IEC 60645-3:2020
(Main)Electroacoustics - Audiometric equipment - Part 3: Test signals of short duration
Electroacoustics - Audiometric equipment - Part 3: Test signals of short duration
IEC 60645-3:2020 specifies a means of describing the physical characteristics, in terms of electrical waveforms, of audiometric reference and test signals of short duration and methods for their measurement.
The object of this document is to ensure that audiometric stimuli of short duration are specified and measured in the same way and that the calibration of equipment using such signals is carried out using defined methods.
This document does not describe the method of use of short-duration test signals.
IEC 60645-3:2020 cancels and replaces the second edition published in 2007. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) new figures of reference signals;
b) changes in definitions.
Electroacoustique - Appareils audiométriques - Partie 3: Signaux d'essai de courte durée
L'IEC 60645-3:2020 spécifie un moyen pour décrire les caractéristiques physiques en tant que formes d'ondes électriques, de signaux audiométriques de courte durée de référence et d'essai, ainsi que leurs méthodes de mesure.
L'objet du présent document est de s'assurer que les stimuli audiométriques de courte sont spécifiés et mesurés de la même manière et que l'étalonnage des appareils qui utilisent de tels signaux est effectué selon des méthodes définies.
Le présent document n'a pas pour objet de décrire la méthode d'utilisation des signaux d'essai de courte durée.
L'IEC 60645-3:2020 annule et remplace la deuxième édition parue en 2007. Cette édition constitue une révision technique.
Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a) ajout de nouvelles figures pour les signaux de référence;
b) modification de certaines définitions.
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IEC 60645-3 ®
Edition 3.0 2020-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electroacoustics – Audiometric equipment –
Part 3: Test signals of short duration
Électroacoustique – Appareils audiométriques –
Partie 3: Signaux d'essai de courte durée
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IEC 60645-3 ®
Edition 3.0 2020-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electroacoustics – Audiometric equipment –
Part 3: Test signals of short duration
Électroacoustique – Appareils audiométriques –
Partie 3: Signaux d'essai de courte durée
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.140.50 ISBN 978-2-8322-8901-3
– 2 – IEC 60645-3:2020 © IEC 2020
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Reference signals . 10
4.1 General . 10
4.2 Reference click . 11
4.3 Reference tone-burst . 11
4.4 Reference broadband chirp . 12
4.5 Reference octave-band chirps . 12
5 Calibration and measurement of short-duration signals . 13
BibIiography . 14
Figure 1 – Basic specification of an electrical reference click . 7
Figure 2 – Illustration of the method of measurement of peak-to-peak equivalent signal
levels . 8
Figure 3 – Temporal characteristics of an electrical reference tone-burst . 8
Figure 4 – Time domain specification of the electrical reference click . 11
Figure 5 – Temporal characteristics of the electrical reference broadband chirp. 12
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROACOUSTICS – AUDIOMETRIC EQUIPMENT –
Part 3: Test signals of short duration
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60645-3 has been prepared by IEC technical committee 29:
Electroacoustics.
This third edition cancels and replaces the second edition published in 2007. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) new figures of reference signals;
b) changes in definitions.
– 4 – IEC 60645-3:2020 © IEC 2020
The text of this International Standard is based on the following documents:
FDIS Report on voting
29/1066/FDIS 29/1070/RVD
Full information on the voting for the approval of this document 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.
A list of all parts of IEC 60645 series, under the general title Electroacoustics – Audiometric
equipment, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the document will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this document using a colour printer.
INTRODUCTION
Developments in the field of hearing measurements for diagnostic, hearing conservation and
rehabilitation purposes have resulted in the availability of a wide range of audiometric
equipment. In addition, it is possible to consider audiometric equipment in terms of a set of
functional units that can be specified independently. By specifying these functional units, it is
then possible to specify the performance of other audiometric equipment that uses these units.
The IEC 60645 series consists of a number of parts. IEC 60645-3 covers the requirements for
reference and other test signals of short duration.
Examples of test methods, where such signals are commonly used, are the recording of auditory
evoked potentials and evoked otoacoustic emissions. Reference signals are described in order
to provide a basis for calibration and as a recommendation for use when there is no specific
reason to have an alternative signal. Measurement methods for short duration acoustic and
vibratory test signals are described.
– 6 – IEC 60645-3:2020 © IEC 2020
ELECTROACOUSTICS – AUDIOMETRIC EQUIPMENT –
Part 3: Test signals of short duration
1 Scope
This part of IEC 60645 specifies a means of describing the physical characteristics, in terms of
electrical waveforms, of audiometric reference and test signals of short duration and methods
for their measurement.
The object of this document is to ensure that audiometric stimuli of short duration are specified
and measured in the same way and that the calibration of equipment using such signals is
carried out using defined methods.
This document does not describe the method of use of short-duration test signals.
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 60318-1, Electroacoustics – Simulators of human head and ear – Part 1: Ear simulator for
the measurement of supra-aural and circumaural earphones
IEC 60318-3, Electroacoustics – Simulators of human head and ear – Part 3: Acoustic coupler
for the calibration of supra-aural earphones used in audiometry
IEC 60318-4, Electroacoustics – Simulators of human head and ear – Part 4: Occluded-ear
simulator for the measurement of earphones coupled to the ear by means of ear inserts
IEC 60318-5, Electroacoustics – Simulators of human head and ear – Part 5: 2 cm coupler for
the measurement of hearing aids and earphones coupled to the ear by means of ear inserts
IEC 60318-6, Electroacoustics – Simulators of human head and ear – Part 6: Mechanical
coupler for the measurement on bone vibrators
IEC 61260-1, Electroacoustics – Octave-band and fractional-octave-band filters – Part 1:
Specifications
ISO 389-6, Acoustics – Reference zero for the calibration of audiometric equipment – Part 6:
Reference threshold of hearing for test signals of short duration
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
short-duration signal
signal having a duration of less than 200 ms
3.2
click
transient acoustic or vibratory signal whose frequency spectrum covers a broad frequency
range, produced by applying a single rectangular electrical pulse to the terminals of the
transducer
Note 1 to entry: See Figure 1 and Figure 2.
Key
1 level
2 time
Figure 1 – Basic specification of an electrical reference click
– 8 – IEC 60645-3:2020 © IEC 2020
Key
1 level
2 time
NOTE The left part of the figure shows an example of the acoustic click signal generated by an electrical rectangular
pulse applied to a transducer (100 µs electrical pulse fed to a TDH-39 earphone with MX-41/AR cushion and
measured on an IEC 60318-1 ear simulator) and the right part presents the long duration sinusoidal signal.
Figure 2 – Illustration of the method of measurement
of peak-to-peak equivalent signal levels
3.3
tone-burst
gated sinusoidal signal having a duration of less than 200 ms
Note 1 to entry: Figure 3 shows a reference tone-burst (see 4.3).
Note 2 to entry: A tone-burst is sometimes called a "brief tone" or a "tone pip".
Key
1 level
2 time
3 rise time
4 duration
5 fall time
Figure 3 – Temporal characteristics of an electrical reference tone-burst
3.4
instantaneous frequency
frequency f which, for a signal s(t) with a waveform
s t = At sinφ t
() () ( ())
,
is defined at time t as
dtφ
1 ()
ft()=
2π dt
with the amplitude modulation A(t) slowly varying compared to the frequency
dA t
()
At f t
() ()
dt
3.5
chirp
short-duration signal in which the instantaneous frequency between two specified values varies
monotonically for the duration of the signal
3.6
upward chirp
chirp which presents the low frequency components in the chirp before the high frequency
components
3.7
broadband chirp
chirp that has a specified electrical amplitude spectrum covering at least 5 octaves of the normal
audible frequency range,
Note 1 to entry: See Figure 5.
3.8
octave-band chirp
chirp with an electrical amplitude spectrum corresponding to the amplitude-frequency
characteristic of an IEC 61260-1 octave-band filter with a specified center frequency
3.9
condensation signal
short-duration signal, the initial wave of which causes an over-pressure relative to ambient
pressure, or an over-force relative to the static force at the plane of the output port of the
transducer
3.10
rarefaction signal
short-duration signal, the initial wave of which causes an under-pressure relative to ambient
pressure, or an under-force relative to the static force at the plane of the output port of the
transducer
3.11
alternating polarity signal
series of short-duration signals, consisting of rarefaction and condensation signals in
alternating order
– 10 – IEC 60645-3:2020 © IEC 2020
3.12
initial wave of a click stimulus signal
first half wave of the stimulus signal, the amplitude of which is larger than 0,5 times the
amplitude of the next half wave with opposite polarity
3.13
duration of initial wave of a click stimulus signal
time interval between the two zero crossings of the initial stimulus signal wave
3.14
duration of a tone-burst
time interval between the half maximum amplitude points on the rising and falling portions of
the envelope of the electrical tone-burst signal
Note 1 to entry: See Figure 3, key 4.
3.15
rise and fall times of a tone-burst
time intervals between the 10 % and 90 % amplitude points of the rising portion and the 90 %
and 10 % amplitude points on the falling portion of the envelope of the electrical tone-burst
signal
Note 1 to entry: See Figure 3, key 3 and key 5.
3.16
peak-to-peak equivalent signal level
root-mean-square (RMS) value of a long duration sinusoidal signal which, when compared
under the same test conditions with a short-duration output signal from the transducer under
test, has the same peak-to-peak value (i.e. amplitude difference between the maximum and
minimum values) as the short-duration signal
Note 1 to entry: See Figure 2.
Note 2 to entry: For clicks and broadband chirps, the long duration sinusoidal signal should have a frequency
of 1 000 Hz, and for tone-bursts its frequency should equal the fundamental frequency of the tone-burst. For octave-
band chirps, its frequency should equal the centre frequency of the band.
Note 3 to entry: The term "peak-to-peak equivalent signal level" is also referred to as "peak equivalent signal level".
Note 4 to entry: The recommended abbreviations for "peak-to-peak equivalent sound pressure level" and "vibratory
force level" are peSPL and peVFL.
3.17
RMS signal level
RMS value of a short-duration signal continuously presented with a given presentation rate,
measured as equivalent continuous sound pressure level or vibratory force level without any
frequency weighting
Note 1 to entry: If short-duration signals are presented with a given presentation rate, their behaviorial threshold
can be described by an RMS signal level, which has, for a given transducer, a given ear simulator, and a given
presentation rate a fixed ratio to the peak-to-peak equivalent signal level of the short-duration signal, see [1].
Note 2 to entry: If a sound level meter is to be used to measure the RMS signal level, the IEC 61672-1 Z frequency
weighting should be applied to realize these conditions.
4 Reference signals
4.1 General
The following reference signals are described for the purposes of standardization.
4.2 Reference click
The reference click is based on an electrical rectangular pulse (single monophasic rectangular
wave) of (100 ± 10) µs duration (see Figure 1) with rise and fall times less than 25 µs
(see Figure 4).
The reference click is specified as an electrical signal meeting the requirements detailed in
Figure 4.
NOTE 1 This specification allows for an acceptable extent of overshoot and transient oscillations, but, at the same
time, sets limits that do not unduly affect reference hearing thresholds and other reference values, determined with
pulses that would follow the strict requirements given by Figure 1, see [2].
NOTE 2 The same definition of rise-/fall times and duration as given in Figure 3 applies to the reference pulse.
NOTE 3 The waveform of the acoustical signal will vary according to the type of transducer and ear simulator used
for measurement.
Figure 4 – Time domain specification of the electrical reference click
4.3 Reference tone-burst
The reference tone-burst shall be an electrical signal consisting of five periods of the
fundamental sine wave and having a linear rise and fall. The tone-burst shall have 1,6 periods
of rise and fall time, and a duration of three periods as shown in Figure 3.
– 12 – IEC 60645-3:2020 © IEC 2020
NOTE 1,6 periods of linear rise or fall corresponds to two periods from zero to 100 % amplitude. The signal envelope
remains at the 100 % amplitude for one period. The reference tone-burst can also be described according to the
"2-1-2" concept where "2" indicates the number of periods from zero to 100 % amplitude and back to zero and "1" is
the 100 % amplitude period.
4.4 Reference broadband chirp
The reference broadband chirp shall be an electrical signal consisting of a broadband chirp with
amplitude and phase spectra specified as follows. The amplitude spectrum shall be designed
to be flat within five octave-bands with a lower and higher amplitude roll-off corresponding to
the lower band edge frequency of a 500 Hz octave-band filter and the upper band edge
frequency of an 8 000 Hz octave-band filter, as specified in IEC 61260-1, respectively.
The reference broadband chirp shall be designed to compensate for the cochlear traveling
delay. This is achieved with the following phase spectrum, θ (see [3]):
k
1− d
θπ= 2 f [rad]
1−d
( )
where
f is the frequency, in Hz;
k and d are the two constants k = 0,092 0 and d = 0,435 6.
Any realization of the phase spectrum, which lies within a phase interval of ±2 [rad] relative to
the stated formula, shall be considered as being in agreement with this document, provided that
the phase spectrum still is a monotonous function of frequency within the specified frequency
range (see Figure 5 and [4]).
NOTE The reference broadband chirp effectively covers the frequency range from 350 Hz to 11 300 Hz.
NOTE The exact temporal location of the 10 000 Hz component is –1,66 ms, and the corresponding locations of the
frequency components at 500, 1 000, 2 000, 4 000, and 8 000 Hz are as indicated by the vertical lines.
Figure 5 – Temporal characteristics of the electrical reference broadband chirp
4.5 Reference octave-band chirps
The reference octave-band chirps shall be five electrical signals each with a phase spectrum
identical to that of the reference broad-band chirp and with a center frequency of 500 Hz,
1 000 Hz, 2 000 Hz, 4 000 Hz, and 8 000 Hz, respectively. See [4].
5 Calibration and measurement of short-duration signals
5.1 Reference equivalent threshold sound pressure levels are given in ISO 389-6 for some
signal/transducer/ear simulator combinations.
5.2 For each signal type, the following characteristics of an instrument generating signals of
short duration shall be provided by the manufacturer:
– type of reference signal used; for reference signals that are not defined in Clause 4, the
characteristics of the signals shall be provided;
– type of transducer and associated type of ear simulator/acoustical coupler, mechanical
coupler and sound level meter used and, if applicable, details describing how to couple the
transducer to the measurement system;
– reference levels as given in ISO 389-6; for transducers and/or reference signals that are not
listed in ISO 389-6, the reference level (including their origin) and measurement method
(including the ear simulator, acoustic coupler or mechanical coupler used) shall be provided;
– polarity of acoustical output signal (i.e. positive (condensation), negative (rarefaction),
alternating or random initial phase);
– the shape of the envelope rise and fall (linear, cos , hanning etc.).
5.3 For air conduction presentation of short-duration signals, the acoustic characteristics of
the short-duration signals shall be measured on an ear simulator (IEC 60318-1) or occluded-
ear simulator (IEC 60318-4). If an acoustic coupler (IEC 60318-5, IEC 60318-3) is used for
routine calibration, the relationship between measurements on the ear simulator (IEC 60318-1)
or occluded-ear simulator (IEC 60318-4) and the acoustic coupler shall be stated by the
manufacturer.
5.4 For bone conduction presentation of short duration signals, the signals shall be measured
on a mechanical coupler according to IEC 60318-6.
5.5 For sound-field presentation of short-duration signals, the signals should be measured
with a class-1 sound-level meter conforming to IEC 61672-1 using the procedures described in
ISO 8253-2. The measuring microphone shall be placed at the reference point in the absence
of the listener. The reference point is the midpoint of a straight line connecting the entrances
to the listener's ear canal openings when positioned in the testing position in the sound field.
5.6 The measurement system shall provide for the measurement of the peak-to-peak
equivalent signal level (see 3.16) or the RMS signal level (see 3.17) of the short duration
signals.
5.7 The amplitude and phase response of the measurement system (including the
transducer) shall be known, in order to determine the polarity of the acoustic or vibratory signal.
...
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