Underwater acoustics - Hydrophones - Calibration of hydrophones - Part 1: Procedures for free-field calibration of hydrophones

IEC 60565-1:2020 specifies methods and procedures for free-field calibration of hydrophones, as well as individual electroacoustic transducers that can be used as hydrophones (receivers) and/or projectors (source transducers). Two general types of calibration are covered within this document: absolute calibration using the method of three-transducer spherical-wave reciprocity, and relative calibration by comparison with a reference device which has already been the subject of an absolute calibration.
The maximum frequency range of the methods specified in this document is from 200 Hz to 1 MHz. The lowest acoustic frequency of application will depend on a number of factors, and will typically be in the range 200 Hz to 5 kHz depending mainly on the dimensions of the chosen test facility, The highest frequency of application for the methods described here is 1 MHz.
Procedures for pressure hydrophone calibration at low frequencies can be found in IEC 60565 2 [1] . Procedures for hydrophone calibration at acoustic frequencies greater than 1 MHz are covered by IEC 62127-2 [2].
Excluded from the scope of this document are low-frequency pressure calibrations of hydrophones, which are described in IEC 60565-2 [1]. Also excluded are calibrations of digital hydrophones and systems, calibration of marine autonomous acoustic recorders, calibration of acoustic vector sensors such as particle velocity sensors and pressure gradient hydrophones, calibration of passive sonar arrays consisting of multiple hydrophones, and calibration of active sonar arrays consisting of projectors and hydrophones.
This document presents a description of the requirements for free-field calibration in terms of test facility, equipment and instrumentation, signal processing, and frequency limitations. A description of achievable uncertainty and rules for the presentation of the calibration data are provided. Also included are informative annexes that provide additional guidance on
• measurement of directional response of a hydrophone or projector,
• measurement of electrical impedance of hydrophones and projectors,
• electrical loading corrections,
• acoustic far-field criteria in underwater acoustic calibration,
• pulsed techniques in free-field calibrations,
• assessment of uncertainty in the free-field calibration of hydrophones and projectors,
• derivation of the formulae for three-transducer spherical-wave reciprocity calibrations,
• calibration using travelling-wave tubes,
• calibration of hydrophones using optical interferometry, and
• calibrations in reverberant water tanks using continuous signals.
IEC 60565-1:2020 together with IEC 60565-2:2019, cancels and replaces the second edition of IEC 60565 published in 2006. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
1) removal of all descriptions of methods for pressure calibrations of hydrophones – these are now included in Part 2;
2) removal of the derivations of formulae for free-field reciprocity calibration (both amplitude sensitivity and phase sensitivity) and placement of these into an informative annex;
3) inclusion within the scope of the calibration of the transmitting response of individual source transducers and hydrophones (but not sonar arrays);
4) re-ordering of the sections within the document such that the more general procedures for calibration such as guidance on obtaining conditions of acoustic free-field, far-field, and steady-state, appear before the descriptions of procedures for absolute or relative calibrations;
5) revision of informative Annex A to include guidance on measurement of directional response of a hydrophone or projector;
6) addition of a new informative Annex B on measurement of electrical impedance of hydrophones and projectors;
7) revision of the previous informative annex on electrical loading corrections to include corrections to account for e

Acoustique sous-marine - Hydrophones - Étalonnage des hydrophones - Partie 1: Procédures d'étalonnage en champ libre des hydrophones

L'IEC 60565-1:2020 spécifie les méthodes et procédures d'étalonnage en champ libre des hydrophones, ainsi que des transducteurs électroacoustiques individuels qui peuvent être utilisés comme hydrophones (récepteurs) et/ou projecteurs (transducteurs sources). Deux grands types d'étalonnage sont couverts par le présent document: l'étalonnage absolu utilisant la méthode par réciprocité d’onde sphérique à trois transducteurs, et l'étalonnage relatif par comparaison avec un dispositif de référence qui a déjà fait l'objet d'un étalonnage absolu.
La plage de fréquences maximale des méthodes spécifiées dans le présent document est comprise entre 200 Hz et 1 MHz. La fréquence acoustique la plus faible de l'application dépend d'un certain nombre de facteurs, et est en général comprise entre 200 Hz et 5 kHz selon les dimensions de l'installation d'essai choisie. La fréquence la plus élevée de l'application pour les méthodes décrites ici est de 1 MHz.
Les procédures d'étalonnage de l'hydrophone à pression aux basses fréquences peuvent être consultées dans l'IEC 60565-2 [1] . Les procédures d'étalonnage de l'hydrophone aux fréquences acoustiques supérieures à 1 MHz sont couvertes par l'IEC 62127-2 [2].
Les étalonnages en pression basse fréquence des hydrophones sont exclus du domaine d'application du présent document. Ils sont décrits dans l'IEC 60565-2 [1]. Sont également exclus les étalonnages des hydrophones et systèmes numériques, des enregistreurs acoustiques marins autonomes, des capteurs vectoriels acoustiques (capteurs de vitesse de particules et hydrophones à gradient de pression, par exemple), des réseaux sonars passifs composés de plusieurs hydrophones et des réseaux sonars actifs composés de projecteurs et d'hydrophones.
Le présent document donne une description des exigences relatives à l'étalonnage en champ libre en ce qui concerne l'installation, le matériel et les appareils d'essai, le traitement du signal et les limites de fréquence. Une description de l'incertitude pouvant être obtenue et les règles de présentation des données d'étalonnage sont fournies. Sont également incluses des annexes informatives donnant des recommandations supplémentaires
• relatives au mesurage de la réponse directionnelle d'un hydrophone ou d'un projecteur,
• relatives au mesurage de l'impédance électrique des hydrophones et des projecteurs,
• sur les corrections de charge électrique,
• relatives aux critères de champ acoustique lointain dans l'étalonnage acoustique sous-marin,
• relatives aux techniques par impulsions dans les étalonnages en champ libre,
• relatives à l'évaluation de l'incertitude dans l'étalonnage en champ libre des hydrophones et des projecteurs,
• sur la déduction des formules pour les étalonnages par réciprocité d'onde sphérique à trois transducteurs,
• relatives à l'étalonnage à l'aide de tubes à ondes progressives,
• relatives à l'étalonnage des hydrophones par interférométrie optique, et
• relatives à l'étalonnage dans des cuves d'eau réverbérées à l'aide de signaux continus.
L'IEC 60565-1:2020 avec l’IEC 60565-2:2019, annule et remplace la deuxième édition de l’IEC 60565 parue en 2006. Cette édition constitue une révision technique.
Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
1) suppression de toutes les descriptions des méthodes d'étalonnages en pression des hydrophones – elles sont désormais incluses dans la Partie 2;
2) suppression des dérivées de formules d'étalonnage par réciprocité en champ libre (amplitude de sensibilité et sensibilité de phase) et leur intégration dans une Annexe informative;
3) inclusion dans le domaine d'application de l'étalonnage de la réponse à l’émission des transducteurs sources individuels et des hydrophones (mais pas des réseaux sonar);
4) réorganisation des sections du document de manière à faire apparaître les procédures d'étalonnage les plus générales (recommandations relatives à l'obtention des condition

General Information

Status
Published
Publication Date
23-Apr-2020
Technical Committee
Current Stage
PPUB - Publication issued
Completion Date
24-Apr-2020
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IEC 60565-1
Edition 1.0 2020-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Underwater acoustics – Hydrophones – Calibration of hydrophones –
Part 1: Procedures for free-field calibration of hydrophones
Acoustique sous-marine – Hydrophones – Étalonnage des hydrophones –
Partie 1: Procédures d'étalonnage en champ libre des hydrophones
IEC 60565-1:2020-04(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 60565-1
Edition 1.0 2020-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Underwater acoustics – Hydrophones – Calibration of hydrophones –
Part 1: Procedures for free-field calibration of hydrophones
Acoustique sous-marine – Hydrophones – Étalonnage des hydrophones –
Partie 1: Procédures d'étalonnage en champ libre des hydrophones
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.140.50 ISBN 978-2-8322-8039-3

Warning! Make sure that you obtained this publication from an authorized distributor.

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® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 60565-1:2020 © IEC 2020
CONTENTS

FOREWORD ........................................................................................................................... 7

INTRODUCTION ..................................................................................................................... 9

1 Scope ............................................................................................................................ 10

2 Normative references .................................................................................................... 11

3 Terms and definitions .................................................................................................... 11

4 Symbols and abbreviated terms ..................................................................................... 16

5 General procedures for calibration ................................................................................. 17

5.1 General alibration requirements ............................................................................ 17

5.1.1 Types of calibration ....................................................................................... 17

5.1.2 Acoustic field requirements ............................................................................ 18

5.2 Acoustic free-field requirements ............................................................................ 18

5.2.1 Continuous signals ........................................................................................ 18

5.2.2 Time-limited signals ....................................................................................... 18

5.3 Acoustic far-field requirements .............................................................................. 18

5.4 Requirements for steady-state conditions.............................................................. 19

5.5 Equipment requirements ....................................................................................... 20

5.5.1 Calibration facility .......................................................................................... 20

5.5.2 Instrumentation .............................................................................................. 20

5.6 Positioning and alignment ..................................................................................... 22

5.6.1 Coordinate system ......................................................................................... 22

5.6.2 Reference direction ....................................................................................... 22

5.6.3 Transducer mounting and support .................................................................. 22

5.6.4 Alignment ...................................................................................................... 23

5.6.5 Separation distance ....................................................................................... 23

5.7 Representation of the frequency response ............................................................ 23

5.8 Frequency limitations ............................................................................................ 24

5.8.1 High-frequency limit ....................................................................................... 24

5.8.2 Low-frequency limit ........................................................................................ 24

5.9 Checks for acoustic interference ........................................................................... 24

6 Electrical measurements................................................................................................ 25

6.1 Signal type ............................................................................................................ 25

6.2 Electrical earthing ................................................................................................. 25

6.3 Measurement of hydrophone output voltage .......................................................... 25

6.3.1 General ......................................................................................................... 25

6.3.2 Signal analysis .............................................................................................. 26

6.3.3 Electrical loading by measuring instruments .................................................. 26

6.3.4 Electrical loading by extension cables ........................................................... 26

6.3.5 Electrical noise .............................................................................................. 26

6.3.6 Cross-talk ...................................................................................................... 27

6.3.7 Integral preamplifiers ..................................................................................... 27

6.4 Measurement of projector drive current ................................................................. 27

6.4.1 Instrumentation .............................................................................................. 27

6.4.2 Signal analysis .............................................................................................. 27

6.5 Measurement of projector drive voltage ................................................................ 28

6.5.1 Instrumentation .............................................................................................. 28

6.5.2 Signal analysis .............................................................................................. 28

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IEC 60565-1:2020 © IEC 2020 – 3 –

7 Preparation and conditioning of transducers .................................................................. 28

7.1 Soaking ................................................................................................................ 28

7.2 Wetting ................................................................................................................. 28

7.3 Extending the hydrophone cable ........................................................................... 29

7.4 Environmental conditions (temperature and depth) ............................................... 29

8 Free-field three-transducer spherical-wave reciprocity calibration .................................. 29

8.1 General principle .................................................................................................. 29

8.2 Calibration to determine sensitivity modulus (without phase) ................................. 30

8.2.1 Acoustic field requirements ............................................................................ 30

8.2.2 Separation distance ....................................................................................... 30

8.2.3 Transducer preparation, mounting and alignment .......................................... 31

8.2.4 Signal type .................................................................................................... 31

8.2.5 Measurement of electrical transfer impedance ............................................... 31

8.2.6 Calculation of the receive sensitivities ........................................................... 31

8.2.7 Calculation of the transmit sensitivities .......................................................... 32

8.2.8 Repeatability ................................................................................................. 32

8.2.9 Verification and checks .................................................................................. 32

8.2.10 Uncertainty .................................................................................................... 34

8.3 Calibration to determine phase of the hydrophone sensitivity ................................ 34

8.3.1 General principle ........................................................................................... 34

8.3.2 Transducer preparation ................................................................................. 35

8.3.3 Acoustic field requirements ............................................................................ 36

8.3.4 Signal type .................................................................................................... 36

8.3.5 Transducer mounting and alignment .............................................................. 36

8.3.6 Measurement of electrical transfer impedance ............................................... 36

8.3.7 Calculation of sensitivity phase angle ............................................................ 36

8.3.8 Repeatability ................................................................................................. 37

8.3.9 Verification and checking ............................................................................... 37

8.3.10 Uncertainty .................................................................................................... 37

9 Free-field calibration by comparison with an acoustic reference device.......................... 37

9.1 Principles .............................................................................................................. 37

9.2 Types of comparison calibration method ............................................................... 38

9.2.1 Hydrophone calibration using a calibrated reference hydrophone .................. 38

9.2.2 Hydrophone calibration using calibrated reference projector .......................... 38

9.2.3 Projector calibration using a calibrated reference hydrophone ....................... 38

9.3 Hydrophone calibration by comparison with a reference hydrophone .................... 38

9.3.1 Acoustic field requirements ............................................................................ 38

9.3.2 Separation distance ....................................................................................... 38

9.3.3 Transducer preparation, mounting and alignment .......................................... 39

9.3.4 Signal type .................................................................................................... 39

9.3.5 Measurement of electrical voltage ................................................................. 39

9.3.6 Free-field sensitivity ...................................................................................... 39

9.3.7 Repeatability ................................................................................................. 39

9.3.8 Verification and checks .................................................................................. 40

9.3.9 Uncertainty .................................................................................................... 40

9.4 Hydrophone calibration using a calibrated projector .............................................. 40

9.4.1 Acoustic field requirements ............................................................................ 40

9.4.2 Separation distance ....................................................................................... 40

9.4.3 Transducer preparation, mounting and alignment .......................................... 41

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– 4 – IEC 60565-1:2020 © IEC 2020

9.4.4 Signal type .................................................................................................... 41

9.4.5 Measurement of electrical transfer impedance ............................................... 41

9.4.6 Calculation of the receive sensitivities ........................................................... 41

9.4.7 Repeatability ................................................................................................. 41

9.4.8 Verification and checks .................................................................................. 42

9.4.9 Uncertainty .................................................................................................... 42

9.5 Projector calibration using a calibrated hydrophone .............................................. 42

9.5.1 Acoustic field requirements ............................................................................ 42

9.5.2 Separation distance ....................................................................................... 42

9.5.3 Transducer preparation, mounting and alignment .......................................... 42

9.5.4 Signal type .................................................................................................... 43

9.5.5 Measurement of electrical transfer impedance ............................................... 43

9.5.6 Calculation of the transmit sensitivity ............................................................. 43

9.5.7 Verification and checks .................................................................................. 43

9.5.8 Uncertainty .................................................................................................... 44

10 Reporting of results ....................................................................................................... 44

10.1 Sensitivity ............................................................................................................. 44

10.2 Sensitivity level ..................................................................................................... 44

10.3 Calibration uncertainties ....................................................................................... 45

10.4 Auxiliary metadata ................................................................................................ 45

11 Recalibration periods ..................................................................................................... 45

Annex A (informative) Directional response of a hydrophone or projector ............................. 46

A.1 General principle .................................................................................................. 46

A.2 Types of measurement implementation ................................................................. 46

A.3 Coordinate system ................................................................................................ 46

A.4 Acoustic field requirements ................................................................................... 47

A.5 Positioning and alignment ..................................................................................... 47

A.6 Signal type ............................................................................................................ 47

A.7 Measurement of transducer directional response .................................................. 47

A.7.1 Projector ........................................................................................................ 47

A.7.2 Hydrophone ................................................................................................... 47

A.8 Calculation of the directional response level (angular deviation loss) .................... 47

A.9 Uncertainty ........................................................................................................... 48

A.10 Graphic representation ......................................................................................... 48

A.11 Directivity factor .................................................................................................... 49

A.12 Directivity index .................................................................................................... 49

Annex B (informative) Measurement of electrical impedance of hydrophones and

projectors ............................................................................................................................. 50

B.1 General principles ................................................................................................. 50

B.2 Measurement of electrical impedance ................................................................... 50

B.3 Derivation of other electrical impedance parameters ............................................. 51

B.4 Graphical representation ....................................................................................... 52

Annex C (informative) Calculation of electrical loading corrections ....................................... 54

C.1 Electrical loading corrections ................................................................................ 54

C.2 Corrections for amplifier loading using complex electrical impedance ................... 54

C.3 Corrections for loading caused by extension cables (using complex electrical

impedance) ........................................................................................................... 54

C.4 Corrections using only capacitances ..................................................................... 55

Annex D (informative) Acoustic far-field criteria in underwater acoustic calibration .............. 56

---------------------- Page: 6 ----------------------
IEC 60565-1:2020 © IEC 2020 – 5 –

D.1 General ................................................................................................................. 56

D.2 The field for piston transducers ............................................................................. 56

D.3 Criteria for far-field conditions ............................................................................... 57

D.4 Far-field criteria in directional response measurements......................................... 58

Annex E (informative) Pulsed techniques in free-field calibrations ........................................ 59

E.1 General ................................................................................................................. 59

E.2 Echo-free time ...................................................................................................... 59

E.3 Minimum separation distance ................................................................................ 61

E.4 Turn-on transients ................................................................................................. 61

E.5 Bandwidth considerations ..................................................................................... 62

E.6 Electrical cross-talk ............................................................................................... 63

E.7 Pulse duration ....................................................................................................... 63

E.8 Reverberation and pulse repetition rate ................................................................ 63

E.9 Typical tank dimensions ........................................................................................ 63

E.10 Spherical-wave conditions .................................................................................... 64

E.11 Reflections from mounting poles and rigging ......................................................... 64

E.12 Analysis methods for tone-burst signals ................................................................ 64

E.13 High-frequency limitations ..................................................................................... 65

E.14 Low-frequency limitations...................................................................................... 66

E.15 Advanced techniques for extending the frequency range beyond the low-

frequency limit ...................................................................................................... 67

Annex F (informative) Assessment of uncertainty in the calibration of hydrophones

and projectors ....................................................................................................................... 69

F.1 General ................................................................................................................. 69

F.2 Type A evaluation of uncertainty ........................................................................... 69

F.3 Type B evaluation of uncertainty ........................................................................... 69

F.4 Reported uncertainty ............................................................................................. 69

F.5 Common sources of uncertainty ............................................................................ 70

Annex G (informative) Derivation of the formulae for three-transducer spherical-wave

reciprocity calibration ............................................................................................................ 72

G.1 General ................................................................................................................. 72

G.2 Calibration to determine the modulus of the sensitivity .......................................... 72

G.3 Calibration to determine the complex sensitivity .................................................... 74

Annex H (informative) Calibration using travelling-wave tubes ............................................. 77

H.1 General ................................................................................................................. 77

H.2 Calibration procedure ............................................................................................ 77

H.3 Limitations of the method ...................................................................................... 77

H.4 Extensions of the method ...................................................................................... 78

Annex I (informative) Calibration of hydrophones using optical interferometry ...................... 79

I.1 General ................................................................................................................. 79

I.2 General principles ................................................................................................. 79

I.3 Procedure ............................................................................................................. 79

I.4 Discussion of method ............................................................................................ 80

Annex J (informative) Calibration in a reverberant water tanks using continuous

signals .................................................................................................................................. 81

J.1 General principle .................................................................................................. 81

J.2 Using a noise signal .............................................................................................. 82

J.3 Using the LFM signal ............................................................................................ 82

J.4 Uncertainties......................................................................................................... 83

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– 6 – IEC 60565-1:2020 © IEC 2020

Bibliography .......................................................................................................................... 84

Figure 1 – Measurement configurations for three-transducer reciprocity ................................ 30

Figure 2 – Measurement framework for supporting in-line the three transducers: a

projector P, a reciprocal transducer T, and a hydrophone H to be calibrated ......................... 35

Figure A.1 – Examples of graphical representations of the level of the directional

response: polar plot (left) and Cartesian plot (right) .............................................................. 48

...

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