IEC 61094-8:2012

Measurement microphones - Part 8: Methods for determining the free-field sensitivity of working standard microphones by comparison

IEC 61094-8:2012 applicable to working standard microphones meeting the requirements of IEC 61094-4. It describes methods of determining the free-field sensitivity by comparison with a laboratory standard microphone or working standard microphone (where applicable) that has been calibrated according to either; IEC 61094-3; IEC 61094-2; IEC 61094-5; IEC 61094-6; or this part of IEC 61094. Methods performed in an acoustical environment that is a good approximation to an ideal free-field (e.g. a high quality free-field chamber), and methods that use post processing of results to minimise the effect of imperfections in the acoustical environment, to simulate free-field conditions, are both covered by this part of IEC 61094. Comparison methods based on the principles described in IEC 61094-3 are also possible but beyond the scope of this part of IEC 61094.

Microphones de mesure - Partie 8: Méthodes pour la détermination de l'efficacité en champ libre par comparaison des microphones étalons de travail

La CEI 61094-8:2012 est applicable aux microphones étalons de travail satisfaisant aux exigences de la CEI 61094-4. Elle décrit des méthodes pour la détermination de l'efficacité en champ libre par comparaison utilisant un microphone étalon de laboratoire ou un microphone étalon de travail (s'il y a lieu) qui a été étalonné d'après les indications d'un des documents suivants: CEI 61094-3; CEI 61094-2; CEI 61094-5; CEI 61094-6; ou a présente partie de la CEI 61094. Les méthodes employées dans un environnement acoustique constituant une bonne approximation d'un champ libre idéal (par exemple une chambre en champ libre de haute qualité) et les méthodes utilisant un post-traitement des résultats pour réduire au maximum l'effet des imperfections de l'environnement acoustique, afin de simuler les conditions d'un champ libre, sont toutes abordées dans la présente partie de la CEI 61094. Des méthodes de comparaison reposant sur les principes décrits dans la 61094-3 peuvent également être utilisées, mais elles sortent du domaine d'application de la présente partie de la CEI 61094.

General Information

• Status: Published
• Publication Date: 18-Sep-2012
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 17.140.50 - Electroacoustics
• Technical Committee: TC 29 - Electroacoustics
• Drafting Committee: WG 5 - TC 29/WG 5
• Current Stage: PPUB - Publication issued
• Start Date: 15-Dec-2012
• Completion Date: 19-Sep-2012

Standards Content (Sample)

IEC 61094-8 ®
Edition 1.0 2012-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Measurement microphones –
Part 8: Methods for determining the free-field sensitivity of working standard
microphones by comparison
Microphones de mesure –
Partie 8: Méthodes pour la détermination de l'efficacité en champ libre par
comparaison des microphones étalons de travail

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester.
If you have any questions about IEC copyright or have an enquiry about obtaining additional rights to this publication,
please contact the address below or your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite ni
utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie et les
microfilms, sans l'accord écrit de la CEI ou du Comité national de la CEI du pays du demandeur.
Si vous avez des questions sur le copyright de la CEI ou si vous désirez obtenir des droits supplémentaires sur cette
publication, utilisez les coordonnées ci-après ou contactez le Comité national de la CEI de votre pays de résidence.

IEC Central Office Tel.: [phone]
3, rue de Varembé Fax: [phone]
CH-1211 Geneva 20 [e-mail]
Switzerland www.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.

Useful links:
IEC publications search - www.iec.ch/searchpub Electropedia - www.electropedia.org
The advanced search enables you to find IEC publications The world's leading online dictionary of electronic and
by a variety of criteria (reference number, text, technical electrical terms containing more than 30 000 terms and
committee,…). definitions in English and French, with equivalent terms in
It also gives information on projects, replaced and additional languages. Also known as the International
withdrawn publications. Electrotechnical Vocabulary (IEV) on-line.

IEC Just Published - webstore.iec.ch/justpublished Customer Service Centre - webstore.iec.ch/csc
Stay up to date on all new IEC publications. Just Published If you wish to give us your feedback on this publication
details all new publications released. Available on-line and or need further assistance, please contact the
also once a month by email. Customer Service Centre: [e-mail].

A propos de la CEI
La Commission Electrotechnique Internationale (CEI) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications CEI
Le contenu technique des publications de la CEI est constamment revu. Veuillez vous assurer que vous possédez
l’édition la plus récente, un corrigendum ou amendement peut avoir été publié.

Liens utiles:
Recherche de publications CEI - www.iec.ch/searchpub Electropedia - www.electropedia.org
La recherche avancée vous permet de trouver des Le premier dictionnaire en ligne au monde de termes
publications CEI en utilisant différents critères (numéro de électroniques et électriques. Il contient plus de 30 000
référence, texte, comité d’études,…). termes et définitions en anglais et en français, ainsi que
Elle donne aussi des informations sur les projets et les les termes équivalents dans les langues additionnelles.
publications remplacées ou retirées. Egalement appelé Vocabulaire Electrotechnique
International (VEI) en ligne.
Just Published CEI - webstore.iec.ch/justpublished
Service Clients - webstore.iec.ch/csc
Restez informé sur les nouvelles publications de la CEI.
Just Published détaille les nouvelles publications parues. Si vous désirez nous donner des commentaires sur
Disponible en ligne et aussi une fois par mois par email. cette publication ou si vous avez des questions
contactez-nous: [e-mail].
IEC 61094-8 ®
Edition 1.0 2012-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Measurement microphones –
Part 8: Methods for determining the free-field sensitivity of working standard

microphones by comparison
Microphones de mesure –
Partie 8: Méthodes pour la détermination de l'efficacité en champ libre par

comparaison des microphones étalons de travail

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX V
ICS 17.140.50 ISBN 978-2-83220-380-4

– 2 – 61094-8 © IEC:2012
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Reference environmental conditions . 8
5 Principles of free-field calibration by comparison . 8
5.1 General principle . 8
5.2 General principles using sequential excitation . 8
5.3 General principles using simultaneous excitation . 8
6 General requirements . 9
6.1 The test space . 9
6.2 Methods of establishing the free-field . 9
6.2.1 General . 9
6.2.2 Using a test space with sound absorbing surfaces . 9
6.2.3 Time selective methods for obtaining the free-field sensitivity . 10
6.3 The sound source . 10
6.4 Reference microphone . 11
6.5 Monitor microphone . 12
6.6 Test signals . 12
6.7 Configuration for the reference microphone and microphone under test . 13
7 Factors influencing the free-field sensitivity . 13
7.1 General . 13
7.2 Polarizing voltage . 13
7.3 Acoustic centre of the microphone . 13
7.4 Angle of incidence and alignment with the sound source . 14
7.5 Mounting configuration . 14
7.6 Dependence on environmental conditions. 14
8 Calibration uncertainty components . 14
8.1 General . 14
8.2 Sensitivity of the reference microphone . 15
8.3 Measurement of the microphone output . 15
8.4 Differences between the sound pressure applied to the reference
microphone and to the microphone under test . 15
8.5 Influence of indirect sound . 15
8.6 Influence of signal processing . 16
8.7 Influence of microphone characteristics and measurement system
performance . 16
8.7.1 Microphone capacitance . 16
8.7.2 Measurement system non-linearity . 16
8.7.3 Validation of calibration system . 16
8.8 Uncertainty on free-field sensitivity level . 16
Annex A (informative) Basic substitution calibration in a free-field chamber . 18
Annex B (informative) Time selective techniques . 22
Bibliography . 30

61094-8 © IEC:2012 – 3 –
Figure A.1 – Illustration of source and receiver setup in a free-field room, where the
monitor microphone has been integrated into the loudspeaker . 18
Figure A.2 – Practical implementation in a hemi-anechoic room with a source flush-
mounted in the floor . 19
Figure A.3 – Examples of loudspeaker sources . 21
Figure B.1 – Illustration of set-up for measurement with time selective techniques . 23

Table 1 – Calibration options for the reference microphone and associated typical
measurement uncertainty . 12
Table 2 – Typical uncertainty components . 17

– 4 – 61094-8 © IEC:2012
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MEASUREMENT MICROPHONES –
Part 8: Methods for determining the free-field sensitivity
of working standard microphones by comparison

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 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 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
agreement 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 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 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 corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the 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
...