IEC 60268-4:2004

INTERNATIONAL IEC
STANDARD
60268-4
Third edition
2004-02
Sound system equipment –
Part 4:
Microphones
Reference number
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INTERNATIONAL IEC
STANDARD
60268-4
Third edition
2004-02
Sound system equipment –
Part 4:
Microphones
 IEC 2004  Copyright - all rights reserved
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 the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch  Web: www.iec.ch
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International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue

– 2 – 60268-4  IEC:2004(E)
CONTENTS
FOREWORD.5

1 Scope.7

2 Normative references.7

3 General conditions.8

3.1 General .8

3.2 Measurement conditions .8

4 Particular conditions .9

4.1 Pre-conditioning .9
4.2 Sound source .10
4.3 Measurement of sound pressure.10
4.4 Voltage measuring system .10
4.5 Acoustical environment.10
4.6 Methods of measuring frequency response .13
4.7 Overall accuracy.14
4.8 Graphical presentation of results.14
5 Type description (acoustical behaviour).14
5.1 Principle of the transducer .14
5.2 Type of microphone .14
5.3 Type of directional response characteristics.14
6 Terminals and controls.15
6.1 Marking .15
6.2 Connectors and electrical interface values .15
7 Reference point and axis .15
7.1 Reference point .15
7.2 Reference axis .15
8 Rated power supply .15
8.1 Characteristic to be specified.15
8.2 Method of measurement .16
9 Electrical impedance.16
9.1 Internal impedance .16
9.2 Rated impedance.17
9.3 Minimum permitted load impedance .17

10 Sensitivity.17
10.1 General .17
10.2 Sensitivities with respect to acoustical environment.18
10.3 Sensitivities with respect to nature of signal .20
11 Response .21
11.1 Frequency response .21
11.2 Effective frequency range .21
12 Directional characteristics .22
12.1 Directional pattern .22
12.2 Directivity index .23
12.3 Front-to-rear sensitivity index (0° – 180°) .23
12.4 Noise-cancelling index .24
12.5 Special characteristics for stereo microphones.24

60268-4 © IEC:2004(E) – 3 –
13 Amplitude non-linearity .25

13.1 General .25

13.2 Total harmonic distortion .26
th
13.3 Harmonic distortion of the n order (n = 2, 3,.).26

13.4 Difference frequency distortion of second order.27

14 Limiting characteristics .28

14.1 Rated maximum permissible peak sound pressure.28

14.2 Overload sound pressure.28

15 Balance .28

15.1 Balance of the microphone output.28
15.2 Balance under working conditions .28
16 Equivalent sound pressure level due to inherent noise.29
16.1 Characteristic to be specified.29
16.2 Method of measurement .29
17 Ambient conditions .29
17.1 General .29
17.2 Pressure range.29
17.3 Temperature range .29
17.4 Relative humidity range .29
18 External influences .30
18.1 General .30
18.2 Equivalent sound pressure due to external magnetic fields.30
18.3 Equivalent sound pressure due to mechanical vibration.31
18.4 Equivalent sound pressure due to wind .32
18.5 Transient equivalent sound pressure due to "pop" effect .33
18.6 Equivalent sound pressure due to electromagnetic interference.34
18.7 Electrostatic discharge.34
19 Magnetic stray field.34
19.1 Characteristic to be specified.34
19.2 Method of measurement .35
20 Physical characteristics.35
20.1 Dimensions .35
20.2 Weight.35
20.3 Cables and connectors .35

21 Classification of the characteristics to be specified.35
21.1 General .35
21.2 Classification.36
Annex A (normative) Sound insulation device .41
Annex B (informative) Simplified procedure for “pop” measurements .42
Bibliography .45
Figure 1a – Balance of the output.37
Figure 1b – Balance under working conditions .37
Figure 2 – Measurement set-up for wind influence .37
Figure 3a – Wind generator with radial fan (front and side view) .38

– 4 – 60268-4  IEC:2004(E)
Figure 3b – Wind generator with axial fan.38

Figure 4 – Electrical and mechanical set-up for the measuring of the "pop" effect .39

Figure 5 – Reference signal and characteristics.40

Figure A.1 – Sound insulation device.41

Figure B.1 – Measurement set-up.43

Figure B.2 – Test fixture for the sound field sensitivity .44

Table 1 – Reverberation time of the empty room.12

Table 2 – Speech power weighting factor at octave-band centre frequencies .20

Table 3 – Cla
...