SIST EN 61094-5:2007
(Main)Measurement microphones -- Part 5: Methods for pressure calibration of working standard microphones by comparison
Measurement microphones -- Part 5: Methods for pressure calibration of working standard microphones by comparison
Applies to working standard microphones with removable protection grids meeting the requirements of IEC 61094-4 and to laboratory standard microphones meeting the requirements of IEC 61094-1. Describes methods of determining the pressure sensitivity by comparison with either a laboratory standard microphone that has been calibrated according to IEC 61094-2, or another working standard microphone that has been calibrated according to this part of IEC 61094.
Messmikrofone -- Teil 5: Verfahren zur Druckkammer-Kalibrierung von Gebrauchs-Normalmikrofonen nach der Vergleichsmethode
Microphones de mesure -- Partie 5: Méthodes pour l'étalonnage en pression par comparaison des microphones étalons de travail
S'applique aux microphones étalons de travail munis d'une grille de protection amovible satisfaisant aux prescriptions de la EN 61094-4 et aux microphones étalons de laboratoire satisfaisant aux prescriptions de la EN 61094-1. Décrit également des méthodes pour déterminer l'efficacité en pression par comparaison, soit à un microphone étalon de laboratoire qui a été étalonné selon la EN 61094-2, soit à un autre microphone étalon de travail qui a été étalonné selon la présente partie de la EN 61094.
Merilni mikrofoni - 5. del: Metode za primerjalno kalibriranje tlaka delujočega standardnega mikrofona (IEC 61094-5:2001)
General Information
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EUROPEAN STANDARD EN 61094-5
NORME EUROPÉENNE
EUROPÄISCHE NORM December 2001
ICS 17.140.50
English version
Measurement microphones
Part 5: Methods for pressure calibration of
working standard microphones by comparison
(IEC 61094-5:2001)
Microphones de mesure Messmikrofone
Partie 5: Méthodes pour l'étalonnage Teil 5: Verfahren zur Druckkammer-
en pression par comparaison des Kalibrierung von Gebrauchs-
microphones étalons de travail Normalmikrofonen nach der
(CEI 61094-5:2001) Vergleichsmethode
(IEC 61094-5:2001)
This European Standard was approved by CENELEC on 2001-12-04. 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, Czech Republic,
Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands,
Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2001 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 61094-5:2001 E
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EN 61094-5:2001 - 2 -
Foreword
The text of document 29/495/FDIS, future edition 1 of IEC 61094-5, prepared by IEC TC 29,
Electroacoustics, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC
as EN 61094-5 on 2001-12-04.
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) 2002-09-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2004-12-01
Annexes designated "normative" are part of the body of the standard.
Annexes designated "informative" are given for information only.
In this standard, annex ZA is normative and annexes A, B, C and D are informative.
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 61094-5:2001 was approved by CENELEC as a European
Standard without any modification.
__________
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- 3 - EN 61094-5:2001
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of any
of these publications apply to this European Standard only when incorporated in it by amendment or
revision. For undated references the latest edition of the publication referred to applies (including
amendments).
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
1) 2)
IEC 61094-1 Measurement microphones EN 61094-1 2000
Part 1: Specifications for laboratory
standard microphones
IEC 61094-2 1992 Part 2: Primary method for pressure EN 61094-2 1993
calibration of laboratory standard
microphones by the reciprocity
technique
1) 2)
IEC 61094-4 Part 4: Specifications for working EN 61094-4 1995
standard microphones
ISO/IEC GUIDE 1995 Guide to the expression of uncertainty--
EXPRES in measurement (GUM)
1)
undated reference.
2)
valid edition at date of issue.
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NORME CEI
INTERNATIONALE IEC
61094-5
INTERNATIONAL
Première édition
STANDARD
First edition
2001-10
Microphones de mesure –
Partie 5:
Méthodes pour l'étalonnage en pression
par comparaison des microphones étalons
de travail
Measurement microphones –
Part 5:
Methods for pressure calibration of working
standard microphones by comparison
IEC 2001 Droits de reproduction réservés Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in
utilisée sous quelque forme que ce soit et par aucun procédé, any form or by any means, electronic or mechanical,
électronique ou mécanique, y compris la photocopie et les including photocopying and microfilm, without permission in
microfilms, sans l'accord écrit de l'éditeur. writing from the publisher.
International Electrotechnical Commission 3, rue de Varembé Geneva, Switzerland
Telefax: +41 22 919 0300 e-mail: inmail@iec.ch IEC web site http://www.iec.ch
CODE PRIX
Commission Electrotechnique Internationale
Q
PRICE CODE
International Electrotechnical Commission
Pour prix, voir catalogue en vigueur
For price, see current catalogue
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61094-5 IEC:2001 – 3 –
CONTENTS
FOREWORD.5
1 Scope.7
2 Normative references.7
3 Terms and definitions .7
4 Reference environmental conditions.9
5 Principles of pressure calibration by comparison .9
5.1 Principles .9
5.2 Measuring the output voltages of the microphones .11
6 Factors influencing the pressure sensitivity .11
6.1 General .11
6.2 Microphone pressure equalizing leakage.11
6.3 Polarising voltage .13
6.4 Ground shield reference configuration.13
6.5 Pressure distribution over the diaphragms.13
6.6 Dependence on environmental conditions .15
6.7 Validation .15
7 Calibration uncertainty components.15
7.1 General .15
7.2 Sensitivity of the reference microphone.15
7.3 Measurements of microphone output .15
7.4 Differences between the sound pressure at the test microphone and that at
the reference microphone .17
7.5 Uncertainty on pressure sensitivity level.17
Annex A (informative) Examples of couplers and jigs for simultaneous excitation.19
Annex B (informative) Examples of couplers for sequential excitation .25
Annex C (informative) Determining the open-circuit sensitivity of a measurement
microphone without using the insert-voltage method .29
Annex D (informative) Typical uncertainty analysis .31
Bibliography .35
Figure A.1 – A coupler for use with WS2 microphones.19
Figure A.2 – A jig fitted with an LS2 and WS2 microphone.21
Figure A.3 – Example arrangement of LS2 and WS2 microphones in a jig.21
Figure A.4 – Example arrangement of LS2 and WS3 microphones in a jig.21
Figure B.1 – A coupler for use with LS1 microphones .25
Figure B.2 – A coupler for use with WS2 microphones.27
Table A.1 – Calculated corrections to be added to the sensitivity level of the WS3
microphone when using the arrangement in figure A.4 .23
Table D.1 – Uncertainties .33
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61094-5 IEC:2001 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MEASUREMENT MICROPHONES –
Part 5: Methods for pressure calibration of working standard
microphones by comparison
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the 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, the IEC publishes International Standards. 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. The 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 the 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 National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61094-5 has been prepared by IEC technical committee 29:
Electroacoustics.
The text of this standard is based on the following documents:
FDIS Report on voting
29/495/FDIS 29/497/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 has been drafted in accordance with the ISO/IEC Directives, Part 3.
Annexes A, B, C and D are for information only.
The committee has decided that the contents of this publication will remain unchanged until
2006. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
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61094-5 IEC:2001 – 7 –
MEASUREMENT MICROPHONES –
Part 5: Methods for pressure calibration of working standard
microphones by comparison
1 Scope
This part of IEC 61094 is applicable to working standard microphones with removable
protection grids meeting the requirements of IEC 61094-4 and to laboratory standard micro-
phones meeting the requirements of IEC 61094-1.
This part of IEC 61094 also describes methods of determining the pressure sensitivity by
comparison with either a laboratory standard microphone that has been calibrated according to
IEC 61094-2, or another working standard microphone that has been calibrated according
to this part of IEC 61094.
Alternative comparison methods based on the principles described in IEC 61094-2 are possible
but beyond the scope of this part of IEC 61094.
2 Normative references
The following normative documents contain provisions which, through reference in this text,
constitute provisions of this part of IEC 61094. For dated references, subsequent amendments
to, or revisions of, any of these publications do not apply. However, parties to agreements
based on this part of IEC 61094 are encouraged to investigate the possibility of applying the
most recent editions of the normative documents indicated below. For undated references, the
latest edition of the normative document referred to applies. Members of IEC and ISO maintain
registers of currently valid International Standards.
IEC 61094-1, Measurement microphones – Part 1: Specifications for laboratory standard
microphones
IEC 61094-2:1992, Measurement microphones – Part 2: Primary method for pressure
calibration of laboratory standard microphones by the reciprocity technique
IEC 61094-4, Measurement microphones – Part 4: Specifications for working standard
microphones
ISO/IEC GUIDE EXPRES:1995, Guide to the expression of uncertainty in measurement (GUM)
3 Terms and definitions
For the purpose of this part of IEC 61094, the following definitions apply in addition to the
definitions given in IEC 61094-1.
3.1
reference microphone
laboratory standard microphone or working standard microphone of previously determined
pressure sensitivity
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61094-5 IEC:2001 – 9 –
3.2
test microphone
laboratory standard microphone or working standard microphone to be calibrated by
comparison with a reference microphone
3.3
monitor microphone
microphone used to measure changes in sound pressure in a coupler
3.4
coupler
device which, when fitted with microphones, forms a gas-filled cavity of predetermined shape
and dimensions and provides an acoustic coupling element between the microphones and
between the microphones and the sound source
3.5
jig
a device which, when fitted with microphones, holds them with their diaphragms face to face
separated by a small distance but does not enclose the space between them
4 Reference environmental conditions
The reference environmental conditions are:
• temperature 23,0 °C
• static pressure 101,325 kPa
• relative humidity 50 %
5 Principles of pressure calibration by comparison
5.1 Principles
5.1.1 General principle
The pressure sensitivity of a measurement microphone is defined in terms of a sound pressure
applied uniformly over the diaphragm. Consequently, the pressure sensitivity can only be
realised in principle for microphones from which the protection grid can be removed and the
diaphragm be exposed to the sound waves.
The principle of these comparison methods is that when the reference microphone and the test
microphone are exposed to the same sound pressure either simultaneously or sequentially,
the ratio of their pressure sensitivities is given by the ratio of their open-circuit output voltages.
The sensitivity (both modulus and phase) of the test microphone can then be calculated from
the sensitivity of the reference microphone.
The principle of the method allows the test microphone to be attached to a particular
preamplifier and the sensitivity may be referred to the output of that preamplifier.
Multi-frequency measurements can be performed particularly rapidly if a wideband sound
source is used and the output voltages of the microphones are analysed in narrow bands.
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61094-5 IEC:2001 – 11 –
5.1.2 General principles using simultaneous excitation
In order for the two microphones to be simultaneously exposed to essentially the same sound
pressure it is usually necessary for the two diaphragms to be separated by less than a tenth of
the wavelength at the highest frequency of interest. For frequencies up to 20 kHz, this can be
achieved by mounting the two microphones face to face separated by less than 1 mm in either
a coupler or a jig. Couplers usually contain an integral sound source; jig mounted microphones
are usually exposed to an externally produced sound field. In order to reduce the effect of
systematic differences in sound pressure between the two microphone positions, for example
caused by some asymmetries, the following procedure shall be used: after the ratio of the
microphone pressure sensitivities is first determined, the microphones shall be interchanged,
and the measurement repeated. The sensitivity is then calculated from the mean of the two
ratios. Examples of practical arrangements and precautions to be taken are given in annex A.
5.1.3 General principles using sequential excitation
In order for the two microphones to be sequentially exposed to essentially the same sound
pressure, either the exchange of microphones shall not change the sound pressure
significantly or any significant change shall be detected and corrected. This can be achieved by
incorporating a sound source, a monitor microphone, and the test/reference microphone in a
coupler. In any design of coupler, the monitor microphone shall accurately sense changes in
the sound pressure at the test/reference microphone position. Examples of practical
arrangements are given in annex B.
5.2 Measuring the output voltages of the microphones
The output of a test or reference microphone may be determined as the open-circuit voltage by
use of the insert voltage technique (see 5.3 of IEC 61094-2) or by using a measuring system
consisting of a high impedance microphone preamplifier and a voltmeter (see annex C).
The method used to measure the output of the test microphone shall be stated on any
calibration certificate.
6 Factors influencing the pressure sensitivity
6.1 General
The pressure sensitivity of a measurement microphone may depend on environmental
conditions. Further, the definition of the pressure sensitivity implies that certain requirements
be fulfilled by the measurements. It is essential during a calibration that these conditions are
controlled sufficiently well so that the resulting uncertainty components are small.
6.2 Microphone pressure equalizing leakage
The cavity behind the diaphragm is normally fitted with a narrow pressure-equalizing tube to
permit the static pressure to be the same on both sides of the diaphragm. Consequently, at
very low frequencies, this tube also partially equalizes the sound pressure. If, during the
calibration, the sound which is coherent with that on the diaphragm is incident on the pressure-
equalizing tube, then this could change the apparent sensitivity at low frequencies and the
result would not be the true pressure sensitivity.
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61094-5 IEC:2001 – 13 –
In a jig, where sound is incident on the pressure equalizing tube, it is necessary to determine
the size of this change by comparing calibrations made in the jig with calibrations made in a
coupler that does not expose the pressure equalizing tube to the sound field.
In a coupler an "O" ring can be used to seal the gap between the coupler and the microphone.
If this is done, care should be taken to ensure that the "O" ring does not exert undue force on
the microphone and cause a change in sensitivity.
6.3 Polarising voltage
If the test microphone requires an external polarising voltage, then th
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