1、BRITISH STANDARD BS EN 61094-6:2005 Measurement microphones Part 6: Electrostatic actuators for determination of frequency response The European Standard EN 61094-6:2005 has the status of a British Standard ICS 17.140.50 BS EN 61094-6:2005 This British Standard was published under the authority of t
2、he Standards Policy and Strategy Committee on 24 February 2005 BSI 24 February 2005 ISBN 0 580 45431 2 National foreword This British Standard is the official English language version of EN 61094-6:2005. It is identical with IEC 61094-6:2004. The UK participation in its preparation was entrusted to
3、Technical Committee EPL/29, Electro-acoustics, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications referred to in this documen
4、t may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Us
5、ers are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible European committee any enquiries on the interpretation, or proposals for change, and keep th
6、e UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the EN title page, pages 2 to 27 and a back cover. The BSI copyright notice displayed in this document indica
7、tes when the document was last issued. Amendments issued since publication Amd. No. Date CommentsEUROPEAN STANDARD EN 61094-6 NORME EUROPENNE EUROPISCHE NORM January 2005 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komit
8、ee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B - 1050 Brussels 2005 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 61094-6:2005 E ICS 17.140.50 English version Measurement microphones Part 6: Electrost
9、atic actuators for determination of frequency response (IEC 61094-6:2004) Microphones de mesure Partie 6: Grilles dentranement pour la dtermination de la rponse en frquence (CEI 61094-6:2004) Messmikrofone Teil 6: Elektrostatische Anregeelektroden zur Ermittlung des Frequenzgangs (IEC 61094-6:2004)
10、This European Standard was approved by CENELEC on 2004-12-01. 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
11、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 CENE
12、LEC 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, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Irela
13、nd, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EN 69014-:60025 - - 2 Foreword The text of document 29/562/FDIS, future edition 1 of IEC 61094-6, prepared by IEC TC 29, Electroacoustics, was su
14、bmitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 61094-6 on 2004-12-01. 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) 2005-09-01 latest date by whi
15、ch the national standards conflicting with the EN have to be withdrawn (dow) 2007-12-01 Annex ZA has been added by CENELEC. _ Endorsement notice The text of the International Standard IEC 61094-6:2004 was approved by CENELEC as a European Standard without any modification. Page2 EN610946:2005 CONTEN
16、TS 1 Scope.5 2 Normative references .5 3 Terms and definitions .6 4 Reference environmental conditions.6 5 Principle of electrostatic actuator operation 6 5.1 General .6 5.2 Electrostatic pressure7 5.3 Electrostatic actuator response .10 6 Actuator design 11 6.1 General .11 6.2 Design.11 7 Validatio
17、n .12 7.1 General .12 7.2 Repeatability of measurements .12 7.3 Uniformity of actuators of a given model12 7.4 Uniformity of the difference between actuator and pressure response levels .12 8 Measurement of electrostatic actuator response.13 8.1 System for measurement of electrostatic actuator respo
18、nse 13 8.2 Uncertainty components14 9 Applications of an electrostatic actuator .16 9.1 General .16 9.2 Verification of the frequency response of a measurement system16 9.3 Determination of the environmental characteristics of microphone measurement systems.16 9.4 Determination of free-field and pre
19、ssure frequency responses.17 9.5 Measurement of actuator response at very high frequencies .17 Annex A (informative) Examples of electrostatic actuator designs18 Annex B (informative) Set-up for measuring electrostatic actuator response 21 Annex C (informative) Typical uncertainty analysis 22 Annex
20、D (informative) Difference between free-field-, pressure- and actuator responses for typical models of measurement microphones.25 Annex ZA (normative) Normative references to international publications with their corresponding European publications .27 Figure 1 Principle of microphone and electrosta
21、tic actuator .8 Figure 2 Lumped parameter model of a measurement microphone excited by an electrostatic actuator 10 Figure A.1 Example of electrostatic actuator for type WS1 microphones 18 Figure A.2 Example of an electrostatic actuator for type WS2 microphones .19 Figure A.3 Examples of electrostat
22、ic actuators forming integral parts of the microphone protection grids20 Page3 EN610946:2005 Figure A.4 Example of an electrostatic actuator combined with weather-resistant protection .20 Figure B.1 Typical set-up for measuring the electrostatic actuator response of a microphone.21 Figure D.1 Exampl
23、es of differences between relative pressure and actuator frequency responses for four different type of measurement microphone: WS1P (a), WS1F (b) of nominal sensitivities 26 dB re 1V/Pa and WS2P (c) and WS2F (d) of nominal sensitivities 38 dB re 1V/Pa .25 Figure D.2 Examples of differences between
24、relative free-field and actuator frequency responses for type WS1, WS2 and WS3 microphones when used without protection grids.25 Figure D.3 Example of model dependent difference between relative free field and actuator frequency responses for a type WS2 microphone when used with its protection grid.
25、26 Figure D.4 Example on the determination of a relative free-field frequency response b) by adding the model dependent free-field to actuator difference as shown in Figure D.3 to the electrostatic actuator response of a microphone a) .26 Table C.1 Uncertainties .24 Page4 EN610946:2005 MEASUREMENT M
26、ICROPHONES Part 6: Electrostatic actuators for determination of frequency response 1 Scope This part of IEC 61094 gives guidelines for the design of actuators for microphones equipped with electrically conductive diaphragms; gives methods for the validation of electrostatic actuators; gives a method
27、 for determining the electrostatic actuator response of a microphone. The applications of electrostatic actuators are not fully described within this standard but may include a technique for detecting changes in the frequency response of a microphone, a technique for determining the environmental in
28、fluence on the response of a microphone, a technique for determining the free-field or pressure response of a microphone without specific acoustical test facilities, by the application of predetermined correction values specific to the microphone model and actuator used, a technique applicable at hi
29、gh frequencies not typically covered by calibration methods using sound excitation. 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 th
30、e referenced document (including any amendments) applies. IEC 61094-1, Measurement microphones Part 1: Specifications for laboratory standard microphones IEC 61094-2, Measurement microphones Part 2: Primary method for pressure calibration of laboratory standard microphones by the reciprocity techniq
31、ue IEC 61094-3, Measurement microphones Part 3: Primary method for free-field calibration of laboratory standard microphones by the reciprocity technique IEC 61094-5, Measurement microphones Part 5: Methods for pressure calibration of working standard microphones by comparison ISO/IEC GUIDE EXPRESS:
32、 1995, Guide to the expression of uncertainty in measurement (GUM) Page5 EN610946:2005 3 Terms and definitions For the purposes of this document, the terms and definitions given in IEC 61094-1 as well as the following apply. 3.1 electrostatic actuator device for determination of microphone frequency
33、 response comprising an electrically conductive stiff plate placed near the microphone diaphragm such that a time-varying voltage, applied between the plate and the diaphragm, produces an electrostatic force that simulates a sound pressure uniformly distributed over the surface of the diaphragm 3.2
34、electrostatic actuator response of a microphone microphone output as a function of frequency measured using a specified design of electro- static actuator driven by a voltage that is of uniform amplitude with frequency, relative to the output at a specified frequency NOTE Electrostatic actuator resp
35、onse is expressed in decibels (dB). 3.3 acoustic radiation impedance acoustic impedance loading the microphone diaphragm on its outer surface NOTE 1 Acoustic radiation impedance is expressed in pascal-second per cubic meter (Pa s m 3 ).NOTE 2 The radiation impedance depends on the presence and desig
36、n of the actuator. 4 Reference environmental conditions The reference environmental conditions are: temperature 23,0 C static pressure 101,325 kPa relative humidity 50 % 5 Principle of electrostatic actuator operation 5.1 General In practice, measurements of sound are made in many different environm
37、ents where different types of sound fields exist. The sensitivity and frequency response of measurement microphones depend on the type of sound field, so ideally the microphone should be calibrated using a similar type of field to that which exists on the measurement site. The various types of sound
38、 fields are generally approximated by three idealized fields: free field, diffuse-field and pressure-field. However, the establishment of such idealized sound fields, which are suitable for calibration of measurement microphones over the frequency ranges of interest is technically difficult and requ
39、ires costly acoustical laboratory facilities. Therefore, the electrostatic actuator method is used for determining a relative frequency response of measurement microphones. This method, which accounts for the type of sound field by using specific predetermined corrections, requires no such facilitie
40、s. Page6 EN610946:2005 At higher frequencies, the free-field sensitivity of a microphone is determined by the behaviour of its diaphragm and the sound diffraction and reflection caused by the microphone. The effect of the diaphragm behaviour, which may cause significant differences in the relative f
41、requency responses between individual microphones of the same model, requires specific determination. This frequency response determination is performed using the electrostatic actuator method. The effect of the diffraction and reflection depends on the type of sound field and on the shape and dimen
42、sions of the microphone. As these parameters are essentially the same for all microphones of the same model, the influence of diffraction and reflection does not differ significantly between individual microphones of the same model. Therefore, corrections for specific types of sound field may be det
43、ermined once for a model of microphone and subsequently applied to the electrostatic actuator response of any microphones of that model. Free-field and pressure-field corrections are calculated by determining the respective frequency responses of one or more microphones of the same model by using ac
44、oustical calibration methods, for example, those in IEC 61094-2 and IEC 61094-3, and by subtracting the respective electrostatic actuator responses. In principle, the electrostatic actuator calibration method may be used from very low to very high frequencies. However, the actuator excites the micro
45、phone diaphragm only and not the static pressure equalisation vent, which is generally exposed to sound when measurements are made in a free-field. The actuator excitation corresponds to that of a pressure-field and thus cannot be used for determination of the lower limiting frequency under free-fie
46、ld conditions. Free-field response determinations by electrostatic actuator should only be made at frequencies which are at least 10 times greater than the lower limiting frequency derived from the time constant of the venting system of the microphone. At low frequencies, a small perforation in the
47、microphone diaphragm will exhibit different effects in the actuator response and in the acoustic responses in a pressure field or a free field. At high frequencies, the degree to which the actuator excitation approximates that of a pressure field depends on the relation between the acoustic impedanc
48、e of the microphone diaphragm and the acoustic radiation impedance of the microphone diaphragm with the actuator in place. This relation is described in 5.3, while 9.3 describes some practical consequences for the determination of the environmental characteristics of a microphone. 5.2 Electrostatic
49、pressure The rigid and electrically conductive plate of the actuator is placed close to and parallel to the microphone diaphragm, see Figure 1. It forms an electrical capacitor together with the microphone diaphragm, which shall also be electrically conductive. When a voltage is applied between the capacitor plates, the actuator produces a force F distributed over the diaphragm surface; see Equation (1) below. The corre
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