SIST EN ISO 5577:2026
(Main)Non-destructive testing - Ultrasonic testing - Vocabulary (ISO 5577:2025)
Non-destructive testing - Ultrasonic testing - Vocabulary (ISO 5577:2025)
This document defines the terms used in ultrasonic non-destructive testing and forms a common basis for standards and general use.
This document does not cover specific terms used in ultrasonic testing with arrays.
NOTE Terms used in ultrasonic testing with arrays are defined in ISO 23243.
Zerstörungsfreie Prüfung - Ultraschallprüfung - Begriffe (ISO 5577:2025)
Dieses Dokument legt die Begriffe fest, die bei der zerstörungsfreien Ultraschallprüfung verwendet werden, und bildet somit eine gemeinsame Grundlage für Normen und den allgemeinen Gebrauch.
Dieses Dokument behandelt keine spezifischen Begriffe, die bei der Ultraschallprüfung mit Arrays verwendet werden.
ANMERKUNG Die bei der Ultraschallprüfung mit Arrays verwendeten Begriffe sind in ISO 23243 festgelegt.
Essais non destructifs - Contrôle par ultrasons - Vocabulaire (ISO 5577:2025)
Le présent document définit les termes utilisés pour le contrôle non destructif par ultrasons et constitue une base commune pour les normes et l’usage général.
Le présent document n’inclut pas les termes spécifiques utilisés pour le contrôle à l’aide de réseaux ultrasonores.
NOTE Les termes utilisés pour le contrôle à l’aide de réseaux ultrasonores sont définis dans l’ISO 23243.
Neporušitvene preiskave - Preskušanje z ultrazvokom - Slovar (ISO 5577:2025)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
oSIST prEN ISO 5577:2024
01-november-2024
Neporušitvene preiskave - Preskušanje z ultrazvokom - Slovar (ISO/DIS 5577:2024)
Non-destructive testing - Ultrasonic testing - Vocabulary (ISO/DIS 5577:2024)
Zerstörungsfreie Prüfung - Ultraschallprüfung - Begriffe (ISO/DIS 5577:2024)
Essais non destructifs - Contrôle par ultrasons - Vocabulaire (ISO/DIS 5577:2024)
Ta slovenski standard je istoveten z: prEN ISO 5577
ICS:
01.040.19 Preskušanje (Slovarji) Testing (Vocabularies)
19.100 Neporušitveno preskušanje Non-destructive testing
oSIST prEN ISO 5577:2024 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
oSIST prEN ISO 5577:2024
oSIST prEN ISO 5577:2024
DRAFT
International
Standard
ISO/DIS 5577
ISO/TC 135/SC 3
Non-destructive testing —
Secretariat: DIN
Ultrasonic testing — Vocabulary
Voting begins on:
Essais non destructifs — Contrôle par ultrasons — Vocabulaire
2024-09-05
Voting terminates on:
ICS: 19.100; 01.040.19
2024-11-28
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Reference number
ISO/DIS 5577:2024(en)
oSIST prEN ISO 5577:2024
DRAFT
ISO/DIS 5577:2024(en)
International
Standard
ISO/DIS 5577
ISO/TC 135/SC 3
Non-destructive testing —
Secretariat: DIN
Ultrasonic testing — Vocabulary
Voting begins on:
Essais non destructifs — Contrôle par ultrasons — Vocabulaire
ICS: 19.100; 01.040.19 Voting terminates on:
THIS DOCUMENT IS A DRAFT CIRCULATED
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Published in Switzerland Reference number
ISO/DIS 5577:2024(en)
ii
oSIST prEN ISO 5577:2024
ISO/DIS 5577:2024(en)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Terms and definitions related to frequencies, waves and pulses . 1
4.1 Frequencies .1
4.2 Waves and pulses .3
4.3 Types of ultrasonic waves .5
5 Terms related to sound . 6
5.1 Sound generation and reception .6
5.2 Sound propagation .7
5.3 Loss of sound pressure .10
5.4 Ultrasonic waves at interfaces .10
6 Terms related to test equipment . 14
6.1 Instrument .14
6.2 Probes .16
6.3 Combined test equipment . 23
6.4 Instrument setting, reference blocks and test blocks .24
7 Terms related to ultrasonic testing .25
7.1 Testing techniques . 25
7.2 Test object . 30
7.3 Coupling .31
7.4 Reflectors .32
7.5 Signals and indications . 33
7.6 Presentations . 35
7.7 Location . 39
7.8 Evaluation of indications . 40
Bibliography .43
iii
oSIST prEN ISO 5577:2024
ISO/DIS 5577:2024(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
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this may not represent the latest information, which may be obtained from the patent database available at
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Any trade name used in this document is information given for the convenience of users and does not
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For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 135, Non-destructive testing, Subcommittee SC
3, Ultrasonic testing.
This third edition cancels and replaces the second edition (ISO 5577:2017), which has been technically
revised.
The main changes are as follows:
— terms pulse overshoot, main lobe, main beam, side lobe, diffraction, contact surface, echo amplitude,
signal amplitude, full screen height were added,
— the term plate wave was replaced by Lamb wave,
— some definitions were modified.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
oSIST prEN ISO 5577:2024
DRAFT International Standard ISO/DIS 5577:2024(en)
Non-destructive testing — Ultrasonic testing — Vocabulary
1 Scope
This document defines the terms used in ultrasonic non-destructive testing and forms a common basis for
standards and general use.
This document does not cover specific terms used in ultrasonic testing with arrays.
NOTE Terms used in ultrasonic testing with arrays are defined in ISO 23243.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the terms and definitions given in Clauses 4, 5, 6 and 7 for sound, test
equipment and ultrasonic testing apply apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Terms and definitions related to frequencies, waves and pulses
4.1 Frequencies
4.1.1
frequency
number of cycles per second
Note 1 to entry: Expressed in Hertz (Hz).
4.1.2
nominal frequency
probe frequency
frequency (4.1.1) of the probe (6.2.1) as stated by the manufacturer
4.1.3
test frequency
effective ultrasonic frequency of a system used to test a material or object
4.1.4
frequency spectrum
distribution of amplitude (4.2.2) in relation to frequency (4.1.1)
Note 1 to entry: See Figure 1.
oSIST prEN ISO 5577:2024
ISO/DIS 5577:2024(en)
4.1.5
centre frequency
arithmetic mean of the upper and lower cut-off frequencies
Note 1 to entry: See Figure 1.
4.1.6
peak frequency
frequency (4.1.1) at which the maximum amplitude is observed
Note 1 to entry: See Figure 1.
4.1.7
cut-off frequency
frequency (4.1.1) at which the amplitude (4.2.2) of the transmitted signal has dropped by a specified amount
from the amplitude at peak frequency (4.1.6), for example, by 3 dB
Note 1 to entry: See Figure 1.
4.1.8
bandwidth
width of the frequency spectrum (4.1.4) between the upper and lower cut-off frequency
Note 1 to entry: See Figure 1.
4.1.9
relative bandwidth
ratio of the bandwidth (4.1.8) to the centre frequency (4.1.5), in per cent
Key
X frequency 4 centre frequency
Y amplitude 5 bandwidth at specified amplitude drop
1 peak frequency 6 peak amplitude
2 upper cut-off frequency 7 specified amplitude drop
3 lower cut-off frequency
Figure 1 — Frequency spectrum and related terms
oSIST prEN ISO 5577:2024
ISO/DIS 5577:2024(en)
4.2 Waves and pulses
4.2.1
ultrasonic wave
any acoustic wave having a frequency (4.1.1) higher than the audible range of the human ear, generally taken
as higher than 20 kHz
4.2.2
amplitude
absolute or relative measure of a sound wave's momentary magnitude
Note 1 to entry: The amplitude is not necessarily the maximum value, see echo amplitude (7.5.6).
4.2.3
phase
momentary condition of a vibration expressed as an arc measurement or an angle
4.2.4
wavelength
distance along the propagating direction between consecutive corresponding points of the same phase (4.2.3)
Note 1 to entry: See Figure 2.
4.2.5
wavefront
continuous surface joining all the most forward points of an ultrasonic wave (4.2.1) that have the same
phase (4.2.3)
4.2.6
time of flight
TOF
time it takes an ultrasonic pulse to travel from the transmitter probe through the test object (7.2.2) to the
receiver probe
4.2.7
pulse
electrical or ultrasonic signal of short duration
4.2.8
pulse amplitude
maximum amplitude of a pulse (4.2.7) (peak-to-peak)
Note 1 to entry: For rectified pulses (A-scan), baseline-to-peak.
4.2.9
pulse rise time
time taken for a pulse amplitude to change from a specified lower level to a specified upper level
4.2.10
pulse duration
time interval between the leading and trailing edges of a pulse (4.2.7) measured at a specified level below
the peak amplitude
4.2.11
pulse shape
diagramatic representation of the amplitude (4.2.2) of a pulse (4.2.7) as a function of time
4.2.12
pulse envelope
contour of a pulse shape (4.2.11) including all the peaks in terms of amplitude (4.2.2) and time
oSIST prEN ISO 5577:2024
ISO/DIS 5577:2024(en)
4.2.13
pulse energy
total energy within a pulse (4.2.7)
4.2.14
pulse overshoot
undesirable voltage peak at the rising or falling edge of a pulse (4.2.7)
Note 1 to entry: See Figure 2.
Key
X time
Y amplitude
1 pulse overshoot at raising edge
2 pulse reverberation at raising edge
3 pulse overshoot at falling edge
4 pulse reverberation at falling edge
Figure 2 — Pulse overshoot and pulse reverberation
4.2.15
pulse reverberation
vibration time after the rising or the falling edge of a pulse (4.2.7)
Note 1 to entry: See Figure 2.
4.2.16
broad-band pulse
pulse (4.2.7) in which the relative bandwidth (4.1.9) is ≥65 %
4.2.17
medium-band pulse
pulse (4.2.7) in which the relative bandwidth (4.1.9) is >35 % and <65 %
4.2.18
narrow-band pulse
pulse (4.2.7) in which the relative bandwidth (4.1.9) is ≤35 %
oSIST prEN ISO 5577:2024
ISO/DIS 5577:2024(en)
4.2.19
pulse repetition frequency
PRF
number of transmitter pulses (6.1.3) generated per second, expressed in Hertz (Hz)
4.3 Types of ultrasonic waves
4.3.1
longitudinal wave
compression wave
wave in which the direction of displacement of particles is in the same direction as the propagation of the wave
Note 1 to entry: See Figure 3 a).
4.3.2
transverse wave
shear wave
wave in which the direction of displacement of particles is perpendicular to the direction of the propagation
of the wave
Note 1 to entry: See Figure 3 b).
4.3.3
Rayleigh wave
surface wave
wave which propagates on the surface of a test object with an effective penetration depth of less than one
wavelength (4.2.4)
4.3.4
creeping wave
wave generated around the first critical angle of incidence and propagating along the surface like a
longitudinal wave with a slightly lower velocity than the longitudinal wave, interacting with the surface and
partially transforming into a transverse wave going into the volume of the test object
Note 1 to entry: It is neither influenced by the test object's surface conditions, nor does the wave follow undulations on
the surface.
4.3.5
Lamb wave
wave which propagates within the whole thickness of a plate and which can only be generated at particular
values of angle of incidence, frequency (4.1.1) and plate thickness
4.3.6
plane wave
wave with a planar wave front
4.3.7
cylindrical wave
wave with a cylindrical wave front
4.3.8
spherical wave
wave with a spherical wave front
oSIST prEN ISO 5577:2024
ISO/DIS 5577:2024(en)
a) Longitudinal wave; compression wave
b) Transverse wave; shear wave
Key
1 direction of oscillation
2 direction of propagation
λ wavelength
Figure 3 — Types of waves
5 Terms related to sound
5.1 Sound generation and reception
5.1.1
transducer
active element of a probe (6.2.1) which converts electrical energy into sound energy and vice versa
5.1.2
piezoelectric transducer
transducer (5.1.1) made from piezoelectric material
Note 1 to entry: Because the first piezoelectric transducers were cut from a quartz crystal, up to now transducers
often misleadingly are called crystals.
5.1.3
composite transducer
plate consisting of piezoelectric ceramic rods embedded in a polymer matrix
oSIST prEN ISO 5577:2024
ISO/DIS 5577:2024(en)
5.1.4
electro-magnetic acoustic transducer
EMAT
transducer (5.1.1) which uses magnetostriction in paramagnetic materials or Lorentz force in conductive
materials to generate ultrasound
5.1.5
focusing transducer
curved transducer
piezoelectric transducer (5.1.2) which is curved for focusing a sound beam (5.2.2)
Note 1 to entry: See focusing probe (6.2.24) for other ways for focusing a sound beam.
5.2 Sound propagation
5.2.1
sound field
three-dimensional pressure distribution produced by transmitted sound waves
5.2.2
sound beam
ultrasonic beam
part of the sound field (5.2.1) within which the major part of the ultrasonic energy is transmitted
5.2.3
beam axis
line through the points of maximum sound pressure at different distances
Note 1 to entry: See Figures 4 b), 9, 10, 11 and 12.
5.2.4
beam profile
curve which shows the signal amplitude along the beam axis (5.2.3) or perpendicular to the beam axis at a
specified distance from the probe (6.2.1)
Note 1 to entry: See Figure 4.
a) Profile along the beam axis
oSIST prEN ISO 5577:2024
ISO/DIS 5577:2024(en)
b) Profiles perpendicular to the beam axis
Key
1 transducer γ angle of divergence (drop to zero)
2 beam boundary a distance
3 beam axis N near-field length
4 beam width at a given distance P sound pressure
Figure 4 — Beam profiles
5.2.5
beam boundary
boundary of the sound beam where the sound pressure has fallen to a given fraction of the value on the
beam axis (5.2.3), measured at the same distance from the probe (6.2.1)
Note 1 to entry: See Figures 4 b), 9, 10 and 12.
5.2.6
beam width
dimension of the beam perpendicular to the beam axis (5.2.3) measured between the beam boundaries at a
specified distance from the probe (6.2.1)
Note 1 to entry: See Figure 4 b).
5.2.7
angle of divergence
angle within the far field (5.2.11) between the beam axis (5.2.3) and the beam boundary (5.2.5)
Note 1 to entry: See Figures 4 b), 9 and 12.
5.2.8
near field
Fresnel zone
zone of the sound beam (5.2.2) where sound pressure does not change monotonically with distance because
of interference
Note 1 to entry: See Figure 9.
5.2.9
near-field point
position on the beam axis (5.2.3) where the sound pressure reaches a final maximum
oSIST prEN ISO 5577:2024
ISO/DIS 5577:2024(en)
5.2.10
near-field length
distance between the transducer (5.1.1) and the near-field point (5.2.9)
Note 1 to entry: See Figure 4.
5.2.11
far field
Fraunhofer zone
zone of the sound beam (5.2.2) that extends beyond the near-field point (5.2.9)
Note 1 to entry: See Figures 9 and 12.
5.2.12
focal point
focus
point where the sound pressure on the beam axis (5.2.3) is at its maximum
5.2.13
focal distance
focal length
distance from the probe (6.2.1) to the focal point (5.2.12)
Note 1 to entry: See Figures 9 and 12.
5.2.14
focal zone
focal range
zone in a sound beam (5.2.2) of a probe (6.2.1) in which the sound pressure remains above a specified level
related to its maximum
5.2.15
length of the focal zone
distance along the beam axis (5.2.3) from the start to the end of the focal zone (5.2.14)
5.2.16
width of the focal zone
dimension of the focal zone (5.2.14) at focal distance (5.2.13) perpendicular to the beam axis (5.2.3)
5.2.17
acoustical properties
characteristic parameters of a material which control the propagation of sound in the material
5.2.18
acoustically anisotropic material
material which has differing sound velocities in differing directions of propagation
5.2.19
sound velocity
velocity of propagation
phase velocity (5.2.20) or group velocity (5.2.21) of a sound wave in a material in the direction of propagation
Note 1 to entry: In a non-dispersive material, there is no difference between phase velocity and group velocity.
Note 2 to entry: In an acoustically anisotropic material, the velocities may depend on the direction of propagation.
5.2.20
phase velocity
velocity of propagation (5.2.19) of a wave front
oSIST prEN ISO 5577:2024
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5.2.21
group velocity
velocity of propagation (5.2.19) of the acoustic energy
5.2.22
main lobe
main beam
sound beam in the intended direction, typically with the highest pressure within the sound field (5.2.1)
5.2.23
side lobe
part of the sound field (5.2.1) which corresponds to a local maximum in the far field, deviating from the
direction of the main lobe (5.2.22) and typically lower in amplitude than the main lobe
5.3 Loss of sound pressure
5.3.1
attenuation
sound attenuation
decrease of pressure when a sound wave travels through a material, arising from absorption (5.3.4) and
scattering (5.3.3)
5.3.2
attenuation coefficient
coefficient used to express attenuation (5.3.1) per unit of distance travelled, dependent on material
properties, wavelength (4.2.4) and type of wave
Note 1 to entry: The attenuation coefficient is usually expressed in dB/m.
5.3.3
scattering
random reflections caused by grain structure and/or by small reflectors (7.4.1) in the beam path when a
wave travels through a material
5.3.4
absorption
part of the attenuation (5.3.1) resulting from transformation of ultrasonic energy into other types of energy,
for example, thermal energy
5.4 Ultrasonic waves at interfaces
5.4.1
interface
boundary between two materials, in acoustic contact, having different acoustical properties
Note 1 to entry: See Figure 5.
oSIST prEN ISO 5577:2024
ISO/DIS 5577:2024(en)
Key
1 interface 6 angle of incidence
2 direction of incident wave 7 angle of reflection
3 direction of refracted wave 8 medium 1
4 direction of reflected wave 9 medium 2
5 angle of refraction
Figure 5 — Refraction and reflection of ultrasonic waves
5.4.2
angle of incidence
angle between the direction of the incident ultrasonic wave (4.2.1) and the normal to the interface (5.4.1)
Note 1 to entry: See Figure 5.
5.4.3
reflection
change of the direction of sound propagation within the same material when impinging on an interface (5.4.1)
Note 1 to entry: See Figure 5.
5.4.4
refraction
change of the direction of sound propagation when passing obliquely through the interface (5.4.1) between
two materials of differing sound velocities
Note 1 to entry: See Figure 5.
5.4.5
diffraction
change of the direction of sound propagation within the same material when impinging on the edge(s) of a
discontinuity
Note 1 to entry: diffraction typically results in (almost) omnidirectional waves which are, as a result, weaker than
reflected waves.
5.4.6
angle of reflection
angle between the direction of the reflected ultrasonic wave (4.2.1) and the normal to the interface (5.4.1)
Note 1 to entry: See Figure 5.
oSIST prEN ISO 5577:2024
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5.4.7
angle of refraction
angle between the direction of the refracted wave and the normal to the interface (5.4.1)
Note 1 to entry: See Figure 5.
5.4.8
acoustic impedance
ratio of sound pressure to particle displacement velocity
Note 1 to entry: In a material with perfect elastic properties for a plane longitudinal wave, it is equal to the product of
sound velocity (5.2.19) and density.
5.4.9
reflection coefficient
ratio of reflected sound pressure to incident sound pressure at a reflecting surface
Note 1 to entry: The corresponding transmission coefficient is defined in 5.4.10.
5.4.10
transmission coefficient
ratio of sound pressure transmitted through an interface (5.4.1) to the incident sound pressure
Note 1 to entry: The corresponding reflection coefficient is defined in 5.4.9.
5.4.11
refractive index
ratio of the sound velocities of two materials in acoustic contact
5.4.12
critical angle
angle of incidence (5.4.2) at which the angle of refraction (5.4.7) is 90° for a specified type of waves
Note 1 to entry: The critcal angle for longitudinal waves (4.3.1) and the critical angle for transverse waves (4.3.2), are
different from each other.
5.4.13
total reflection
reflection (5.4.3) which occurs when the angle of incidence (5.4.2) is larger than both critical angles (5.4.12)
or if the reflection coefficient (5.4.9) is unity
5.4.14
corner reflection
reflection (5.4.3) of ultrasonic waves (4.2.1) backward to the probe from a corner formed by two or three
surfaces mutually perpendicular regardless of angles of incidence.
Note 1 to entry: See Figure 6 for a corner reflection on two surfaces.
oSIST prEN ISO 5577:2024
ISO/DIS 5577:2024(en)
Key
α angle of incidence to horizontal surface
β angle of incidence to vertical surface
γ angle of reflection to vertical surface
α angle to vertical surface (=α )
2 1
Figure 6 — Corner reflection (two surfaces)
5.4.15
wave mode conversion
change of one wave mode to another by refraction (5.4.4) or reflection (5.4.3) or diffraction (5.4.5)
5.4.16
edge effect
phenomenon resulting from the diffraction of an ultrasonic wave (4.2.1) by the edges of a reflector (7.4.1)
5.4.17
beam displacement
displacement of the sound beam (5.2.2) due to reflection (5.4.3) from a surface of a solid
Note 1 to entry: It mainly depends on frequency (4.1.1) and beam angle (6.2.16).
Note 2 to entry: See Figure 7.
Key
1 beam displacement due to reflection
Figure 7 — Beam displacement
5.4.18
acoustic shadow
region in an object which cannot be reached by ultrasonic waves (4.2.1) travelling in a given direction because
of the geometry of the object or a discontinuity in it
Note 1 to entry: See Figure 8.
oSIST prEN ISO 5577:2024
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Key
1 acoustic shadow
Figure 8 — Acoustic shadow
6 Terms related to test equipment
6.1 Instrument
6.1.1
ultrasonic instrument
instrument used together with the probe or probes (6.2.1), which transmits, receives, processes and displays
ultrasonic signals for non-destructive testing purposes
6.1.2
transmitter
electrical device or component which generates the transmitter pulses (6.1.3)
6.1.3
transmitter pulse
electrical pulse generated by thetransmitter (6.1.2) of the ultrasonic instrument (6.1.1) for exciting the
transducer (5.1.1)
6.1.4
receiver
electrical device or component which amplifies or converts signals coming from the ultrasonic probe into
usable electric signals
6.1.5
amplifier
electronic device or component which converts a small signal into a larger signal
Note 1 to entry: This can be a linear amplifier using a linear characteristic or a logarithmic amplifier using a logarithmic
characteristic.
6.1.6
attenuator
electronic device or component which reduces the amplitude (4.2.2) or power of a signal without distortion
6.1.7
gain
level of amplification of signals
Note 1 to entry: Usually expressed in decibels (dB).
6.1.8
gain control
instrument control with which a signal may be adjusted to a given height
oSIST prEN ISO 5577:2024
ISO/DIS 5577:2024(en)
6.1.9
dynamic range
ratio of the amplitudes (4.2.2) of the largest and smallest signal which an ultrasonic instrument (6.1.1) can
display without distortion
Note 1 to entry: Dynamic range is usually expressed in decibels (dB).
6.1.10
linearity of amplitude
vertical linearity
proportionality of the amplitude of signals on the vertical scale of the display or within a gate (6.1.21) of the
ultrasonic instrument (6.1.1)
6.1.11
suppression
reduction of noise indications by eliminating all indications (7.5.14) below a predetermined amplitude level
(threshold value)
6.1.12
analogue-to-digital converter
device which converts analogue signals into discrete numbers representing the pattern of the signal
6.1.13
digitization error
inaccuracy introduced as a result of analogue-to-digital conversion
6.1.14
time base
abscissa of an A-scan adjusted in time or distance
Note 1 to entry: See Figure 21.
6.1.15
time base control
control of the ultrasonic instrument (6.1.1) which is used to adjust the time base (6.1.14) to a required range
6.1.16
time base range
maximum ultrasonic path length that is displayed on a particular time base (6.1.14)
6.1.17
delayed time base sweep
time base sweep triggered with a given delay, fixed or adjustable, in relation to the transmitter pulse (6.1.3)
or a reference echo (6.4.4)
6.1.18
linearity of time base
horizontal linearity
proportionality of the positions of signals on the time base (6.1.14) of the display or within a gate (6.1.20) of
the ultrasonic instrument (6.1.1)
6.1.19
monitor
component of an ultrasonic instrument (6.1.1) which provides a gate (6.1.20) within which the presence of
echoes (7.5.1) above or below a specified level can be indicated
6.1.20
gate
time gate
window
electronic means of selecting a segment of the time base (6.1.14) for monitoring or further processing of
signals within the gate
oSIST prEN ISO 5577:2024
ISO/DIS 5577:2024(en)
6.1.21
gate threshold
monitor level
specified amplitude level (threshold) above or below which signals in a gate (6.1.20) are selected for further
processing
6.1.22
proportional gate
gate (6.1.20) which provides a proportional output of any signal that is received during the period of the gate
Note 1 to entry: The output can be voltage or current.
6.2 Probes
6.2.1
probe
electro-acoustical device, incorporating one or more transducers (5.1.1), and possibly a delay line (6.2.7)
intended for transmission and/or reception of ultrasonic waves (4.2.1)
6.2.2
single-transducer probe
probe (6.2.1) with a single transducer (5.1.1) for the transmission and reception of ultrasonic waves (4.2.1)
6.2.3
multi-transducer probe
probe (6.2.1) with several separated transducers (5.1.1), which through switching permits the creation of
certain sound beam (5.2.2) configurations
6.2.4
transducer backing
material coupled to the rear surface of a transducer (5.1.1) to damp the transducer oscillation
Note 1 to entry: See Figures 9, 10 and 12.
6.2.5
probe shoe
shaped piece of material which is interposed between the probe (6.2.1) and the test object (7.2.1) for the
purpose of improving the coupling and/or protecting the probe
6.2.6
protection layer
layer of protective material forming an integral part of the probe (6.2.1) and separating the transducer (5.1.1)
from direct contact with the test object (7.2.1)
Note 1 to entry: See Figure 9.
6.2.7
contact surface
part of the probe that is brought into contact with the test surface (7.2.2) for contact technique (7.1.4), or
which is close to the test surface (7.2.2) for gap technique (7.1.5)
6.2.8
delay line
delay block
component introduced to create the delay path (6.2.9)
6.2.9
delay path
path on the beam axis (5.2.3) between transducer (5.1.1) and point of entry into the test object (7.2.1)
oSIST prEN ISO 5577:2024
ISO/DIS 5577:2024(en)
6.2.10
nominal transducer size
physical size of the transducer (5.1.1)
6.2.11
effective transducer size
reduced area of the physical size of the transducer (5.1.1)
Note 1 to entry: The effective transducer size is determined from the measured focal distance (5.2.13), frequency
(4.1.1), sound velocity (5.2.19) and, for angle-beam probes (6.2.14), from the measured beam angle (6.2.16).
6.2.12
wedge
wedge-shaped component usually made of plastic material which causes an ultrasonic wave (4.2.1) to be
refracted into the test object (7.2.1) at a defined angle
Note 1 to entry: See Figure 10.
6.2.13
straight-beam probe
normal-beam probe
probe (6.2.1) whose beam axis (5.2.3) is perpendicular to the contact surface
Note 1 to entry: See Figure 8.
oSIST prEN ISO 5577:2024
ISO/DIS 5577:2024(en)
Key
1 transducer 7 beam boundary
2 transducer backing 8 far field
3 protection layer 9 beam axis
4 near field 10 connector
5 focal distance 11 test object
6 angle of divergence
Figure 9 — Straight-beam probe
6.2.14
angle-beam probe
probe (6.2.1) generating a beam at an angle other than normal to the test surface (7.2.2)
Note 1 to entry: See Figure 10.
oSIST prEN ISO 5577:2024
ISO/DIS 5577:2024(en)
Key
1 transducer 6 probe index point
2 transducer backing 7 beam boundary
3 wedge 8 connector
4 beam axis 9 test object
5 beam angle 10 damping material
Figure 10 — Angle-beam probe
6.2.15
variable-angle-beam probe
probe (6.2.1) generating a beam at angles that can be changed
6.2.16
beam angle
angle between the beam axis (5.2.3) and the normal to the interface (5.4.1) for a particular probe (6.2.1) and
a particular material
Note 1 to entry: See Figure 10.
6.2.17
probe index point
intersection point of the sound beam axis with the probe contact surface
Note 1 to entry: See Figure 10 and Figure 16.
Note 2 to entry: The projection of the probe index point may be marked on the housing of an angle-beam probe (6.2.14).
6.2.18
nominal probe angle
quoted value of the refraction angle of a probe (6.2.1) for a given material and temperature
oSIST prEN ISO 5577:2024
ISO/DIS 5577:2024(en)
6.2.19
probe axis
geometrical reference axis through the probe (6.2.1), serving as the origin for angular coordinates used in
describing the directional characteristics of a probe
Note 1 to entry: See Figure 11.
Note 2 to entry: For straight-beam probes (6.2.13), the probe axis is perpendicular to the test surface (7.2.2). For angle-
beam probes (6.2.14), the probe axis is projected onto the test surface (7.2.2).
6.2.20
squint angle
angle between the probe axis (6.2.19) and the projection of the beam axis (5.2.3) on the test surface (7.2.2)
Note 1 to entry: See Figure 10.
Note 2 to entry: The squint angle may be intentionally by probe design or unintentionally e.g. by non-uniform wear.
Key
1 probe axis
2 squint angle
3 beam axis
Figure 11 — Squint angle
6.2.21
Longitudinal-wave probe
compression-wave probe
probe (6.2.1) generating and/or receiving longitudinal waves (4.3.1)
6.2.22
transverse-wave probe
shear-wave probe
probe (6.2.1) generating and/or receiving transverse waves (4.3.2) usually via wave mode conversion (5.4.14)
by refraction (5.4.4)
6.2.23
surface-wave probe
probe (6.2.1) generating and/or receiving surface waves (4.3.3)
6.2.24
contoured probe
probe (6.2.1) having a contact surface which is shaped to fit a curved test surface (7.2.2)
oSIST prEN ISO 5577:2024
ISO/DIS 5577:2024(en)
6.2.25
focusing probe
probe (6.2.1) which concentrates the sound beam (5.2.2) by special devices, by a curved transducer, a lens or
electronic mean, to generate a focused beam
6.2.26
cross talk
signal interference across an intended acoustic or electric barrier
Note 1 to entry: An example of electrical cross talk is that between adjacent transmit and receive channels of an
ultrasonic instrument (6.1.1).
Note 2 to entry: An example of acoustical cross talk is that between probes (6.2.1) or between transducers (5.1.1) [dual-
transducer probe (6.2.27)].
Note 3 to entry: Cross talk is usually expressed in decibels (dB).
6.2.27
dual-transducer probe
dual-element probe
probe (6.2.1) in which the transmit and receive transducers (5.1.1) are separate and are electrically and
acoustically isolated from each other
Note 1 to entry: See Figure 12.
oSIST prEN ISO 5577:2024
ISO/DIS 5577:2024(en)
Key
1 transmitting transducer 8 far field
2 transducer backing 9 beam axis
3 delay block 10 receiving transducer
4 acoustic barrier 11 transmitting connector
5 focal distance 12 receiving connector
6 angle of divergence 13 test object
7 beam boundary
Figure 12 — Dual-transducer probe
6.2.28
roof angle
for dual-transducer probes (6.2.27), this angle indicates the orientation of each transducer to a reference plane
Note 1 to entry: See Figure 13.
oSIST prEN ISO 5577:2024
ISO/DIS 5577:2024(en)
Key
1 transducers
δ roof angle
Figure 13 — Dual-transducer probe with roof angles
6.2.29
convergence zone
zone at the intersection of the transmitting and receiving beams of a dual-transducer probe (6.2.27)
6.2.30
immersion probe
probe (6.2.1) generating and/or receiving longitudinal waves (4.3.1) to be used in a liquid
6.2.31
wheel probe
probe (6.2.1) generating and/or receiving ultrasonic waves (4.2.1) incorporating one or more transducers
(5.1.1) mounted inside a liquid-filled flexible tyre
6.3 Combined test equipment
6.3.1
ultrasonic test equipment
equipment consisting of an ultrasonic instrument (6.1.1), probes (6.2.1), cables and all devices connected to
the instrument during testing
6.3.2
ultrasonic test system
UT system
ultrasonic test equipment (6.3.1) combined with an electro-mechanical system, e.g. manipulator or robot for
moving the probe(s) and/or the test object
6.3.3
dead zone
zone on the display representing the depth zone directly under the test surface (7.2.2) at the point of incidence
(7.2.7) in which discontinuities are undetectable
Note 1 to entry: The depth of the zone is dependent on various factors, e.g. probe (6.2.1), instrument setting, material
of the test object (7.2.1).
6.3.4
detection sensitivity
characteristic of an ultrasonic test system (6.3.2) defined by the smallest detectable reflector (7.4.1)
6.3.5
lateral resolution
capability of an ultrasonic test system (6.3.2) to resolve two separate targets at the same distance
6.3.6
axial resolution
capability of an ultrasonic test system (6.3.2) to resolve two separate targets at different distances
oSIST prEN ISO 5577:2024
ISO/DIS 5577:2024(en)
6.4 Instrument setting, reference blocks and test blocks
6.4.1
standard block
calibration block
standardized piece of material of specified composition, surface finish, heat treatment and geometric
form, by means of which an ultrasonic test system (6.3.1) can be assessed and the setting of the ultrasonic
instrument (6.1.1) can be performed
Note 1 to entry: For example, see ISO 2400, ISO 7963, ISO 16946 and ISO 19675.
6.4.2
reference block
piece of material representative of the material to be tested with similar acoustic properties containing well-
defined reflectors (7.4.1), used to adjust the sensitivity and/or time base (6.1.15) of the ultrasonic instrument (6.1.1)
in order to compare detected discontinuity indications with those arising from the known reflectors (7.4.1)
6.4.3
test block
defined piece of material which allows tests for the accuracy and/or performance of an ultrasonic test
system (6.3.2)
6.4.4
reference echo
echo (7.5.1) from a specified reference reflector (7.4.2)
Note 1 to entry: Example shown in Figure 14.
a) Generation of reference echoes b) Display of the reference echoes and the dis-
tance-amplitude curve
Key
1 reference echo from position A (direct) 4 reference block
2 reference echo from position B (indirect) 5 reference reflector
3 reference echo from position C (indirect) 6 distance–amplitude curve (DAC)
Figure 14 — Generation of a distance-amplitude curve
oSIST prEN ISO 5577:2024
ISO/DIS 5577:2024(en)
6.4.5
transfer correction
correction of the gain setting of the ultrasonic instrument (6.1.1) when transferring the probe (6.2.1) from a
standard block (6.4.1) or reference block (6.4.2) to the test object (7.2.1)
Note 1 to entry: Transfer correction includes
...
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