IEC 60268-21:2018
(Main)Sound system equipment - Part 21: Acoustical (output-based) measurements
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.
Équipements pour systèmes électroacoustiques – Partie 21 : Mesures acoustiques (basées sur la 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.
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IEC 60268-21 ®
Edition 1.0 2018-11
INTERNATIONAL
STANDARD
colour
inside
Sound system equipment –
Part 21: Acoustical (output-based) measurements
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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
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
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
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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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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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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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
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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.
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.
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 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.
NOTE Some measurement methods defined in this document can be applied to headphones, headsets,
earphones and earsets in accordance with [1] . This document does not apply to microphones and other sensors.
This document does not require access to the state variables (voltage, current) at the electrical terminals of the
transducer. Sensitivity, electric input power and other characteristics based on the electrical impedance will be
described in a separate future standard document, IEC 60268-22, dedicated to electrical and mechanical
measurements.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 60263, Scales and sizes for plotting frequency characteristics and polar diagrams
IEC 60268-1, Sound system equipment – Part 1: General
IEC 60268-2:1987, Sound system equipment – Part 2: Explanation of general terms and
calculation methods
IEC 61094-4, Measurement microphones – Part 4: Specifications for working standard
microphones
IEC 61260-1, Electroacoustics – Octave-band and fractional-octave-band filters – Part 1:
Specifications
ISO 3, Preferred numbers – Series of preferred numbers
ISO 3741:2010, Acoustics – Determination of sound power levels and sound energy levels of
noise sources using sound pressure – Precision methods for reverberation test rooms
___________
Numbers in square brackets refer to the Bibliogaphy.
– 12 – IEC 60268-21:2018 IEC 2018
ISO 3744, Acoustics – Determination of sound power levels and 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 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), 02/01/2015
CTA 2010-B, Standard Method of Measurement for Powered Subwoofers, standard by
Consumer Technology Association (Formerly CEA), 11/28/2014
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.2 Abbreviated terms
DUT device under test
4 Type description
The type description shall be provided by the manufacturer, including the following
information:
• type, principles and number of the transducers used in the loudspeaker system;
• acoustical loading (e.g. enclosure, horn, bass reflex, column, line array);
• power amplification;
• DSP processing (e.g. equalizer, active protection).
5 Physical characteristics
5.1 Marking of terminals and controls
The terminals and controls shall be marked in accordance with IEC 60268-1 and IEC 60268-2.
5.2 Dimensions
The outer dimensions of the DUT shall be specified.
5.3 Mass
The total mass of the DUT when ready for use shall be specified.
...
IEC 60268-21 ®
Edition 1.0 2018-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Sound system equipment –
Part 21: Acoustical (output-based) measurements
Équipements pour systèmes électroacoustiques –
Partie 21: Mesures acoustiques (basées sur la sortie)
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About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.
About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.
IEC publications search - webstore.iec.ch/advsearchform Electropedia - www.electropedia.org
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and withdrawn publications. Also known as the International Electrotechnical Vocabulary
(IEV) online.
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IEC 60268-21 ®
Edition 1.0 2018-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Sound system equipment –
Part 21: Acoustical (output-based) measurements
Équipements pour systèmes électroacoustiques –
Partie 21: Mesures acoustiques (basées sur la sortie)
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.160.01 ISBN 978-2-8322-6657-1
– 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
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
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
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
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
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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-
governmental organizations liaising with the IEC also participate in this preparation. 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 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 IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
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.
This bilingual version (2019-03) corresponds to the monolingual English version, published in
2018-11.
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.
The French version of this standard has not been voted upon.
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.
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.
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.
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 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.
NOTE Some measurement methods defined in this document can be applied to headphones, headsets,
earphones and earsets in accordance with [1] . This document does not apply to microphones and other sensors.
This document does not require access to the state variables (voltage, current) at the electrical terminals of the
transducer. Sensitivity, electric input power and other characteristics based on the electrical impedance will be
described in a separate future standard document, IEC 60268-22, dedicated to electrical and mechanical
measurements.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendmen
...
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