IEC 60645-6:2022

IEC 60645-6 ®
Edition 2.0 2022-03
REDLINE VERSION
INTERNATIONAL
STANDARD
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inside
Electroacoustics – Audiometric equipment –
Part 6: Instruments for the measurement of otoacoustic emissions

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IEC 60645-6 ®
Edition 2.0 2022-03
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Electroacoustics – Audiometric equipment –
Part 6: Instruments for the measurement of otoacoustic emissions
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.140.50 ISBN 978-2-8322-4334-3

– 2 – IEC 60645-6:2022 RLV © IEC 2022
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 8
4 Requirements for specific instruments . 9
5 General specifications . 10
5.1 Acoustic stimulus system . 10
5.1.1 General requirements . 10
5.1.2 Stimulus types . 10
5.1.3 Stimulus frequency range . 11
5.1.4 Stimulus level . 11
5.1.5 Harmonic Intermodulation distortion. 12
5.2 Test quality assuring system . 12
5.2.1 General Stability of acoustic response in the external auditory meatus . 12
5.2.2 Test quality assurance . 13
5.2.3 Individual stimulus recordings . 13
5.3 Measuring system . 13
5.3.1 Units of measurement . 13
5.3.2 Measurement range . 13
5.3.3 Accuracy of measurement . 13
5.3.4 Frequency range . 13
5.3.5 Noise reduction . 13
5.3.6 Response detection . 14
5.3.7 Response quality estimates . 14
5.3.8 Normative values . 14
5.4 Presentation of results . 14
5.4.1 General .
5.4.2 Primary results .
5.4.3 Secondary results .
6 Demonstration of conformity with specifications . 15
6.1 General . 15
6.2 Probe signal . 15
6.2.1 Probe signal frequency spectrum . 15
6.2.2 Probe signal level and harmonic distortion . 15
6.2.3 Probe measurement accuracy . 16
6.3 Complete system . 16
6.4 Function of the complete system .
6.4 Maximum permitted expanded uncertainty of measurements U . 16
max
7 General requirements . 17
7.1 Marking . 17
7.2 Instruction manual . 17
7.3 Safety requirements . 17
7.4 Immunity to power and radiofrequency fields. 17
7.5 Warm-up time . 18

7.6 Voltage supply variation and environmental conditions. 18
7.6.1 Mains operation . 18
7.6.2 Battery operation . 18
7.6.3 Environmental conditions . 18
8 Additional characteristics to be specified by the manufacturer . 18
9 Routine Periodic calibration . 18
Bibliography . 20

Table 1 – Mandatory functions for otoacoustic emission instruments. 9
Table 2 – Documentation of test conditions, parameters and results . 14
Table 3 – Values of U for basic conformance and periodic calibration
max
measurements . 17

– 4 – IEC 60645-6:2022 RLV © IEC 2022
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROACOUSTICS –
AUDIOMETRIC EQUIPMENT –
Part 6: Instruments for the measurement of otoacoustic emissions

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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6) All users should ensure that they have the latest edition of this publication.
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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.
This redline version of the official IEC Standard allows the user to identify the changes made to
the previous edition IEC 60645-6:2009. A vertical bar appears in the margin wherever a change
has been made. Additions are in green text, deletions are in strikethrough red text.

IEC 60645-6 has been prepared by IEC technical committee 29: Electroacoustics. It is an
International Standard.
This second edition cancels and replaces the first edition published in 2009. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) the nominal test frequency used in DPOAE is now defined as the higher of the two
;
frequencies, f
b) the permitted deviation of the stimulus signal for TEOAE has been specified;
c) the frequency range for DPOAE stimulus signals has been redefined,
d) the stimulus level requirements for TEOAE have been redefined;
e) the stimulus level requirements for DPOAE have been redefined;
f) the harmonic distortion requirements for DPOAE have been redefined;
g) a minimum measurement range for DPOAE has been added.
The text of this International Standard is based on the following documents:
Draft Report on voting
29/1109/FDIS 29/1114/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at http://www.iec.ch/standardsdev/publications.
A list of all parts in the IEC 60645 series, published 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
stability date indicated on the IEC website under 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.
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.

– 6 – IEC 60645-6:2022 RLV © IEC 2022
INTRODUCTION
Developments in the field of diagnostic hearing measurement have resulted in a number of
instruments designed to evaluate the otoacoustic emissions of the human ear. Such emissions
may be evoked by acoustic test signals having different spectral and temporal characteristics.
The practical use of such instruments concerns the measurement of sound energy emitted by
the inner ear and its separation from sounds emerging from other physiological or artificial other
sources.
The spontaneous otoacoustic emissions (SOAE) and stimulus frequency otoacoustic emissions
(SFOAE), which comprise part of the otoacoustic emissions, are not covered by this document.
Conformance to the performance specification in this document is demonstrated when a
measured deviation from a design goal equals or does not exceed the corresponding
acceptance limit(s), and the laboratory has demonstrated that the associated uncertainty of
measurement equals or does not exceed the maximum permitted uncertainty specified in this
document.
ELECTROACOUSTICS –
AUDIOMETRIC EQUIPMENT –
Part 6: Instruments for the measurement of otoacoustic emissions

1 Scope
This part of IEC 60645 applies to instruments designed primarily for the measurement of
otoacoustic emissions in the human external acoustic auditory meatus evoked by acoustic
probe pulses or tones stimuli. This document defines the characteristics to be specified by the
manufacturer, lays down performance specifications for two types of instruments and specifies
the functions to be provided on these types. This part of IEC 60645 describes methods of test
to be used for approval testing and guidance on methods for undertaking routine calibration
specifies minimum mandatory functions for two types of instruments and provides performance
specifications applicable to both instrument types. This document describes methods to be used
to demonstrate conformance with the specifications in this document and guidance on methods
for periodic calibration.
The purpose of this document is to ensure that measurements made under comparable test
conditions with different instruments complying with this document will be consistent.
Instruments which can provide a measurement function not specifically within the scope of this
document shall and still comply with any the relevant requirements of this document for the
functions that are within the scope. This document is not intended to restrict development or
incorporation of new features, nor to discourage innovative approaches.
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 60318-4, 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 60601-1, Medical electrical equipment – Part 1: General requirements for basic safety and
essential performance
IEC 60601-1-2, Medical electrical equipment – Part 1-2: General requirements for basic safety
and essential performance – Collateral standard: Electromagnetic compatibility disturbances –
Requirements and tests
IEC 60601-1-4, Medical electrical equipment – Part 1-4: General requirements for safety –
Collateral standard: Programmable electrical medical systems
___________
Screening and full diagnostics.
To be published.
– 8 – IEC 60645-6:2022 RLV © IEC 2022
IEC 60645-1:20012017, Electroacoustics – Audiological Audiometric equipment – Part 1: Pure-
tone audiometers Equipment for pure-tone and speech audiometry
IEC 60645-3:20072020, Electroacoustics – Audiometric equipment – Part 3: Test signals of
short duration
ISO/IEC Guide 98-3, Uncertainty of measurement – Part 3: Guide to the expression of
uncertainty in measurement (GUM:1995)
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
otoacoustic emissions
OAE
general term covering all types of acoustic signals generated in the inner ear which can be
recorded in the external acoustic auditory meatus
NOTE The spontaneous otoacoustic emissions (SOAE) and stimulus frequency otoacoustic emissions (SFOAE)
which are also a part of the otoacoustic emissions are not be covered by this standard.
3.2
transient-evoked otoacoustic emissions
TEOAE
acoustic signals emitted by the inner ear after stimulation with a stimulus of short duration
3.3
distortion product otoacoustic emissions
DPOAE
acoustic signals generated in the inner ear during stimulation with two pure tones
Note 1 to entry: The pure tones are frequencies f and f , f being the lower frequency.
1 2 1
Note 2 to entry: The frequencies of the DPOAE are given by the formulas for distortions 3f , 2f -f , 2f -f , 3f
1 1 2 2 1 2
intermodulation distortions (IMD), i.e. 2f – f , 2f – f , etc.
1 2 2 1
3.4
nominal test frequency
frequency for which a DPOAE measurement is reported
3.5
primary tones
pure-tone stimuli used to evoke DPOAE
3.6
probe
part of the instrument, usually containing acoustic transducers, interfacing the instrument to the
ear
3.7
ear tip
device used to provide a seal between the probe and the external acoustic meatus
device used to assist acoustic coupling, to reduce acoustic leakage, to reduce the influence of
environmental noise on measurements and to aid retention of the probe in the external auditory
meatus
3.8
probe signal
acoustic stimulus signal that is emitted into the external auditory meatus by means of a probe
3.9
peak-to-peak equivalent sound pressure level
peSPL
root mean squared (RMS) value of a long-duration sinusoidal sound 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., difference between the extreme positive and
the extreme negative values) as the short-duration signal
Note 1 to entry: See IEC 60645-3:20072020, Figure 2.
4 Requirements for specific instruments
Two different types of otoacoustic emission instruments are specified by the requirements for
minimum mandatory functions (see Table 1). Additional functions are not precluded. The two
types relate to their presumed primary application (diagnostic/clinical or screening); however,
a device of one type is not required to comply with the additional specifications of the other
type.
Instrument types
1 Diagnostic/clinical: Adjustable stimulus and recording parameters, result shown in a
graphical format
2 Screening: Automatic testing, automatic evaluation, results as pass/refer
Table 1 – Mandatory functions for otoacoustic emission instruments
Type
1 2
Diagnostic/clinical Screening
Automatic test x x
Manual test x
Presentation of results
Display of full result x
Display of PASS/REFER x
Display of a quality measure estimate x
Display of response significance x
Digital storage of full result x
Printout x
– 10 – IEC 60645-6:2022 RLV © IEC 2022

Type
1 2
Diagnostic/clinical Screening
Automatic test x x
Manual test x
Display of PASS/REFER x
Display of detailed result in graphical and/or tabular x
format
Display of stability of acoustic response in the x
external auditory meatus (see 5.2.1)
Display of response quality estimate (see 5.3.7) x
Digital storage of detailed result x
Export of full test report x
Type 1. This type of devices shall include the ability to manually start the test and to adjust the parameters of the
test.
Type 2. This type of device shall include the ability to automatically start the test.

5 General specifications
5.1 Acoustic stimulus system
5.1.1 General requirements
Specifications for the acoustic stimulus system are as given in the relevant parts of Clause 6,
Clause 8 and Clause 10 of IEC 60645-1:20012017 and Clause 5 of IEC 60645-3:20072020 with
the exceptions specified below.
NOTE If the instrument is designed to also allow the measurement of hearing thresholds, the full text of the relevant
clauses of IEC 60645-1:20012017 should apply applies.
5.1.2 Stimulus types
5.1.2.1 General
The general properties and temporal characteristics of the acoustic stimulus signals are
specified within 5.1.2.2 and 5.1.2.3 depending on the type of OAE being measured.
5.1.2.2 TEOAE
The full characteristics of the short-duration signal used for the measurements of TEOAE shall
be specified by the manufacturer (i.e., as specified in IEC 60645-3:20072020).
NOTE A series of clicks with different polarity and levels is often used and this is usually referred to as a "non-
linear click series". The specifications found in IEC 60645-3 are applicable to each single click in the series.
5.1.2.3 DPOAE
The stimulus signal used for the measurement of DPOAE shall be composed of two primary
tones with frequencies f and f . Although the DPOAE of principal interest is at a frequency of
1 2
– f , the nominal test frequency of the measurement normally refers to f f . If f f is used
2f
1 2 1 2 2 1
as the nominal test frequency, this shall be stated by the manufacturer. If additional test signals
are used (such as those used for masking), their full characteristics shall be specified by the
manufacturer.
5.1.3 Stimulus frequency range
5.1.3.1 General
The frequency content of the stimulus signal shall, as a minimum, meet the requirements
specified in 5.1.3.2 and 5.1.3.3 depending on the type of OAEs being measured.
5.1.3.2 TEOAE
The frequency spectrum of the transient stimulus signal shall at least cover the range from
0,5 kHz to 4 kHz for Type 1 instruments and the range from 1,5 kHz to 3 kHz for Type 2
instruments. The stimulus level frequency spectrum shall be flat within a limit of ±5 dB as
measured in an occluded-ear simulator according to IEC 60318-4 or a 2 cm coupler according
to IEC 60318-5, using the ear simulator or 2 cm coupler microphone, over the frequency range.
5.1.3.3 DPOAE
For the measurement of DPOAE, nominal stimulus frequencies between 0,5 0,75 kHz and 8 kHz
in at least three steps per octave shall be provided in instruments of Type 1 and at least two
frequencies between 1 kHz and 4 kHz for Type 2. The frequency ratio of the two primary tones
shall be stated by the manufacturer and shall normally be from 1:1,15 to 1:1,25. The actual
frequencies shall not differ from their nominal values by more than ±1 %.
The acceptance limit of the actual frequencies is ±1 %.
5.1.4 Stimulus level
5.1.4.1 General
The sound pressure level of the stimulus signals shall be variable within the ranges specified
in 5.1.4.2 and 5.1.4.3 depending on the type of OAEs. Its actual value within the residual
ear-canal volume shall be measured prior to each recording with the probe microphone.
5.1.4.2 TEOAE
The stimulus level shall provide the range from 30 dB peSPL to 90 dB peSPL for instruments
of Type 1 and from 60 dB peSPL to 80 dB peSPL for instruments of Type 2 as measured
according to IEC 60318-4 or IEC 60318-5.
For Type 1 instruments, the stimulus level shall be adjustable with a step size no greater than
5 dB and include a range of at least 60 dB peSPL to 85 dB peSPL. For Type 2 instruments, a
single fixed level of stimulus is acceptable, and this level shall be stated clearly in the
documentation since it impacts on the specificity of screening for a certain level of hearing loss.
The stimulus levels stated shall be measured in an occluded-ear simulator according to
IEC 60318-4 or a 2 cm coupler according to IEC 60318-5, using the occluded-ear simulator or
2 cm coupler microphone.
To combat possible probe placement movement during the test, it is recommended that the
stimulus level be confirmed regularly during data acquisition for both Type 1 and Type 2
instruments.
The acceptance limit of the stimulus signal given above is ±1,5 dB.
NOTE Type 2 instruments are expected to provide a stimulus level between 80 dB peSPL and 86 dB peSPL to
maintain compatibility with established neonatal hearing screening programs.

– 12 – IEC 60645-6:2022 RLV © IEC 2022
5.1.4.3 DPOAE
The levels of the primary tones under test conditions shall not deviate from the nominal levels
by more than 1,5 dB.
The stimulus levels of the primary tones shall, as a minimum, be adjustable over the range from
0 dB SPL to 70 dB SPL for instruments of Type 1 and from 50 dB SPL to 65 dB SPL for
instruments of Type 2 at all signal frequencies as measured in an occluded-ear simulator
according to IEC 60318-4 or in a reference coupler according to IEC 60318-5. The level L of
the primary tone with the lower frequency must be equal to or higher than L but shall not
exceed 90 dB SPL.
NOTE The levels should be optionally tested at regular intervals during data acquisition in instruments of Type 1.
For Type 1 instruments, the stimulus levels of the primary tones shall be adjustable with a step
size no greater than 5 dB and include a range from 30 dB SPL to 70 dB SPL. For Type 2
instruments, a single fixed level for each of the two stimuli is acceptable but shall be stated
clearly in the documentation since it impacts on the specificity of screening for a certain level
of hearing loss. This measurement shall be performed in an occluded-ear simulator according
to IEC 60318-4 or in a 2 cm coupler according to IEC 60318-5 using the occluded-ear simulator
or 2 cm coupler microphone. The level L of the primary tone with the lower frequency shall be
equal to or higher than L but shall not exceed 90 dB SPL.
To combat possible probe placement movement during the test, it is recommended that the
stimuli level be confirmed regularly during data acquisition for both Type 1 and Type 2
instruments.
The acceptance limit of the primary tones given above under test conditions is 1,5 dB.
NOTE Type 2 instruments are expected to provide stimuli levels that fall between 55 dB SPL and 70 dB SPL at all
signal frequencies to maintain compatibility with established neonatal hearing screening programs.
5.1.5 Harmonic Intermodulation distortion
For DPOAE stimuli, the total harmonic distortion of the acoustic test signal shall be less than
0,1 %. The total cubic distortion due to non-linear interactions between the two primary tones
shall be less than 0,01 %.
The intermodulation distortion due to non-linear interactions between the two primary tones
shall be less than 0,01 % at the clinically important distortion product frequency of 2f – f . This
1 2
measurement shall be performed in an occluded-ear simulator according to IEC 60318-4 or in
a 2 cm coupler according to IEC 60318-5 using the microphone and measurement system of
the OAE instrument. The maximum distortion limit of 0,01 % shall be achieved over the entire
frequency range and stimuli levels offered by the instrument.
NOTE No requirements are specified for TEOAE.
5.2 Test quality assuring system
5.2.1 General Stability of acoustic response in the external auditory meatus
The acoustic conditions in the ear canal shall be checked by the ear probe and optionally
adapted automatically to a predefined waveform and level before starting data acquisition and
after its completion. From the comparison of the initial and the final state, stability shall be
derived.
The acoustic conditions in the external auditory meatus shall be checked by measuring the
acoustic response and optionally adapting this to a pre-defined level and waveform. The
acoustic conditions shall be checked again after the data acquisition is completed before the

probe is removed from the ear and the stability of the measurement shall be derived from these
checks. Optionally, intermediate checks can be performed.
5.2.2 Test quality assurance
The following functions shall be available: ambient noise detection, leak detection, blocked
probe detection.
5.2.3 Individual stimulus recordings
An oscillogram and a frequency spectrum of the stimulus recorded in the ear canal shall be
generated and stored for TEOAE results in Type 1 instruments.
NOTE Additional intermediate oscillograms and spectra should be provided during the recording process in
instruments of Type 1.
For Type 1 TEOAE instruments, the waveform and/or frequency spectrum of the stimulus
recorded in the external auditory meatus shall be stored. An option may be provided to display
the stored results.
It is recommended that intermediate recordings of this stimulus are used to provide an indication
of the probe stability during the measurement.
5.3 Measuring system
5.3.1 Units of measurement
SI units or derived SI units shall be used. The units of measurement shall be indicated.
5.3.2 Measurement range
The minimum measurement range for OAE shall be from -20 dB SPL to +30 dB SPL.
Instruments shall be able to measure TEOAE over a range of at least –20 dB SPL to +30 dB
SPL and DPOAE over a range of at least –10 dB SPL to +30 dB SPL.
5.3.3 Accuracy of measurement
The difference between indicated and actual sound pressure levels shall not exceed ±3 dB for
frequencies up to 4 kHz and ±5 dB for higher frequencies.
The probe microphone shall measure the actual sound pressure level over the OAE frequency
range. The acceptance limit for this measurement is ±3 dB for frequencies up to 4 kHz and
±5 dB at higher frequencies. If measurement points other than the probe microphone position
are used, then the actual measurement points shall be stated by the manufacturer.
NOTE This performance limit of the standard relates to the probe microphone and input channel calibration accuracy
(see 6.2.3 for details).
5.3.4 Frequency range
The frequency range of the measuring system shall be according to the applicable stimulus
frequency range in 5.1.3 with accuracy defined in 5.3.3.
5.3.5 Noise reduction
The ambient noise shall be reduced by at least 30 dB in the relevant frequency range when
measured in an occluded-ear simulator according to IEC 60318-4 or in a reference coupler
according to IEC 60318-5.
– 14 – IEC 60645-6:2022 RLV © IEC 2022
Instruments shall be able to reduce the influence of ambient noise by at least 30 dB in the
relevant frequency range when measured in an occluded-ear simulator according to
IEC 60318-4 or in a 2 cm coupler according to IEC 60318-5.
NOTE Methods employed to reduce the influence of ambient noise include sound isolation provided by the probe
tip and signal averaging and/or other signal processing techniques.
5.3.6 Response detection
If an algorithm is used for automatic detection, the statistical significance of the algorithm shall
be validated by the manufacturer. Instruments that provide an automated PASS/REFER
decision algorithm shall document and make available the statistical sensitivity of the algorithm
under realistic test conditions of no OAE present (see 6.3). During the measurement, a stimulus
artefact rejection system shall be used, and its characteristics shall be specified by the
manufacturer.
5.3.7 Response quality estimates
The method used for determination of the residual noise shall be described.
The instrument shall provide indication(s) as to the degree that the result is contaminated by
the presence of noise (and/or other measurement quality metrics). The method used to
determine the degree of contamination shall be described in the documentation.
5.3.8 Normative values
If normative values are used (e.g. for calibration, PASS/REFER criteria), the source of these
values shall be stated in the instruction manual.
5.4 Presentation of results
5.4.1 General
All relevant information shall be stored and be available on demand. The information shall be
presented on the display of the instrument, in electronic form and/or as a paper printout. The
explanation of the relevant information required is given in Table 2.
Table 2 – Documentation of test conditions, parameters and results
Type
1 2
Diagnostic/clinical Screening
Stimulus level x
Recorded OAEs Number of epochs or time of recorded
x
data
Number of artefacts epochs or time of rejected data x
Artefact rejection limit x
a
x
Graphic display of full detailed result
Display of PASS/REFER x
Residual noise estimate x
OAE to noise ratio x
a
Oscillogram Waveform (TEOAE) and/or frequency spectrum (TEOAE and DPOAE), respectively.

5.4.2 Primary results
5.4.2.1 Presentation
Averaged signal, estimated residual noise and total signal (OAE and noise) separately.
5.4.2.2 TEOAE
Time domain (oscillogram).
5.4.2.3 DPOAE
Frequency domain (spectrum).
5.4.3 Secondary results
5.4.3.1 TEOAE
Time slices and frequency ranges, estimated true level (noise correction), cross correlation
(reproducibility).
5.4.3.2 DPOAE
Estimated true level (corrected for noise), signal-to-noise ratio.
6 Demonstration of conformity with specifications
6.1 General
The following procedures shall be used for ensuring that an instrument meets the specifications
given in this document. Guidelines for routine periodic calibration are described in Clause 9.
6.2 Probe signal
6.2.1 Probe signal frequency spectrum
The probe signal frequency spectrum shall be measured by coupling the probe to an occluded-
ear simulator or reference 2 cm coupler according to IEC 60318-4 and IEC 60318-5,
respectively, and according to the instructions provided by the manufacturer. The occluded-ear
simulator or 2 cm coupler to be used and the method of coupling shall be stated by the
manufacturer.
Since both the occluded-ear simulator and 2 cm couplers have ¼ wave resonances within the
frequency range of typical OAE measurements, the manufacturer shall state clearly whether
the probe signal spectrum is measured using the test-cavity measurement microphone or the
probe microphone.
6.2.2 Probe signal level and harmonic distortion
The signal level and the harmonic distortion of the probe signal shall be measured by means of
an occluded-ear simulator according to IEC 60318-4 or a reference 2 cm coupler according to
IEC 60318‑5, to which the probe is coupled with the ear tip placed according to instructions
provided by the manufacturer.
Since both the simulator and 2 cm couplers have ¼ wave resonances within the frequency
range of typical OAE measurements, the manufacturer shall state clearly whether the probe
signal spectrum is measured using the cavity measurement microphone or the probe
microphone.
– 16 – IEC 60645-6:2022 RLV © IEC 2022
6.2.3 Probe measurement accuracy
The probe microphone accuracy is determined by measuring the output of the probe microphone
in the presence of a known sound field presented over the range of frequencies stipulated in
5.1.3.
Suggested verification methods are:
– free-field with a calibrated measurement microphone in the same sound field as the probe
microphone;
– the use of a measurement microphone and a test cavity with dimensions such that the first
¼ wave resonance is above the highest OAE measurement frequency of the instrument.
If other measurement methods are used, these shall be specified by the manufacturer.
6.3 Complete system
The performance of the complete test system shall be tested by coupling the probe to an
occluded-ear simulator according to IEC 60318-4 or a 2 cm coupler according to IEC 60318-5,
with the ear tip placed according to the instructions provided by the manufacturer. On
completion of the test, no response shall be detected.
If the instrument provides automatic PASS/REFER decision algorithms, these tests shall be
performed in the presence of acoustic noise with a typical frequency spectrum and at a level
which triggers the noise rejection at least 10 % of the time. The procedures employed during
this testing and the corresponding results shall be documented by the manufacturer.
Some test equipment specifically designed for neonatal hearing screening cannot perform these
tests in the occluded-ear simulator or 2 cm coupler specified above due to the cavity size. In
this instance, the manufacturer shall provide the necessary information on how to perform the
function test of the complete system using an alternative neonatal test cavity or ear simulator.
NOTE One example of an alternative neonatal test cavity is given in IEC 60318-8.
6.4 Maximum permitted expanded uncertainty of measurements U
max
Table 3 specifies the maximum permitted expanded uncertainty U calculated with a
max
coverage factor of k = 2 to give a level of confidence of approximately 95 %, associated with
the measurements undertaken in this part of IEC 60645, according to ISO/IEC Guide 98-3. One
set of values for U is given for basic type approval measurements.
max
Table 3 specifies the maximum permitted expanded uncertainty for a coverage factor of k = 2
according to ISO/IEC Guide 98-3, associated with the measurements undertaken in this
document. One set of values for U is given for conformance testing and periodic calibration.
max
The expanded uncertainties of measurement given in Table 3 are the maximum permitted for
demonstration of conformance to the requirements of this document. If the actual expanded
uncertainty of a measurement performed by the test laboratory or maintenance service exceeds
the maximum permitted value in Table 3, the measurement shall not be used to demonstrate
conformance to the requirements of this document.

Table 3 – Values of U for basic conformance and periodic calibration measurements
max
Measured Relevant Basic
quantity subclause number U (k = 2)
max
Stimulus levels 5.1.4.2, 5.1.4.3 1,0 dB
Stimulus level deviation 5.1.4.3 0,4 dB
Frequency 5.1.3.2, 5.1.3.3 0,5 %
Total harmonic distortion 5.1.5 0,05 %
Cubic Intermodulation distortion 5.1.5 0,005 %
Measurement range 5.3.2 1,0 dB
Accuracy of measurement up to 4 kHz 5.3.3 0,7 dB
Accuracy of measurement higher than 4 kHz 5.3.3 1,2 dB
Noise reduction 5.3.5 1,0 dB
Temperature 7.6.3
0,5 °C
Relative humidity 7.6.3 5 %
Ambient pressure 7.6.3 0,1 kPa
6.4 Function of the complete system
The function of the complete test system shall be proven by coupling the probe to an occluded-
ear simulator according to IEC 60318-4 or a reference coupler according to IEC 60318-5, with
the ear tip placed according to the instructions provided by the manufacturer and performing
the test. No response shall be detected.
NOTE If the test cannot be performed with the occluded-ear simulator or reference coupler specified above, the
manufacturer should provide the necessary information on how to perform the function test of the complete system.
7 General requirements
7.1 Marking
The instrument shall be marked with the name of the manufacturer, the type as defined in
Clause 4, the model and its serial number as well as the identification of the transducer(s)
employed.
If a transducer can be detached by the user, the transducer and/or the instrument shall be
marked or identified, for example with a serial number, to prevent unintended interchange of
transducers.
7.2 Instruction manual
An instruction manual shall be supplied with each instrument. In this manual,
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