IEC 60565-2:2019

Underwater acoustics - Hydrophones - Calibration of hydrophones - Part 2: Procedures for low frequency pressure calibration

IEC 60565-2:2019 specifies the methods for low frequency pressure calibration of hydrophones at frequencies from 0,01 Hz to several kilohertz depending on calibration method.
IEC 60565-2:2019, together with IEC 60565-1, replaces the second edition of IEC 60565 published in 2006. This edition constitutes a technical revision.
IEC 60565-2:2019 includes the following significant technical changes with respect to the previous edition.
1) IEC 60565 has been divided into two parts:
• Part 1: Procedures for free-field calibration;
• Part 2: Procedures for low frequency pressure calibration (this document).
2) A relative calibration method has been added to Clause 8: Calibration by piezoelectric compensation.
3) A relative calibration method has been added to Clause 11: Calibration by vibrating column.
4) Clause 12: Calibration by static pressure transducer, has been added.
5) Annex A: Equivalent circuit of the excitation system for calibration with a vibrating column, has been deleted.
6) Subclauses 9.6, 9.7 and 9.8 have been moved to form a new Annex A: Advanced acoustic coupler calibration methods.

Acoustique sous-marine – Hydrophones – Étalonnage des hydrophones - Partie 2: Procédures pour l'étalonnage à basse pression de fréquence

L’IEC 60565-2:2019 spécifie les méthodes d’étalonnage à basse pression de fréquence des hydrophones à des fréquences comprises entre 0,01 Hz et plusieurs kilohertz selon la méthode d’étalonnage.
L’IEC 60565-2:2019, avec l’IEC 60565-1, remplace la deuxième édition de l’IEC 60565 parue en 2006. Cette édition constitue une révision technique.
L’IEC 60565-2:2019 inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
1) L’IEC 60565 a été divisée en deux parties:
• Partie 1: Procédures pour l’étalonnage en champ libre;
• Partie 2: Procédures pour l’étalonnage à basse pression de fréquence (le présent document).
2) Une méthode d’étalonnage relatif a été ajoutée à l’Article 8: Étalonnage par compensation piézoélectrique.
3) Une méthode d’étalonnage relatif a été ajoutée à l’Article 11: Etalonnage par colonne vibrante.
4) L’Article 12: Etalonnage par transducteur de pression statique a été ajouté.
5) L’Annexe A: Circuit équivalent du système d’excitation pour l’étalonnage avec une colonne vibrante, a été supprimée.
6) Les paragraphes 9.6, 9.7 et 9.8 ont été déplacés pour constituer une nouvelle Annexe A: Méthodes d’étalonnage par coupleur acoustique évolué.

General Information

• Status: Published
• Publication Date: 18-Sep-2019
• ICS: 17.140.50 - Electroacoustics
• Technical Committee: TC 87 - Ultrasonics
• Drafting Committee: WG 15 - TC 87/WG 15
• Current Stage: PPUB - Publication issued
• Start Date: 19-Sep-2019
• Completion Date: 27-Sep-2019

Relations

• Replaces: IEC 60565:2006 - Underwater acoustics - Hydrophones - Calibration in the frequency range 0,01 Hz to 1 MHz
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 60565-2 ®
Edition 1.0 2019-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Underwater acoustics – Hydrophones – Calibration of hydrophones –
Part 2: Procedures for low frequency pressure calibration

Acoustique sous-marine – Hydrophones – Étalonnage des hydrophones –
Partie 2: Procédures pour l’étalonnage à basse pression de fréquence

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IEC 60565-2 ®
Edition 1.0 2019-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Underwater acoustics – Hydrophones – Calibration of hydrophones –

Part 2: Procedures for low frequency pressure calibration

Acoustique sous-marine – Hydrophones – Étalonnage des hydrophones –

Partie 2: Procédures pour l’étalonnage à basse pression de fréquence

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.140.50 ISBN 978-2-8322-7346-3

– 2 – IEC 60565-2:2019 © IEC 2019
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 8
4 Symbols . 12
5 Procedures for calibration . 13
5.1 Principles . 13
5.2 Field limitations . 14
5.3 Schematic survey of procedures . 14
5.4 Reporting of results . 14
5.5 Recalibration periods . 15
5.6 Temperature and pressure considerations for calibration . 15
5.7 Preparation of transducers . 15
6 Electrical measurements. 15
6.1 Signal type . 15
6.2 Earthing . 15
6.3 Measurement of hydrophone output voltage . 15
6.3.1 General . 15
6.3.2 Electrical loading by measuring instrument . 15
6.3.3 Electrical loading by extension cable . 16
6.3.4 Cross-talk and acoustic interference . 16
6.3.5 Integral pre-amplifier . 16
6.4 Measurement of projector current . 16
7 Calibration by hydrostatic excitation . 16
7.1 General . 16
7.2 Principle . 16
7.2.1 Determination of the alternating pressure . 16
7.2.2 Determination of the correction factor . 18
7.2.3 Determination of the equivalent height . 18
7.2.4 Calculation of the pressure sensitivity of hydrophone . 20
7.3 Design of vibration system . 20
7.4 Alternative method for hydrostatic excitation . 20
7.5 Uncertainty . 21
8 Calibration by piezoelectric compensation . 21
8.1 General . 21
8.2 Principle . 21
8.2.1 Determination of the sound pressure . 21
8.2.2 Determination of the characteristic constant . 22
8.2.3 Calculation of the pressure sensitivity of hydrophone . 23
8.3 Design of the calibration chamber . 23
8.3.1 General . 23
8.3.2 Low frequency chamber . 23
8.3.3 High frequency chamber . 23
8.4 Practical limitations of the piezoelectric compensation method . 24
8.5 Relative calibration method . 24

8.6 Uncertainty . 25
9 Calibration by acoustic coupler reciprocity . 25
9.1 General . 25
9.2 Principle . 25
9.2.1 Theory of acoustic coupler reciprocity . 25
9.2.2 Procedures for the reciprocity calibration . 26
9.2.3 Calculation of transfer impedance . 27
9.2.4 Determination of acoustic compliance . 27
9.3 Limitation of acoustic coupler reciprocity . 27
9.3.1 Frequency limit . 27
9.3.2 Hydrophone limit. 28
9.4 Measurement . 28
9.4.1 General . 28
9.4.2 Evidence of interference effects . 28
9.4.3 Reciprocity verification . 28
9.4.4 Linearity verification . 29
9.5 Uncertainty . 29
10 Calibration by pistonphone . 29
10.1 General . 29
10.2 Principle . 29
10.2.1 Determination of the sound pressure . 29
10.2.2 Determination of the compliance of the medium . 30
10.2.3 Calculation of the pressure sensitivity . 30
10.3 Limitations . 30
10.4 Relative calibration . 31
10.4.1 Comparison with a reference transducer . 31
10.4.2 Comparison using air–water pistonphone . 31
10.5 Uncertainty . 32
11 Calibration by vibrating column . 32
11.1 General . 32
11.2 Principle . 32
11.2.1 General . 32
11.2.2 Expression for the pressure . 33
11.2.3 Determination of the sensitivity . 34
11.3 Conditions of measurement . 35
11.3.1 Mechanical . 35
11.3.2 Acoustical . 36
11.4 Relative calibration method . 36
11.5 Uncertainty . 37
12 Calibration by static pressure transducer . 37
12.1 General . 37
12.2 Principle . 38
12.2.1 Theory of static pressure calibration . 38
12.2.2 Determination of the sensitivity of static pressure transducer . 38
12.2.3 Calculation of the pressure sensitivity . 39
12.3 Limitations . 39
12.4 Uncertainty . 39
Annex A (informative) Advanced acoustic coupler calibration methods . 40

– 4 – IEC 60565-2:2019 © IEC 2019
A.1 General . 40
A.2 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 . 41
A.2.1 General . 41
A.2.2 Theory . 42
A.3 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 . 43
A.3.1 General . 43
A.3.2 Theory . 44
A.4 Acoustic-coupler calibration using a coupler, a reciprocal transducer, a
projector, a hydrophone to be calibrated, and a subsidiary body of known
compliance . 45
A.4.1 General . 45
A.4.2 Theory . 45
Annex B (informative) Assessment of uncertainty in the low frequency pressure

calibration of hydrophone . 48
B.1 General . 48
B.2 Type A evaluation of uncertainty . 48
B.3 Type B evaluation of uncertainty . 48
B.4 Reported uncertainty . 48
B.5 Common sources of uncertainty . 49
Bibliography . 51

Figure 1 – Diagram of calibration by hydrostatic excitation . 17
Figure 2 – Schematic drawing of calibration by piezoelectric compensation . 22
Figure 3 – Diagram of the chamber for high frequency . 24
Figure 4 – Reciprocity coupler with three transducers: a projector P, a reciprocal

transducer T, and a hydrophone H to be calibrated . 26
Figure 5 – Comparison calibration using pistonphone with calibrated hydrophone . 32
Figure 6 – Diagram of calibration by vibrating column . 33
Figure 7 – Diagram of calibration by vibrating column using comparison . 37
Figure 8 –Diagram of comparison calibration using static pressure transducer . 38
Figure A.1 – Reference coupler with two transducers: a projector P and a reciprocal
transducer T . 42
Figure A.2 – Auxiliary coupler with three transducers: a projector P, a reciprocal
transducer T and a hydrophone H to be calibrated . 42
Figure A.3 – Auxiliary coupler with four transducers: a projector P, a reciprocal

transducer T, a sound source S and a hydrophone H to be calibrated . 44
Figure A.4 – Schematic drawing of the measuring system . 46

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
UNDERWATER ACOUSTICS – HYDROPHONES –
CALIBRATION OF HYDROPHONES –
Part 2: Procedures for low frequency pressure calibration

FOREWORD
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60565-2 has been prepared by IEC technical committee 87:
Ultrasonics.
This first edition of IEC 60565-2, together with IEC 60565-1, replaces the second edition of
IEC 60565 published in 2006. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition.
1) IEC 60565 has been divided into two parts:
• Part 1: Procedures for free-field calibration;
• Part 2: Procedures for low frequency pressure calibration (this document).
2) A relative calibration method has been added to Clause 8: Calibration by piezoelectric
compensation.
– 6 – IEC 60565-2:2019 © IEC 2019
3) A relative calibration method has been added to Clause 11: Calibration by vibrating
column.
4) Clause 12: Calibration by static pressure transducer, has been added.
5) Annex A: Equivalent circuit of the excitation system for calibration with a vibrating
column, has been deleted.
6) Subclauses 9.6, 9.7 and 9.8 have been moved to form a new Annex A: Advanced acoustic
coupler calibration methods.
The text of this International Standard is based on the following documents:
FDIS Report on voting
87/720/FDIS 87/723/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
NOTE Words in bold in the text are terms defined in Clause 3.
A list of all parts in the IEC 60565 series, published under the general title Underwater
acoustics – Hydrophones – Calibration of hydrophones, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
INTRODUCTION
The purpose of this document is to establish the procedures for low frequency pressure
calibrations of hydrophones in the frequency range from 0,01 Hz to several kilohertz.
To ensure the correctness of the calibrations, the hydrophones to be calibrated are "rigid"
hydrophones with small size compared to the acoustic wavelength, and are not sensitive to
vibration when calibrated.
Principles, procedures, and uncertainties of physical calibrations such as hydrostatic
excitation, piezoelectric compensation, pistonphone, vibrating column, static pressure
transducer, etc., and reciprocity calibrations in acoustic couplers are given in this document.
Calibrations are carried out using one of these methods, depending on the different principles
to be used, and its limitations to the sound field and the frequency range.

– 8 – IEC 60565-2:2019 © IEC 2019
UNDERWATER ACOUSTICS – HYDROPHONES –
CALIBRATION OF HYDROPHONES –
Part 2: Procedures for low frequency pressure calibration

1 Scope
This part of IEC 60565 specifies the methods for low frequency pressure calibration of
hydrophones at frequencies from 0,01 Hz to several kilohertz depending on calibration
method.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements 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 (available at http://www.electropedia.org/)
IEC 60500:2017, Underwater acoustics – Hydrophones – Properties of the hydrophone in the
frequency range 1 Hz to 500 kHz
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-801,
IEC 60500:2017 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
coupler
apparatus comprising a rigid fluid-filled chamber into which transducers and hydrophones
can be inserted whose largest dimension is small compared to the wavelength
Note 1 to entry: In this document, the term small chamber is used interchangeably with coupler.
[SOURCE: IEC 60565:2006 [1] , 3.3, modified – In the definition, "small dimensions" has
been replaced by "whose largest dimension is small compared to the wavelength".]
___________
Numbers in square brackets refer to the Bibliography.

3.2
diffraction factor
ratio of the root-mean-square value of the sound pressure, averaged over the part of the
hydrophone designed to receive an incident plane wave sound pressure from a given
direction to the free-field root-mean-square sound pressure that would exist at the position of
the reference centre of the hydrophone if the hydrophone was removed
Note 1 to entry: Spatial average is undertaken first and then time average.
[SOURCE: IEC 60500:2017, 3.3, modified – In the definition, "the root-mean-square sound
pressure" has been replaced by "the root-mean-square value of the sound pressure,", and
"the position of" has been added after "that would exist at".]
3.3
electrical transfer impedance
Z
PH
quotient of the Fourier transform of the open circuit voltage
ℑ(U (t)) across the hydrophone electrical terminals, to the Fourier transform of the electrical
H
current ℑ(I (t)) through the projector, when projector and hydrophone are mounted in a
P
coupler
ℑ Ut
( ())
H
Z = (1)
PH
ℑ It
( ())
P
Note 1 to entry: The electrical transfer impedance is a complex-valued parameter. The modulus of the
electrical transfer impedance is expressed in ohm, Ω. The phase angle is expressed in degrees, and represents
the phase difference between the hydrophone voltage and the projector current.
Note 2 to entry: Because the electrical transfer 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, are specified.
[SOURCE: IEC 60565:2006 [1], 3.10, modified – In the term, "transducer pair" has been
deleted. The domain "" has been added. In the definition,
"complex ratio of the open circuit instantaneous voltage U " has been replaced by "quotient of
H
the Fourier transform of the open circuit voltage ℑ(U (t))", "the instantaneous current I " has
H P
( )
been replaced by "Fourier transform of the electrical current ℑ I (t) ", and "if projector and
P
hydrophone are mounted in a free field with their principal axes in line and directed towards
each other" has been replaced by "when projector and hydrophone are mounted in a
coupler".]
3.4
hydrophone
electroacoustic transducer that produces electrical voltages in response to water borne
pressure signals
Note 1 to entry: A hydrophone is designed to respond principally to underwater sound pressure.
Note 2 to entry: In general, a hydrophone can also produce a signal in response to non-acoustic pressure
fluctuations (for example, those existing in a turbulent boundary layer during conditions of high water flow).
Note 3 to entry: Hydrophone types include reference hydrophones and measuring hydrophones. Measuring
hydrophones are used in general measurements of sound fields, and reference hydrophones are principally used
for calibration purposes (for example in comparison calibrations with measuring hydrophones).
Note 4 to entry: Hydrophones are principally used as listening devices, but in reciprocity calibration, a
hydrophone is used as reciprocal transducer, not only acting as a hydrophone, but also as a projector (sound
source).
Note 5 to entry: A hydrophone which is integrated with a digital acquisition system is sometimes termed a "digital
hydrophone", but the combination is best considered as a measuring system, not a hydrophone alone.

– 10 – IEC 60565-2:2019 © IEC 2019
Note 6 to entry: If a hydrophone is connected to a charge amplifier, the sensitivity of the hydrophone is
sometimes described in terms of charge sensitivity, which is related to the voltage sensitivity of the hydrophone by
its electrical capacitance.
[SOURCE: IEC 60500:2017, 3.17, modified – In the definition, "electrical signals" has been
replaced by "electrical voltages".]
3.5
pistonphone
apparatus having a rigid piston which can be given a reciprocating motion of a known
frequency and amplitude to establish a known sound pressure in a closed small chamber
[SOURCE: IEC 60565:2006 [1], 3.20, modified – In the definition, "so permitting the
establishment of" has been replaced by "to establish", and "a closed chamber of small
dimensions" by "a closed small chamber".]
3.6
pressure sensitivity
M
p
quotient of the Fourier transform of the hydrophone open-circuit voltage
signal ℑ(U (t)) to the Fourier transform of the acoustic pressure signal ℑ(p(t)) averaged over
H
the hydrophone active element, at a specified frequency
ℑ Ut
( ())
H
M = (2)
p
ℑ pt()
( )
Note 1 to entry: The hydrophone pressure sensitivity is a complex-valued parameter. The modulus of the
pressure sensitivity of a hydrophone is expressed in units of volt per pascal, V/Pa. The phase angle of the
sensitivity is expressed in degrees, and represents the phase difference between the electrical voltage and the
sound pressure.
Note 2 to entry: The term "response" is sometimes used instead of "sensitivity".
Note 3 to entry: The hydrophone active element is the electroacoustic element of the hydrophone which is
sensitive to sound pressure.
[SOURCE: IEC 60500:2017, 3.23, modified – In the definition, "ratio of the root-mean-square
output voltage" has been replaced by "quotient of the Fourier transform of the hydrophone
open-circuit output voltage signal ℑ(U (t))", and "root-mean-square of the sound pressure"
H
has been replaced by "Fourier transform of the sound pressure ℑ(p(t))".The description of the
hydrophone active element has been moved to a Note to entry.]
3.7
pressure sensitivity level
L
M
twenty times the logarithm to the base 10 of the ratio of the modulus of the pressure
sensitivity M to a reference sensitivity of M , in decibels
p
ref
M
p
L =20 log dB
(3)
M 10
M
ref
Note 1 to entry: The value of reference sensitivity is 1 V/μPa.
M
ref
[SOURCE: IEC 60500:2017, 3.24, modified – In the definition, "modulus of the" has been
added before "pressure sensitivity", and "in decibels" has been added after " M ".]
ref
3.8
projector
electro-acoustic transducer that converts electric signals into sound signals propagating in
water
[SOURCE: IEC 60565:2006 [1], 3.37]
3.9
ratio of specific heats
γ
ratio of specific heats under constant pressure and under constant volume
Note 1 to entry: For dry air and temperature 0 °C to 17 °C, γ = 1,40.
3.10
reciprocal transducer
linear, passive, and reversible electroacoustic transducer such that the coupling coefficients
are equal for transduction in either direction
[SOURCE: IEC 60565:2006 [1], 3.24, modified – In the definition, "transducer" has been
replaced by "electroacoustic transducer", and "such that the coupling coefficients are equal
for transduction in either direction" has been added at the end of the definition.]
3.11
signal
specified time-varying electric current, voltage, sound pressure, sound particle displacement,
or other field quantity of interest
[SOURCE: ISO 18405:2017 [2], 3.1.5.8]
3.12
transmitting response to current
S
I,T
quotient of the Fourier transform of the acoustic pressure
signal ℑ(p(t)) to the Fourier transform of the electrical current signal ℑ(𝐼𝐼(t)) through a
transducer T inserted into the coupler at a given frequency
ℑ pt
( ())
S =  (4)
I,T
ℑ It()
( )
Note 1 to entry: Transmitting response to current is expressed in units of pascal per ampere, Pa/A.
Note 2 to entry: Different with the free-field calibration, no distance term is required here.
Note 3 to entry: The acoustic pressure signal is assumed uniform in a coupler.
[SOURCE: IEC 60565:2006 [1], 3.36, modified – In the term, "small chamber transmitting
response to current of a transducer" has been replaced by "transmitting response to
current". The domain "" has been added. In the definition, "a
small chamber" has been replaced by "a coupler", and "flowing through the electrical
terminals of a transducer inside the chamber" by "through a transducer inserted into the
coupler". Also, "current" has been replaced by "Fourier transform of the electrical current
signal ℑ(U (t))", and "ratio of the acoustical pressure (assumed uniform)" has been replaced
H
by "quotient of the Fourier transform of the acoustic pressure signal ℑ(p(t))".]

– 12 – IEC 60565-2:2019 © IEC 2019
3.13
uncertainty
non-negative parameter characterizing the dispersion of the quantity
values being attributed to a measurand, based on the information used
[SOURCE: ISO/IEC Guide 99:2007 [3], 2.26]
3.14
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 to entry: The length of the column is sufficiently small compared with the wavelength of the sound in the
water. The cross-sectional dimension of the column is small compared with its length.
[SOURCE: IEC 60565:2006 [1], 3.38]
3.15
wavenumber
k
reciprocal of the acoustic wavelength multiplied by 2π
k =2π/λ (5)
−1
Note 1 to entry: Wavenumber is expressed in units of per metre, m .
Note 2 to entry: In different branches of physics, the term wavenumber can be considered equal to either 2π/λ or
1/λ, but in the technical field of acoustics, 2π/λ is preferred. This term given in IEC 60050-103:2009, 103-10-12 is
"angular wavenumber".
[SOURCE: IEC 60050-726:1982 [4], 726-05-02, modified – In the definition, "the reciprocal
of the waveguide wavelength or the" and "for a plane wave" have been deleted, and
"acoustic" and "multiplied by 2π" have been added before and after "wavelength",
respectively.]
4 Symbols
C acoustic compliance of chamber
t
C compliance of the medium
M
c speed of sound in water
c speed of sound in a fluid
f
d depth or distance of the hydrophone
d piezoelectric modulus of the shell material
jk
E Young’s modulus
f frequency
g acceleration due to gravity
h displacement of the water surface in the open vessel
H equivalent height
e
ΔH change of the water level
I current through projector
P
I current through transducer
T
I compensation current through null projector
c
K characteristic constant of piezoelectric null transducer

K hydrostatic pressure correction factor
k wavenumber
L length of column or coupler
L pressure sensitivity level of the hydrophone
M
M sensitivity of the hydrophone
H
M pressure sensitivity
p
M sensitivity of the static pressure transducer
T
M sensitivity of the microphone
M
p sound pressure
p static pressure
s
Q mechanical quality factor
r radius of transducer shell
transmitting response to current of a projector in a coupler
S
P
S transmitting response to current of a transducer in a coupler
T
U compensation voltage
C
U open-circuit voltage at hydrophone
H
U open-circuit voltage at microphone
M
U open-circuit voltage at hydrophone with a projector as sound source
PH
U open-circuit voltage at transducer with a projector as sound source
PT
U open-circuit voltage at hydrophone with a transducer as sound source
TH
U open-circuit voltage at a reference hydrophone
R
u volume velocity
V volume of the subsidiary body
b
V total volume
t
ΔV volume change
x vibration amplitude
Z contains all the terms involving transfer impedance
Z acoustic impedance
AI
Z electrical transfer impedance of projector and hydrophone in a coupler
PH
Z electrical transfer impedance of projector and transducer in a coupler
PT
Z electrical transfer impedance of transducer and hydrophone in a coupler
TH
Z electrical transfer impedance of transducer to projector in a coupler
TP
γ ratio of specific heats
ρ density of water
ρ density of fluid
f
σ Poisson’s modulus
ω angular frequency
ω resonance angular frequency
r
5 Procedures for calibration
5.1 Principles
a) Absolute calibration
– 14 – IEC 60565-2:2019 © IEC 2019
Calibration without a reference transducer.
b) Relative calibration
Calibration with a calibrated reference transducer.
5.2 Field limitations
The sound fields of calibrations conducted in accordance with Clauses 7 to 12 shall be
restricted within a small chamber.
5.3 Schematic survey of procedures
Calibration shall be carried out by one of the following methods, depending on the different
principles, with its limitations on the sound field and the frequency range.
a) Calibration by hydrostatic excitation in accordance with Clause 7 is valid in the frequency
range 0,01 Hz to 1 Hz.
b) Calibration by piezoelectric compensation in accordance with Clause 8 is valid in the
frequency range 1,0 Hz to 4 kHz, but with a reference transducer is usually valid in the
frequency range 1,0 Hz to 2 kHz.
c) Calibration by acoustic coupler reciprocity in accordance with Clause 9 is valid in the
frequency range 0,1 Hz to 5 kHz.
d) Calibration by pistonphone in accordance with Clause 10 with or without a reference
transducer is valid in the frequency range from a few hertz to several hundred hertz.
e) Calibration by vibrating column in accordance with Clause 11 with or without a reference
transducer is valid in the frequency range 10 Hz to 2 kHz.
f) Calibration by static pressure transducer in accordance with Clause 12 with a reference
transducer is valid in the frequency range 0,5 Hz to 3,15 kHz.
5.4 Reporting of results
Calibration of pressure sensitivity or pressure sensitivity level is only valid on the date of
calibration and for the environmental conditions which existed during the calibration. When
the calibration result of a hydrophone is reported, the environmental conditions that pertain
to that calibration shall be stated, including all those conditions that may influence the
sensitivity of the device [5] to [9].
Conditions to be reported may include:
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