EN IEC 60268-21:2018

Sound system equipment - Part 21: Acoustical (output-based) measurements

IEC 60268-21:2018 specifies an acoustical measurement method that applies to electro-acoustical transducers and passive and active sound systems, such as loudspeakers, TV-sets, multi-media devices, personal portable audio devices, automotive sound systems and professional equipment. The device under test (DUT) can be comprised of electrical components performing analogue and digital signal processing prior to the passive actuators performing a transduction of the electrical input into an acoustical output signal. This document describes only physical measurements that assess the transfer behaviour of the DUT between an arbitrary analogue or digital input signal and the acoustical output at any point in the near and far field of the system. This includes operating the DUT in both the small and large signal domains. The influence of the acoustical boundary conditions of the target application (e.g. car interior) can also be considered in the physical evaluation of the sound system. This document does not assess the perception and cognitive evaluation of the reproduced sound and the impact of perceived sound quality.

Elektroakustische Geräte - Teil 21: Akustische (ausgabebasierte) Messungen

Équipements pour systèmes électroacoustiques - Partie 21 : Mesures acoustiques (en sortie)

IEC 60268-21:2018 spécifie une méthode de mesure acoustique qui s’applique aux transducteurs électroacoustiques ainsi qu’aux systèmes électroacoustiques passifs et actifs tels que les haut-parleurs, les téléviseurs, les appareils multimédias, les appareils audio personnels portables, les systèmes électroacoustiques pour automobile et les équipements professionnels. L'appareil soumis à essai (DUT) peut être constitué de composants électriques qui effectuent un traitement analogique et numérique des signaux avant la transduction de l’entrée électrique en un signal de sortie acoustique par les excitateurs passifs. Le présent document décrit uniquement les mesures physiques qui évaluent le comportement de transfert du DUT entre un signal d’entrée analogique ou numérique arbitraire et la sortie acoustique en un point quelconque dans le champ proche et lointain du système. Cela inclut le fonctionnement du DUT dans les domaines à la fois des signaux faibles et des signaux forts. L’influence des conditions de limite acoustique de l’application visée (par exemple habitacle de véhicule) peut également être prise en considération dans l’évaluation physique du système électroacoustique. Le présent document n’évalue pas la perception et l’évaluation cognitive du son reproduit ni l’impact de la qualité perçue du son.

Elektroakustične naprave - 21. del: Akustične (izhodne) meritve (IEC 60268-21:2018)

Ta del standarda IEC 60268 določa metodo akustične meritve, ki se uporablja za elektroakustične
pretvornike ter pasivne in aktivne zvočne sisteme, kot so zvočniki, televizorji, večpredstavnostne naprave, osebne prenosne zvočne naprave, avtomobilski zvočni sistemi in profesionalna oprema. Napravo, ki se preskuša (DUT), lahko sestavljajo električne komponente, ki obdelujejo analogni in digitalni signal pred pasivnimi aktuatorji, ki pretvarjajo električni vhodni signal v akustični izhodni signal. Ta dokument opisuje samo fizične meritve za ocenjevanje prenosnega delovanja naprave, ki se preskuša, med poljubnim analognim ali digitalnim vhodnim signalom ter akustičnim izhodnim signalom na kateri koli točki bližnjega in daljnega polja sistema. To vključuje delovanje naprave, ki se preskuša, tako v domenah majhnega kot velikega signala. Pri fizični oceni zvočnega sistema je mogoče upoštevati tudi vpliv akustičnih mejnih pogojev ciljne uporabe (npr. notranjost avtomobila). Ta dokument se ne uporablja za ocenjevanje zaznavanja ter kognitivno vrednotenje
reproduciranega zvoka in vpliva zaznane kakovosti zvoka.
OPOMBA: Nekatere merilne metode, opredeljene v tem dokumentu, je mogoče uporabiti za slušalke, telefone, ušesne slušalke in druge komplete v skladu z določbo [1]1. Ta dokument se ne uporablja za mikrofone in druge senzorje.
Ta dokument ne zahteva dostopa do spremenljivk stanja (napetost, tok) na električnih terminalih pretvornika. Občutljivost, električna vhodna moč in druge značilnosti na podlagi električne impedance bodo opisane v ločenem prihodnjem dokumentu standarda IEC 60268-22, namenjenem električnim in mehanskim meritvam.

General Information

• Status: Published
• Publication Date: 20-Dec-2018
• Withdrawal Date: 11-Dec-2021
• ICS: 33.160.01 - Audio, video and audiovisual systems in general
• Technical Committee: CLC/TC 100X - Audio, video and multimedia systems and equipment and related sub-systems
• Drafting Committee: IEC/TC 100 - IEC_TC_100
• Current Stage: 6060 - Document made available - Publishing
• Start Date: 21-Dec-2018
• Completion Date: 21-Dec-2018
• Ref Project: SIST EN IEC 60268-21:2019 - Sound system equipment - Part 21: Acoustical (output-based) measurements (IEC 60268-21:2018)

Overview

EN IEC 60268-21:2018 - "Sound system equipment - Part 21: Acoustical (output-based) measurements" specifies standardized, physical acoustical measurement methods for electro‑acoustic transducers and complete sound systems. It covers output‑based measurements from an analogue or digital input to the acoustical output in the near and far field, for devices ranging from loudspeakers and TV sets to automotive audio systems and portable personal audio devices. The standard focuses on objective transfer‑behaviour measurements and explicitly excludes perceptual or cognitive sound‑quality assessment.

Key topics and requirements

EN IEC 60268-21 defines the measurement framework and practical requirements for acoustical testing, including:

• Scope of DUTs (Devices Under Test): Passive and active systems, analogue/digital signal paths, and actuator transduction.
• Measurement environments: Near‑field, far‑field, free‑field, half‑space, diffuse fields and simulated target‑application boundary conditions (e.g., car interiors).
• Positioning and geometry: Reference plane, reference point/axis, orientation vectors, evaluation points and distances for repeatable microphone placement.
• Test signals: Sinusoidal chirps, steady‑state tones, two‑tone tests, sparse multi‑tone, broadband and narrow‑band noise, Hann bursts and impulsive signals.
• Acoustical outputs and metrics: Sound‑pressure output, SPL (short‑ and long‑term maxima), mean SPL in frequency bands, frequency response of the fundamental component, and amplitude compression behaviours.
• Measurement equipment and uncertainty: Requirements for microphones and instrumentation, and guidance on measurement accuracy and uncertainty reporting.
• Test conditions and preconditioning: Rated ambient/climatic conditions, mounting and acoustic loading of drive units/system, and preconditioning procedures to ensure consistent results.

Practical applications and users

EN IEC 60268-21 is used where objective, repeatable acoustical output data are required:

• Manufacturers of loudspeakers, TVs, portable audio devices and professional sound equipment - for product specification, design verification and compliance testing.
• Automotive audio engineers - to evaluate system behaviour in target boundary conditions (e.g., vehicle interior simulations).
• Test laboratories and certification bodies - to produce standardized, traceable SPL and frequency response measurements.
• R&D and QA teams - for design optimization, regression testing and production verification.
• AV integrators and standards specialists - when specifying equipment performance or comparing systems objectively.

Keywords: EN IEC 60268-21:2018, acoustical measurements, sound system equipment, SPL, frequency response, near-field, far-field, loudspeaker testing, measurement microphones.

Related standards

Commonly referenced standards and complementary documents include:

• IEC 60268‑1, IEC 60268‑2, IEC 60268‑7 (other parts of the sound system equipment series)
• IEC 61094‑4 (measurement microphones)
• IEC 61260‑1 (fractional‑octave filters)
• ISO 3741 / 3744 / 3745 (sound power and test room methods)
• CTA standards for consumer loudspeaker and subwoofer measurement methods

This standard provides the objective, output‑based measurement framework audio professionals rely on for consistent acoustical characterization of modern sound systems.

Standards Content (Sample)

SLOVENSKI STANDARD
01-oktober-2019
Elektroakustične naprave - 21. del: Akustične (izhodne) meritve (IEC 60268-
21:2018)
Sound system equipment - Part 21: Acoustical (output-based) measurements (IEC
60268-21:2018)
Elektroakustische Geräte - Teil 21: Akustische(Ausgabebasierte) Messungen (IEC 60268
-21:2018)
Équipements pour systèmes électroacoustiques - Partie 21 : Mesures acoustiques (en
sortie) (IEC 60268-21:2018)
Ta slovenski standard je istoveten z: EN IEC 60268-21:2018
ICS:
17.140.01 Akustična merjenja in Acoustic measurements and
blaženje hrupa na splošno noise abatement in general
33.160.01 Avdio, video in avdiovizualni Audio, video and audiovisual
sistemi na splošno systems in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 60268-21

NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2018
ICS 33.160.01
English Version
Sound system equipment - Part 21: Acoustical (output-based)
measurements
(IEC 60268-21:2018)
Équipements pour systèmes électroacoustiques - Partie 21 Elektroakustische Geräte - Teil 21:
: Mesures acoustiques (en sortie) Akustische(Ausgabebasierte) Messungen
(IEC 60268-21:2018) (IEC 60268-21:2018)
This European Standard was approved by CENELEC on 2018-12-12. 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 CEN-CENELEC
Management Centre 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 CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden,
Switzerland, Turkey and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2018 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 60268-21:2018 E

European foreword
The text of document 100/2957/CDV, future edition 1 of IEC 60268-21, prepared by IEC/TC 100
"Audio, video and multimedia systems and equipment" was submitted to the IEC-CENELEC parallel
vote and approved by CENELEC as EN IEC 60268-21:2018.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2019-09-12
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2021-12-12
document have to be withdrawn
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.

Endorsement notice
The text of the International Standard IEC 60268-21:2018 was approved by CENELEC as a European
Standard without any modification.

In the official version, for Bibliography, the following notes have to be added for the standards
indicated:
IEC 60268-7:2010 NOTE Harmonized as EN 60268-7:2011 (not modified)
IEC 62777 NOTE Harmonized as EN 62777

Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
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.
NOTE 1  Where an International Publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available here:
www.cenelec.eu.
Publication Year Title EN/HD Year
IEC 60263 -  Scales and sizes for plotting frequency characteristics - -
and polar diagrams
IEC 60268-1 -  Sound system equipment. Part 1: General HD 483.1 S2 -
IEC 60268-2 1987 Sound system equipment. Part 2: Explanation of HD 483.2 S2 1993
general terms and calculation methods
IEC 61094-4 -  Measurement microphones - Part 4: Specifications EN 61094-4 -
for working standard microphones
IEC 61260-1 -  Electroacoustics - Octave-band and fractional-octave- EN 61260-1 -
band filters - Part 1: Specifications
ISO 3 -  Preferred numbers - Series of preferred numbers - -
ISO 3741 2010 Acoustics - Determination of sound power levels and EN ISO 3741 2010
sound energy levels of noise sources using sound
pressure - Precision methods for reverberation test
rooms
ISO 3744 -  Acoustics - Determination of sound power levels and EN ISO 3744 -
sound energy levels of noise sources using sound
pressure - Engineering methods for an essentially
free field over a reflecting plane
ISO 3745 -  Acoustics - Determination of sound power levels and EN ISO 3745 -
sound energy levels of noise sources using sound
pressure - Precision methods for anechoic rooms and
hemi-anechoic rooms
CTA 2034-A - Standard Method of Measurement for In-Home - -
Loudspeakers, Consumer Technology Association
(Formerly CEA)
CTA 2010-B - Standard Method of Measurement for Powered - -
Subwoofers, standard by Consumer Technology
Association (Formerly CEA)
IEC 60268-21 ®
Edition 1.0 2018-11
INTERNATIONAL
STANDARD
colour
inside
Sound system equipment –
Part 21: Acoustical (output-based) measurements

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.160.01 ISBN 978-2-8322-6176-7

– 2 – IEC 60268-21:2018  IEC 2018
CONTENTS
FOREWORD . 8
INTRODUCTION . 10
1 Scope . 11
2 Normative references . 11
3 Terms, definitions and abbreviated terms . 12
3.1 Terms and definitions . 12
3.2 Abbreviated terms . 12
4 Type description . 12
5 Physical characteristics . 12
5.1 Marking of terminals and controls . 12
5.2 Dimensions . 12
5.3 Mass . 12
5.4 Connectors and cable assemblies . 13
6 Design data . 13
7 Conditions . 13
7.1 Rated conditions . 13
7.2 Climatic conditions . 13
7.3 Normal measuring conditions . 13
8 Test signals . 14
8.1 General . 14
8.2 Sinusoidal chirp . 14
8.3 Steady-state single-tone signal . 15
8.4 Steady-state two-tone signal . 15
8.5 Sparse multi-tone complex . 15
8.6 Broadband noise signal . 16
8.7 Narrow-band noise signal . 16
8.8 Hann-burst signal . 16
8.9 Impulsive signal . 17
9 Acoustical environment . 17
9.1 General . 17
9.2 Free-field conditions . 17
9.3 Half-space, free-field conditions . 17
9.4 Simulated free-field conditions . 17
9.5 Half-space simulated free-field conditions . 17
9.6 Diffuse sound field conditions . 18
9.7 Target application conditions . 18
10 Positioning of the DUT . 18
10.1 Rated geometrical conditions . 18
10.1.1 General . 18
10.1.2 Reference plane and normal vector . 18
10.1.3 Reference point . 18
10.1.4 Reference axis . 19
10.1.5 Orientation vector . 19
10.1.6 Evaluation point . 19
10.1.7 Evaluation distance . 19

IEC 60268-21:2018  IEC 2018 – 3 –
10.2 Measuring distance between DUT and microphone . 20
10.2.1 Far-field conditions . 20
10.2.2 Near-field conditions . 20
10.2.3 Diffuse field conditions . 20
10.2.4 Target application condition . 21
11 Measurement equipment and test results . 21
12 Accuracy of the acoustical measurement . 21
12.1 General . 21
12.2 Measurement uncertainty . 21
13 Mounting of the DUT . 22
13.1 Mounting and acoustic loading of drive units . 22
13.2 Mounting and acoustic loading of an electro-acoustic system . 22
14 Preconditioning . 23
15 Rated ambient conditions . 23
15.1 Temperature ranges . 23
15.1.1 Performance limited temperature range . 23
15.1.2 Damage limited temperature range . 23
15.2 Humidity ranges . 23
15.2.1 Relative humidity range . 23
15.2.2 Damage limited humidity range . 23
16 Rated frequency range . 23
17 Input signal . 23
17.1 Rated maximum input value . 23
17.1.1 Condition to be specified . 23
17.1.2 Direct measurement . 24
17.1.3 Indirect measurement based on SPL . 25
max
17.2 Maximum input level . 25
18 Sound-pressure output . 26
18.1 Rated maximum sound pressure . 26
18.1.1 Conditions to be specified . 26
18.1.2 Direct measurement . 26
18.1.3 Indirect measurement based on maximum input value . 27
18.2 Rated maximum sound-pressure level . 27
18.3 Short term maximum sound pressure level . 27
18.3.1 Conditions to be specified . 27
18.3.2 Method of measurement . 28
18.4 Long term maximum sound pressure level . 28
18.4.1 Conditions to be specified . 28
18.4.2 Method of measurement . 29
18.5 Sound pressure in a stated frequency band . 29
18.5.1 Condition to be specified . 29
18.5.2 Method of measurement . 29
18.6 Sound-pressure level in a stated frequency band . 30
18.7 Mean sound-pressure in a stated frequency range . 30
18.7.1 Condition to be specified . 30
18.7.2 Method of measurement . 30
18.8 Mean sound-pressure level in a stated frequency range . 30

– 4 – IEC 60268-21:2018  IEC 2018
19 Frequency response of the fundamental component . 30
19.1 Transfer function . 30
19.1.1 Conditions to be specified . 30
19.1.2 Method of measurements . 30
19.2 SPL frequency response . 32
19.2.1 Conditions to be specified . 32
19.2.2 Method of measurement . 32
19.3 Time-varying amplitude compression of the fundamental component . 33
19.3.1 General . 33
19.3.2 Method of measurement . 33
19.4 Amplitude compression at maximum input . 33
19.4.1 Short term amplitude compression . 33
19.4.2 Method of measurement . 33
19.4.3 Long-term amplitude compression . 34
19.4.4 Method of measurement . 34
19.5 Corrections based on a free-field reference measurement . 34
19.5.1 General . 34
19.5.2 Correction of the measured sound pressure signal . 34
19.5.3 Correction of the amplitude response . 35
19.6 Effective frequency range . 36
19.6.1 Conditions to be specified . 36
19.6.2 Method of measurement . 36
19.7 Internal latency . 36
19.7.1 Conditions to be specified . 36
19.7.2 Methods of measurement . 36
20 Directional characteristics . 37
20.1 General . 37
20.2 Direct sound field in 3D space . 37
20.2.1 Directional transfer function . 37
20.2.2 Extrapolated far-field data . 37
20.2.3 Parameters of the holographic sound field expansion . 38
20.2.4 Extrapolated near-field data . 39
20.3 Directional far field characteristics . 39
20.3.1 Directional factor . 39
20.3.2 Directional gain . 41
20.3.3 Directivity factor. 41
20.3.4 Directivity index . 41
20.4 Acoustic output power . 42
20.4.1 Conditions to be specified . 42
20.4.2 Methods of measurement . 42
20.5 Sound power level . 44
20.6 Mean acoustic output power in a frequency band . 44
20.6.1 Conditions to be specified . 44
20.6.2 Method of measurement . 44
20.7 Radiation angle . 44
20.7.1 Conditions to be specified . 44
20.7.2 Method of measurement . 44

IEC 60268-21:2018  IEC 2018 – 5 –
20.8 Coverage angle or angles . 45
20.8.1 Conditions to be specified . 45
20.8.2 Method of measurement . 45
20.9 Mean sound pressure level in an acoustical zone . 45
20.9.1 General . 45
20.9.2 Method of measurement . 45
21 Harmonic distortion. 46
21.1 General . 46
th
21.2 N -order harmonic component . 46
21.2.1 Conditions to be specified . 46
21.2.2 Method of measurement . 46
21.3 Total harmonic components . 47
21.3.1 Conditions to be specified . 47
21.3.2 Method of measurement . 47
21.4 Total harmonic distortion . 47
21.4.1 Conditions to be specified . 47
21.4.2 Method of measurement . 47
21.5 Higher-order harmonic distortion . 48
21.5.1 Conditions to be specified . 48
21.5.2 Method of measurement . 48
21.6 Maximum sound pressure level limited by total harmonic distortion . 49
21.6.1 Conditions to be specified . 49
21.6.2 Method of measurement . 49
th
21.7 N -order equivalent input harmonic distortion component . 50
21.7.1 Conditions to be specified . 50
21.7.2 Method of measurement . 50
21.8 Equivalent input total harmonic distortion . 51
21.8.1 Conditions to be specified . 51
21.8.2 Method of measurement . 51
22 Two-tone distortion . 52
22.1 Variation of excitation frequencies . 52
22.2 Modulation distortion . 52
22.2.1 Conditions to be specified . 52
22.2.2 Method of measurement . 52
22.3 Amplitude modulation distortion . 53
22.3.1 Conditions to be specified . 53
22.3.2 Method of measurement . 54
23 Multi-tone distortion . 54
23.1 Conditions to be specified . 54
23.2 Method of measurement . 55
24 Impulsive distortion . 55
24.1 Impulsive distortion level . 55
24.1.1 Conditions to be specified . 55
24.1.2 Method of measurement . 56
24.2 Maximum impulsive distortion ratio . 56
24.2.1 Conditions to be specified . 56
24.2.2 Method of measurement . 56

– 6 – IEC 60268-21:2018  IEC 2018
24.3 Mean impulsive distortion level . 57
24.3.1 Conditions to be specified . 57
24.3.2 Method of measurement . 57
24.4 Crest factor of impulsive distortion . 57
24.4.1 Conditions to be specified . 57
24.4.2 Method of measurement . 57
25 Stray magnetic fields . 58
25.1 General . 58
25.2 Static component . 58
25.2.1 Characteristic to be specified . 58
25.2.2 Method of measurement . 58
25.3 Dynamic components . 59
25.3.1 Characteristics to be specified . 59
25.3.2 Method of measurement . 59
Annex A (informative) Uncertainty analysis . 60
(normative) Transducer mounting . 62
B.1 Standard baffle . 62
B.2 Standard measuring enclosures . 64
B.2.1 General . 64
B.2.2 Type A . 64
B.2.3 Type B . 64
Annex C (normative) Simulated programme signal . 66
(informative) Rating the maximum input and output values . 68
(informative) Spherical wave expansion . 70
E.1 Coefficients of spherical wave expansion . 70
E.2 Directional factor . 70
E.3 Directivity factor . 71
E.4 Acoustic output power . 71
Annex F (informative) Non-linearity . 72
F.1 Equivalent harmonic input distortion. 72
F.2 Two-tone intermodulation . 72
F.3 Signal distortion generated in audio systems . 73
Annex G (informative) Stray magnetic field . 75
Bibliography . 76

Figure 1 – Rated conditions used to describe the position of the DUT in the coordinate
system . 18
Figure 2 – Recommended position and orientation of the DUT . 19
Figure 3 – Valid region of expansion of the sound pressure p(r) at the observation point
r at the distance r > a . 39
Figure 4 – Measurement of the distortion generated by a multi-tone stimulus . 55
Figure 5 – Measurement of impulsive distortion . 56
Figure A.1 – Relationship between tolerance limits, corresponding acceptance
intervals and the maximum permitted uncertainty of measurement, U . . 60
MAX
Figure B.1 – Standard baffle, dimensions . 62
Figure B.2 – Standard baffle with chamfer . 63
Figure B.3 – Standard baffle with sub-baffle . 63

IEC 60268-21:2018  IEC 2018 – 7 –
Figure B.4 – Standard measuring enclosure type A (net volume is about 600 l) . 64
Figure B.5 – Standard measuring enclosure type B (net volume is about 450 l) . 65
Figure C.1 – Block diagram of test setup for generating the simulated noise signal
used for testing passive loudspeaker systems comprising a network filter . 66
Figure F.1 – Signal flow chart of the electro-acoustical system . 72
Figure F.2 – Variation of the frequencies of the two-tone stimulus in the
intermodulation measurement . 73
Figure F.3 – Generation of the signal distortion in audio systems . 73
Figure G.1 – Measuring apparatus for stray magnetic field . 75

Table A.1 – Example uncertainty budget – acoustical loudspeaker evaluation . 61
Table C.1 – Power spectrum of simulated programme signal in 1/3 octave bandsrated . 67

– 8 – IEC 60268-21:2018  IEC 2018
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SOUND SYSTEM EQUIPMENT –
Part 21: Acoustical (output-based) measurements

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
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consensus of opinion on the relevant subjects since each technical committee has representation from all
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60268-21 has been prepared by IEC technical committee 100:
Audio, video and multimedia systems and equipment.
The text of this standard is based on the following documents:
CDV Report on voting
100/2957/CDV 100/3019/RVC
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 60628, published under the general title Sound system equipment,
can be found on the IEC website.

IEC 60268-21:2018  IEC 2018 – 9 –
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 10 – IEC 60268-21:2018  IEC 2018
INTRODUCTION
Loudspeakers, headphones and other actuators have become more versatile and, as a result,
new measurement techniques are required to evaluate these systems. The following is a list
of examples where new measurement techniques are required:
• Limited access to the electrical terminals of the transducer
The higher integration of electrical, acoustical and mechanical elements limit the access to
the electrical terminals of the transducer.
• Analogue or digital audio input signals
Audio inputs can accept analogue or digital signals in various formats.
• Latency and other kinds of distortion associated with digital signal processing
Digital signal processing is used to correct the transfer behaviour of the passive system
and to generate a desired sound output and as a result, latency and other kinds of
distortion not found in analogue equipment can be generated.
• Excessive equalization
Excessive equalization can force the transducer to operate in the large signal domain
causing thermal and nonlinear effects.
• Active protection
Active protection attenuates the input signal to prevent a mechanical and thermal overload
of the transducer and other components.
• Other transducer principles
Although most loudspeaker systems use a moving coil in an electro-dynamical transducer,
there is a need to expand the application to electro-static, electro-magnetic or any other
transduction principles.
• Other mechanical and acoustical elements
To improve sound radiation, vented enclosures, sealed enclosures, passive radiators,
horns, wave guides, flat panels, and other mechanical and acoustical elements are
implemented.
• Impulsive distortions
Defects in manufacturing (e.g. voice coil rubbing) or operating under overload conditions
can create impulsive distortions, which have a high impact on perceived sound quality but
cannot be detected by conventional measurements (e.g. total harmonic distortion).
• Directional characteristics and complex near field properties
The comprehensive evaluation of professional equipment, including directional
characteristics, can be realized by considering the complex near-field properties as a
supplement to the existing far-field measurement techniques. In addition, devices intended
for use in the near field, such as hand-held personal audio devices (e.g. laptops, tablets,
smart phones) and other portable sound systems, need to be evaluated in a manner
appropriate to their intended use.

IEC 60268-21:2018  IEC 2018 – 11 –
SOUND SYSTEM EQUIPMENT –
Part 21: Acoustical (output-based) measurements

1 Scope
This part of IEC 60268 specifies an acoustical measurement method that applies to electro-
acoustical transducers and passive and active sound systems, such as loudspeakers, TV-sets,
multi-media devices, personal portable audio devices, automotive sound systems and
professional equipment. The device under test (DUT) can be comprised of electrical
components performing analogue and digital signal processing prior to the passive actuators
performing a transduction of the electrical input into an acoustical output signal. This
document describes only phy
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