EN 61094-2:2009

SLOVENSKI STANDARD
01-junij-2009
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Electroacoutstics - Measurement microphones - Part 2: Primary method for the pressure
calibration of laboratory standard microphones by the reciprocity technique (IEC 61094-
2:2009)
Elektroakustik - Messmikrofone - Teil 2: Primärverfahren zur Druckkammer-Kalibrierung
von Laboratoriums-Normalmikrofonen nach der Reziprozitätsmethode (IEC 61094-
2:2009)
Electroacoustique - Microphones de mesure - Partie 2: Méthode primaire pour
l’étalonnage en pression des microphones etalons de laboratoire par la méthode de
réciprocité (CEI 61094-2:2009)
Ta slovenski standard je istoveten z: EN 61094-2:2009
ICS:
17.140.50 Elektroakustika Electroacoustics
33.160.50 Pribor Accessories
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 61094-2
NORME EUROPÉENNE
April 2009
EUROPÄISCHE NORM
ICS 17.140.50 Supersedes EN 61094-2:1993

English version
Electroacoustics -
Measurement microphones -
Part 2: Primary method for pressure calibration
of laboratory standard microphones
by the reciprocity technique
(IEC 61094-2:2009)
Electroacoustique -  Elektroakustik -
Microphones de mesure - Messmikrofone -
Partie 2: Méthode primaire Teil 2: Primärverfahren
pour l’étalonnage en pression zur Druckkammer-Kalibrierung
des microphones étalons de laboratoire von Laboratoriums-Normalmikrofonen
par la méthode de réciprocité nach der Reziprozitätsmethode
(CEI 61094-2:2009) (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 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, 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 Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: avenue Marnix 17, B - 1000 Brussels

© 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
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 supersedes 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 humid air.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
(dop) 2009-12-01
national standard or by endorsement
– latest date by which the national standards conflicting
(dow) 2012-03-01
with the EN have to be withdrawn
Annex 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.
__________
- 3 - EN 61094-2:2009
Annex ZA
(normative)
Normative references to international publications
with 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  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 - EN 61094-1 2000
Part 1: Specifications for laboratory standard
microphones
1)
ISO/IEC Guide 98-3 - Uncertainty of measurement - - -
Part 3: Guide to the expression of uncertainty
in measurement (GUM:1995)
1)
Undated reference.
IEC 61094-2 ®
Edition 2.0 2009-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electroacoustics – Measurement microphones –
Part 2: Primary method for pressure calibration of laboratory standard
microphones by the reciprocity technique

Electroacoustique – Microphones de mesure –
Partie 2: Méthode primaire pour l’étalonnage en pression des microphones
étalons de laboratoire par la méthode de réciprocité

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
X
CODE PRIX
ICS 17.140.50 ISBN 2-8318-1030-4
– 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 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 impedance.9
5.5 Heat-conduction correction.11
5.6 Capillary tube correction.11
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 microphones.13
6.1 General .13
6.2 Polarizing voltage.13
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 Temperature.14
6.5.3 Humidity .14
6.5.4 Transformation to reference environmental conditions .15
7 Calibration uncertainty components .15
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 theory.17
7.5 Uncertainty on pressure sensitivity level.18
Annex A (normative) Heat conduction and viscous losses in a closed cavity .20
Annex B (normative) Acoustic impedance of a capillary tube.23
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 determining microphone parameters .34
Annex F (informative) Physical properties of humid air.37

61094-2 © IEC:2009 – 3 –
Figure 1 – Equivalent circuit for evaluating the acoustic transfer impedance Z .9
a,12
Figure 2 – Equivalent circuit for evaluating Z’ when coupler dimensions are small
a,12
compared with wavelength.10
Figure 3 – Equivalent circuit for evaluating Z’ when plane wave transmission in the
a,12
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
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/f .32
o
Figure D.2 – General frequency dependence of that part of the temperature coefficient
for LS1P and LS2P microphones caused by the variation in the impedance of the
enclosed air .33

Table 1 – Uncertainty components .19
Table A.1 – Values for E .21
V
Table B.1 – Real part of Z in gigapascal-seconds per cubic metre (GPa⋅s/m ).24
a,C
Table B.2 – Imaginary part of Z in gigapascal-seconds per cubic metre (GPa⋅s/m ).25
a,C
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 microphones.
Table F.1 – Calculated 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

– 4 – 61094-2 © 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 organization 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 publishes International Standar
...