SIST EN 62127-2:2008/A1:2014

Ultrasonics - Hydrophones - Part 2: Calibration for ultrasonic fields up to 40 MHz

This part of IEC 62127 specifies: absolute hydrophone calibration methods; relative (comparative) hydrophone calibration methods. Recommendations and references to accepted literature are made for the various relative and absolute calibration methods in the frequency range covered by this standard. This standard is applicable to hydrophones used for measurements made in water and in the ultrasonic frequency range up to 40 MHz; hydrophones employing circular piezoelectric sensor elements, designed to measure the pulsed wave and continuous wave ultrasonic fields generated by ultrasonic equipment; hydrophones with or without a hydrophone pre-amplifier.

Ultraschall - Hydrophone - Teil 2: Kalibrierung für Ultraschallfelder bis zu 40 MHz

Ultrasons - Hydrophones - Partie 2: Etalonnage pour les champs ultrasonores jusqu'à 40 Mhz

Ultrazvok - Hidrofoni - 2. del: Kalibracija za ultrazvočna polja do 40 MHz (IEC 62127-2:2007/A1:2013)

General Information

• Status: Published
• Publication Date: 02-Jan-2014
• ICS: 11.040.01 - Medical equipment in general
• ICS: 17.140.50 - Electroacoustics
• Technical Committee: I11 - Imaginarni 11
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 16-Dec-2013
• Due Date: 20-Feb-2014
• Completion Date: 03-Jan-2014
• Ref Project: EN 62127-2:2007/A1:2013 - Ultrasonics - Hydrophones - Part 2: Calibration for ultrasonic fields up to 40 MHz

Relations

• Amends: SIST EN 62127-2:2008 - Ultrasonics - Hydrophones -- Part 2: Calibration for ultrasonic fields up to 40 MHz
• Effective Date: 27-Sep-2011
• Amends: SIST EN 62127-2:2008 - Ultrasonics - Hydrophones -- Part 2: Calibration for ultrasonic fields up to 40 MHz
• Effective Date: 28-Jan-2023

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 62127-2:2008/A1:2014
01-februar-2014
8OWUD]YRN+LGURIRQLGHO.DOLEUDFLMD]DXOWUD]YRþQDSROMDGR0+],(&
$
Ultrasonics - Hydrophones - Part 2: Calibration for ultrasonic fields up to 40 MHz
Ultraschall - Hydrophone - Teil 2: Kalibrierung für Ultraschallfelder bis zu 40 MHz
Ultrasons - Hydrophones - Partie 2: Etalonnage pour les champs ultrasonores jusqu'à 40
Mhz
Ta slovenski standard je istoveten z: EN 62127-2:2007/A1:2013
ICS:
11.040.01 Medicinska oprema na Medical equipment in general
splošno
17.140.50 Elektroakustika Electroacoustics
SIST EN 62127-2:2008/A1:2014 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------

SIST EN 62127-2:2008/A1:2014

---------------------- Page: 2 ----------------------

SIST EN 62127-2:2008/A1:2014

EUROPEAN STANDARD
EN 62127-2/A1

NORME EUROPÉENNE
March 2013
EUROPÄISCHE NORM

ICS 11.040.50


English version


Ultrasonics - Hydrophones -
Part 2: Calibration for ultrasonic fields up to 40 MHz
(IEC 62127-2:2007/A1:2013)


Ultrasons - Hydrophones -  Ultraschall - Hydrophone -
Partie 2: Etalonnage des champs Teil 2: Kalibrierung für Ultraschallfelder
ultrasoniques jusqu'à 40 Mhz bis zu 40 MHz
(CEI 62127-2:2007/A1:2013) (IEC 62127-2:2007/A1:2013)





This amendment A1 modifies the European Standard EN 62127-2:2007; it was approved by CENELEC on 2013-
03-15. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate
the conditions for giving this amendment 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 CEN-CENELEC Management Centre or to any CENELEC member.

This amendment 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
CEN-CENELEC Management Centre has the same status as the official versions.

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

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

Management Centre: Avenue Marnix 17, B - 1000 Brussels


© 2013 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 62127-2:2007/A1:2013 E

---------------------- Page: 3 ----------------------

SIST EN 62127-2:2008/A1:2014
EN 62127-2:2007/A1:2013 - 2 -
Foreword
The text of document 87/519/FDIS, future amendment 1 to edition 1 of IEC 62127-2, prepared by
IEC/TC 87 "Ultrasonics" was submitted to the IEC-CENELEC parallel vote and approved by
CENELEC as EN 62127-2:2007/A1:2013.
The following dates are fixed:
(dop) 2013-12-15
• latest date by which the document has
to be implemented at national level by
publication of an identical national
standard or by endorsement
(dow) 2016-03-15
• latest date by which the national
standards conflicting with the
document have to be withdrawn

Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such
patent rights.

Endorsement notice
The text of the International Standard IEC 62127-2:2007/A1:2013 was approved by CENELEC as a
European Standard without any modification.

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SIST EN 62127-2:2008/A1:2014
- 3 - EN 62127-2:2007/A1:2013
Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications

Modification in Annex ZA of EN 62127-2:2007:

Publication Year Title EN/HD Year

In Annex ZA of EN 62127-2:2007, replace the references to IEC 60050-801:1994,
IEC 61161:2006, IEC 61828:2001 and IEC 62127-1 by the following new references:
IEC 60050-801 - International Electrotechnical Vocabulary - -
(IEV) -
Chapter 801: Acoustics and electroacoustics


IEC 61161 - Ultrasonics - Power measurement - EN 61161 -
Radiation force balances and performance
requirements


IEC 61828 - Ultrasonics - Focusing transducers - EN 61828 -
Definitions and measurement methods for
the transmitted fields


IEC 62127-1 2007 Ultrasonics - Hydrophones - EN 62127-1 2007
+ corr. August 2008 Part 1: Measurement and characterization of + A1 2013
+ A1 2013 medical ultrasonic fields up to 40 MHz

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SIST EN 62127-2:2008/A1:2014

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SIST EN 62127-2:2008/A1:2014



IEC 62127-2

®


Edition 1.0 2013-02




INTERNATIONAL



STANDARD




NORME



INTERNATIONALE




AMENDMENT 1

AMENDEMENT 1





Ultrasonics – Hydrophones –

Part 2: Calibration for ultrasonic fields up to 40 MHz




Ultrasons – Hydrophones –

Partie 2: Etalonnage des champs ultrasoniques jusqu’à 40 MHz
















INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE

PRICE CODE
INTERNATIONALE

CODE PRIX T


ICS 11.040.50 ISBN 978-2-83220-616-4



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

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

---------------------- Page: 7 ----------------------

SIST EN 62127-2:2008/A1:2014
– 2 – 62127-2 Amend.1 © IEC:2013
FOREWORD
This amendment has been prepared by IEC technical committee 87: Ultrasonics.
The text of this amendment is based on the following documents:
FDIS Report on voting
87/519/FDIS 87/527/RVD

Full information on the voting for the approval of this amendment can be found in the report
on voting indicated in the above table.
The committee has decided that the contents of this amendment and the base publication will
remain unchanged until the stability 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.
_____________
Replace throughout the document:
“non-linear” by “nonlinear”,
This replacement applies to the English text only.
Replace throughout the document:
“non-linearity” by “nonlinearity”
This replacement applies to the English text only.
Replace throughout the document:
“non-linearities” by “nonlinearities”
This replacement applies to the English text only.
Replace throughout the document:
“non-linearly” by “nonlinearly”
This replacement applies to the English text only.
2 Normative references
Replace the references to IEC 60050-801:1994, IEC 61161:2006, IEC 61828:2006 and
IEC 62127-1, by the following new references:
IEC 60050-801, International Electrotechnical Vocabulary – Chapter 801: Acoustics and
electroacoustics
IEC 61161, Ultrasonics – Power measurement – Radiation force balances and performance
requirements
IEC 61828, Ultrasonics – Focusing transducers – Definitions and measurement methods for
the transmitted fields

---------------------- Page: 8 ----------------------

SIST EN 62127-2:2008/A1:2014
62127-2 Amend.1 © IEC:2013 – 3 –
IEC 62127-1:2007, Ultrasonics - Hydrophones - Part 1: Measurement and characterization of
medical ultrasonic fields up to 40 MHz
Amendment 1:2013
3 Terms, definitions and symbols
3.9
effective radius of a non-focused ultrasonic transducer
Replace the term by effective radius of a non-focusing ultrasonic transducer

Replace the term in the Note by effective radius of a non-focusing ultrasonic transducer

3.14
external transducer aperture
Replace, in Note 1, "Figure 2" by "Figure 1".

3.15
far field
Replace the existing text of the definition (not including Note 1 and Note 2) by the following:
region of the field where z>z aligned along the beam axis for planar non-focusing transducers.
T
Add the following new Note 3:
NOTE 3 If the shape of the transducer aperture produces several transition distances, the one furthest from the
transducer shall be used.
[SOURCE: IEC 62127-1:2007/Amendment 1:2013, definition 3.28]

3.23
instantaneous intensity
Replace the existing text of Note 1 by the following:
NOTE 1 Instantaneous intensity is the product of instantaneous acoustic pressure and particle velocity. It is
difficult to measure intensity in the ultrasound frequency range. For the measurement purposes referred to in this
International Standard and under conditions of sufficient distance from the external transducer aperture (at least
one transducer diameter, or an equivalent transducer dimension in the case of a non-circular transducer) the
instantaneous intensity can be approximated by the derived instantaneous intensity.
Replace the existing text of Note 2 by the following:
2
Instantaneous intensity is expressed in watts per square metre (W/m )

Add the following new definitions:
3.26
derived instantaneous intensity
approximation of the instantaneous intensity
For the measurement purposes referred to in this International Standard, and under
conditions of sufficient distance from the transducer (at least one transducer diameter, or an
equivalent transducer dimension in the case of a non-circular transducer) the derived
instantaneous intensity is determined by

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SIST EN 62127-2:2008/A1:2014
– 4 – 62127-2 Amend.1 © IEC:2013
2
p(t)
  (1)
I(t) =
ρ c
where:
p(t) is the instantaneous acoustic pressure;
ρ is the density of the medium;
c is the speed of sound in the medium.
NOTE 1 For measurement purposes referred to in this International Standard, the derived instantaneous
intensity is an approximation of the instantaneous intensity.
NOTE 2 Increased uncertainty should be taken into account for measurements very close to the transducer.
2
NOTE 3 Derived instantaneous intensity is expressed in watts per square metre (W/m ).
[SOURCE: IEC 62127-1:2007/ Amendment 1:2013, definition 3.78]

3.27
effective wavelength
λ
longitudinal speed of sound in the propagation medium divided by the arithmetic-mean
working frequency
NOTE Effective wavelength is expressed in metres (m).
[SOURCE:IEC 61828:2001, definition 4.2.24].

3.28
longitudinal plane
plane defined by the beam axis and a specified orthogonal axis
NOTE See Figure 1 in IEC 62127-1.
[SOURCE: IEC 62127-1:2007, definition 3.35].

3.29
source aperture plane
closest possible measurement plane to the external transducer aperture, that is
perpendicular to the beam axis
[SOURCE:IEC 61828:2001, definition 4.2.67].

3.30
source aperture width
L
SA
in a specified longitudinal plane, the greatest –20 dB beamwidth along the line of
intersection between the designated longitudinal plane and the source aperture plane
NOTE 1 See Figure 2 in IEC 61828 2001.
NOTE 2 Source aperture width is expressed in metres (m).
[SOURCE:IEC 61828, definition 4.2.68].

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SIST EN 62127-2:2008/A1:2014
62127-2 Amend.1 © IEC:2013 – 5 –
3.31
transducer aperture width
L
TA
full width of the transducer aperture along a specified axis orthogonal to the beam axis of the
unsteered beam at the centre of the transducer
NOTE 1 See Figure 4 in IEC 62127-1 .
NOTE 2 Transducer aperture width is expressed in metres (m).
[SOURCE:IEC 62127-1:2007/ Amendment 1:2013, definition 3.87].

3.32
transition distance
z
T
for a given longitudinal plane, the transition distance is defined based on the transducer
design (when known) or from measurement:
a) from design: the transition distance is the equivalent area of the ultrasonic
transducer aperture width divided by π times the effective wavelength, λ;
b) for measurements, the transition distance is the equivalent area of the source
aperture width divided by π times the effective wavelength.
NOTE 1 Using method a), an unapodized ultrasonic transducer with circular symmetry about the beam axis, the
2 2
equivalent area is πa , where a is the radius. Therefore the transition distance is z = a /λ. For the first example
T
2
of a square ultrasonic transducer, the equivalent area is (L ) , where L is the transducer aperture width in
TA TA
the longitudinal plane. Therefore, the transition distance for both orthogonal longitudinal planes containing the
2
sides or transducer aperture widths, is z = (L ) /(πλ). For the second example, for a rectangular ultrasonic
T TA
transducer with transducer aperture widths L and L , the equivalent area for the first linear transducer
TA1 TA2
aperture width for the purpose of calculating the transition distance for the associated longitudinal plane is
2
(L ) , where L is the transducer aperture width in this longitudinal plane. Therefore, the transition
TA1 TA1
2
distance for this plane is z = (L ) /(πλ). For the orthogonal longitudinal plane that contains the other
T1 TA1
transducer aperture width, L , the equivalent area for the other for the purpose of calculating the transition
TA2
2
distance for the associated longitudinal plane is (L ) , where L is the transducer aperture width in this
TA2 TA2
2
longitudinal plane. Therefore, the transition distance for this plane is z = (L ) /(πλ).
T2 TA2
NOTE 2 Using method b) for measurements in a longitudinal plane, the source aperture width, L , in the same
SA
2
plane is used in z = (L ) /(πλ).
T SA
NOTE 3 Transition distance is expressed in metre (m).
[SOURCE IEC 61828:2001, definition 4.2.75, modified: There is significant difference in the
layout of the definition]

4 List of symbols
Replace:
a effective radius of a non-focused ultrasonic transducer
t
by
a effective radius of a non-focusing ultrasonic transducer
t
Add the following new symbols:
L transducer aperture width
TA
L source aperture width
SA
z transition distance
T

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SIST EN 62127-2:2008/A1:2014
– 6 – 62127-2 Amend.1 © IEC:2013
5 Overview of calibration procedures
5.3 Reporting of results
Add, after the sixth bullet point ("in situations where the mounting arrangement…") the
following new Note 5 and renumber existing Notes 5 and 6 accordingly:
NOTE 5 Care should be taken in designing the hydrophone mount at low frequencies (below 200 kHz) where the
acoustic wavelengths are sufficiently large that the use of long-bursts may lead to the direct acoustic signal being
contaminated by reflections from the mount. The importance of the effect may be investigated through varying the
burst length and observing the influence of reflections on the hydrophone signal. Acoustic absorbers may be
useful in suppressing these reflections. Hydrophone sensitivity may also be affected by the way the hydrophone
is clamped, and again this may be evaluated by systematically investigating the various configurations.

6 Generic requirements of a hydrophone calibration system
6.1 Mechanical positioning
6.1.2 Accuracy of the axial hydrophone position
Add, after Note 1, the following new Note 2 and renumber existing Notes 3 and 4 accordingly.:
NOTE 2 The distance of the hydrophone from the transducer can be estimated from a knowledge of the time
elapsed between the electrical excitation applied to the transducer and the arrival time of the acoustic wave at the
hydrophone, through a knowledge of the speed of sound in water at that particular temperature.
6.1.3 Accuracy of the lateral hydrophone position
Replace the existing first sentence of the subclause by the following:
The variation of the hydrophone output voltage should be checked when the lateral
hydrophone position is changed to ensure that the signal is maximized.
6.3 Hydrophone size
Number the existing note as Note 1 and add the following new Note 2:
NOTE 2 Guidance in assessing the influence of spatial-averaging on calibrations may be found in IEC 62127-1
and Annex J.
6.4 Measurement vessel and water properties
Replace the existing first paragraph with the following:
The test tank shall be sufficiently large to allow the establishment of free field conditions at
the lowest frequency of interest. It should also be large enough to allow the transducer-
hydrophone separation to be varied to a degree consistent with the requirements of the
applied calibration technique.

7.2 Earthing
Add the following new note:
NOTE This condition may be relaxed when a tone burst is used such that the acoustic signal arrives at the
hydrophone after the electrical excitation is completed.

---------------------- Page: 12 ----------------------

SIST EN 62127-2:2008/A1:2014
62127-2 Amend.1 © IEC:2013 – 7 –
7.3.5 Cross-talk (radio-frequency rf pick-up) and acoustic interference
Add, after the second paragraph, the following new Note 1 and renumber the existing note as
Note 2:
NOTE 1 In these situations, cross-talk will contaminate the direct acoustic signal. The effect can be evaluated
through varying the tone-burst length and observing any consequent changes in the hydrophone waveform using
an oscilloscope.
8.2 Wetting
Replace the existing text by the following:
The user shall ensure that the hydrophone is wetted properly and that all air bubbles are
removed from the hydrophone and faces taking active part in the calibration. After
measurements are completed, the active faces shall again be inspected, and the
measurements shall be discarded if any air bubbles are found.

9 Free field reciprocity calibration
9.4 Two-transducer reciprocity calibration method
Add the following new note:
NOTE Within this standard, information on this calibration technique is also presented in Annex K and is provided
for information purposes.
9.4.2 Procedure
Replace the existing text by the following:
In the configuration, the auxiliary transducer is calibrated and then the reflector is removed to
calibrate the hydrophone.
When calibrating the auxiliary transducer, rotate the reflector through an angle of
approximately 10° about an axis parallel to its surface and perpendicular to the line joining the
acoustic centres of the hydrophones and auxiliary transducer.
NOTE This method has been improved through a coaxial configuration of the hydrophone and the auxiliary
transducer with the reflector in the middle of them. This can avoid the error caused by rotation of the reflector and
make the alignment of the hydrophone and the auxiliary transducer easier, and the error can be reduced to about
0,5 dB.

10.5.3 Measurement conditions
Replace, in the Note, the terms "effective radius of a non-focused ultrasonic transducer"
by "effective radius of a non-focusing ultrasonic transducer".

12.5.1 Measurement (Type 1): determination of the directional response of a
hydrophone
Replace the existing Note 4 by the following:
NOTE 4 The effective hydrophone radius is important for the assessment of spatial averaging effects (see
Annex J and IEC 62127-1). The effective hydrophone radius might be frequency dependent for some types of

---------------------- Page: 13 ----------------------

SIST EN 62127-2:2008/A1:2014
– 8 – 62127-2 Amend.1 © IEC:2013
hydrophone and for any particular hydrophone might be dependent on the chosen axis. Further information on
the effective hydrophone radius may be found in IEC 62127-3.

Annex D – Absolute calibration of hydrophones using the planar scanning
technique
D.3.6 Noise
Replace, in the first sentence of the first paragraph, the term "beam axis centre" by "beam
axis".

Annex E – Properties of water
Add, at the end of the existing text, the following new sentence:
Procedures to prepare degassed water are given in IEC/TS 62781.

Annex F – The absolute calibration of hydrophones by optical interferometry up
to 40 MHz
F.2.3.1.4 Multipass effects in the foil
Replace, in the last sentence of the subclause "transmission factor, T," by "transmission
factor, TF,".

Annex G – Waveform concepts
G.5.2 Influence of edge-waves
Replace, in the first sentence, "transducer, x," by "transducer, z,".

Annex I – Determination of the phase response of hydrophones
I.1 Overview
Add, at the end of the penultimate sentence in the first paragraph, the following bibliographic
references [76], [77], [78]

Add, after Annex J, the following new annex:

---------------------- Page: 14 ----------------------

SIST EN 62127-2:2008/A1:2014
62127-2 Amend.1 © IEC:2013 – 9 –
Annex K
(informative)

Two-transducer reciprocity calibration method

K.1 Overview
A number of techniques are described in technical literature addressing the absolute
determination of acoustic field parameters. The absolute determination of acoustic pressure
amplitude at a single point within an acoustic field may be accomplished through the use of a
calibrated hydrophone. The choice of technique used to calibrate the hydrophone may be
made in terms of the resultant accuracy and convenience of applying the method. For
example, whilst the optical interferometry described in Annex F represents a direct primary-
standard method where the lowest calibration uncertainties can be achieved, it is highly
demanding in terms of the facility requirements and it may be difficult to establish. Of the
other hydrophone calibration methods, the two which have found most favor are reciprocity
and planar scanning (see Annex D), the latter involving the measurement of total power in
combination with the acoustic beam profile measured using a hydrophone.
The reciprocity technique involves measurement of the effect of the field on a second
transducer (for the two-transducer method), or even the transducer generating the acoustic
field (for the self-reciprocity method). The technique requires a relatively simple experimental
facility compared to the two alternative methods: optical interferometry and planar scanning,
and does not involve complex measurement procedures. It can therefore be established in
any laboratory equipped for routine ultrasonic measurements. All of the measurements
involved are electrical and the technique therefore can be made absolute, if indirect, as it
does not involve the realization of the acoustic pascal. Nevertheless, electrical and acoustical
corrections must be applied to the data, and the analysis of the results is rather complicated.
The now obsolete standard, IEC 60866, 1987, described detailed procedures to be followed in
order to perform reciprocity calibration. For the reasons described above, it is considered
valuable to include a virtual copy of the IEC 60866 descriptions within the present standard.
K.2 Additional terms, definitions and symbols
For the purpose of this annex, the following terms and definitions apply.
K.2.1
reversible transducer
transducer capable of acting as a projector as well as a hydrophone
[SOURCE: IEC 60565:2006, definition 3.26]
K.2.2
reciprocal transducer
linear, passive and reversible transducer
[SOURCE: IEC 60565:2006, definition 3.24]
K.2.3
open-circuit voltage at hydrophone
U
voltage appearing at the electrical terminals of a hydrophone when no current passes
through the terminals

---------------------- Page: 15 ----------------------

SIST EN 62127-2:2008/A1:2014
– 10 – 62127-2 Amend.1 © IEC:2013
NOTE Open-circuit voltage at hydrophone is expressed in volt (V).
[SOURCE:IEC 60565:2006, definition 3.19]
K.2.4
free-field sensitivity of a hydrophone
M
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
NOTE 1 The pressure is sinusoidal.
NOTE 2 The term ‘response’ is sometimes used instead of ‘sensitivity’.
NOTE 3 Free-field sensitivity of a hydrophone is expressed in volt per pascal (V/Pa).
[SOURCE: IEC 60565:2006, definition 3.15 ]
K.2.5
transmitting response to current of a projector
S
at a given frequency, the ratio of the acoustic pressure in the sound wave, at a point to be
specified, in the absence of interference effects, to the current flowing through the electrical
terminals of a projector
NOTE Transmitting response to current of a projector is expressed in pascal per ampere (Pa/A).
K.2.6
reciprocity coefficient
J
for any system in which a reciprocal transducer acts as a projector and receiver, the ratio of
the free-field voltage sensitivity of the transducer, M, to its transmitting response to current, S;
where the transmitted sound waves approximate plane waves, the reciprocity coefficient
approaches 2A/ρc and is called the plane wave reciprocity coefficient
NOTE 1 The plane wave reciprocity coefficient applies to plane wave propagation, as realized in the far field of a
transducer, but pure far field conditions are not used in the procedure described in K.5.6. To cope with this, a
correction factor is described in K.4.4 which includes an allowance for deviations from plane wave conditions.
2
NOTE 2 Reciprocity coefficient is expressed in watt per squared pascal (W/Pa )
K.2.7
end-of-cable leakage resistance
R
L
the ratio of the voltage across the electrical terminals at the end of the hydrophone cable to
the direct current flowing through these terminals
NOTE 1 The value of the voltage used during the determination of the R should be stated.
L
NOTE 2 End-of-cable leakage resistance is expressed in ohm (Ω)
K.2.8
mechanical Q of hydrophone element
the ratio of the resonance frequency to the bandwidth between the two frequencies at which
the motional impedance of the hydrophone is 1/ 2 times that at resonance
K.3 List of symbols used in this annex
A Effective area of auxiliary transducer
1
a Effective radius of the hydrophone

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SIST EN 62127-2:2008/A1:2014
62127-2 Amend.1 © IEC:2013 – 11 –
a Effective radius of auxiliary transducer
1
a Factor by which the reference voltage U must be reduced to make it equal to
u ref
voltage U
a Factor by which the reference voltage U must be reduced to make it equal to
u1 ref
voltage U
1
a Factor by which the reference voltage U must be reduced in order to drive a
I1 ref
current I through the impedance R
1 0
c Speed of sound in a medium (usually water)
d Distance between hydrophone and reflector
d Distance between auxiliary transducer and reflector
1
G Correction factor for diffraction loss with auxiliary transducer alone
1
G Correction factor for diffraction loss with auxiliary transducer and hydrophone
2
G Correction factor combining G and G , applicable only under certain measurement
c 1 2
conditions
I Current through auxiliary transducer
1
I Current through short circuit introduced in place of the auxiliary transducer
k
J Reciprocity coefficient
J { = 2 A/ρc } Reciprocity coefficient for plane waves
p
k Correction to open-circuit voltage for the auxiliary transducer
u1
k Correction to open-circuit voltage at a hydrophone
u
M Free-field sensitivity of a hydrophone
*
M Apparent free-field sensitivity of a hydrophone, assuming ideal plane wave
measurement conditions
N Near field distance
p Sound pressure
p Sound pressure in plane wave omitted by auxiliary transducer
1
R Impedance of standard load equal to the characteristic impedance of the precision
0
attenuator
R End-of-cable leakage resistance of hydrophone
L
r Amplitude reflection coefficient for the reflector/water interface
2
s { = (d + d) λ/a } Normalized distance from auxiliary transducer to hydrophone
1 1
S Transmitting response to current of a projector
S Transmitting response to current of auxiliary transducer
1
*
S Apparent transmitting response to current of auxiliary transducer, assuming ideal
1
plane wave measurement conditions
U Open-circuit voltage at a hydrophone
U Open-circuit voltage for auxiliary transducer
1
U Reference voltage
ref
v Velocity of the radiating surface of the transducer
z Distance along the acoustic axis from the transducer
α Amplitude attenuation coefficient of plane waves in a medium (usually water)
λ Ultrasonic wavelength
ρ (mass) Density of the measurement liquid (water)

---------------------- Page: 17 ----------------------

SIST EN 62127-2:2008/A1:2014
– 12 – 62127-2 Amend.1 © IEC:2013
K.4 Principle of the two-transducer reciprocity method
K.4.1 General
The recommended calibration procedure is based on the principles presented in K.4.2 to
K.4.4.
K.4.2 Transmitting current response by self-reciprocity
A plane, reciprocal transducer (parameters relating to which will be identified by the suffix 1)
is first calibrated by the self-reciprocity method (see K.9). Its apparent transmitting current
∗
response assuming ideal plane wave measurement conditions, S , is determined by
1
measuring the current, I , and the received signal voltage, U , by means of the following
1 1
relationship (Equation K.20):
1/2
 
p U
∗
1 1
 
S = = (K.1)
1
 
I I J
1 1 p
 
and
2 A
1
J = (K.2)
p
ρc
where:
...