BS EN IEC 60565-1:2020
$215.11
Underwater acoustics. Hydrophones. Calibration of hydrophones – Procedures for free-field calibration of hydrophones
| Published By | Publication Date | Number of Pages |
| BSI | 2020 | 96 |
This part of IEC 60565 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 threetransducer 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]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
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measurement of directional response of a hydrophone or projector,
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measurement of electrical impedance of hydrophones and projectors,
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electrical loading corrections,
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acoustic far-field criteria in underwater acoustic calibration,
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pulsed techniques in free-field calibrations,
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assessment of uncertainty in the free-field calibration of hydrophones and projectors,
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derivation of the formulae for three-transducer spherical-wave reciprocity calibrations,
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calibration using travelling-wave tubes,
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calibration of hydrophones using optical interferometry, and
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calibrations in reverberant water tanks using continuous signals.
PDF Catalog
| PDF Pages | PDF Title |
|---|---|
| 2 | undefined |
| 5 | Annex ZA(normative)Normative references to international publicationswith their corresponding European publications |
| 7 | English CONTENTS |
| 12 | FOREWORD |
| 14 | INTRODUCTION |
| 15 | 1 Scope |
| 16 | 2 Normative references 3 Terms and definitions |
| 21 | 4 Symbols and abbreviated terms |
| 22 | 5 General procedures for calibration 5.1 General calibration requirements 5.1.1 Types of calibration |
| 23 | 5.1.2 Acoustic field requirements 5.2 Acoustic free-field requirements 5.2.1 Continuous signals 5.2.2 Time-limited signals 5.3 Acoustic far-field requirements |
| 24 | 5.4 Requirements for steady-state conditions |
| 25 | 5.5 Equipment requirements 5.5.1 Calibration facility 5.5.2 Instrumentation |
| 27 | 5.6 Positioning and alignment 5.6.1 Coordinate system 5.6.2 Reference direction 5.6.3 Transducer mounting and support |
| 28 | 5.6.4 Alignment 5.6.5 Separation distance 5.7 Representation of the frequency response |
| 29 | 5.8 Frequency limitations 5.8.1 High-frequency limit 5.8.2 Low-frequency limit 5.9 Checks for acoustic interference |
| 30 | 6 Electrical measurements 6.1 Signal type 6.2 Electrical earthing 6.3 Measurement of hydrophone output voltage 6.3.1 General |
| 31 | 6.3.2 Signal analysis 6.3.3 Electrical loading by measuring instruments 6.3.4 Electrical loading by extension cables 6.3.5 Electrical noise |
| 32 | 6.3.6 Cross-talk 6.3.7 Integral preamplifiers 6.4 Measurement of projector drive current 6.4.1 Instrumentation 6.4.2 Signal analysis |
| 33 | 6.5 Measurement of projector drive voltage 6.5.1 Instrumentation 6.5.2 Signal analysis 7 Preparation and conditioning of transducers 7.1 Soaking 7.2 Wetting |
| 34 | 7.3 Extending the hydrophone cable 7.4 Environmental conditions (temperature and depth) 8 Free-field three-transducer spherical-wave reciprocity calibration 8.1 General principle |
| 35 | 8.2 Calibration to determine sensitivity modulus (without phase) 8.2.1 Acoustic field requirements 8.2.2 Separation distance Figures Figure 1 – Measurement configurations for three-transducer reciprocity |
| 36 | 8.2.3 Transducer preparation, mounting and alignment 8.2.4 Signal type 8.2.5 Measurement of electrical transfer impedance 8.2.6 Calculation of the receive sensitivities |
| 37 | 8.2.7 Calculation of the transmit sensitivities 8.2.8 Repeatability 8.2.9 Verification and checks |
| 39 | 8.2.10 Uncertainty 8.3 Calibration to determine phase of the hydrophone sensitivity 8.3.1 General principle |
| 40 | 8.3.2 Transducer preparation 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 |
| 41 | 8.3.3 Acoustic field requirements 8.3.4 Signal type 8.3.5 Transducer mounting and alignment 8.3.6 Measurement of electrical transfer impedance 8.3.7 Calculation of sensitivity phase angle |
| 42 | 8.3.8 Repeatability 8.3.9 Verification and checking 8.3.10 Uncertainty 9 Free-field calibration by comparison with an acoustic reference device 9.1 Principles |
| 43 | 9.2 Types of comparison calibration method 9.2.1 Hydrophone calibration using a calibrated reference hydrophone 9.2.2 Hydrophone calibration using calibrated reference projector 9.2.3 Projector calibration using a calibrated reference hydrophone 9.3 Hydrophone calibration by comparison with a reference hydrophone 9.3.1 Acoustic field requirements 9.3.2 Separation distance |
| 44 | 9.3.3 Transducer preparation, mounting and alignment 9.3.4 Signal type 9.3.5 Measurement of electrical voltage 9.3.6 Free-field sensitivity 9.3.7 Repeatability |
| 45 | 9.3.8 Verification and checks 9.3.9 Uncertainty 9.4 Hydrophone calibration using a calibrated projector 9.4.1 Acoustic field requirements 9.4.2 Separation distance |
| 46 | 9.4.3 Transducer preparation, mounting and alignment 9.4.4 Signal type 9.4.5 Measurement of electrical transfer impedance 9.4.6 Calculation of the receive sensitivities 9.4.7 Repeatability |
| 47 | 9.4.8 Verification and checks 9.4.9 Uncertainty 9.5 Projector calibration using a calibrated hydrophone 9.5.1 Acoustic field requirements 9.5.2 Separation distance 9.5.3 Transducer preparation, mounting and alignment |
| 48 | 9.5.4 Signal type 9.5.5 Measurement of electrical transfer impedance 9.5.6 Calculation of the transmit sensitivity 9.5.7 Verification and checks |
| 49 | 9.5.8 Uncertainty 10 Reporting of results 10.1 Sensitivity 10.2 Sensitivity level |
| 50 | 10.3 Calibration uncertainties 10.4 Auxiliary metadata 11 Recalibration periods |
| 51 | Annex A (informative)Directional response of a hydrophone or projector A.1 General principle A.2 Types of measurement implementation A.3 Coordinate system |
| 52 | A.4 Acoustic field requirements A.5 Positioning and alignment A.6 Signal type A.7 Measurement of transducer directional response A.7.1 Projector A.7.2 Hydrophone A.8 Calculation of the directional response level (angular deviation loss) |
| 53 | A.9 Uncertainty A.10 Graphic representation Figure A.1 – Examples of graphical representations of the level of the directional response: polar plot (left) and Cartesian plot (right) |
| 54 | A.11 Directivity factor A.12 Directivity index |
| 55 | Annex B (informative)Measurement of electrical impedance of hydrophones and projectors B.1 General principles B.2 Measurement of electrical impedance |
| 56 | B.3 Derivation of other electrical impedance parameters |
| 57 | B.4 Graphical representation |
| 58 | Figure B.1 – Examples of plots of transducer electrical impedance for a small spherical hydrophone of capacitance 3 nF |
| 59 | Annex C (informative)Calculation of electrical loading corrections C.1 Electrical loading corrections C.2 Corrections for amplifier loading using complex electrical impedance C.3 Corrections for loading caused by extension cables (using complex electrical impedance) |
| 60 | C.4 Corrections using only capacitances |
| 61 | Annex D (informative)Acoustic far-field criteria in underwater acoustic calibration D.1 General D.2 The field for piston transducers Figure D.1 – Acoustic pressure as a function of range from the source for a point source and for a piston source of dimensions ka = 10 |
| 62 | D.3 Criteria for far-field conditions Figure D.2 – Difference in measured acoustic pressure on axis compared to spherical spreading measured by a point receiver and a piston receiver |
| 63 | D.4 Far-field criteria in directional response measurements |
| 64 | Annex E (informative)Pulsed techniques in free-field calibrations E.1 General E.2 Echo-free time |
| 65 | Figure E.1 – Schematic diagram of a projector and receiver in a water tank showing the main sources of reflections |
| 66 | E.3 Minimum separation distance E.4 Turn-on transients Figure E.2 – Echo arrival time in a 6 m x 6 m x 5 m tank with optimally placed transducers |
| 67 | E.5 Bandwidth considerations Figure E.3 – Hydrophone signals for a pair of spherical transducers (projector: 18 kHz resonance frequency, Q-factor of 3,5; hydrophone: 350 kHz resonance frequency; drive frequency: 2 kHz (left) and 18 kHz (right)) |
| 68 | E.6 Electrical cross-talk E.7 Pulse duration E.8 Reverberation and pulse repetition rate E.9 Typical tank dimensions |
| 69 | E.10 Spherical-wave conditions E.11 Reflections from mounting poles and rigging E.12 Analysis methods for tone-burst signals |
| 70 | E.13 High-frequency limitations Figure E.4 – Examples of acoustic waveforms showing time-windows for analysis |
| 71 | E.14 Low-frequency limitations Figure E.5 – Values for the sound absorption in pure water and sea water, including contributions due to component factors |
| 72 | E.15 Advanced techniques for extending the frequency range beyond the low-frequency limit |
| 74 | Annex F (informative)Assessment of uncertainty in the calibration of hydrophones and projectors F.1 General F.2 Type A evaluation of uncertainty F.3 Type B evaluation of uncertainty F.4 Reported uncertainty |
| 75 | F.5 Common sources of uncertainty |
| 77 | Annex G (informative)Derivation of the formulae for three-transducer spherical-wave reciprocity calibration G.1 General G.2 Calibration to determine the modulus of the sensitivity |
| 79 | G.3 Calibration to determine the complex sensitivity |
| 82 | Annex H (informative)Calibration using travelling-wave tubes H.1 General H.2 Calibration procedure H.3 Limitations of the method |
| 83 | H.4 Extensions of the method |
| 84 | Annex I (informative)Calibration of hydrophones using optical interferometry I.1 General I.2 General principles I.3 Procedure |
| 85 | I.4 Discussion of method Figure I.1 – Configurations for calibration of hydrophones using heterodyne optical interferometry |
| 86 | Annex J (informative)Calibration in a reverberant water tanks using continuous signals J.1 General principle |
| 87 | J.2 Using a noise signal J.3 Using the LFM signal |
| 88 | J.4 Uncertainties |
| 89 | Bibliography |
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IEC 60565-1:2020
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