IEC TR 61094-10:2022

Electroacoustics - Measurement microphones - Part 10: Absolute pressure calibration of microphones at low frequencies using calculable pistonphones

IEC TR 61904-10:2022
- is applicable to laboratory standard microphones meeting the requirements of IEC 61094-1 and other types of measurement microphones,
- describes one possible absolute method for determining the complex pressure sensitivity, based on a device capable of generating a known sound pressure, especially at low frequencies, and
- provides a reproducible and accurate basis for the measurement of sound pressure at low frequencies.
All quantities are expressed in SI units.

General Information

• Status: Published
• Publication Date: 03-Aug-2022
• 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: 26-Aug-2022
• Completion Date: 04-Aug-2022

Standards Content (Sample)

IEC TR 61094-10 ®
Edition 1.0 2022-08
TECHNICAL
REPORT
colour
inside
Electroacoustics – Measurement microphones –
Part 10: Absolute pressure calibration of microphones at low frequencies using
calculable pistonphones
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.

IEC Secretariat Tel.: [phone]
3, rue de Varembé [e-mail]
CH-1211 Geneva 20 www.iec.ch
Switzerland
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 corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform IEC Products & Services Portal - products.iec.ch
The advanced search enables to find IEC publications by a Discover our powerful search engine and read freely all the
variety of criteria (reference number, text, technical publications previews. With a subscription you will always
committee, …). It also gives information on projects, replaced have access to up to date content tailored to your needs.
and withdrawn publications.
Electropedia - www.electropedia.org
IEC Just Published - webstore.iec.ch/justpublished
The world's leading online dictionary on electrotechnology,
Stay up to date on all new IEC publications. Just Published
containing more than 22 300 terminological entries in English
details all new publications released. Available online and
and French, with equivalent terms in 19 additional languages.
once a month by email.
Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Customer Service Centre - webstore.iec.ch/csc

If you wish to give us your feedback on this publication or
need further assistance, please contact the Customer Service
Centre: [e-mail].
IEC TR 61094-10 ®
Edition 1.0 2022-08
TECHNICAL
REPORT
colour
inside
Electroacoustics – Measurement microphones –

Part 10: Absolute pressure calibration of microphones at low frequencies using

calculable pistonphones
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.140.50 ISBN 978-2-8322-4374-9

– 2 – IEC TR 61904-10:2022 © IEC 2022
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Reference environmental conditions . 7
5 Principles of absolute pressure calibration of microphones using a calculable
pistonphone . 7
5.1 General principle . 7
5.2 Basic expressions . 7
5.3 Heat conduction correction . 9
5.4 Operating frequency range . 9
6 General characteristics . 9
6.1 The pistonphone . 9
6.2 Measuring the piston volume velocity . 10
6.3 Test signals . 10
6.4 Mounting the microphone and pressure-equalizing tube . 10
6.5 Measuring the output voltages of the microphones . 10
7 Factors influencing the pressure sensitivity. 10
7.1 General . 10
7.2 Polarizing voltage . 11
7.3 Shield configuration . 11
7.4 Dependence on environmental conditions . 11
7.4.1 General . 11
7.4.2 Static pressure . 11
7.4.3 Temperature . 11
7.4.4 Humidity . 12
7.5 Vibration . 12
7.6 Distortion . 12
8 Calibration uncertainty components . 12
8.1 General . 12
8.2 Measurements of microphone output voltage . 12
8.3 Piston . 12
8.3.1 Frequency . 12
8.3.2 Measurement of the volume velocity . 12
8.4 Acoustic transfer impedance . 13
8.4.1 Cavity properties . 13
8.4.2 Physical quantities . 13
8.5 Microphone parameters . 13
8.5.1 Front cavity. 13
8.5.2 Acoustic impedance . 13
8.5.3 Polarizing voltage . 14
8.6 Uncertainty on pressure sensitivity level . 14
Annex A (informative) Example designs of pistonphones using laser interferometry . 16

IEC TR 61904-10:2022 © IEC 2022 – 3 –
Annex B (informative) Measurement uncertainties . 18
B.1 General . 18
B.2 Example of a typical uncertainty analysis . 18
B.2.1 General . 18
B.2.2 Uncertainty budget . 18
B.2.3 Combined and expanded uncertainties . 19
Bibliography . 20

Figure 1 – Equivalent circuit for evaluating the sound pressure over the exposed
surface of the diaphragm of the microphone . 8
Figure A.1 – Schematic cross-section of a laser pistonphone . 16
Figure A.2 – Example of laser pistonphone . 17
Figure A.3 – Example of laser pistonphone . 17

Table 1 – Uncertainty components . 14
Table B.1 – Example of uncertainty budget at 1 Hz . 19

– 4 – IEC TR 61904-10:2022 © IEC 2022
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROACOUSTICS –
MEASUREMENT MICROPHONES –
Part 10: Absolute pressure calibration of microphones
at low frequencies using calculable pistonphones

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 nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC TR 61094-10 has been prepared by IEC technical committee 29: Electroacoustics. It is a
Technical Report.
The text of this Technical Report is based on the following documents:
Draft Report on voting
29/1113/DTR 29/1124/RVDTR
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this Technical Report is English.

IEC TR 61904-10:2022 © IEC 2022 – 5 –
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
A list of all parts in the IEC 61094 series, published under the general title Electroacoustics –
Measurement microphones, can be found on the IEC website.
Future documents in this series will c
...