EN 60565:2007

SLOVENSKI STANDARD
01-januar-2008
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Underwater acoustics - Hydrophones - Calibration in the frequency range 0,01 Hz to 1
MHz (IEC 60565:2006)
Wasserschall - Hydrophone - Kalibrierung im Frequenzbereich von 0,01 Hz bis 1 MHz
(IEC 60565:2006)
Acoustique sous-marine - Hydrophones - Etalonnage dans la bande de fréquences de
0,01 Hz a 1 MHz (IEC 60565:2006)
Ta slovenski standard je istoveten z: EN 60565:2007
ICS:
17.140.50 Elektroakustika Electroacoustics
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 60565
NORME EUROPÉENNE
January 2007
EUROPÄISCHE NORM
ICS 17.140.50
English version
Underwater acoustics -
Hydrophones -
Calibration in the frequency range 0,01 Hz to 1 MHz
(IEC 60565:2006)
Acoustique sous-marine -  Wasserschall -
Hydrophones - Hydrophone -
Etalonnage dans la bande de fréquences Kalibrierung im Frequenzbereich
de 0,01 Hz à 1 MHz von 0,01 Hz bis 1 MHz
(CEI 60565:2006) (IEC 60565:2006)

This European Standard was approved by CENELEC on 2006-12-01. CENELEC members are bound to comply
with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard
the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and notified
to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, the Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2007 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60565:2007 E
Foreword
The text of document 87/357/FDIS, future edition 2 of IEC 60565, prepared by IEC TC 87, Ultrasonics,
was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 60565 on
2006-12-01.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2007-09-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2009-12-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 60565:2006 was approved by CENELEC as a European
Standard without any modification.
__________
- 3 - EN 60565:2007
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.

NOTE  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.
Publication Year Title EN/HD Year

1)
IEC 60050-801 - International Electrotechnical Vocabulary - -
(IEV)
Chapter 801: Acoustics and electroacoustics

IEC 60500 1974 IEC standard hydrophone - -

IEC 60866 1987 Characteristics and calibration of - -
hydrophones for operation in the frequency
range 0,5 MHz to 15 MHz
1)
Undated reference.
NORME CEI
INTERNATIONALE
IEC
INTERNATIONAL
Deuxième édition
STANDARD
Second edition
2006-11
Acoustique sous-marine –
Hydrophones –
Étalonnage dans la bande de
fréquences de 0,01 Hz à 1 MHz
Underwater acoustics –
Hydrophones –
Calibration in the frequency
range 0,01 Hz to 1 MHz
© IEC 2006 Droits de reproduction réservés ⎯ Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in any
utilisée sous quelque forme que ce soit et par aucun procédé, form or by any means, electronic or mechanical, including
électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from
microfilms, sans l'accord écrit de l'éditeur. 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
CODE PRIX
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PRICE CODE
Commission Electrotechnique Internationale
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
Pour prix, voir catalogue en vigueur
For price, see current catalogue

60565 © IEC:2006 – 3 –
CONTENTS
FOREWORD.9

1 Scope.13
2 Normative references .13
3 Terms and definitions .13
4 Symbols and abbreviated terms.25
5 Procedures for calibrations.29
5.1 Principles .29
5.2 Field limitations .31
5.3 Schematic survey of procedures.31
5.4 Reporting of results .31
5.5 Recalibration periods.33
5.6 Temperature and pressure considerations for calibration.33
6 Preparation of transducers .33
6.1 Wetting.33
6.2 Hydrophone support .33
6.3 Influence of cable .33
7 Electrical measurements .35
7.1 Signal type .35
7.2 Earthing .35
7.3 Measurement of hydrophone output voltage .35
7.4 Measurement of projector current.37
7.5 Measurement of transfer impedance.39
8 Free-field reciprocity calibration.39
8.1 General principle .39
8.2 Theory.41
8.3 Separation distance.51
8.4 Minimum distance from transducers to boundary surface.51
8.5 Frequency limitation .51
8.6 Measurements and checks .53
8.7 Uncertainty.59
9 Free-field calibration by comparison .59
9.1 Principle.59
9.2 Comparison with a standard hydrophone.59
9.3 Calibration with a calibrated projector.61
10 Calibration by hydrostatic excitation .63
10.1 Principle.63
10.2 Determination of equivalent pressure .63
10.3 Measurement of the sensitivity of hydrophones .71
10.4 Design of vibration system .73
10.5 Uncertainty.75
10.6 Alternative method for hydrostatic excitation .75
11 Calibration by piezoelectric compensation .75
11.1 Principle.75
11.2 Procedure .77

60565 © IEC:2006 – 5 –
11.3 Design of the calibration chamber .81
11.4 Practical limitations of the piezoelectric compensation method .85
11.5 Uncertainty.85
12 Acoustic coupler reciprocity calibration.85
12.1 Principle……….85
12.2 Procedure .85
12.3 Theory……….87
12.4 Acoustic compliance.89
12.5 High-frequency limit .89
12.6 Low-frequency limit .89
12.7 Measurement .89
12.8 Uncertainty.91
12.9 Limitations.91
12.10 Acoustic-coupler calibration using a reference coupler with two reciprocal
transducers and an auxiliary coupler with the same two transducers and a
hydrophone to be calibrated .91
12.11 Acoustic-coupler calibration using a reference coupler with two reciprocal
transducers and an auxiliary coupler with the same two transducers, a
hydrophone to be calibrated, and a sound source.95
12.12 Acoustic-coupler calibration using a coupler, a reciprocal transducer, a
projector, a hydrophone to be calibrated, and a subsidiary body of known
compliance.99
13 Calibration with a pistonphone.103
13.1 Principle……….103
13.2 Procedure .103
13.3 Limitations.109
13.4 Uncertainty.111
14 Calibration with a vibrating column .111
14.1 Principle……….111
14.2 Procedure .113
14.3 Expression for the pressure.115
14.4 Determination of the sensitivity.115
14.5 Conditions of measurement .119
14.6 Uncertainty.121

Annex A (informative) Directional response of a hydrophone .123
Annex B (informative) Electrical loading corrections.127
Annex C (informative) Pulsed techniques in free-field calibrations .131
Annex D (informative) Assessment of uncertainty in the calibration of hydrophones.149
Annex E (informative) Equivalent circuit of the excitation system for calibration with a
vibrating column .157

Bibliography.159

60565 © IEC:2006 – 7 –
Figure 1 – Left-hand co-ordinate system .15
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.49
Figure 3 – Diagram of the method of hydrostatic excitation. .65
Figure 4 – Schematic drawing of the measuring system .77
Figure 5 – Diagram of the chamber for high-frequency.83
Figure 6 – Reciprocity coupler with three transducers; a projector P , a reciprocal
transducer T , and a hydrophone H to be calibrated.87
Figure 7 – Reference coupler with two transducers: a projector P and a reciprocal
transducer T .93
Figure 8 – Auxiliary coupler with three transducers: a projector P , a reciprocal
transducer T , and a hydrophone H to be calibrated.93
Figure 9 – Auxiliary coupler with four transducers; a projector P , a reciprocal
transducer T , a sound source S , and a hydrophone H to be calibrated.97
Figure 10 – Schematic drawing of the measuring system. .103
Figure 11 – Pistonphone .111
Figure 12 – Vibrating column .113
Figure C.1 – Schematic diagram of a projector and receiver in a water tank showing
the main sources of reflections .135
Figure C.2 – Echo arrival time in a 6 m × 6 m × 5 m tank with optimally placed
transducers.137
Figure C.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)] .139
Figure E.1 – Simplified equivalent circuit of the vibrating column .157

60565 © IEC:2006 – 9 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
UNDERWATER ACOUSTICS – HYDROPHONES –
CALIBRATION IN THE FREQUENCY RANGE
0,01 Hz TO 1 MHz
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 provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
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.
International Standard IEC 60565 has been prepared by IEC technical committee 87:
Ultrasonics.
This second edition cancels and replaces the first edition published in 1977 and its first
supplement IEC 60565A (1980). This edition constitutes a technical revision. The significant
technical changes with respect to the previous edition are as follows:
– updating of procedures to reflect the use of digital acquisition and signal processing
techniques as opposed to the analogue techniques described in the first edition;
– inclusion of more detailed information regarding the preparation of hydrophones for
measurement, and the influences of environmental conditions on hydrophone calibration;
– revision of procedures for magnitude calibration of hydrophone response by the method of
three-transducer spherical-wave reciprocity;
– inclusion of procedures for phase calibration into the method of three-transducer
spherical-wave reciprocity;
60565 © IEC:2006 – 11 –
– revision of procedures for calibration of hydrophones by the comparison methods;
– inclusion of procedures for low frequency hydrophone calibration utilising the method of
hydrostatic excitation;
– revision of the procedures for low frequency hydrophone calibration utilising the method of
piezoelectric compensation;
– inclusion of procedures for low frequency hydrophone calibration utilising the method of
coupler reciprocity;
– revision of the procedures for low frequency hydrophone calibration utilising the
pistonphone method;
– revision of procedures for low frequency hydrophone calibration utilising the method of
vibrating column (previously issued as a supplement to the standard);
– deletion of Appendix A of first edition (transfer impedance by substitution method) since
method no longer used;
– deletion of Appendix B of first edition (transfer impedance by direct read-out method)
since method no longer used;
– retention of Appendix C of first edition, but now substantially updated and included as
Annex C (informative);
– retention of Appendix D of first edition, now included as Annex A (informative);
– addition of new Annex B describing methods for accounting for electrical loading of
hydrophones by pre-amplifiers;
– addition of new Annex D describing the assessment of uncertainty in free-field hydrophone
calibrations;
– addition of new Annex E describing an equivalent electrical circuit of the excitation system
for calibration with a vibrating column.
The text of this standard is based on the following documents:
FDIS Report on voting
87/357/FDIS 87/360/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
60565 © IEC:2006 – 13 –
UNDERWATER ACOUSTICS – HYDROPHONES –
CALIBRATION IN THE FREQUENCY RANGE
0,01 Hz TO 1 MHz
1 Scope
This International Standard specifies methods for calibration of hydrophones or reversible
transducers when used as a hydrophone, particularly in the frequency range from 0,01 Hz to
1 MHz. Rules for the presentation of the calibration data are established.
2 Normative references
The following referenced data are indispensable for the application of this document. For
dated references, only the edition cited applies. For undated references, the latest edition of
the referenced document (including any amendments) applies.
IEC 60050-801, International Electrotechnical Vocabulary - Chapter 801: Acoustics and
electroacoustics
IEC 60500:1974, IEC Standard hydrophone
IEC 60866:1987, Characteristics and calibration of hydrophones for operation in the
frequency range 0,5 MHz to 15 MHz
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
angular deviation loss
sensitivity level of the transducer on the principal axis minus the sensitivity level of the
transducer for a specified direction
[IEV 801-25-69]
3.2
co-ordinate system
system used to designate the directivity pattern of the transducer

60565 © IEC:2006 – 15 –
+Z
+X
+Y
IEC  1994/06
Figure 1 – Left-hand co-ordinate system
Line transducer: central line of symmetry along the Z-axis;
Dipole transducer: both components equidistant from the origin, along the +Z and –Z axis;
Piston transducer: piston plane in ZOY-plane; principal axis along X-axis.
NOTE 1 The terms ’horizontal directivity pattern’ and ’vertical directivity pattern’ are often used for representation
of directivity in the XY- and XZ- (or YZ-) planes respectively.
NOTE 2 See Annex A, [1] , [2].
3.3
coupler
apparatus comprising a rigid fluid-filled chamber of small dimensions into which transducers
and hydrophones can be inserted
3.4
diffraction factor
ratio of the average pressure over the part of the hydrophone designed to receive sound to
the free-field sound pressure that would exist at the reference centre of the hydrophone
3.5
directional response
description, generally presented graphically, of the response of an electro-acoustic
transducer, as a function of the direction of propagation of the radiated or incident sound in a
specified plane through the reference centre and at a specified frequency
NOTE See Annex A.
3.6
dynamic range
ratio of the maximum free field sound pressure that produces an undistorted hydrophone
output to the equivalent noise pressure at the hydrophone
3.7
electrical impedance of a transducer
complex ratio of the instantaneous voltage applied across the electrical terminals of a
transducer at a given frequency, to the resulting instantaneous current
NOTE 1 The unit is the ohm, Ω.
NOTE 2 Because the electrical impedance depends on the field conditions, the hydrostatic pressure, water
temperature and the length of the cable attached to the transducer, these parameters, as well as the frequency and
the electrical terminals where the electrical impedance is measured should be specified.
___________
Numbers in square brackets refer to the bibliography

60565 © IEC:2006 – 17 –
3.8
electrical terminals of a reciprocal transducer
terminals across which the open circuit hydrophone voltage , as well as the projector current
are measured
NOTE If the transducer is immersed in water, the electrical terminal with the lowest electrical impedance with
respect to water is called the ’low terminal’. Consequently, the other electrical terminal is called the ‘high terminal’.
3.9
electrical transfer impedance magnitude
magnitude of the electrical transfer impedance of a transducer pair
NOTE The unit is the ohm, Ω.
3.10
electrical transfer impedance of a transducer pair
complex ratio of the open circuit instantaneous voltage U across the hydrophone electrical
H
terminals to the instantaneous current I through the projector, if projector and hydrophone
P
are mounted in a free field with their principal axes in line and directed towards each other
U
H
NOTE 1 Z = (1)
PH
I
P
NOTE 2 The unit is the ohm, Ω.
NOTE 3 The electrical transfer impedance is a complex quantity. It has both real and imaginary components and
can be represented as a magnitude Z times a phase term exp()jϕ , where ϕ is the phase angle between the
PH
real and imaginary impedance components.
NOTE 4 The definition of principal axis is given in 3.23.
NOTE 5 See 7.5.
3.11
equivalent noise pressure
sound pressure applied at the hydrophone to cause a voltage at the hydrophone electrical
terminals, in the absence of noise, that is equal to the noise voltage present at the same
electrical terminals when the sound pressure is absent
NOTE When the equivalent noise pressure cannot be measured, it can be calculated from the equivalent series
resistance [2].
3.12
far field
sound field at a distance from the sound source where the instantaneous values of sound
pressure and particle velocity are substantially in phase
NOTE 1 In the far field, the sound pressure appears to be spherically divergent from a point on or near the
radiating surface. Hence, the pressure produced by the sound source is inversely proportional to the distance from
that source.
NOTE 2 For all practical calibrations, the separation distance between the sound source and the point where the
pressure is measured is sufficiently large that the sound pressure is measured in the far field of the source.
3.13
free field
sound field in a homogeneous and isotropic medium in which the effects of the boundaries are
negligible
60565 © IEC:2006 – 19 –
3.14
free-field sensitivity level
twenty times the logarithm to the base 10 of the ratio of the free-field sensitivity M to a
f
reference sensitivity M
ref
NOTE 1 The unit is the decibel, dB.
-1
NOTE 2 M is equal to 1 V·μPa .
ref
NOTE 3 The use of units differing by a factor 10 to the power of n, (n being a positive or negative whole number)
is allowed in accordance with the general rules for the SI system. In such cases, the value of M is specially
ref
indicated.
3.15
free-field sensitivity of a hydrophone
ratio of the open circuit voltage of the hydrophone to the sound pressure in the undisturbed
free field in the position of the reference centre of the hydrophone if the hydrophone were
removed
-1
NOTE 1 The unit is the volt per pascal, V·Pa .
NOTE 2 The pressure is sinusoidal.
NOTE 3 The term ’response’ is sometimes used instead of ‘sensitivity’.
3.16
hydrophone
transducer that produces electric signals in response to water borne acoustic signals
NOTE Most hydrophones are reversible and satisfy the principle of reciprocity. Consequently, they may operate
as projectors, unless they are permanently equipped with a preamplifier.
3.17
measurement uncertainty
range of values surrounding a measured value that has a specified probability of containing
the correct value for the quantity being measured
NOTE Uncertainties given in this standard will represent expended uncertainty and be identified with 95 %
confidence limits. Components of uncertainty include Type A, those that are evaluated by statistical methods and
Type B, those that are evaluated by other means [3], see Annex D.
3.18
omnidirectionality
transducer response which shows variations smaller than a given limit as the direction is
changed
NOTE Omnidirectionality in a two-dimensional space can occur in one plane only, while in three dimensions a
transducer can be omnidirectional in all planes through the reference centre.
3.19
open-circuit voltage at hydrophone
voltage appearing at the electrical terminals of a hydrophone when no current passes through
the terminals
NOTE 1 The unit is the volt, V.
NOTE 2 Throughout this standard, all voltages, currents and sound pressures are root mean square quantities,
unless otherwise stated.
3.20
pistonphone
apparatus having a rigid piston which can be given a reciprocating motion of a known
frequency and amplitude, so permitting the establishment of a known sound pressure in a
closed chamber of small dimensions
NOTE The largest dimension of the enclosed space should be sufficiently small compared with the wavelength of
the sound in the acoustic medium. See Clause 13.

60565 © IEC:2006 – 21 –
3.21
pressure sensitivity level
twenty times the logarithm to the base 10 of the ratio of the pressure sensitivity M to a
p
reference sensitivity of M
ref
NOTE 1 The unit is the decibel, dB.
NOTE 2 See 3.10, Notes 3 and 4.
3.22
pressure sensitivity of a hydrophone
ratio of the output voltage to the actual sound pressure existing over the region of the
hydrophone designed to receive sound
NOTE 1 See 3.15, NOTES 2 and 3.
-1
NOTE 2 The unit is the volt per pascal, V·Pa
3.23
principal axis
reference direction serving as an origin for angular co-ordinates used in describing the
directional characteristics of the transducer
NOTE 1 Generally, the axis of structural symmetry or the direction of maximum response is chosen for the
principal axis.
NOTE 2 The direction of maximum response may vary with the frequency of the sound.
3.24
reciprocal transducer
linear, passive, reversible transducer
NOTE An example of a non-reciprocal transducer is one that mixes a magnetic field device with an electric field
device.
3.25
reference centre
point on or near a transducer about which its acoustic receiving sensitivity and transmitting
responses are defined
NOTE Generally, the reference centre should be chosen to be at or near the centre of the active portion of the
transducer. This often corresponds to the geometric centre of the transducer. For example, the reference centre for
a transducer utilizing a piezoelectric ceramic spherical shell should be located at the centre of the sphere. The
reference centre of a piezoelectric spherical cap should be located on the axis of symmetry between the centre of
curvature of the cap and the geometric centre of the cap. It should be located closer to the geometric centre of the
cap for smaller cap angles. In the limiting case of a piston transducer, the reference centre should be located at
the centre of the radiating piston face. This choice tends to minimize the measurement uncertainty introduced by
performing calibrations at separation distances less than that required to achieve far-field conditions. (See 3.12).
3.26
reversible transducer
transducer capable of acting as a projector as well as a hydrophone
3.27
transmitting current response level
twenty times the logarithm to the base 10 of the ratio of the transmitting response S to a
reference response S
ref
NOTE 1 The unit is the decibel, dB.
-1
NOTE 2 S is equal to 1 μPa·m·A .
ref
60565 © IEC:2006 – 23 –
3.28
transmitting response to current of a projector
ratio of the sound pressure at a reference distance from the reference centre of a projector (at
a given frequency and in a specified direction) multiplied by the reference distance, to the
current flowing through the electrical terminal.
NOTE 1 Reference distance is 1 m.
-1
NOTE 2 The unit is the pascal metre per ampere, Pa·m·A .
3.29
transmitting response to voltage of a projector
ratio of the sound pressure at a reference distance from the reference centre of a projector (at
a given frequency and in a specified direction), multiplied by the reference distance, to the
voltage across the electrical terminals
NOTE 1 Reference distance is 1 m.
-1
NOTE 2 The unit is the pascal metre per volt, Pa·m·V .
3.30
transmitting voltage response level
twenty times the logarithm to the base 10 of the ratio of the transmitting response S to a
V
reference response S
V, ref
NOTE 1 The unit is the decibel, dB.
-1
NOTE 2 S is equal to 1 μPa·m·V .
Vr, ef
3.31
point transducer
transducer which is omnidirectional in all planes and may have its axis in any direction
3.32
line transducer
transducer which is omnidirectional in one plane and may have its axis in any direction within
that plane
3.33
dipole transducer
transducer which is bidirectional and has two axes in opposite directions
3.34
flat piston transducer
transducer which is unidirectional and has one axis, generally perpendicular to the piston
surface
3.35
unidirectional transducer
transducer which is responsive predominately to sound radiated or incident within a solid
angle not greater than one hemisphere
NOTE See [4] to [7].
3.36
small chamber transmitting response to current of a transducer
ratio of the acoustical pressure (assumed uniform) in a small chamber to the current flowing
through the electrical terminals of a transducer inside the chamber at a given frequency
-1
NOTE The unit is the Pascal per ampere, Pa·A .

60565 © IEC:2006 – 25 –
3.37
projector
electro-acoustic transducer that converts electric signals into sound signals propagating in
water
3.38
vibrating column
apparatus in which a column of water in a vertically placed cylindrical container is set in
vibration, causing a depth-dependent sound pressure in the water column
NOTE 1 The length of the column should be sufficiently small compared with the wavelength of the sound in the
water. The cross-sectional dimensions of the column should be small compared with its length.
NOTE 2 See Clause 14.
4 Symbols and abbreviated terms

Symbol Meaning
Effective sensitive area of transducer
A
a Linear dimension of transducer
Flux density of magnetic field through transducer coil
B
Capacitance
C
Acoustic compliance of chamber walls
C
c
Acoustic compliance of fluid volume in chamber
C
f
Mechanical compliance of chamber
C
mt
Acoustic compliance of chamber
C
t
Acoustic compliance of water volume in chamber
C
w
c
Speed of sound in water
Speed of sound in a fluid
c
f
Mean diameter of cylindrical shell
D
Directivity index
D
i
Distance between projector and hydrophone
d
Piezoelectric modulus
d
Differential area on a sphere
dS
Young’s modulus
E
Frequency
f
g
Acceleration due to gravity
Height of water column
h
Current
I
Current through projector
I
P
Current through transducer
I
T
60565 © IEC:2006 – 27 –
Compensation current through null projector
I
c
Characteristic constant of piezoelectric null transducer
K
Correction factor
K
f
Increasing factor
K
Length of column
l
Width of tank
l
Free-field sensitivity
M
f
Free-field sensitivity of hydrophone
M
H
Pressure sensitivity of microphone
M
M
Free-field sensitivity of transducer
M
T
M Free-field sensitivity of projector
P
Pressure sensitivity
M
p
m
Mass of water inside chamber
p
Sound pressure
Projector
P
Quality factor
Q
Resistance
R
Directivity factor
R
θ
r Radius of transducer shell
Transmitting response to current
S
Transmitting response to current of a hydrophone when used as a projector
S
H
Transmitting response to current of a projector
S
P
Transmitting response to current of a transducer
S
T
Transmitting response to voltage of a projector
S
V
t Thickness of cylindrical shell
Voltage
U
Compensating voltage at null projector
U
c
Open circuit voltage at hydrophone
U
H
Open circuit voltage at microphone
U
M
Transmitting voltage at projector
U
P
Transmitting voltage at transducer
U
T
Open circuit voltage at hydrophone, from a projector as sound source
U
PH
Open circuit voltage at hydrophone, from a transducer as sound source
U
TH
60565 © IEC:2006 – 29 –
Open circuit voltage at transducer, from a projector as sound source
U
PT
Water volume, chamber volume
V
Volume displacement
V
D
Bandwidth
W
x
Displacement of null transducer, vibration amplitude
Impedance
Z
Z A function of transfer impedances having the dimension of impedance
eq
Electrical transfer impedance of projector and hydrophone
Z
PH
Electrical transfer impedance of transducer and hydrophone
Z
TH
Electrical transfer impedance of transducer and projector
Z
PT
γ
Ratio of specific heats
Vertical angle
θ
Wavelength of sound in water
λ
Wavelength of sound in a fluid
λ
f
ν
Rotational velocity
ρ
Density of water
ρ Density of fluid
f
σ
Poisson’s modulus
τ Pulse duration
ϕ
Azimuth angle
ω
Angular frequency =2π f
S Small chamber transmitting response to current of a transducer
T
5 Procedures for calibrations
5.1 Principles
a) Calibration without a standard transducer
1) Reciprocity calibration:
Calibration is based upon the reciprocity principle, in which at least one transducer is
a reciprocal transducer.
2) Physical calibration:
The sound pressure at the hydrophone is calculated from the measurement of physical
parameters such as displacement, velocity or acceleration, medium compliance, etc.
(e.g.: null transducer, pistonphone, vibrating column, etc.).
b) Calibration with a standard transducer:
A hydrophone or a projector is calibrated by comparison with a calibrated standard
transducer.
NOTE In the latter case, the calibrated projector can be used to calibrate another hydrophone.

60565 © IEC:2006 – 31 –
5.2 Field limitations
Calibration shall be carried out by one of the following methods.
a) Free-field calibration in accordance with Clauses 8 or 9.
NOTE The boundaries of the sound field are such that calibration is possible in free field conditions (see
3.13).
b) Small chamber calibration in accordance with Clauses 10, 11, 12 or 13.
NOTE In this case, the sound field is restricted within a small space of which the largest dimension is
sufficiently less than one wavelength of the sound (see 11.4 and 11.5).
5.3 Schematic survey of procedures
Calibration shall be carried out by one of the following methods, depending on the different
principles and on the limitations in the sound field and in the frequency range.
a) Free-field reciprocity calibration in accordance with Clause 8 for calibration without a
standard transducer in a free field, between 1 kHz and 1 MHz.
b) Free-field calibration by comparison in accordance with Clause 9 for calibration with a
standard transducer in a free field, between 10 Hz and 1 MHz.
c) Calibration by hydrostatic excitation in accordance with Clause 10 for physical calibration
without a standard transducer in a small chamber, between 0,01 Hz and 2 Hz.
d) Calibration by piezoelectric compensation in accordance with Clause 11 for physical
calibration without a standard transducer in a small closed chamber, between 1,0 Hz and
5 kHz.
e) Acoustical coupler reciprocity calibration in accordance with Clause 12 for calibration
without a standard transducer in a small closed chamber, between 0,1 Hz and 5 kHz.
f) Calibration with a pistonphone in accordance with Clause 13 for physical calibration with
and without a standard transducer in a small chamber, from a few her
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