IEC 60268-4:2014

Sound system equipment - Part 4: Microphones

IEC 60268-4:2014 specifies methods of measurement for the electrical impedance, sensitivity, directional response pattern, dynamic range and external influences of sound system microphones, and also details the characteristics to be specified by the manufacturer. This fifth edition cancels and replaces the fourth edition published in 2010, and constitutes a technical revision. It includes the following changes:
- clarification of Table 5 of classification of characteristics;
- clarification of graphical representation;
- clarification of environmental influences;
- rewritten clause for EMC;
- tolerances and more specific values for noise measurements;
- inclusion of near-field response for sound source-to-microphone distances of the order of 30 cm.

Equipements pour systèmes électroacoustiques - Partie 4: Microphones

L'IEC 60268-4 :2014 spécifie les méthodes de mesure portant sur l'impédance électrique, l'efficacité, le diagramme de directivité, la dynamique, et les perturbations extérieures des microphones pour les systèmes électroacoustiques, et détaille également les caractéristiques à spécifier par le constructeur. Cette cinquième édition annule et remplace la quatrième édition parue en 2010. Elle constitue une révision technique. Cette édition inclut les modifications suivantes:
- clarification du Tableau 5 de classification des caractéristiques;
- clarification de la représentation graphique;
- clarification des influences de l'environnement;
- réécriture de l'article relatif à la CEM;
- tolérances et valeurs plus spécifiques pour les mesures de bruit;
- inclusion de la réponse en champ proche pour des distances source sonore-microphone de l'ordre de 30 cm.

Electromagnetic compatibility (EMC) - Part 2: Environment – Section 5: Classification of electromagnetic environments - Basic EMC publication

General Information

• Status: Published
• Publication Date: 18-Jun-2014
• ICS: 33.100 - Electromagnetic compatibility (EMC)
• ICS: 33.160.50 - Accessories
• Technical Committee: TA 20 - Analogue and digital audio
• Drafting Committee: MT 60268-4 - TC 100/TA 20/MT 60268-4
• Current Stage: DELPUB - Deleted Publication
• Completion Date: 12-Sep-2018
• Ref Project: SIST-TP IEC/TR2 61000-2-5:2004 - Electromagnetic compatibility (EMC) - Part 2: Environment - Section 5: Classification of electromagnetic environments. Basic EMC publication

Relations

• Revises: IEC 60268-4:2010 - Sound system equipment - Part 4: Microphones
• Effective Date: 05-Sep-2023
• Revised: IEC 60268-4:2018 - Sound system equipment - Part 4: Microphones
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 60268-4


®


Edition 5.0 2014-06



INTERNATIONAL



STANDARD



NORME
INTERNATIONALE


Sound system equipment –
Part 4: Microphones

Équipements pour systèmes électroacoustiques –
Partie 4: Microphones


IEC 60268-4:2014-06(en-fr)

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IEC 60268-4



®



Edition 5.0 2014-06







INTERNATIONAL





STANDARD







NORME



INTERNATIONALE











Sound system equipment –

Part 4: Microphones




Équipements pour systèmes électroacoustiques –

Partie 4: Microphones

















INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE

PRICE CODE
INTERNATIONALE

CODE PRIX XA


ICS 33.160.50 ISBN 978-2-8322-1586-9



Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

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– 2 – IEC 60268-4:2014 © IEC 2014


CONTENTS




FOREWORD . 6

1 Scope . 8


2 Normative references . 8

3 Terms and definitions . 9

4 General conditions . 10


4.1 General . 10

4.2 Measurement conditions . 10
4.2.1 General . 10
4.2.2 Rated conditions . 11
5 Particular conditions . 11
5.1 Pre-conditioning . 11
5.2 Sound source . 12
5.3 Measurement of sound pressure . 12
5.4 Voltage measuring system . 12
5.5 Acoustical environment . 12
5.5.1 General . 12
5.5.2 Free-field conditions . 12
5.5.3 Diffuse field conditions . 14
5.5.4 Microphone coupled to a sound source by means of a small cavity
coupler . 15
5.6 Methods of measuring frequency response . 15
5.6.1 Point-by-point and continuous sweep frequency methods . 15
5.6.2 Calibration methods . 16
5.7 Overall accuracy . 16
5.8 Graphical presentation of results . 16
6 Type description (acoustical behaviour) . 16
6.1 Principle of the transducer . 16
6.2 Type of microphone . 16
6.3 Type of directional response characteristics . 17
6.4 Application profile . 17
7 Terminals and controls . 17
7.1 Marking . 17

7.2 Connectors and electrical interface values . 17
8 Reference point and axis . 17
8.1 Reference point . 17
8.2 Reference axis . 18
9 Rated power supply . 18
9.1 Characteristics to be specified . 18
9.2 Method of measurement . 18
10 Electrical impedance . 18
10.1 Internal impedance . 18
10.1.1 Characteristic to be specified . 18
10.1.2 Methods of measurement . 18
10.2 Rated impedance . 19
10.3 Rated minimum permitted load impedance . 19

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IEC 60268-4:2014 © IEC 2014 – 3 –


11 Sensitivity . 19

11.1 General . 19


11.2 Sensitivities with respect to acoustical environment . 20

11.2.1 Free-field sensitivity . 20

11.2.2 Diffuse-field sensitivity . 20

11.2.3 Close-talking or near-field sensitivity . 21

11.2.4 Pressure sensitivity . 21

11.3 Rated sensitivity . 22

12 Response . 22


12.1 Frequency response . 22
12.1.1 Characteristic to be specified . 22
12.1.2 Method of measurement . 23
12.1.3 Graphical presentation of results . 23
12.2 Effective frequency range . 23
12.2.1 Characteristic to be specified . 23
12.2.2 Method of measurement . 23
13 Directional characteristics . 23
13.1 Directional pattern . 23
13.1.1 Characteristic to be specified . 23
13.1.2 Methods of measurement . 23
13.1.3 Graphical presentation of results . 24
13.2 Directivity index . 25
13.2.1 Characteristic to be specified . 25
13.2.2 Method of measurement . 25
14 Amplitude non-linearity . 25
14.1 General . 25
14.2 Total harmonic distortion . 25
14.2.1 Characteristic to be specified . 25
14.2.2 Method of measurement . 25
th
14.3 Harmonic distortion of the n order (n = 2, 3,.) . 26
14.3.1 Characteristic to be specified . 26
14.3.2 Method of measurement . 26
14.4 Difference frequency distortion of second order . 27
14.4.1 Characteristic to be specified . 27
14.4.2 Method of measurement . 27
15 Limiting characteristics . 27
15.1 Rated maximum permissible peak sound pressure . 27
15.2 Overload sound pressure . 27
15.2.1 Characteristic to be specified . 27
15.2.2 Method of measurement . 28
16 Balance . 28
16.1 Balance of the microphone output . 28
16.2 Balance under working conditions . 28
17 Equivalent sound pressure level due to inherent noise . 29
17.1 Characteristic to be specified . 29
17.2 Method of measurement . 29
18 Ambient conditions . 30
18.1 General . 30

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– 4 – IEC 60268-4:2014 © IEC 2014


18.2 Pressure range . 30

18.3 Temperature range . 30

18.4 Relative humidity range . 30

19 External influences . 30

19.1 General . 30

19.1.1 Specification and methods of measurement . 30

19.1.2 Other external interferences . 31

19.2 Equivalent sound pressure due to mechanical vibration . 31

19.2.1 Characteristic to be specified . 31


19.2.2 Method of measurement . 31
19.3 Equivalent sound pressure due to wind . 31
19.3.1 Characteristic to be specified . 31
19.3.2 Method of measurement . 31
19.4 Transient equivalent sound pressure due to "pop" effect . 34
19.4.1 Characteristic to be specified . 34
19.4.2 Method of measurement . 36
20 Electromagnetic compatibility (EMC) . 36
20.1 Regulatory requirements . 36
20.2 Requirements for preserving programme quality . 37
20.3 Performance criteria . 38
20.3.1 Criterion A . 38
20.3.2 Criterion B . 38
20.4 Testing for immunity to disturbances in the presence of acoustical noise . 38
20.5 Immunity to frequency-modulated radiated disturbances . 38
20.6 Immunity to magnetic fields . 39
20.7 Immunity to ripple on d.c. power supply . 39
20.8 Permanent magnetic field . 39
20.9 Evaluation and reporting of the test results . 39
21 Physical characteristics . 40
21.1 Dimensions . 40
21.2 Weight . 40
21.3 Cables and connectors . 40
22 Classification of the characteristics to be specified . 40
Annex A (normative) Additional characteristics . 43

A.1 Characteristic sensitivity for speech . 43
A.1.1 Characteristic to be specified . 43
A.1.2 Method of measurement . 43
A.2 Front-to-rear sensitivity index (0° – 180°) . 44
A.2.1 Characteristic to be specified . 44
A.2.2 Method of measurement . 44
A.3 Noise-cancelling index . 44
A.3.1 Characteristic to be specified . 44
A.3.2 Method of measurement . 44
A.4 Special characteristics for stereo microphones . 45
A.4.1 General . 45
A.4.2 Included angle of an XY (left-right) microphone . 45
A.4.3 Acceptance angle . 45
Annex B (informative) Sound insulation device . 46

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IEC 60268-4:2014 © IEC 2014 – 5 –


Annex C (informative) Simplified procedure for “pop” measurements . 47

C.1 General . 47


C.2 Measurement set-up . 47

C.3 Measurement procedure . 47

C.4 Approximate inclusion of different frequency responses . 48

Annex D (informative) Recommendations for professional digital microphones . 50

D.1 General . 50

D.2 Data sheets for digital microphones . 50


Bibliography . 53


Figure 1 – Balance of the output . 28
Figure 2 – Balance under working conditions . 29
Figure 3 – Measurement set-up for wind influence . 32
Figure 4 – Wind generators, type 1 (Figure 4a) and type 2 (Figure 4b) . 33
Figure 5 – Electrical and mechanical set-up for the measuring of the "pop" effect . 35
Figure B.1 – Sound insulation device . 46
Figure C.1 – Measurement set-up . 49
Figure C.2 – Test fixture for the sound field sensitivity . 49

Table 1 – Reverberation time of the empty room . 14
Table 2 – Reference signal and characteristics . 36
Table 3 – Examples of EMC regulations and standards . 37
Table 4 – Basic EMC standards and their application to microphones . 37
Table 5 – Classification of characteristics . 41
Table A.1 – Speech power weighting factor at octave-band centre frequencies . 43
Table D.1 – Classification of the characteristics recommended to be specified . 50
Table D.2 – Additional digital characteristics to be specified . 52

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– 6 – IEC 60268-4:2014 © IEC 2014



INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________




SOUND SYSTEM EQUIPMENT –



Part 4: Microphones



FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of 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, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). 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-
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with the International Organization for Standardization (ISO) in accordance with conditions determined by
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consensus of opinion on the relevant subjects since each technical committee has representation from all
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8) Attention is drawn to the Normative references cited in th
...

SLOVENSKI SIST-TP IEC/TR2 61000-2-
5:2004

STANDARD
april 2004
Electromagnetic compatibility (EMC) - Part 2: Environment – Section 5:
Classification of electromagnetic environments - Basic EMC publication
ICS 33.100.01 Referenčna številka
SIST-TP IEC/TR2 61000-2-5:2004(en)
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

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1000-2-5 IEC:1995 − 3 −
CONTENTS
Page
FOREWORD . 7
Clause
1 General . 11
1.1 Scope and object. 11
1.2 Normative reference. 11
1.3 Approach. 11
2 Definitions . 15
2.1 Annotated definitions on electromagnetic compatibility. 17
2.2 Acronyms. 19
3 User's guide for this report. 19
3.1 Rationale for classification system . 19
3.2 Environmental phenomena. 19
3.3 Simplification of the environmental database. 21
4 Low-frequency electromagnetic phenomena . 25
4.1 Conducted low-frequency phenomena. 25
4.2 Radiated low-frequency phenomena. 33
5 High-frequency electromagnetic phenomena . 37
5.1 Conducted high-frequency phenomena . 37
5.2 Radiated high-frequency phenomena . 45
6 Electrostatic discharge. 49
6.1 ESD currents. 49
6.2 Fields produced by ESD currents. 51
7 Classification of environments .53
7.1 Types of location . 53
7.2 Impinging disturbances and equipment ports . 53
8 Principles of the selection of immunity levels. 57
8.1 Approach. 57
8.2 Uncertainties. 57
8.3 Criticality criteria. 59

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1000-2-5 IEC:1995 − 5 −
Tables Page
1 Principal phenomena causing electromagnetic disturbances. 23
2 Range of disturbance degrees for harmonics in low-voltage power systems. 27
3 Range of disturbance degrees for signalling voltages in power systems . 29
4 Sources and range of disturbance degrees for voltage amplitude and frequency
in power systems . 31
5 Sources and range of disturbance degrees for low-frequency, common-mode
induced voltages in signal and control cables. 33
6 Sources and range of disturbance degrees for low-frequency magnetic fields . 35
7 Sources and range of disturbance degrees for low-frequency electric fields. 37
8 Disturbance degrees of induced CW voltages with respect to reference ground. 39
9 Sources and range of disturbance degrees for conducted unidirectional transients
in low-voltage a.c. power systems . 43
10 Sources and range of disturbance degrees for conducted oscillatory transients
in low-voltage a.c. power systems . 45
11 Sources and range of disturbance degrees for radiated oscillatory disturbances . 47
12 Sources and range of disturbance degrees for radiated pulsed disturbances. 49
13 Sources and range of disturbance degrees for ESD . 51
14 Range of disturbance degrees for field gradients caused by ESD . 51
A.1 Location class type 1. 65
A.2 Location class type 2. 69
A.3 Location class type 3. 73
A.4 Location class type 4. 77
A.5 Location class type 5. 81
A.6 Location class type 6. 85
A.7 Location class type 7. 89
A.8 Location class type 8. 93
B Typical waveforms for radiated oscillatory disturbances. 95
Annexes
A Examples of compatibility levels for typical location classes. 63
B Radiated oscillatory disturbances . 95
C Radiated pulsed disturbances. 99

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1000-2-5 IEC:1995 − 7 −
INTERNATIONAL ELECTROTECHNICAL COMMISSION
_________
ELECTROMAGNETIC COMPATIBILITY (EMC) −−−−
Part 2: Environment −−−−
Section 5: Classification of electromagnetic environments
Basic EMC publication
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 interest 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, prepared by technical committees on
which all the National Committees having a special interest therein are represented, express as nearly as
possible, an international consensus of opinion on the subjects dealt with.
3) They have the form of recommendations for international use published in the form of standards, 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.
The main task of IEC technical committees is to prepare International Standards. In
exceptional circumstances, a technical committee may propose the publication of a technical
report of one of the following types:
• type 1, when the required support cannot be obtained for the publication of an
International Standard, despite repeated efforts;
• type 2, when the subject is still under technical development or where for any other
reason there is the future but not immediate possibility of an agreement on an International
Standard;
• type 3, when a technical committee has collected data of a different kind from that which
is normally published as an International Standard, for example “state of the art”.
Technical reports of types 1 and 2 are subject to review within three years of publication to
decide whether they can be transformed into International Standards. Technical reports of type
3 do not necessarily have to be reviewed until the data they provide are considered to be no
longer valid or useful.

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1000-2-5 IEC:1995 − 9 −
IEC 1000-2-5, which is a technical report of type 2, has been prepared by sub-committee 77B:
High-frequency phenomena, of IEC technical committee 77: Electromagnetic compatibility.
The text of this technical report is based on the following documents:
Committee draft Report on voting
77B(SEC)122 77B/142/RVC
Full information on the voting for the approval of this technical report can be found in the report
on voting indicated in the above table.
This document is issued in the type 2 technical report series of publications (according to
G.4.2.2 of part 1 of the IEC/ISO Directives) as a “prospective standard for provisional
application” in the field of electromagnetic compatibility because there is an urgent requirement
for guidance on how standards in this field should be used to meet an identified need.
This document is not to be regarded as an “International Standard”. It is proposed for
provisional application so that information and experience of its use in practice may be
gathered. Comments on the content of this document should be sent to the IEC Central Office.
A review of this type 2 technical report will be carried out not later than three years after its
publication, with the options of either extension for a further three years or conversion to an
International Standard or withdrawal.
Annexes A, B and C are for information only.

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1000-2-5 IEC:1995 − 11 −
ELECTROMAGNETIC COMPATIBILITY (EMC) −−
−−
Part 2: Environment −−−−
Section 5: Classification of electromagnetic environments
Basic EMC publication
1 General
1.1 Scope and object
This section of IEC 1000-2 is a technical report intended for guidance, not as a specification,
for those who are in charge of writing immunity standards for an equipment or system. Its
purpose is to classify electromagnetic environments and help improve the specification of the
immunity requirements of an item containing electrical or electronic parts, and consequently
obtain electromagnetic compatibility. It also gives basic guidance for the selection of immunity
levels. The data are applicable to any equipment, subsystem or system making use of
electromagnetic energy and operating in a specific location as defined by this report. The
environment inside transportation equipment (vehicles, traction, ships, aircraft) is not described
in this report, but their effect on the surrounding environment is included.
It should be noted that the immunity level requirements chosen for the items are not only
inevitably bound to their environment, but also to the requirements of the applications (e.g. for
reliability or safety purposes). That could lead to more stringent requirements than usual.
These levels may also be established for more general purposes such as generic and product
standards, taking into account statistical and economical aspects as well as common
experiences in certain application fields.
1.2 Normative reference
The following normative document contains provisions which, through reference in this text,
constitute provisions of this section of IEC 1000-2. At the time of publication, the edition
indicated was valid. All normative documents are subject to revision and parties to agreements
based on this section of IEC 1000-2 are encouraged to investigate the possibility of applying
the most recent edition of the normative document indicated below. Members of IEC and ISO
maintain registers of currently valid International Standards.
IEC 50(161): 1990, International Electrotechnical Vocabulary (IEV) – Chapter 161: Electro-
magnetic compatibility
1.3 Approach
Classification of the electromagnetic environment is based on the classification or a description
of the electromagnetic phenomena prevailing at typical locations, not on existing test
specifications. However, given a choice among equal possibilities, harmonization with existing
test specifications (if appropriate) will simplify the situation and promote easier acceptance of
the recommendations. The definition of electromagnetic environment in IEC 50(161) makes
reference to “electromagnetic phenomena”. The term disturbance degree is used in this report
for quantifying the phenomena contributing to the electromagnetic environment, independently

---------------------- Page: 6 ----------------------

1000-2-5 IEC:1995 − 13 −
of any consideration of test levels. The term “severity level” will not be used in this report to
describe the environment, as it is reserved for specifying immunity test levels in other IEC
publications.
Thus, the concept and term of electromagnetic phenomenon is the starting point for defining
the environment and selecting disturbance degrees in a classification document. Clauses 4, 5
and 6 of this report are the first step of the process. Three basic categories of phenomena
have been identified: low-frequency phenomena, high-frequency phenomena and electrostatic
discharge. In the first stage, attributes of the phenomena (amplitudes, waveforms, source
impedance, frequency of occurrence, etc.) will be defined generically, and the expected range
of disturbance degrees established. Then, in the second stage, ONE SINGLE value from that
range has been identified as most representative for each phenomenon at a specific class of
location and set forth as the compatibility level for that location class.
The process is illustrated in figure 1, showing how two sets of tables are used: a set of input
tables that are phenomena-oriented and establish a range of disturbance degrees for a given
phenomenon, and a set of output tables that are location-oriented and propose a table for each
class, with one value of compatibility level for each of the phenomena identified in the set of
input tables.
The final classification of environments into location classes and corresponding compatibility
levels is discussed in clause 7, with specific examples of location classes given in the tables of
annex A. The attributes of these location classes are based on the significant electromagnetic
characteristics of a location, rather than geographical or structural aspects. For instance, the
term “factory” is insufficient to categorize the location: in a factory, different localized
conditions such as a computer room, general office space, as well as the manufacturing floor,
proper, will be found.
The locations labels of the final classification imply specific definition of significant
electromagnetic attributes. Classes of locations other than those listed in annex A may be
identified and added to the set as the need arises.
It should be noted that this classification is based on environment data encountered circa 1990
with an acceptable probability factor. The disturbance degrees shown in annex A are offered as
examples of compatibility levels for the guidance of product committees, not as normative
permitted levels or immunity requirements. Those values are affected by uncertainties, and
might not describe extreme environments.

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1000-2-5 IEC:1995 − 15 −
INPUT TABLES OUTPUT TABLES
Phenomenon oriented Location oriented
LF conducted Specification of one value
per phenomenon and
HF radiated interface port, with one
table for each location
Classification according to
class.
the disturbance degrees,
with one table for each
phenomenon:
A = controlled environment
1 =
2 =
natural
3 =
environments
4 =
. . . .
X = harsh environment
Phenomenon abc Location Class xyz
Port
Attribute
Degree
Phenom.
Figure 1 – Schematic of the two-step approach used for classification
with phenomenon-oriented input tables and location-oriented
output tables
2 Definitions
For definitions related to the general subject of electromagnetic compatibility, see IEC 50(161).
For the purpose of this section of IEC 1000-2, the following definitions apply.
Notes shown in normal characters are part of the IEC 50(161) definition. For the purpose of
this report, notes shown in italic characters have been added to the definition given in
IEC 50(161).

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1000-2-5 IEC:1995 − 17 −
2.1 Annotated definitions on electromagnetic compatibility
2.1.1 (electromagnetic) compatibility level: Specified maximum electromagnetic
disturbance level expected to be impressed on a device, equipment or system operated in
particular conditions. [161-03-10]
NOTE – In practice the electromagnetic disturbance level is not an absolute maximum level but may be
exceeded by a small probability.
2.1.2 disturbance degree: Specified, quantified intensity within a range of disturbance levels
corresponding to a particular electromagnetic phenomenon encountered in the environment of
interest.
2.1.3 disturbance level: Level of a given electromagnetic disturbance, measured in a
specified way.
2.1.4 electromagnetic compatibility (EMC): Ability of a device, equipment or system to
function satisfactorily in its electromagnetic environment without introducing intolerable
electromagnetic disturbances to anything in that environment. [161-01-07, modified]
NOTE – For brevity, instead of repeating the wording "device, equipment or system", the term "item" is used
in this report.
2.1.5 (electromagnetic) environment: Totality of electromagnetic phenomena existing at a
given location. [161-01-01]
NOTES
1 In general, this totality is time-dependent and its description might need a statistical approach.
2 It is very important not to confuse the electromagnetic environment and the location itself.
2.1.6 (electromagnetic) disturbance: Any electromagnetic phenomenon which might degrade
the performance of a device, equipment or system, or adversely affect living or inert matter.
[161-01-05]
NOTE – An electromagnetic disturbance might be electromagnetic noise, an unwanted signal or a change in
the propagation medium itself.
2.1.7 (electromagnetic) susceptibility: Inability of a device, equipment or system to perform
without degradation in the presence of an electromagnetic disturbance. [161-01-21]
NOTE – Susceptibility is a lack of immunity.
2.1.8 immunity (to a disturbance): Ability of a device, equipment or system to perform
without degradation in the presence of an electromagnetic disturbance. [161-01-20]
2.1.9 immunity level: Maximum level of a given electromagnetic disturbance incident on a
particular device, equipment or system, for which it remains capable of operating at a required
degree of performance. [161-03-14]
2.1.10 location (EMC): Position or site marked by distinguishing electromagnetic features.
2.1.11 location class: Set of locations having a common property related to the types and
density of electrical and electronic equipment in use, including installation conditions and
external influences (see annex A).

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1000-2-5 IEC:1995 − 19 −
2.2 Acronyms
ASD adjustable speed drive (also variable speed drive)
CW continuous wave
ESD electrostatic discharge
EUT equipment under test
ISM industrial, scientific and medical equipment
ITE information technology equipment
MRI magnetic resonance imaging (also nuclear magnetic resonance).
3 User's guide for this report
3.1 Rationale for classification system
The purpose of a classification system is to identify a limited set of parameters and associated
values which may be chosen when identifying performance requirements. The purpose of such
a system is primarily economic, in that it limits the number of variations in the number of types
of equipment which a manufacturer may produce. It also identifies the need (if any) for
appropriate interfaces.
The classification system proposed is rather exhaustive, and shows numerous electromagnetic
phenomena. It does not necessarily mean that the immunity of a given device shall be tested
against all these phenomena, but that a limited set of them may be chosen according to the
environment of concern and inherent characteristics of the device.
3.2 Environmental phenomena
The electromagnetic environment in which electronic systems are expected to operate without
interference is very complex. For the purpose of this classification, three categories of
environmental phenomena have been defined to describe all disturbances:
− low-frequency phenomena (conducted and radiated, from any source except ESD);
– high-frequency phenomena (conducted and radiated, from any source except ESD);
– electrostatic discharge (ESD) phenomena (conducted and radiated).
This distinction is necessary in order to recognize that electromagnetic disturbances occur in a
particular medium. Formally, when dealing with the electromagnetic environment, the
wavelength λ of the considered disturbance is the gauge for “long or large” and for “short or
small”. A system is small or a line is short if the wavelength is much greater than its
dimensions. Consequently, in that situation the frequency is low, as the frequency is inversely
proportional to wavelength. Large, long and high apply when the dimensions are, say, greater
than 1. However, in the context of the present report, low means that the dominant part of the
frequency spectrum of the disturbance is below 9 kHz and high if it is at frequencies (much)
higher than 9 kHz.

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1000-2-5 IEC:1995 − 21 −
Radiated disturbances occur in the medium surrounding the equipment, while conducted
disturbances occur in various metallic media. The concept of ports, through which disturbances
have an impact on the equipment, allows a distinction among these various media: 1)
enclosure; 2) a.c. power mains; 3) d.c. power mains; 4) control/signal lines; 5) interface
between systems and earth or reference. The source, the coupling and the propagation
characteristics depend on the type of medium. The final tables of annex A show the
compatibility levels for various location classes, and are structured along this concept of
corresponding ports.
3.3 Simplification of the environmental database
It is neither possible nor absolutely necessary to describe completely an electromagnetic
environment. Consequently, any description is limited to certain properties of this environment.
The first step of a description should be the selection of appropriate electromagnetic properties
corresponding to the various phenomena that can create electromagnetic disturbances. Table
1 lists the types of phenomena. In this report, the boundary between low frequency and high
frequency is generally understood as being 9 kHz; however, when addressing a type of
disturbance prevailing in one frequency range with a small overlap into the other range, the
boundary might be slightly shifted to keep the phenomenon within one descriptive range.
An appropriate selection is only valid if its purpose is also specified. Considering the many
possible coupling mechanisms between an item and its electromagnetic environment, it
becomes apparent that, in order to accurately assess the necessary level of immunity for any
item, more information than is available about the environment would be needed. Accuracy of
electromagnetic environment descriptions are necessarily limited, as follows:
− some aspects of the environment are disregarded because the information is not
available;
− some aspects of the environment are disregarded because a classification system taking
them into account would become too complex;
− a statistical approach may be necessary, in order to consider only those events for which
the occurrence is likely.
The first two limitations are embedded in the selection of the disturbance types, while the
statistical aspect appears in the definition of environment classes and the selection of a single
value for compatibility levels, rather than a range of values.
Available databases at the time of elaboration of this report indicate the wide variety of
conducted and radiated disturbances that can be expected to occur in the diverse
environments encountered in the use of equipment. Evaluation by laboratory tests of the ability
of equipment to withstand these environments, or of the effectiveness of mitigation methods,
can be facilitated by a synthesis of the database. This synthesis leads to selecting a few
representative disturbance phenomena that will make tests uniform, meaningful and replicable.

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1000-2-5 IEC:1995 − 23 −
Table 1 −− Principal phenomena causing electromagnetic disturbances
−−
Conducted low-frequency phenomena
– harmonics, interharmonics
– signalling voltages
– voltage fluctuations
– voltage dips and interruptions
– voltage unbalance
– power-frequency variations
– induced low-frequency voltages
– d.c. in a.c. networks
Radiated low-frequency phenomena
– magnetic fields
– electric fields
Conducted high-frequency phenomena
– induced CW voltages or currents
– unidirectional transients
– oscillatory transients
Radiated high-frequency phenomena
– magnetic fields
– electric fields
– electromagnetic fields
. continuous waves
. transients
Electrostatic discharge phenomena (ESD)
Nuclear electromagnetic pulse (NEMP) *
* Not considered in this report.
To assist equipment designers and users in making appropriate choices in defining immunity
test levels, the classification shows, for each phenomenon, only one compatibility level per
class of location. The characterization of each phenomenon is presented in tabular form, from
which a selection can be made. This approach gives a common base of reference for
specifying performance requirements for an equipment expected to be installed at various
types of locations, and yet provides the appropriate degree of compromise between a
conservative overdesign and a cost-conscious reduction of margins. The specification of these
requirements for specific equipment remains the field of product standards and, therefore,
cannot be addressed in the present report.
For a given equipment, the surrounding environment in which it is required to operate results
from the presence and nature of disturbance sources, as well as from the installation
conditions adopted. Typical installation practices take into consideration the mitigation which
can be obtained by separation, shielding and suppression. Therefore, it is important to take into
consideration the effect of these practices when suggesting disturbance degrees in specific
locations where various installation practices are generally applied. This report assigns a
representative degree for the various types of installations likely to be found at those locations.

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1000-2-5 IEC:1995 − 25 −
The listing of disturbance degrees includes an "A" degree, for an environment where some
mitigation or control might be necessary to satisfy specific requirements, and an "X" degree
recognizing that in some situations exceptional conditions could prevail that need specific
recognition. The "A" degree corresponds to a situation where the environment is somewhat
controlled by the nature of the building, or installation practices inherent to a p
...