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
Technical Committee
Drafting Committee
Current Stage
PPUB - Publication issued
Start Date
26-Aug-2022
Completion Date
04-Aug-2022
Ref Project

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IEC TR 61094-10:2022 - Electroacoustics - Measurement microphones - Part 10: Absolute pressure calibration of microphones at low frequencies using calculable pistonphones
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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
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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
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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
...

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