Amendment 1 - Ultrasonics - Hydrophones - Part 2: Calibration for ultrasonic fields up to 40 MHz

Amendement 1 - Ultrasons - Hydrophones - Partie 2: Etalonnage des champs ultrasoniques jusqu'à 40 MHz

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Status
Published
Publication Date
07-Feb-2013
Technical Committee
Current Stage
PPUB - Publication issued
Start Date
08-Feb-2013
Completion Date
08-Feb-2013
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IEC 62127-2:2007/AMD1:2013 - Amendment 1 - Ultrasonics - Hydrophones - Part 2: Calibration for ultrasonic fields up to 40 MHz
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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
IEC 62127-2:2007/A1:2013
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
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: 3 ----------------------
– 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: 4 ----------------------
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.

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:
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
---------------------- Page: 5 ----------------------
– 4 – 62127-2 Amend.1 © IEC:2013
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.

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

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

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].
---------------------- Page: 6 ----------------------
62127-2 Amend.1 © IEC:2013 – 5 –
3.31
transducer aperture width

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

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

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

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

(L ) , where L is the transducer aperture width in this longitudinal plane. Therefore, the transition

TA1 TA1

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

distance for the associated longitudinal plane is (L ) , where L is the transducer aperture width in this

TA2 TA2

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

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
a effective radius of a non-focusing ultrasonic transducer
Add the following new symbols:
L transducer aperture width
L source aperture width
z transition distance
---------------------- Page: 7 ----------------------
– 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: 8 ----------------------
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: 9 ----------------------
– 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: 10 ----------------------
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

voltage appearing at the electrical terminals of a hydrophone when no current passes

through the terminals
---------------------- Page: 11 ----------------------
– 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

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

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

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.

NOTE 2 Reciprocity coefficient is expressed in watt per squared pascal (W/Pa )
K.2.7
end-of-cable leakage resistance

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.

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
a Effective radius of the hydrophone
---------------------- Page: 12 ----------------------
62127-2 Amend.1 © IEC:2013 – 11 –
a Effective radius of auxiliary transducer
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
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
G Correction factor for diffraction loss with auxiliary transducer alone

G Correction factor for diffraction loss with auxiliary transducer and hydrophone

G Correction factor combining G and G , applicable only under certain measurement

c 1 2
conditions
I Current through auxiliary transducer
I Current through short circuit introduced in place of the auxiliary transducer
J Reciprocity coefficient
J { = 2 A/ρc } Reciprocity coefficient for plane waves
k Correction to open-circuit voltage for the auxiliary transducer
k Correction to open-circuit voltage at a hydrophone
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

R Impedance of standard load equal to the characteristic impedance of the precision

attenuator
R End-of-cable leakage resistance of hydrophone
r Amplitude reflection coefficient for the reflector/water interface
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

S Apparent transmitting response to current of auxiliary transducer, assuming ideal

plane wave measurement conditions
U Open-circuit voltage at a hydrophone
U Open-circuit voltage for auxiliary transducer
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: 13 ----------------------
– 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

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)
 
I I J
1 1 p
 
and
2 A
J = (K.2)
where:
is the acoustic pressure in the plane wave emitted by transducer 1;
J is the reciprocity coefficient for plane waves;
is the effective area of the surface of transducer 1;
ρ is the density of the propagation medium (water);
c is the speed of sound in the propagation medium.

The acoustic pressure in the plane wave field transmitted by transducer 1 is then known as a

function of the current.
K.4.3 Free-field voltage sensitivity by substitution

The hydrophone to be calibrated is immersed in the known sound field generated by

transducer 1, and its output open-circuit voltage U determined. The apparent free-field

voltage sensitivity, assuming ideal plane wave measurement conditions, M , is then given by:

1 2
 I J 
U U
1 p
 
M = = (K.3)
 
p I U
1 1 1
 
K.4.4 Correction for non-plane wave conditions
It is not generally possible to realize either plane (or sphe
...

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