1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI British StandardsWB9423_BSI_StandardColCov_noK_AW:BSI FRONT COVERS 5/9/08 12:55 Page 1Electroacoustics Measurement microphones Part 2: Primary method for pressure calibration of laboratory standard m
2、icrophones by the reciprocitytechniqueBS EN 61094-2:2009National forewordThis British Standard is the UK implementation of EN 61094-2:2009. It isidentical to IEC 61094-2:2009. It supersedes BS EN 61094-2:1994 which iswithdrawn.The UK participation in its preparation was entrusted to Technical Commit
3、teeEPL/29, Electroacoustics.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisions of acontract. Users are responsible for its correct application. BSI 2009ISBN 978 0 580 57904 2ICS 17
4、.140.50; 33.160.50Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of the StandardsPolicy and Strategy Committee on 30 June 2009Amendments issued since publicationAmd. No. Date Text affectedBRITISH STANDARDBS EN 6
5、1094-2:2009EUROPEAN STANDARD EN 61094-2 NORME EUROPENNE EUROPISCHE NORM April 2009 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: avenue Marnix 17, B - 1000 Brussels
6、 2009 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 61094-2:2009 E ICS 17.140.50 Supersedes EN 61094-2:1993English version Electroacoustics - Measurement microphones - Part 2: Primary method for pressure calibration of laborator
7、y standard microphones by the reciprocity technique (IEC 61094-2:2009) Electroacoustique - Microphones de mesure - Partie 2: Mthode primaire pour ltalonnage en pression des microphones talons de laboratoire par la mthode de rciprocit (CEI 61094-2:2009) Elektroakustik - Messmikrofone - Teil 2: Primrv
8、erfahren zur Druckkammer-Kalibrierung von Laboratoriums-Normalmikrofonen nach der Reziprozittsmethode (IEC 61094-2:2009) This European Standard was approved by CENELEC on 2009-03-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for givi
9、ng 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 v
10、ersions (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
11、 of Austria, Belgium, Bulgaria, 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 Ki
12、ngdom. BS EN 61094-2:2009EN 61094-2:2009 - 2 - Foreword The text of document 29/671/FDIS, future edition 2 of IEC 61094-2, prepared by IEC TC 29, Electroacoustics, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 61094-2 on 2009-03-01. This European Standard supersede
13、s EN 61094-2:1993. EN 61094-2:2009 includes the following significant technical changes with respect to EN 61094-2:1993: 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 humi
14、d air. 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) 2009-12-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2012-03-01 Ann
15、ex ZA has been added by CENELEC. _ Endorsement notice The text of the International Standard IEC 61094-2:2009 was approved by CENELEC as a European Standard without any modification. _ BS EN 61094-2:2009- 3 - EN 61094-2:2009 Annex ZA (normative) Normative references to international publications wit
16、h 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
17、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 61094-1 2000 Measurement microphones - Part 1: Specifications for laboratory standard microphones EN 61094-1 2000 ISO/IEC Guide 98-3 -1)U
18、ncertainty of measurement - Part 3: Guide to the expression of uncertainty in measurement (GUM:1995) - - 1)Undated reference. BS EN 61094-2:2009 4 61094-2 IEC:2009 CONTENTS 1 Scope.6 2 Normative references .6 3 Terms and definitions .6 4 Reference environmental conditions .7 5 Principles of pressure
19、 calibration by reciprocity 7 5.1 General 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
20、impedance.9 5.5 Heat-conduction correction11 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 microphone
21、s13 6.1 General .13 6.2 Polarizing voltage13 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 cond
22、itions .15 7 Calibration uncertainty components15 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
23、A (normative) Heat conduction and viscous 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
24、 31 Annex E (informative) Methods for determining microphone parameters 34 Annex F (informative) Physical properties of humid air.37 BS EN 61094-2:200961094-2 IEC:2009 5 Figure 1 Equivalent circuit for evaluating the acoustic transfer impedance Za,12.9 Figure 2 Equivalent circuit for evaluating Za,1
25、2when 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 .27 Figure C.2 Mechanical configuration of large-volume couplers.29
26、 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 coefficient for LS1P and LS2P microphones caused by the variation in
27、 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 cubic metre (GPas/m3)25 Table C.1 Nominal dimensions for plane-wave
28、 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 Calculated values of the quantities in Clauses F.1 to F.5 for two sets
29、 of environmental conditions 40 Table F.2 Coefficients used in the equations for humid air properties.41 BS EN 61094-2:2009 6 61094-2 IEC:2009 ELECTROACOUSTICS MEASUREMENT MICROPHONES Part 2: Primary method for pressure calibration of laboratory standard microphones by the reciprocity technique 1 Sc
30、ope This part of International Standard IEC 61094 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 t
31、o establish a reproducible and accurate basis 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 u
32、ndated references, the latest edition of the referenced 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 m
33、easurement (GUM:1995)13 Terms and definitions 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 impedance
34、s are equal in magnitude 3.2 phase angle of pressure 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 p
35、ublished as a reissue of the Guide to the expression of uncertainty in measurement (GUM), 1995. BS EN 61094-2:200961094-2 IEC:2009 7 3.3 electrical transfer impedance for a system of two acoustically coupled microphones the quotient of the open-circuit voltage of the microphone used as a receiver by
36、 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 IEC 61094-1:2000. 3.4 acoustic transfer impedance for a syste
37、m 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 transfer impedance is expressed in pascal-seconds per cubic me
38、tre (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 environmental conditions are: temperature 23,0 C static pressur
39、e 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 reciprocal, or by means of an auxiliary sound source and two
40、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 a coupler. Using one of them as a sound source and the oth
41、er 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), t
42、hree such mutually independent products are available, from which an expression for the pressure sensitivity of each of the three microphones can be derived. 5.1.3 General principles using two microphones and an auxiliary sound source First, let the two microphones be connected acoustically by a cou
43、pler, and the product of the pressure sensitivities of the two microphones be determined (see 5.1.2). Next, let the two microphones be presented to the same sound pressure, set up by the auxiliary sound source. The ratio of the two output voltages will then equal the ratio of the two pressure sensit
44、ivities. BS EN 61094-2:2009 8 61094-2 IEC:2009 Thus, from the product and the ratio of the pressure sensitivities of the two microphones, an expression for the pressure sensitivity of each of the two microphones can be derived. NOTE In order to obtain the ratio of pressure sensitivities, a direct co
45、mparison method may be used, and the auxiliary sound source may be a third microphone having mechanical or acoustical characteristics which differ from those of the microphones being calibrated. 5.2 Basic expressions Laboratory standard microphones and similar microphones are considered reciprocal a
46、nd thus the two-port equations of the microphones can be written as: pqzizUqziz=+=+22211211(1) where p is the sound pressure, uniformly applied, at the acoustical terminals (diaphragm) of the microphone in pascals (Pa); U is the signal voltage at the electrical terminals of the microphone in volts (
47、V); q is the volume velocity through the acoustical terminals (diaphragm) of the microphone in cubic metres per second (m3/s); i is the current through the electrical terminals of the microphone in amperes (A); z11= Zeis the electrical impedance of the microphone when the diaphragm is blocked in ohm
48、s (); z22= Zais the acoustic impedance of the microphone when the electrical terminals are unloaded in pascal-seconds per cubic metre (Pasm3), z12= z21= MpZais equal to the reverse and forward transfer impedances in volt-seconds per cubic metre (Vsm3), Mpbeing the pressure sensitivity of the microph
49、one in volts per pascal (VPa1). NOTE Underlined symbols represent complex quantities. Equations (1) may then be rewritten as: pqZiZMUqZMiZ=+=+aapape(1a) which constitute the equations of reciprocity for the microphone. Let microphones (1) and (2) with the pressure sensitivities p,1M and p,2M be connected acoustically by a coupler. From Equations (1a) it is seen that a current i1through the electrical terminals of microphone
