1、 Collection of SANS standards in electronic format (PDF) 1. Copyright This standard is available to staff members of companies that have subscribed to the complete collection of SANS standards in accordance with a formal copyright agreement. This document may reside on a CENTRAL FILE SERVER or INTRA
2、NET SYSTEM only. Unless specific permission has been granted, this document MAY NOT be sent or given to staff members from other companies or organizations. Doing so would constitute a VIOLATION of SABS copyright rules. 2. Indemnity The South African Bureau of Standards accepts no liability for any
3、damage whatsoever than may result from the use of this material or the information contain therein, irrespective of the cause and quantum thereof. ISBN 978-0-626-22292-5 SANS 61094-2:2009Edition 1IEC 61094-2:2009Edition 2SOUTH AFRICAN NATIONAL STANDARD Electroacoustics Measurement microphones Part 2
4、: Primary method for pressure calibration of laboratory standard microphones by the reciprocity technique This national standard is the identical implementation of IEC 61094-2:2009 and is adopted with the permission of the International Electrotechnical Commission. Published by SABS Standards Divisi
5、on 1 Dr Lategan Road Groenkloof Private Bag X191 Pretoria 0001Tel: +27 12 428 7911 Fax: +27 12 344 1568 www.sabs.co.za SABS SANS 61094-2:2009 Edition 1 IEC 61094-2:2009 Edition 2 Table of changes Change No. Date Scope National foreword This South African standard was approved by National Committee S
6、ABS TC 76, Acoustics, electro-acoustics and vibration, in accordance with procedures of the SABS Standards Division, in compliance with annex 3 of the WTO/TBT agreement. This SANS document was published in July 2009. IEC 61094-2Edition 2.0 2009-02INTERNATIONAL STANDARD NORME INTERNATIONALEElectroaco
7、ustics Measurement microphones Part 2: Primary method for pressure calibration of laboratory standard microphones by the reciprocity technique Electroacoustique Microphones de mesure Partie 2: Mthode primaire pour ltalonnage en pression des microphones talons de laboratoire par la mthode de rciproci
8、t INTERNATIONAL ELECTROTECHNICAL COMMISSION COMMISSION ELECTROTECHNIQUE INTERNATIONALE XICS 17.140.50 PRICE CODECODE PRIXISBN 2-8318-1030-4 Registered trademark of the International Electrotechnical Commission Marque dpose de la Commission Electrotechnique Internationale SANS 61094-2:2009This s tand
9、ard may only be used and printed by approved subscription and freemailing clients of the SABS . 2 61094-2 IEC:2009 CONTENTS FOREWORD.4 1 Scope.6 2 Normative references .6 3 Terms and definitions .6 4 Reference environmental conditions .7 5 Principles of pressure calibration by reciprocity 7 5.1 Gene
10、ral principles .7 5.1.1 General .7 5.1.2 General principles using three microphones 7 5.1.3 General principles using two microphones and an auxiliary sound source .7 5.2 Basic expressions .8 5.3 Insert voltage technique 9 5.4 Evaluation of the acoustic transfer impedance.9 5.5 Heat-conduction correc
11、tion11 5.6 Capillary tube correction11 5.7 Final expressions for the pressure sensitivity 12 5.7.1 Method using three microphones .12 5.7.2 Method using two microphones and an auxiliary sound source 12 6 Factors influencing the pressure sensitivity of microphones13 6.1 General .13 6.2 Polarizing vol
12、tage13 6.3 Ground-shield reference configuration.13 6.4 Pressure distribution over the diaphragm 13 6.5 Dependence on environmental conditions .14 6.5.1 Static pressure 14 6.5.2 Temperature14 6.5.3 Humidity 14 6.5.4 Transformation to reference environmental conditions .15 7 Calibration uncertainty c
13、omponents15 7.1 General .15 7.2 Electrical transfer impedance 15 7.3 Acoustic transfer impedance .15 7.3.1 General .15 7.3.2 Coupler properties.15 7.3.3 Microphone parameters .16 7.4 Imperfection of theory17 7.5 Uncertainty on pressure sensitivity level18 Annex A (normative) Heat conduction and visc
14、ous losses in a closed cavity 20 Annex B (normative) Acoustic impedance of a capillary tube23 Annex C (informative) Examples of cylindrical couplers for calibration of microphones 26 Annex D (informative) Environmental influence on the sensitivity of microphones 31 Annex E (informative) Methods for
15、determining microphone parameters 34 Annex F (informative) Physical properties of humid air.37 SANS 61094-2:2009This s tandard may only be used and printed by approved subscription and freemailing clients of the SABS .61094-2 IEC:2009 3 Figure 1 Equivalent circuit for evaluating the acoustic transfe
16、r impedance Za,12.9 Figure 2 Equivalent circuit for evaluating Za,12when coupler dimensions are small compared with wavelength10 Figure 3 Equivalent circuit for evaluating Za,12 when plane wave transmission in the coupler can be assumed .10 Figure C.1 Mechanical configuration of plane-wave couplers
17、.27 Figure C.2 Mechanical configuration of large-volume couplers.29 Figure D.1 Examples of static pressure coefficient of LS1P and LS2P microphones relative to the low-frequency value as a function of relative frequency f/fo32 Figure D.2 General frequency dependence of that part of the temperature c
18、oefficient for LS1P and LS2P microphones caused by the variation in the impedance of the enclosed air 33 Table 1 Uncertainty components19 Table A.1 Values for EV.21 Table B.1 Real part of Za,Cin gigapascal-seconds per cubic metre (GPas/m3)24 Table B.2 Imaginary part of Za,Cin gigapascal-seconds per
19、cubic metre (GPas/m3)25 Table C.1 Nominal dimensions for plane-wave couplers.28 Table C.2 Nominal dimensions and tolerances for large-volume couplers 29 Table C.3 Experimentally determined wave-motion corrections for the air-filled large-volume coupler used with type LS1P microphones30 Table F.1 Cal
20、culated values of the quantities in Clauses F.1 to F.5 for two sets of environmental conditions 40 Table F.2 Coefficients used in the equations for humid air properties.41 SANS 61094-2:2009This s tandard may only be used and printed by approved subscription and freemailing clients of the SABS . 4 61
21、094-2 IEC:2009 INTERNATIONAL ELECTROTECHNICAL COMMISSION _ ELECTROACOUSTICS MEASUREMENT MICROPHONES Part 2: Primary method for pressure calibration of laboratory standard microphones by the reciprocity technique FOREWORD 1) The International Electrotechnical Commission (IEC) is a worldwide organizat
22、ion 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
23、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
24、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 agre
25、ement 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
26、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
27、 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 cor
28、responding national or regional publication shall be clearly indicated in the latter. 5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any equipment declared to be in conformity with an IEC Publication. 6) All users should ensure that they have the
29、 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,
30、 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
31、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 IE
32、C 61094-2 has been prepared by IEC technical committee 29: Electroacoustics. This second edition cancels and replaces the first edition published in 1992. This second edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previ
33、ous edition: an update of Clause 6 to fulfil the requirements of ISO/IEC Guide 98-3; an improvement of the heat conduction theory in Annex A; a revision of Annex F: Physical properties of humid air. SANS 61094-2:2009This s tandard may only be used and printed by approved subscription and freemailing
34、 clients of the SABS .61094-2 IEC:2009 5 The text of this standard is based on the following documents: FDIS Report on voting 29/671/FDIS 29/676/RVD 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 ha
35、s been drafted in accordance with the ISO/IEC Directives, Part 2. A list of all parts of the IEC 61094 series, published under the general title Electroacoustics Measurement microphones, can be found on the IEC website. The committee has decided that the contents of this publication will remain unch
36、anged 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. SANS 61094-2:2009This s tandard may only be us
37、ed and printed by approved subscription and freemailing clients of the SABS . 6 61094-2 IEC:2009 ELECTROACOUSTICS MEASUREMENT MICROPHONES Part 2: Primary method for pressure calibration of laboratory standard microphones by the reciprocity technique 1 Scope This part of International Standard IEC 61
38、094 is applicable to laboratory standard microphones meeting the requirements of IEC 61094-1 and other types of condenser microphone having the same mechanical dimensions; specifies a primary method of determining the complex pressure sensitivity so as to establish a reproducible and accurate basis
39、for the measurement of sound pressure. All quantities are expressed in SI units. 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 r
40、eferenced document (including any amendments) applies. IEC 61094-1:2000, Measurement microphones Part 1: Specifications for laboratory standard microphones ISO/IEC Guide 98-3, Uncertainty of measurement Part 3: Guide to the expression of uncertainty in measurement (GUM:1995)13 Terms and definitions
41、For the purposes of this document, the terms and definitions given in IEC 61094-1 and ISO/IEC Guide 98-3 as well as the following apply. 3.1 reciprocal microphone linear passive microphone for which the open circuit reverse and forward transfer impedances are equal in magnitude 3.2 phase angle of pr
42、essure sensitivity of a microphone for a given frequency, the phase angle between the open-circuit voltage and a uniform sound pressure acting on the diaphragm NOTE Phase angle is expressed in degrees or radians ( or rad). _ 1ISO/IEC Guide 98-3:2008 is published as a reissue of the Guide to the expr
43、ession of uncertainty in measurement (GUM), 1995. SANS 61094-2:2009This s tandard may only be used and printed by approved subscription and freemailing clients of the SABS .61094-2 IEC:2009 7 3.3 electrical transfer impedance for a system of two acoustically coupled microphones the quotient of the o
44、pen-circuit voltage of the microphone used as a receiver by the input current through the electrical terminals of the microphone used as a transmitter NOTE 1 Electrical transfer impedance is expressed in ohms (). NOTE 2 This impedance is defined for the ground-shield configuration given in 7.2 of IE
45、C 61094-1:2000. 3.4 acoustic transfer impedance for a system of two acoustically coupled microphones the quotient of the sound pressure acting on the diaphragm of the microphone used as a receiver by the short-circuit volume velocity produced by the microphone used as a transmitter NOTE Acoustic tra
46、nsfer impedance is expressed in pascal-seconds per cubic metre (Pas/m3). 3.5 coupler device which, when fitted with microphones, forms a cavity of predetermined shape and dimensions acting as an acoustic coupling element between the microphones 4 Reference environmental conditions The reference envi
47、ronmental conditions are: temperature 23,0 C static pressure 101,325 kPa relative humidity 50 % 5 Principles of pressure calibration by reciprocity 5.1 General principles 5.1.1 General A reciprocity calibration of microphones may be carried out by means of three microphones, two of which shall be re
48、ciprocal, or by means of an auxiliary sound source and two microphones, of which one shall be reciprocal. NOTE If one of the microphones is not reciprocal it can only be used as a sound receiver. 5.1.2 General principles using three microphones Let two of the microphones be connected acoustically by
49、 a coupler. Using one of them as a sound source and the other as a sound receiver, the electrical transfer impedance is measured. When the acoustic transfer impedance of the system is known, the product of the pressure sensitivities of the two coupled microphones can be determined. Using pair-wise combinations of three microphones marked (1), (2) and (3), three such mutually independent products are available, from which an expression for
