolute value of the difference between the measured sound pressure level and the
corresponding specified sound pressure level, extended by the expanded uncertainty of
measurement, shall not exceed the tolerance limits given in Table 1 for the class of sound
calibrator. These tolerance limits apply to measurements made at and around reference
environmental conditions within the following ranges: 97 kPa to 105 kPa, 20 °C to 26 °C and
40 % relative humidity to 65 % relative humidity.
5.2.3 Short-term level fluctuation
Fluctuation in the sound pressure level shall be measured with time-weighting F (nominal time
constant of 125 ms as specified in IEC 61672-1), by making a minimum of 10 measurements at
regular intervals during a period of 20 s of operation of the sound calibrator. One-half of the
difference between the maximum and minimum levels measured, extended by the expanded
uncertainty of measurement, shall not exceed the short-term level fluctuation limits given in
Table 1 for the class of sound calibrator. These short-term level fluctuation limits apply to
measurements made at and around reference environmental conditions within the following
ranges: 97 kPa to 105 kPa, 20 °C to 26 °C and 40 % relative humidity to 65 % relative humidity.

60942 © IEC:2003 – 23 –
Table 1 – Tolerance limits for sound pressure level and short-term level fluctuation,
at and around reference environmental conditions
Sound pressure level tolerance limits Short-term level fluctuation limits
Range of nominal
frequencies dB dB
Hz Class LS Class 1 Class 2 Class LS Class 1 Class 2
31,5 to <160 – 0,50 – – 0,20 –
160 to 1 250 0,20 0,40 0,75 0,05 0,10 0,20
>1 250 to 4 000 – 0,60 – – 0,10 –
>4 000 to 8 000 – 0,80 – – 0,10 –
>8 000 to 16 000 – 1,00 – – 0,10 –
NOTE 1 Sound pressure level tolerance limits are for the absolute value of the difference between the
sound pressure level generated by the sound calibrator and the specified sound pressure level, extended by
the expanded uncertainty of measurement.
NOTE 2 Short-term level fluctuation limits are for the corresponding measured short-term level fluctuation,
extended by the expanded uncertainty of measurement.
NOTE 3 For a class LS or class 2 sound calibrator the ‘–’ symbols in the table indicate ranges of nominal
frequency for which this standard provides no tolerance limits.
5.2.4 Sound pressure level over range of supply voltage
The absolute value of the difference between the sound pressure level generated by the sound
calibrator, determined according to 5.2.2 over the range of supply voltages specified in the
instruction manual, and the sound pressure level measured at the nominal supply voltage
under reference environmental conditions, extended by the expanded uncertainty of
measurement, shall not exceed the tolerance limits given in Table 2 for the class of sound
calibrator. Also, the tolerance limits given in Table 1 for the absolute value of the difference
between the measured sound pressure level and the specified sound pressure level shall not
be exceeded for any supply voltage within the range.
Table 2 – Tolerance limits for the effect of supply voltage on sound pressure level,
under reference environmental conditions
Tolerance limits
dB
Class LS Class 1 Class 2
0,05 0,10 0,20
NOTE Tolerance limits are for the absolute value of the difference between the
sound pressure level generated by the sound calibrator over the range of operating
voltage, and the sound pressure level measured at the nominal supply voltage,
extended by the expanded uncertainty of measurement.
5.3 Frequency
5.3.1 General
5.3.1.1 The principal frequency of the sound generated by the sound calibrator shall be in the
range from 160 Hz to 1 250 Hz. Specified frequencies shall be calculated from the equation for
exact frequency given in 3.1 of ISO 266, or taken from Table 1 of ISO 266 which gives the
calculated frequency.
60942 © IEC:2003 – 25 –
5.3.1.2 The principal sound pressure level shall be available at the principal frequency.
5.3.2 Frequency of sound generated by the sound calibrator
The absolute value of the difference in per cent between the frequency of the sound generated
by the sound calibrator and the corresponding specified frequency, extended by the expanded
uncertainty of measurement, shall not exceed the tolerance limits given in Table 3 for the class
of sound calibrator. These tolerance limits apply to measurements made at and around
reference environmental conditions within the following ranges: 97 kPa to 105 kPa, 20 °C to
26 °C and 40 % relative humidity to 65 % relative humidity.
Table 3 – Tolerance limits for frequency,
at and around reference environmental conditions
Tolerance limits
%
Class LS Class 1 Class 2
1,0 1,0 2,0
NOTE 1 Tolerance limits are for the absolute value of the difference in per cent
between the frequency of the sound generated by the sound calibrator and the
specified frequency, extended by the expanded uncertainty of measurement.
NOTE 2 Tolerance limits are expressed as a percentage of the specified frequency.
5.4 Influence of static pressure, air temperature and humidity
5.4.1 For environmental conditions outside the range of 97 kPa to 105 kPa, 20 °C to 26 °C
and 40 % relative humidity to 65 % relative humidity, sound calibrators shall operate within the
tolerance limits given in Tables 4 and 5 relative to the values measured under reference
environmental conditions, and shall not exceed the tolerance limits for Table 6, for the class of
sound calibrator, over any combination of the range of environmental conditions given below.
Class LS static pressure: 65 kPa to 108 kPa
air temperature: +16 °C to +30 °C
relative humidity: 25 % to 90 %
Class 1 static pressure: 65 kPa to 108 kPa
air temperature: –10 °C to +50 °C
relative humidity: 25 % to 90 %
Combinations of air temperature and relative humidity that would yield a dewpoint greater than
+39 °C are excluded from the tests of conformance with these specifications.
Class 2 static pressure: 65 kPa to 108 kPa
air temperature: 0 °C to +40 °C
relative humidity: 25 % to 90 %
NOTE The range of environmental conditions for class 1 and class 2 sound calibrators is the same as specified in
IEC 61672-1 for class 1 and class 2 sound level meters.

60942 © IEC:2003 – 27 –
5.4.2 Class LS and class 1 sound calibrators that conform to the requirements of Tables 4, 5
and 6 for the given class of sound calibrator, over the appropriate range of environmental
conditions specified in 5.4.1, but which require corrections for the influence of static pressure
to achieve conformance to the requirements specified in Table 4 and Table 5, shall be
designated class LS/C or class 1/C sound calibrator, as appropriate. Similarly, class 2 sound
calibrators that conform to the requirements of Tables 4, 5 and 6 for the class of sound
calibrator, over the appropriate range of environmental conditions specified in 5.4.1, but which
require corrections for any of the environmental conditions to achieve conformance to the
requirements specified in Tables 4 and 5, shall be designated class 2/C sound calibrators. All
relevant corrections, together with their associated expanded uncertainties of measurement
corresponding to a confidence level of approximately 95 %, shall be given in the instruction
manual. A statement shall be included in the instruction manual giving the maximum expanded
uncertainty of the measurement of environmental conditions required so that the ability of a
sound calibrator to conform to the requirements for the relevant class is not affected.
Table 4 – Tolerance limits for sound pressure level,
over the specified range of environmental conditions
Range of nominal Tolerance limits
dB
frequencies
Hz Class LS Class 1 Class 2
31,5 to <160 – 0,50 –
160 to 1 250 0,20 0,40 0,60
>1 250 to 4 000 – 0,60 –
>4 000 to 8 000 – 0,80 –
>8 000 to 16 000 – 1,00 –
NOTE 1 Tolerance limits are for the absolute value of the difference between the sound pressure level generated
by the sound calibrator over the specified range of environmental conditions (excluding the conditions covered by
Table 1) and the sound pressure level measured under reference environmental conditions, extended by the
expanded uncertainty of measurement.
NOTE 2 For a class LS or class 2 sound calibrator the ‘–’ symbols in the table indicate ranges of nominal
frequency for which this standard provides no tolerance limits.
Table 5 – Tolerance limits for frequency,
over the specified range of environmental conditions
Tolerance limits
%
Class LS Class 1 Class 2
1,0 1,0 2,0
NOTE 1 Tolerance limits are for the absolute value of the difference in per cent between the frequency
of the sound generated by the sound calibrator over the specified range of environmental conditions
(excluding the conditions covered by Table 3) and the frequency measured under reference
environmental conditions, extended by the expanded uncertainty of measurement.
NOTE 2 Tolerance limits are expressed as a percentage of the specified frequency.

60942 © IEC:2003 – 29 –
5.5 Total distortion
The total distortion, measured over the frequency range from at least 22,5 Hz to 20 kHz,
extended by the expanded uncertainty of measurement, shall not exceed the maximum values
given in Table 6, for the applicable range of environmental conditions specified in 5.4.1.
NOTE A distortion meter may indicate the ratio of the magnitude of the unwanted components to the magnitude of
the fundamental component of the signal. For the maximum distortion limits specified in this standard, the
difference between distortion measured as a ratio of the root-mean-square of the total distortion components to the
root-mean-square of the entire signal, or to the root-mean-square of the fundamental, is insignificant compared with
the uncertainty of measurement.
Table 6 – Maximum total distortion
Total distortion
Range of nominal
frequencies %
Hz Class LS Class 1 Class 2
31,5 to <160 – 4,0 –
160 to 1 250 2,5 3,0 4,0
>1 250 to 16 000 – 4,0 –
NOTE 1 Tolerance limits are for the maximum total distortion generated by the sound calibrator, extended by the
expanded uncertainty of measurement.
NOTE 2 For a class LS or class 2 sound calibrator the ‘–’ symbols in the table indicate ranges of nominal
frequency for which this standard provides no tolerance limits.
5.6 Power supply requirements
The sound calibrator shall include as an integral part some means of checking that the supply
voltage is sufficient to operate the sound calibrator in accordance with the requirements of this
standard, or shall ensure that the sound calibrator ceases to produce any sound output when
the supply voltage falls below that required to operate the sound calibrator in accordance with
the requirements of this standard.
5.7 Specification and calibration of microphones
5.7.1 Microphone models and adaptors
5.7.1.1 The instruction manual for the sound calibrator shall state the microphone
configuration as designated in IEC 61094-1 or IEC 61094-4, or alternatively (and in addition if
desired), the name of the manufacturer or supplier, model designation and configurations (for
example, with or without protective grid) of those microphones with which the sound calibrator
is specified to operate in conformity with the requirements of this standard. In each case, the
instruction manual shall state the required adaptor configuration (if any).
5.7.1.2 For class LS sound calibrators, at least one of the microphone configurations or
models specified shall be a laboratory standard microphone as specified in IEC 6
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