BS EN 62489-2-2014 Electroacoustics Audio-frequency induction loop systems for assisted hearing Methods of calculating and measuring the low-frequency magnetic field emissions frome.pdf

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1、BSI Standards PublicationElectroacoustics Audio-frequency induction loop systems for assisted hearingPart 2: Methods of calculating and measuring the low-frequency magnetic field emissions from the loop for assessing conformity with guidlines on limits for human exposureBS EN 62489-2:2014National fo

2、rewordThis British Standard is the UK implementation of EN 62489-2:2014. It is identical to IEC 62489-2:2014. It supersedes BS EN 62489-2:2011 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee EPL/29, Electroacoustics.A list of organizations represented o

3、n this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisions ofa contract. Users are responsible for its correct application. The British Standards Institution 2014.Published by BSI Standards Limited 2014ISBN 978 0 580 82175 2I

4、CS 17.140.50Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 30 November 2014. Amendments/corrigenda issued since publicationDate Text affectedBRITISH STANDARDBS EN

5、 62489-2:2014EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN 62489-2 October 2014 ICS 17.140.50 Supersedes EN 62489-2:2011 English Version Electroacoustics - Audio-frequency induction loop systems for assisted hearing - Part 2: Methods of calculating and measuring the low-frequency magnetic field

6、emissions from the loop forassessing conformity with guidelines on limits for humanexposure (IEC 62489-2:2014) Electroacoustique - Systmes de boucles dinductionaudiofrquences pour amliorer laudition - Partie 2: Mthodes de calcul et de mesure des missions de champ magntique basse frquence partir de l

7、a boucle pourlvaluation de la conformit aux instructions sur les limitesdexposition humaine (CEI 62489-2:2014) Akustik - Audiofrequenz-Induktionsschleifenanlagen zurUntersttzung von Hrsystemen - Teil 2: Verfahren zur Berechnung und Messung der niederfrequenten Emissionen des durch die Schleife erzeu

8、gten Magnetfeldes zur Einschtzung der Konformitt mit Richtlinien zuGrenzwerten fr die Belastung des Menschen (IEC 62489-2:2014) This European Standard was approved by CENELEC on 2014-10-29. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions f

9、or 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

10、 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

11、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

12、, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. European Committee for Electrotechnical Standardization Comit Europen de Normalisation ElectrotechniqueEuropisches Komitee fr Elektrotechnische Normung CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Br

13、ussels 2014 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members. Ref. No. EN 62489-2:2014 E EN 62489-2:2014 - 2 - Foreword The text of document 29/847/FDIS, future edition 2 of IEC 62489-2, prepared by IEC/TC 29 “Electroacoustics“ was submitted to t

14、he IEC-CENELEC parallel vote and approved by CENELEC as EN 62489-2:2014. The following dates are fixed: latest date by which the document has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2015-07-29 latest date by which the national stan

15、dards conflicting with the document have to be withdrawn (dow) 2017-10-29 This document supersedes EN 62489-2:2011. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CENELEC and/or CEN shall not be held responsible for identifying a

16、ny or all such patent rights. Endorsement notice The text of the International Standard IEC 62489-2:2014 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 62233 NOT

17、E Harmonized as EN 62233. IEC 62311:2007 NOTE Harmonized as EN 62311:2008 (modified). BS EN 62489-2:2014- 3 - EN 62489-2:2014 Annex ZA (normative) Normative references to international publications with their corresponding European publications The following documents, in whole or in part, are norma

18、tively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. NOTE 1 When an International Publication has been modified by

19、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 60118-4 2006 Electroacoustics - Hearing aids - Part 4: In

20、duction 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 1989 IEC 60268-2 1987 Sound system equipment - Part 2: Explanation of general terms and calculation methods HD 483.2 S2 1993 IEC 60268-10 1991

21、 Sound system equipment - Part 10: Peak programme level meters HD 483.10 S1 1993 BS EN 62489-2:2014 2 IEC 62489-2:2014 IEC 2014 CONTENTS INTRODUCTION . 5 1 Scope 6 2 Normative references 6 3 Rated values . 6 4 Situation regarding current standards 6 5 Configurations of loops 7 5.1 Main types of conf

22、iguration . 7 5.2 General considerations . 7 5.3 Large-area loops . 7 5.4 Medium-area loops . 7 5.5 Small-area loops . 8 5.6 Solenoid antennas 8 6 Calculations . 8 6.1 General . 8 6.2 Solenoid antennas 9 7 Measurements . 9 7.1 General . 9 7.2 Input signal . 9 7.3 Measuring instrument 9 8 Comparison

23、of calculated or measured results with guidelines or limits . 10 9 Meeting limits or guidelines . 10 10 Measurement uncertainty 10 Annex A (informative) Rationale for this product-family magnetic field emission standard for audio-frequency induction-loop systems (AFILS) in the context of human expos

24、ure to non-ionizing radiation 11 Bibliography 14 Figure 1 An ear-hook induction transducer, with a BTE (behind the ear) hearing aid body for scale . 8 Figure A.1 ICNIRP magnetic field reference levels . 11 Table 1 Basic restrictions . 10 Table A.1 Application to AFILS of Table 1 of IEC 62311:2007 “C

25、haracteristics and parameters of the equipment to be considered“ 12 BS EN 62489-2:2014IEC 62489-2:2014 IEC 2014 5 INTRODUCTION A revision of IEC 62489-2 is necessary because, while the standard does not call up any particular set of exposure limits, it has numerous references to the ICNIRP Guide, wh

26、ich has profoundly changed between the 1998 and 2010 editions. This has resulted in a change in the physical quantity on which the basic restrictions are established, from tissue current density to induced electric field, resulting in changes to the reference levels and a considerable simplification

27、 of the application of the guidelines. The recommendations of the new Guide have not yet been adopted at the regulatory level in the European Union. However, since the references to the Guide in IEC 62489-2 are purely informative, it does not appear that this revision should be unacceptable in Europ

28、e. BS EN 62489-2:2014 6 IEC 62489-2:2014 IEC 2014 ELECTROACOUSTICS AUDIO-FREQUENCY INDUCTION LOOP SYSTEMS FOR ASSISTED HEARING Part 2: Methods of calculating and measuring the low-frequency magnetic field emissions from the loop for assessing conformity with guidelines on limits for human exposure 1

29、 Scope This part of IEC 62489 applies to 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. The standard is intended for assessment of human exposure to low-frequency magnetic fields produced by the

30、 system, by calculation and by in-situ testing. This standard does not deal with other aspects of safety, for which IEC 60065 applies, or with EMC. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its applicati

31、on. 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 IE

32、C 60268-1:1985, Sound system equipment Part 1: General IEC 60268-2:1987, Sound system equipment Part 2: Explanation of general terms and calculation methods IEC 60268-10:1991, Sound system equipment Part 10: Peak programme level meters 3 Rated values The term “rated“ means “the value stated by the m

33、anufacturer“. Rated values are of two kinds: rated conditions, which are fundamental values that cannot be verified by measurement, and others that can be so verified. For a full explanation, see IEC 60268-2. 4 Situation regarding current standards Current published and draft IEC standards on EMF ex

34、posure can be ambiguous in their guidance on the approach that should be taken by product committees. The differences between the signals that are of concern and those considered in depth in EMF exposure standards are the following: wide relative bandwidth, i.e. the ratio of highest to lowest freque

35、ncy present, 5 kHz and 100 Hz; no predominant frequency within the band; BS EN 62489-2:2014IEC 62489-2:2014 IEC 2014 7 rapidly varying amplitude; high ratio of peak amplitude to average r.m.s. amplitude (at least 4). 5 Configurations of loops 5.1 Main types of configuration There are four main types

36、 of configuration: a) large area loops, with the smallest dimension larger than 1 m, usually installed at floor level in a room; b) medium-area loops, with dimensions of the order of 1 m, often oriented in a vertical plane, installed at service desks and similar positions; c) small area loops, with

37、the largest dimension less than 1 m; d) solenoid antennas, including the ear-hook. NOTE Examples of small-area loops are portable systems, clipboards, neck loops, cushion loops (including those for use in vehicles) and chair loops. 5.2 General considerations All loops produce strong fields close to

38、the loop conductor(s). This is shown by the relationship between current I in a long, straight wire and the magnetic field strength H produced at a distance R from the centre of the wire, where R is greater than the radius r of the wire: H = I/2R (1) NOTE 1 Within the wire, the field strength decrea

39、ses linearly from I/2r at the surface to zero at the centre. NOTE 2 For n parallel conductors very close together (i.e. a multi-turn loop), the magnetic field strength is n times that produced by a single conductor. For calculations of field strengths in the high field strength regions, very close t

40、o the conductor(s), the long, straight wire approximation is almost always sufficiently accurate, except for solenoids, which need a completely different treatment (see 6.2). 5.3 Large-area loops The occupants of a room are likely to come close to the loop conductor only by stepping on the floor at

41、a point below which the conductor is installed. Such proximity is normally transient. However, in places of worship, devotional postures can bring parts of the body other than the feet into proximity. This can also apply in hospitals, treatment rooms and gymnasia. Maintenance staff might come into c

42、loser contact and for longer periods, but it is unlikely that the system would then be operating. 5.4 Medium-area loops For these, there are three considerations. a) The hearing-aid user is normally at a distance from the loop comparable to its dimensions. Thus the loop current required to produce a

43、 maximum r.m.s. field strength of 400 mA/m (in compliance with IEC 60118-4) at the hearing-aid is much larger than the current required to produce it at the centre of the plane of the loop. b) Nevertheless, the separation ensures that the hearing-aid user is not exposed to the high fields strengths

44、near the loop conductor. BS EN 62489-2:2014 8 IEC 62489-2:2014 IEC 2014 c) However, staff can come into close proximity of the loop conductor while the system is working unless steps are taken to maintain a minimum separation. NOTE These loops often have more than one turn, so that the loop current

45、can be kept reasonably small. 5.5 Small-area loops For these, again, there are three considerations. a) The separation for portable loops is very much greater than the loop dimensions, but for other types, the separation distance can be small or very small unless steps are taken to maintain a minimu

46、m separation. b) The current apparently required is quite large, because of the large separation. c) Both users and staff can come into close proximity of the loop, even that of a portable system. NOTE These loops usually have many turns, so that the actual current is not so large. 5.6 Solenoid ante

47、nnas One example that is commercially available is the ear-hook. This device is typically as shown in Figure 1. A very small solenoid is incorporated in the stem of the device. Figure 1 An ear-hook induction transducer, with a BTE (behind the ear) hearing aid body for scale 6 Calculations 6.1 Genera

48、l Calculation of the field strength can be reliably made using Equation (1) in almost all cases, except where the loop is very small or is a solenoid of length which is not very small compared with its plan dimensions, such as for the ear-hook device. It is necessary to calculate the current require

49、d in the loop to produce a field strength of 400 mA/m at the hearing-aid position, taking into account the orientation of the pick-up coil in the hearing-aid relative to the plane of the loop. In general, this calculation is not easy, but simple, approximate methods give sufficiently accurate results when used with insight. Proprietary calculation software, based on published mathematical analyses, exists. General-purpose mathematics software can also be used. Translating the calculated