Electroacoustics - Audio-frequency induction loop systems for assisted hearing - Part 1: Methods of measuring and specifying the performance of system components

IEC 62489-1:2010 applies to the components of audio-frequency induction-loop systems for assisted hearing. It may also be applied to such systems used for other purposes, as far as it is applicable. This standard is intended to encourage accurate and uniform presentation of manufacturers' specifications, which can be verified by standardized methods of measurement. It is intended for type testing. The components considered are the following: - amplifiers; - microphones; - other components, such as playback equipment. IEC 62489-1:2010 does not deal with safety, for which IEC 60065 applies. It also does not deal with EMC (Electromagnetic compatibility) and EMF (Electromagnetic fields, in the context of human exposure).

Akustik – Audiofrequenz-Induktionsschleifenanlagen zur Unterstützung von Hörsystemen – Teil 1: Verfahren zur Messung und Angabe des Betriebsverhaltens der Systemkomponenten

Electroacoustique - Systèmes de boucles d'induction audiofréquences pour améliorer l'audition - Partie 1: Méthodes de mesure et de spécification des performances des composants de systèmes

La CEI 62489-1:2010 s'applique aux composants des systèmes de boucles d'induction audiofréquences pour améliorer l'audition. Elle peut également être appliquée à ce type de systèmes utilisés à d'autres fins, si ladite application est possible. La présente norme est destinée à favoriser une présentation exacte et uniforme des spécifications des fabricants, qui peuvent être vérifiées par des méthodes de mesure normalisées. Elle est destinée à des essais de type. Les composants étudiés sont les suivants: - amplificateurs; - microphones; - autres composants, tels que les équipements de reproduction. La CEI 62489-1:2010 ne traite pas de la sécurité, pour laquelle la CEI 60065 s'applique. Elle ne traite pas non plus de la CEM (Compatibilité électromagnétique) ni des champs électromagnétiques (dans le contexte de l'exposition d'un sujet humain).

Elektroakustika - Sistemi z avdiofrekvenčno indukcijsko zanko za slušne pripomočke - 1. del: Metode za merjenje in specificiranje lastnosti sistemskih komponent (IEC 62489-1:2010)

Ta del serije IEC 62489 velja za komponente sistemov z avdiofrekvenčno indukcijsko zanko za slušne pripomočke. Do takšne mere, kot se lahko uporabi, lahko velja tudi za sisteme, ki se uporabljajo v druge namene. Ta standard je namenjen spodbujanju natančne in enotne predstavitve specifikacij proizvajalcev, ki se lahko preverijo s standardiziranimi merilnimi metodami.  Namenjen je preskušanju vrst. Obravnavane so naslednje komponente: - ojačevalniki; - mikrofoni; - druge komponente, na primer oprema za ponovno predvajanje. Ta standard ne obravnava varnosti, za katero velja IEC 60065. Ne obravnava niti EMC (elektromagnetne združljivosti) niti EMF (elektromagnetnih polj, v kontekstu človeške izpostavljenosti).

General Information

Status
Published
Publication Date
22-Apr-2010
Technical Committee
Drafting Committee
Parallel Committee
Current Stage
6060 - Document made available
Completion Date
23-Apr-2010

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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.VOXãQHAkustik - Audiofrequenz-Induktionsschleifenanlagen zur Unterstützung von Hörsystemen - Teil 1: Verfahren zur Messung und Angabe des Betriebsverhaltens der Systemkomponenten (IEC 62489-1:2010)Electroacoustique - Systèmes de boucles d'induction audiofréquences pour améliorer l'audition - Partie 1: Méthodes de mesure et de spécification des performances des composants de systèmes (CEI 62489-1:2010)Electroacoustics - Audio-frequency induction loop systems for assisted hearing - Part 1: Methods of measuring and specifying the performance of system components (IEC 62489-1:2010)17.140.50ElektroakustikaElectroacoustics11.180.15Aids for deaf and hearing impaired peopleICS:Ta slovenski standard je istoveten z:EN 62489-1:2010SIST EN 62489-1:2010en01-september-2010SIST EN 62489-1:2010SLOVENSKI

STANDARD
SIST EN 62489-1:2010
EUROPEAN STANDARD EN 62489-1 NORME EUROPÉENNE
EUROPÄISCHE NORM April 2010

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

Management Centre: Avenue Marnix 17, B - 1000 Brussels
© 2010 CENELEC -

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

Ref. No. EN 62489-1:2010 E
ICS 17.140.50
English version
Electroacoustics -
Audio-frequency induction loop systems for assisted hearing -

Part 1: Methods of measuring and specifying the performance of system components (IEC 62489-1:2010)

Electroacoustique -

Systèmes de boucles d'induction audiofréquences pour améliorer l'audition - Partie 1: Méthodes de mesure

et de spécification des performances
des composants de systèmes (CEI 62489-1:2010)
Akustik – Audiofrequenz-Induktionsschleifenanlagen
zur Unterstützung von Hörsystemen –
Teil 1: Verfahren zur Messung
und Angabe des Betriebsverhaltens
der Systemkomponenten (IEC 62489-1:2010)

This European Standard was approved by CENELEC on 2010-04-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom.

SIST EN 62489-1:2010

EN 62489-1:2010 - 2 - Foreword The text of document 29/667/CDV, future edition 1 of IEC 62489-1, prepared by IEC TC 29, Electroacoustics, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 62489-1 on 2010-04-01. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and CENELEC shall not be held responsible for identifying any or all such patent rights. The following dates were fixed: – latest date by which the EN has to be implemented

at national level by publication of an identical
national standard or by endorsement
(dop)
2011-01-01 – latest date by which the national standards conflicting
with the EN have to be withdrawn
(dow)

2013-04-01 Annex ZA has been added by CENELEC. __________ Endorsement notice The text of the International Standard IEC 64289-1:2010 was approved by CENELEC as a European Standard without any modification. In the official version, for Bibliography, the following note has to be added for the standards indicated: [1]

IEC 60065 NOTE
Harmonized as EN 60065. __________ SIST EN 62489-1:2010
- 3 - EN 62489-1:2010
Annex ZA
(normative)

Normative references to international publications with their corresponding European publications

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

NOTE

When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD applies.

Publication Year Title EN/HD Year
IEC 60118-4 2006 Electroacoustics - Hearing aids -

Part 4: Induction loop systems for hearing aid purposes - Magnetic field strength EN 60118-4 2006

IEC 60268-1 1985 Sound system equipment -
Part 1: General HD 483.1 S2 1)
1989
IEC 60268-2 - Sound system equipment -
Part 2: Explanation of general terms and calculation methods HD 483.2 S2 2)
IEC 60268-3 2000 Sound system equipment -
Part 3: Amplifiers EN 60268-3 + corr. January
2000 2002
IEC 60268-4 2004 Sound system equipment -
Part 4: Microphones EN 60268-4 2004

IEC 61938 - Audio, video and audiovisual systems - Interconnections and matching values - Preferred matching values of analogue signals EN 61938 -

ISO/IEC Guide 98-3 - Uncertainty of measurement -
Part 3: Guide to the expression of uncertainty in measurement (GUM:1995) - -

1) HD 483.1 S2 includes A1 to IEC 60268-1. 2) HD 483.2 S2 includes A1 to IEC 60268-2. SIST EN 62489-1:2010

SIST EN 62489-1:2010

IEC 62489-1Edition 1.0 2010-01INTERNATIONAL STANDARD NORME INTERNATIONALEElectroacoustics – Audio-frequency induction loop systems for assisted

hearing –
Part 1: Methods of measuring and specifying the performance of system components

Électroacoustique – Systèmes de boucles d’induction audiofréquences pour améliorer l'audition –

Partie 1: Méthodes de mesure et de spécification des performances des composants de systèmes

INTERNATIONAL ELECTROTECHNICAL COMMISSION COMMISSION ELECTROTECHNIQUE INTERNATIONALE SICS 17.140.50 PRICE CODECODE PRIXISBN 2-8318-1077-8

® Registered trademark of the International Electrotechnical Commission

Marque déposée de la Commission Electrotechnique Internationale ® SIST EN 62489-1:2010 colourinside

– 2 – 62489-1 © IEC:2010 CONTENTS FOREWORD...........................................................................................................................4 1 Scope...............................................................................................................................6 2 Normative references.......................................................................................................6 3 Terms and definitions.......................................................................................................7 4 Rated values....................................................................................................................7 5 Amplifiers.........................................................................................................................7 5.1 General...................................................................................................................7 5.2 Rated conditions and standard measuring conditions..............................................7 5.2.1 Rated conditions..........................................................................................7 5.2.2 Standard measurement conditions...............................................................8 5.3 Pre-conditioning......................................................................................................8 5.4 Characteristics to be specified, methods of measurement and presentation of results.....................................................................................................................8 5.4.1 Rated source impedance.............................................................................9 5.4.2 Rated source e.m.f......................................................................................9 5.4.3 Rated load...................................................................................................9 5.4.4 Rated temperature-limited output current.....................................................9 5.4.5 Rated time for delivery of rated distortion-limited output current................10 5.4.6 Rated total harmonic distortion of the output current..................................10 5.4.7 Maximum (distortion-limited) output current...............................................10 5.4.8 Compliance voltage...................................................................................10 5.4.9 Noise.........................................................................................................11 5.4.10 Magnetic field strength..............................................................................12 5.4.11 Loop dimensions.......................................................................................13 5.4.12 Frequency response..................................................................................13 5.4.13 Automatic gain control and compression....................................................13 5.4.14 Phase error of quadrature networks for phased loop arrays.......................14 5.4.15 Installation.................................................................................................14 5.4.16 Physical characteristics.............................................................................14 6 Microphones...................................................................................................................14 6.1 General.................................................................................................................14 6.2 Characteristics to be specified, methods of measurement and presentation of results...................................................................................................................14 7 Other components..........................................................................................................15 7.1 General.................................................................................................................15 7.2 Characteristics to be specified, methods of measurement and presentation of results...................................................................................................................15 8 Measurement uncertainty...............................................................................................15 Annex A (informative)

Automatic gain control and compression...........................................16 Annex B (informative)

Loop conductors and some typical impedance values........................17 Annex C (informative)

Microphones.....................................................................................20 Bibliography..........................................................................................................................21

Figure A.1 – Typical steady-state output/input characteristics...............................................16

SIST EN 62489-1:2010

62489-1 © IEC:2010 – 3 – Table B.1 – Typical loop characteristics................................................................................18 Table B.2 – Cable characteristics..........................................................................................19

SIST EN 62489-1:2010
– 4 – 62489-1 © IEC:2010 INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROACOUSTICS –
AUDIO-FREQUENCY INDUCTION LOOP
SYSTEMS FOR ASSISTED HEARING –
Part 1: Methods of measuring and specifying
the performance of system components

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-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 62489-1 has been prepared by IEC technical committee 29: Electroacoustics. The text of this standard is based on the following documents: CDV Report on voting 29/667/CDV 29/668/RVC

Full information on the voting for the approval of this standard can be found in the report on voting indicated in the above table. This publication has been drafted in accordance with the ISO/IEC Directives, Part 2. SIST EN 62489-1:2010

62489-1 © IEC:2010 – 5 – This part is to be used in conjunction with IEC 60118-4:2006, Electroacoustics – Hearing aids – Part 4: Induction loop systems for hearing aid purposes – Magnetic field strength. A list of all the parts in the IEC 62489 series, under the general title Electroacoustics – Audio-frequency induction loop systems for assisted hearing, can be found on the IEC website. The committee has decided that the contents of this publication will remain unchanged until the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in the data related to the specific publication. At this date, the publication 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.

SIST EN 62489-1:2010
– 6 – 62489-1 © IEC:2010 ELECTROACOUSTICS –
AUDIO-FREQUENCY INDUCTION LOOP
SYSTEMS FOR ASSISTED HEARING –
Part 1: Methods of measuring and specifying
the performance of system components

1 Scope This part of the IEC 62489 series applies to the components of audio-frequency induction-loop systems for assisted hearing. It may also be applied to such systems used for other purposes, as far as it is applicable. This standard is intended to encourage accurate and uniform presentation of manufacturers' specifications, which can be verified by standardized methods of measurement. It is intended for type testing. The components considered are the following: – amplifiers; – microphones; – other components, such as playback equipment. This standard does not deal with safety, for which IEC 60065 applies. It also does not deal with EMC (Electromagnetic compatibility) and EMF (Electromagnetic fields, in the context of human exposure). 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60118-4:2006, Electroacoustics – Hearing aids – Part 4: Induction loop systems for hearing aid purposes – Magnetic field strength IEC 60268-1:1985, Sound system equipment – Part 1: General IEC 60268-2, Sound system equipment – Part 2: Explanation of general terms and calculation methods IEC 60268-3:2000, Sound system equipment – Part 3: Amplifiers IEC 60268-4:2004, Sound system equipment – Part 4: Microphones IEC 61938, Audio, video and audiovisual systems – Interconnections and matching values – Preferred matching values of analogue signals ISO/IEC Guide 98-3, Uncertainty of measurement – Part 3: Guide to the expression of uncertainty in measurement (GUM:1995 )

SIST EN 62489-1:2010

62489-1 © IEC:2010 – 7 – 3 Terms and definitions For the purposes of this document, the following definition applies. 3.1

useful magnetic field volume volume within which the system provides hearing-aid users with a signal of acceptable quality (see 6.7 of IEC 60118-4:2006) 4 Rated values The term “rated” means the value stated by the manufacturer. Rated values are of two kinds; rated conditions, fundamental values that can be determined only by the manufacturer, and others that can be measured. See 5.2.1. For a full explanation, see IEC 60268-2.

5 Amplifiers 5.1 General In most systems, the amplifier(s) accepts input from microphone(s) and delivers current to the induction loop(s). If there are separate preamplifier or mixer and final amplifier components, the methods described can be used with the interpretation that input signals are applied to the preamplifier or mixer and measurements of output characteristics are made at the output of the final amplifier. The characteristics to be specified are consistent with the lists in Annex C of IEC 60118-4:2006. NOTE For characteristics not mentioned in this standard, the provisions of IEC 60268-3 can be applied, with the provisions of 5.2 of this standard replacing those of 3.1 of IEC 60268-3:2000. 5.2 Rated conditions and standard measuring conditions

5.2.1 Rated conditions The rated conditions for amplifiers are the following: • rated power supply voltage; • rated source impedance; • rated source e.m.f. (electromotive force); • rated load; • rated temperature-limited output current; • rated maximum time for delivery of rated distortion-limited output current (see below); • rated total harmonic distortion of the output current; • rated mechanical and climatic conditions. NOTE 1 Total harmonic distortion and (distortion-limited) output current are interdependent. Both cannot be taken as rated conditions simultaneously because normally a given sample amplifier produces less than rated total harmonic distortion at rated output current. NOTE 2 If the power supply frequency is critical, it is also a rated condition. NOTE 3 The rated temperature-limited output current and the rated maximum time for delivery of rated distortion-limited output current need not be included in published specifications, provided they are supplied on request. To obtain the correct conditions for measurements, the values for the above-mentioned rated conditions shall be taken from the manufacturer's specification. These values themselves are SIST EN 62489-1:2010

– 8 – 62489-1 © IEC:2010 not subject to verification, but they constitute the basis for measuring the other characteristics. Methods of measurement for these other characteristics are given in this standard and the manufacturer is required or permitted to state rated values for these characteristics in the specification of the equipment. These include • rated maximum distortion limited output current; • rated equivalent noise source e.m.f., or a measure of noise performance related to it. An amplifier, considered as a four-terminal network with regard to a specified pair of input terminals and a specified pair of output terminals, shall be understood to be working under rated conditions when the following conditions are fulfilled: a) the amplifier is connected to its rated power supply; b) the source e.m.f. is connected in series with the rated source impedance to the input terminals; c) the output terminals are terminated with the rated load; d) the terminals which are not used during the measurement are terminated, if necessary, as specified by the manufacturer; e) the source e.m.f. is a sinusoidal voltage equal to the rated source e.m.f. at 1 000 Hz according to IEC 60268-1; f) the volume control, if any, is set to such a position that the rated distortion-limited output current appears at the output terminals; g) the tone controls, if any, are set to a specified position to give as flat a frequency response as possible; h) other controls, if any, are set to their normal positions as specified by the manufacturer; i) the climatic conditions given in Clause 8 of IEC 60268-1:1985 are complied with. Amplifiers for which the rated distortion-limited output current exceeds the rated temperature-limited output current are likely to be subject to unacceptable effects when operated under rated conditions for an extended period of time. For these amplifiers, rated conditions shall be maintained for no longer than can be tolerated by the amplifier. 5.2.2 Standard measurement conditions Standard measurement conditions are obtained by bringing the amplifier under rated conditions (see 5.2.1) and then reducing the output current to a level of –10 dB referred to the rated output current. NOTE 1 Since testing for temperature rise is carried out according to IEC 60065 under conditions normally requiring an input source e.m.f. greater than that specified above, it is not expected that amplifier would overheat under standard measuring conditions. NOTE 2 Many amplifiers have an output current control that can be adjusted for the above purpose. For an amplifier without such a control, the source e.m.f. can be adjusted instead. 5.3 Pre-conditioning Immediately before any measurements are made, the amplifier shall be operated under standard measuring conditions for at least 10 min. The measurements may be made in any order. 5.4 Characteristics to be specified, methods of measurement and presentation of results NOTE 5.4.1 to 5.4.5 describe rated conditions, which can be determined only by the manufacturer. See 5.2.1. SIST EN 62489-1:2010

62489-1 © IEC:2010 – 9 – 5.4.1 Rated source impedance 5.4.1.1 Characteristic to be specified For each input, the internal impedance of the signal source, or range of acceptable impedances, stated by the manufacturer. This is a rated condition. NOTE The relevant provisions of IEC 61938 should be applied. 5.4.1.2 Presentation of results The value or range shall be stated in ohms or a suitable SI multiple, and is assumed to be a pure resistance unless otherwise stated. 5.4.2 Rated source e.m.f. 5.4.2.1 Characteristic to be specified For each input, the e.m.f. of the signal source, stated by the manufacturer, which, when connected through the rated source impedance to the input, produces rated output current into the rated load impedance, with all controls set as specified in 5.2.1. This is a rated condition. NOTE The signal levels and impedance values given in IEC 61938 should be applied. 5.4.2.2 Presentation of results The value for each input shall be stated in volts or millivolts, or as a level in decibels referred to 1 V or 0,775 V. See IEC 60268-1. 5.4.3 Rated load 5.4.3.1 Characteristic to be specified The load, stated by the manufacturer, to which the amplifier output shall be connected for measurement purposes. This is a rated condition. NOTE 1 Example of values for typical loops are given in Annex B. NOTE 2 It is essential that both the resistor and the inductor do not introduce amplitude distortion, and are able to carry the output current without overheating or changing in value. The inductor can usually be made as an air-cored component of acceptable size for use in measurements. 5.4.3.2 Presentation of results The load shall be stated as a series combination of resistance and inductance. 5.4.4 Rated temperature-limited output current 5.4.4.1 Characteristic to be specified The maximum output current, stated by the manufacturer, that can be delivered for an indefinite period to the rated load without unacceptable effects. This is a rated condition. 5.4.4.2 Presentation of results The value is expressed in amperes. SIST EN 62489-1:2010

– 10 – 62489-1 © IEC:2010 5.4.5 Rated time for delivery of rated distortion-limited output current 5.4.5.1 Characteristic to be specified The time, stated by the manufacturer, for which rated distortion-limited output current can be delivered to the rated load without unacceptable effects. 5.4.5.2 Presentation of results The value is expressed in seconds or minutes. NOTE A value of less than 30 s is likely to make some measurements difficult. 5.4.6 Rated total harmonic distortion of the output current 5.4.6.1 Characteristic to be specified The value of total harmonic distortion, stated by the manufacturer, which is not exceeded when delivering the rated maximum (distortion-limited) current to the rated load. This is a rated condition. 5.4.6.2 Presentation of results The value shall be stated as a percentage of the total output current or as a level in decibels referred to that current. 5.4.7 Maximum (distortion-limited) output current 5.4.7.1 Characteristic to be specified The maximum current, produced by a sinusoidal input signal at 1 kHz, deliverable for at least 10 s into the rated load without exceeding the rated total harmonic distortion (THD). NOTE The value of 10 s is chosen as long enough to make the measurement, while not so long as to cause damage through unacceptable effects. See 5.4.4 and 5.4.5. 5.4.7.2 Method of measurement With the amplifier initially working under standard measuring conditions, the load current is increased (by adjusting the loop current control, if fitted, or the source e.m.f. if not) until the total harmonic distortion measured, as specified in IEC 60268-3, across the resistive part of the load, is equal to the rated value. The current is then calculated from the total voltage across the resistive part of the load and the resistance value. NOTE It is usual for neither end of the load resistor to be at signal common potential, so it is necessary to make a balanced floating connection of the THD meter to the resistor. Alternatively, a current transformer or clip-on current probe may be used, provided its own harmonic distortion is negligible. 5.4.7.3 Presentation of results The result shall be stated in amperes. 5.4.8 Compliance voltage 5.4.8.1 Characteristic to be specified The average, divided by √2, of the maximum positive-going and negative-going peak voltages that the amplifier can deliver to the rated load when the signal is a specified pink-noise signal. SIST EN 62489-1:2010

62489-1 © IEC:2010 – 11 – 5.4.8.2 Method of measurement a) With the amplifier working under standard measuring conditions, the loop current is increased to achieve the maximum output current as defined in 5.4.5. The value of this current is noted.

NOTE 1 The measurement should be made as quickly as possible. See 5.4.4 and 5.4.5. b) An input signal is applied, in accordance with the following specification.

The signal shall be bandwidth limited, with a peak-to-peak voltage (as measured with an oscilloscope) to true RMS voltage ratio of 18 dB ± 2 dB (crest factor = 4), with a third-octave-band spectrum flat within ± 1 dB from 100 Hz to 5 kHz.

Bandwidth limitation shall be carried out by means of at least third-order Butterworth high pass and low pass filters giving −3 dB responses at 75 Hz and 6,5 kHz.

NOTE 2 This specification is given to ensure that the test signal stimulates the system in a manner similar to normal speech.

NOTE 3 The tolerance of ±1 dB is necessary because the theoretical responses of the specified 3rd order Butterworth filters are −0,8 dB at 100 Hz and −0,7 dB at 5 kHz, and component tolerances affect the exact values.

The input signal level is adjusted so that automatic gain control (AGC), if fitted, is fully in operation, or until the RMS output current is 6 dB below the maximum output current, measured in step a) above

...

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