IEC 60645-1:2012

IEC 60645-1 ®
Edition 3.0 2012-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electroacoustics – Audiometric equipment –
Part 1: Equipment for pure-tone audiometry

Électroacoustique – Appareils audiométriques –
Partie 1: Appareils pour l’audiométrie tonale

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IEC 60645-1 ®
Edition 3.0 2012-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electroacoustics – Audiometric equipment –

Part 1: Equipment for pure-tone audiometry

Électroacoustique – Appareils audiométriques –

Partie 1: Appareils pour l’audiométrie tonale

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX V
ICS 17.140.50 ISBN 978-2-88912-915-7

– 2 – 60645-1 © IEC:2012
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 9
4 Requirements for specific types of fixed frequency audiometer . 12
5 General requirements . 13
5.1 General safety requirements . 13
5.2 Acoustic safety requirements . 13
5.3 Environmental conditions . 13
5.4 Warm-up time . 13
5.5 Power supply variation . 13
5.5.1 Interruption of power supply . 13
5.5.2 Mains operation . 14
5.5.3 Battery operation . 14
5.5.4 Other power supplies . 14
5.6 Electromagnetic compatibility . 14
5.7 Unwanted sound . 14
5.7.1 General . 14
5.7.2 Unwanted sound from an earphone . 14
5.7.3 Unwanted sound from a bone vibrator . 14
5.7.4 Unwanted sound radiated by an audiometer . 15
5.8 Testing of automatic-recording audiometers . 15
5.9 Interface connections . 15
6 Test signals . 15
6.1 Pure tones . 15
6.1.1 Frequency range and hearing level range . 15
6.1.2 Frequency accuracy . 16
6.1.3 Total harmonic distortion . 16
6.1.4 Rate of frequency change . 17
6.2 Frequency modulation . 17
6.3 External signal source . 17
6.3.1 Signals . 17
6.3.2 Frequency response . 17
6.3.3 Electrical sensitivity . 18
6.3.4 Reference level for external signal source . 18
6.3.5 Operator to subject speech communication . 18
6.3.6 Subject to operator speech communication . 18
6.4 Masking sound . 18
6.4.1 General . 18
6.4.2 Narrow-band noise . 18
6.4.3 Other masking sound . 20
7 Transducers . 20
7.1 Type of transducers . 20
7.2 Headband. 20

60645-1 © IEC:2012 – 3 –
7.3 Loudspeaker . 20
8 Signal level control . 20
8.1 Marking . 20
8.2 Signal indicator . 20
8.3 Accuracy of sound pressure level and vibratory force level . 21
8.4 Hearing level control . 21
8.4.1 Manual audiometers . 21
8.4.2 Automatic-recording audiometers . 21
8.4.3 Accuracy of control . 21
8.5 Masking level control . 22
8.5.1 General . 22
8.5.2 Masking level . 22
8.5.3 Accuracy of masking levels. 22
8.5.4 Masking level range . 22
8.6 Tone switching . 22
8.6.1 Tone switch for manual audiometers . 22
8.6.2 On/off ratio for manual audiometers . 22
8.6.3 Rise/fall times for manual audiometers . 23
8.6.4 Automatic pulsed presentation . 23
8.6.5 Subject’s response time for automated test procedures . 24
8.6.6 Subject’s response system . 24
9 Reference tone . 24
9.1 General . 24
9.2 Frequencies . 24
9.3 Reference tone level control . 25
9.3.1 Range . 25
9.3.2 Intervals . 25
9.3.3 Marking . 25
9.3.4 Accuracy . 25
9.3.5 Operation . 25
10 Calibration . 25
11 Electrical output of test signals . 26
12 Audiogram format . 26
13 Test requirements to demonstrate conformity . 27
13.1 General . 27
13.2 Environmental conditions and power supply variation . 27
13.3 Electromagnetic compatibility . 27
13.4 Unwanted sound . 28
13.4.1 Unwanted sound from an earphone . 28
13.4.2 Unwanted sound from a bone vibrator . 28
13.4.3 Unwanted sound radiated by an audiometer . 29
13.5 Total harmonic distortion of test signals . 29
13.6 Signal accuracy . 29
13.6.1 Accuracy of sound pressure level and vibratory force level . 29
13.6.2 Accuracy of hearing level control . 29
13.7 Masking sound . 29
13.7.1 Narrow-band noise . 29
13.7.2 Masking level . 30

– 4 – 60645-1 © IEC:2012
13.8 Headbands . 30
13.8.1 General . 30
13.8.2 Supra-aural and circumaural earphone headband . 30
13.8.3 Bone vibrator headband . 30
14 Maximum permitted expanded uncertainty of measurements U . 30
max
15 Marking and instruction manual . 31
15.1 Marking . 31
15.2 Instruction manual . 31
Bibliography . 33

Figure 1 – Rise/fall envelope of test tones . 24

Table 1 – Minimum facilities for fixed-frequency audiometers . 12
Table 2 – Minimum number of frequencies to be provided and the minimum range of
values of hearing level for fixed frequency audiometers . 15
Table 3 – Minimum range of values of hearing level for EHF audiometers . 16
Table 4 – Maximum permissible acoustic total harmonic distortion, for supra-aural,

circumaural, insert earphones and bone vibrators . 17
Table 5 – Narrow-band masking noise: upper and lower cut-off frequencies for a
sound pressure spectrum density level of –3 dB referred to the level at the centre
frequency of the band . 19
Table 6 – Reference standards for obtaining audiometric zero . 26
Table 7 – Symbols for the graphical presentation of hearing threshold levels . 26
Table 8 – Values of U for basic measurements . 31
max
60645-1 © IEC:2012 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROACOUSTICS –
AUDIOMETRIC EQUIPMENT –
Part 1: Equipment for pure-tone audiometry

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 co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
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 60645-1 has been prepared by IEC technical committee 29:
Electroacoustics.
This third edition cancels and replaces the second edition, published in 2001, and
IEC 60645-4 published in 1994. It constitutes an editorial revision.
The text of this standard is based on the following documents:
FDIS Report on voting
29/754/FDIS 29/757/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

– 6 – 60645-1 © IEC:2012
A list of all parts of the IEC 60645 series can be found, under the general title
Electroacoustics, on the IEC website.
Future standard in this series will carry the new general title as cited above. Titles of existing
standards in this series will be updated at the time of the next edition.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
60645-1 © IEC:2012 – 7 –
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 audiometers. In
addition it is possible to consider the audiometer in terms of a set of functional units which
can be specified independently. By specifying these functional units it is then possible to
specify the performance of other audiometric equipment which use these units. IEC 60645
series consists of a number of parts. IEC 60645-1 is the first in the series and covers the
requirements for pure tone audiometers.
This standard describes equipment which is designed for the measurement of hearing in the
frequency range from 125 Hz to 16 000 Hz.
Due to the development of the later parts of IEC 60645, no reference is now made in part 1 to
the use of broad-band noise for masking. Requirements for broad-band masking noise now
only relate to its use with speech signals as described in IEC 60645-2.
The test requirements to demonstrate conformity are now specified separately. Conformance
to the specifications in this standard is demonstrated only when the result of a measurement,
extended by the actual expanded uncertainty of measurement of the testing laboratory, lies
fully within the tolerances specified in this standard. The tolerances that are to be met by the
manufacturer of an audiometer are essentially the same as in the first edition of IEC 60645-1,
while the tolerances as applicable to the testing of the audiometer are increased by U
max
compared with those of the previous edition.
IEC 60645 series consists of the following parts:
IEC 60645-1, Electroacoustics – Audiometric equipment – Part 1: Equipment for pure-tone
audiometry
IEC 60645-2, Audiometers – Part 2: Equipment for speech audiometry
IEC 60645-3, Electroacoustics – Audiometric equipment – Part 3: Test signals of short
duration
IEC 60645-4, Audiometers – Part 4: Equipment for extended high-frequency audiometry
IEC 60645-5, Electroacoustics – Audiometric equipment – Part 5: Instruments for the
measurement of aural acoustic impedance/admittance
IEC 60645-6, Electroacoustics – Audiometric equipment – Part 6: Instruments for the
measurement of otoacoustic emissions
IEC 60645-7, Electroacoustics – Audiometric equipment – Part 7: Instruments for the
measurement of auditory brainstem responses

– 8 – 60645-1 © IEC:2012
ELECTROACOUSTICS –
AUDIOMETRIC EQUIPMENT –
Part 1: Equipment for pure-tone audiometry

1 Scope
This part of IEC 60645 specifies general requirements for audiometers and particular
requirements for pure-tone audiometers designed for use in determining hearing threshold
levels, relative to standard reference threshold levels established by means of psychoacoustic
test methods.
The object of this standard is to ensure:
a) that tests of hearing in the frequency range 125 Hz to 16 000 Hz on a given human ear,
performed with different audiometers which comply with this standard shall give
substantially the same results;
b) that the results obtained represent a valid comparison between the hearing of the ear
tested and the reference threshold of hearing;
c) that audiometers are classified according to the range of test signals they generate,
according to the mode of operation or according to the complexity of the range of auditory
functions they test.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60268-3, Sound system equipment – Part 3: Amplifiers
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 cm³ 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 of bone vibrators
IEC 60601-1, Medical electrical equipment – Part 1: General requirements for basic safety
and essential performance
60645-1 © IEC:2012 – 9 –
IEC 60601-1-2, Medical electrical equipment – Part 1-2: General requirements for basic safety
and essential performance – Collateral standard: Electromagnetic compatibility –
Requirements and tests
IEC 60645-2, Audiometers – Part 2: Equipment for speech audiometry
IEC 61672-1, Electroacoustics – Sound level meters – Part 1: Specifications
ISO 266, Acoustics – Preferred frequencies
ISO 389-1, Acoustics – Reference zero for the calibration of audiometric equipment – Part 1:
Reference equivalent threshold sound pressure levels for pure tones and supra-aural
earphones
ISO 389-2, Acoustics – Reference zero for the calibration of audiometric equipment – Part 2:
Reference equivalent threshold sound pressure levels for pure tones and insert earphones
ISO 389-3, Acoustics – Reference zero for the calibration of audiometric equipment – Part 3:
Reference equivalent threshold force levels for pure tones and bone vibrators
ISO 389-4:1994, Acoustics – Reference zero for the calibration of audiometric equipment –
Part 4: Reference levels for narrow-band masking noise
ISO 389-5, Acoustics – Reference zero for the calibration of audiometric equipment – Part 5:
Reference equivalent threshold sound pressure levels for pure tones in the frequency range
8 kHz to 16 kHz
ISO 389-7, Acoustics – Reference zero for the calibration of audiometric equipment – Part 7:
Reference threshold of hearing under free-field and diffuse-field listening conditions
ISO 389-8, Acoustics – Reference zero for the calibration of audiometric equipment – Part 8:
Reference equivalent threshold sound pressure levels for pure tones and circumaural
earphones
ISO 4869-1, Acoustics – Hearing protectors – Part 1: Subjective method for the measurement
of sound attenuation
ISO 8253-1:2010, Acoustics – Audiometric test methods – Part 1: Pure-tone air and bone
conduction audiometry
ISO 8253-2, Acoustics – Audiometric test methods – Part 2: Sound field audiometry with pure-
tone and narrow-band test signals
ISO 8253-3, Acoustics – Audiometric test methods – Part 3: Speech audiometry
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
equipment for pure-tone audiometry
pure-tone audiometer
instrument for the measurement of hearing for pure tones and in particular the threshold of
hearing
Note 1 to entry The pure-tone audiometer may be either of a fixed or continuous sweep frequency type.

– 10 – 60645-1 © IEC:2012
3.2
manual audiometer
audiometer in which signal presentations and recording of results are performed manually
3.3
automatic-recording audiometer
audiometer in which signal presentations, hearing level variation, frequency selection or
frequency variation, and recording of subject’s responses are implemented automatically
Note 1 to entry Hearing level change is under subject’s control and is recorded automatically.
3.4
equipment for speech audiometry
speech audiometer
instrument for the measurement of hearing for speech test material
3.5
air conduction
transmission of sound through the external and middle ear to the inner ear
3.6
bone conduction
stimulation of the inner ear mediated primarily by mechanical vibration of the cranial bones
3.7
extended high frequency
EHF
audiometric test frequency in the range from 8 000 Hz to 16 000 Hz
Note 1 to entry The frequency 8 000 Hz is considered both as the highest frequency in the conventional range
and as the lowest frequency of the extended high-frequency range.
3.8
otologically normal person
person in a normal state of health who is free from all signs and symptoms of ear disease and
from obstructing wax in the ear canal and has no history of undue exposure to noise, to
potentially ototoxic drugs, or of familial hearing loss
3.9
equivalent threshold sound pressure level
monaural earphone listening
for a given ear, at a specified frequency, for a specified type of earphone and for a stated
force of application of the earphone to a human ear, the sound pressure level set up by the
earphone in a specified ear simulator or acoustic coupler when the earphone is activated by
that electrical input which, with the earphone applied to the ear concerned, would correspond
to the threshold of hearing
3.10
equivalent threshold force level
monaural listening
for a given ear, at a specified frequency, for a specified configuration of bone vibrator on a
specified mechanical coupler, the force level set up by the bone vibrator in a specified
mechanical coupler when the bone vibrator is activated by that voltage which, with the bone
vibrator applied to the mastoid prominence or to the forehead, would correspond to the
threshold of hearing
Note 1 to entry This definition requires the non-test ear to be masked in accordance with ISO 389-4.

60645-1 © IEC:2012 – 11 –
3.11
reference equivalent threshold sound pressure level
RETSPL
at a specified frequency, the median, mean or modal value of the equivalent threshold sound
pressure levels of a sufficiently large number of ears of otologically normal persons of both
sexes aged between 18 years and 25 years inclusive, expressing the threshold of hearing in a
specified ear simulator or acoustic coupler for a specified earphone
Note 1 to entry Values of RETSPL are specified in ISO 389-1, ISO 389-2, ISO 389-5 and ISO 389-8.
Note 2 to entry Some parts of the ISO 389 series specify reference equivalent threshold levels for the age group
18 years to 30 years inclusive.
3.12
reference equivalent threshold force level
RETFL
at a specified frequency, the mean value of the equivalent threshold force levels of a
sufficiently large number of ears of otologically normal persons of both sexes aged between
18 years and 25 years inclusive, expressing the threshold of hearing in a specified
mechanical coupler for a specified configuration of bone vibrator
Note 1 to entry Mean values of reference equivalent threshold force levels are specified in ISO 389-3.
Note 2 to entry In some parts of the ISO 389 series an age range of 18 years to 30 years have been used.
3.13
hearing level of a pure tone
HL
at a specified frequency, for a specific type of transducer and for a specified manner of
application, the sound pressure level or the vibratory force level set up by the transducer in a
specified ear simulator, acoustic coupler or mechanical coupler minus the appropriate
RETSPL or RETVFL
3.14
hearing threshold level for pure tones
at a specified frequency, the threshold of hearing at that frequency expressed as hearing level
Note 1 to entry Methods of determining thresholds of hearing are specified in ISO 8253-1:2010.
3.15
ear simulator
device for measuring the acoustic output of sound sources where the sound pressure is
measured by a calibrated microphone coupled to the source so that the overall acoustical
impedance of the device approximates that of the normal human ear at a given location and in
a given frequency band
Note 1 to entry Two types of ear simulator are specified in IEC 60318-1 and IEC 60318-4.
3.16
acoustic coupler
device for measuring the acoustic output of sound sources where the sound pressure is
measured by a calibrated microphone coupled to the source by a cavity of predetermined
shape and volume which does not necessarily approximate the acoustical impedance of the
normal human ear
Note 1 to entry Two types of acoustic coupler are specified in IEC 60318-3 and IEC 60318-5.
3.17
mechanical coupler
device designed to present a specified mechanical impedance to a vibrator applied with a
specified static force and equipped with a mechano-electric transducer to enable the

– 12 – 60645-1 © IEC:2012
alternating force level at the surface of contact between the vibrator and the mechanical
coupler to be determined
Note 1 to entry A mechanical coupler is specified in IEC 60318-6.
3.18
masking
process by which the threshold of hearing of a sound is raised by the presence of another
(masking) sound
3.19
effective masking level
level of a specified masking sound which is numerically equal to that hearing level to which
the tone threshold of the notional normal person would be raised by the presence of that
masking sound
Note 1 to entry The notional normal person is one whose hearing conforms to the standards for threshold and for
masking efficiency (ISO 389-1, ISO 389-2, ISO 389-4 and ISO 389-8).
Note 2 to entry Effective masking is thus analogous to hearing level (see 3.14), i.e. it is a measure of sound on a
physical scale, independent of a particular ear under test.
Note 3 to entry Reference values for effective masking are given in ISO 389-4.
4 Requirements for specific types of fixed frequency audiometer
Four different types of audiometers are specified by the requirements for minimum mandatory
facilities in Table 1. Other facilities are not precluded. The four types relate to their presumed
primary application.
Table 1 – Minimum facilities for fixed-frequency audiometers
Type 1 Type 2 Type 3 Type 4
Facility
Advanced Clinical Basic diagnostic Screening/
clinical/research monitoring
Air conduction
– two earphones X X X X
– additional insert X
earphone
Bone conduction X X X
Hearing levels and test
frequencies (see Table 2
and Table 3)
Narrow-band masking X X X
noise
Input for external signals X X
Tone switching
a
– tone presentation X X X X
b
– tone interruption X X X
– pulsed tone X X
Routing of masking
– contralateral earphone X X X
– ipsilateral earphone X
– bone vibrator X
c
Reference tone
– alternate presentation X X
– simultaneous X
presentation
b
Subject’s response system X X X X

60645-1 © IEC:2012 – 13 –
Type 1 Type 2 Type 3 Type 4
Facility
Clinical Basic diagnostic
Advanced Screening/
clinical/research monitoring
Electrical signal output X X
Signal indicator X X
Audible monitoring of test
signal
– pure tones and noise X
– external input X
Speech communication
– operator to subject X X
– subject to operator X
NOTE The extended high-frequency range (EHF range) is optional for all four types of audiometers.
a
Not mandatory for automatic recording audiometers, except for calibration purposes.
b
Not mandatory for manual audiometers.
c
The minimum requirement is for presentation of reference tones of the same frequency as the test tones.

5 General requirements
5.1 General safety requirements
Audiometers shall conform to IEC safety requirements (see IEC 60601-1) except where
otherwise specified in this standard.
5.2 Acoustic safety requirements
As audiometers are capable of producing sound pressure levels that could cause hearing
damage, a non-auditory warning indication to the operator is required for all settings above
100 dB hearing level.
5.3 Environmental conditions
The specifications shall be met for combinations of temperature within the range of 15°C to
35°C, relative humidity within the range of 30 % to 90 % and ambient pressure within the
range of 98 kPa to 104 kPa.
The actual values of the environmental parameters at the time of calibration shall be stated.
NOTE Reference equivalent threshold sound pressure levels may differ significantly with ambient pressures
outside the above range. Therefore recalibration around the nominal ambient pressure at the site of the user
should be undertaken in those circumstances where the calibration site and the user site do not share similar
ambient conditions.
5.4 Warm-up time
The performance requirements shall be met after the stated warm-up time has elapsed and
after any setting up adjustments have been carried out in accordance with the manufacturer’s
instructions. The minimum warm-up time shall be specified by the manufacturer but shall not
exceed 10 min when the audiometer has been kept at the ambient temperature of the test
environment.
5.5 Power supply variation
5.5.1 Interruption of power supply
If any interruption of the power supply occurs for up to 5 s, the audiometer shall revert to a
condition that will neither endanger the subject’s hearing, nor yield invalid results.

– 14 – 60645-1 © IEC:2012
5.5.2 Mains operation
The specifications shall be met when any long term deviation in mains supply voltage or
frequency, in combination, is the least favourable within the limits of ± 10 % of the stated
mains supply voltage and ± 5 % of the stated mains frequency.
5.5.3 Battery operation
The manufacturer shall specify the limits of battery voltage within which the specifications
shall be met. A suitable indicator shall be provided to ensure that the battery voltage is within
the specified limits. The specification of the audiometer shall be met at all battery voltages
within the specified limits.
5.5.4 Other power supplies
If the audiometer is powered by means other than by mains or battery, the manufacturer shall
state the type of power supply, its characteristics and tolerances within which the
specifications of the audiometer shall be met.
5.6 Electromagnetic compatibility
During, and as a result of, any EMC immunity testing, under the EMC test conditions
according to IEC 60601-1-2, the unwanted sound from any air conduction transducer shall not
exceed a hearing level corresponding to 80 dB. Subclause 13.3 provides methods for showing
conformity.
5.7 Unwanted sound
5.7.1 General
Objective acoustical measurements (see 13.4) may be impracticable for testing for the
presence of unwanted sound from the audiometer. Therefore, subjective tests shall be
performed using at least two otologically normal test subjects whose hearing threshold levels
shall not exceed 10 dB for the test frequencies 250 Hz to 8 kHz. The test room for subjective
tests shall meet the requirements of Table 4 of ISO 8253-1:2010, (see right hand column of
table). For EHF audiometers these tests shall cover frequencies up to the highest frequency
available.
NOTE For the frequency range above 8 kHz test rooms according to ISO 8253-1:2010 have shown in practice to
provide sufficiently low ambient noise levels.
5.7.2 Unwanted sound from an earphone
Unwanted sound from an earphone may arise from electrical signals generated in a variety of
ways within the audiometer when the tone switch is “OFF”. An unwanted tone (commonly
called breakthrough or cross talk) may also occur in the non-test earphone when the test tone
is “ON”. Specific requirements and an indirect electrical measurement method and a
subjective method of verifying performance are described in 13.4.1.
An unwanted tone may also occur in the earphone due to the tone switch not being
completely effective. Requirements for the tone switch are described in 8.6.
5.7.3 Unwanted sound from a bone vibrator
The manufacturer shall state at which test frequencies the bone vibrator might radiate sound
to such an extent that the sound reaching the test ear by air conduction through the
unoccluded ear canal might impair the validity of the bone conduction measurement. The
manufacturer shall also state the possible extent of this impairment. A method to show
conformity with this requirement is given in 13.4.2.

60645-1 © IEC:2012 – 15 –
5.7.4 Unwanted sound radiated by an audiometer
Where audiometers are intended to be used with the subject in the same room, any sound
due to the operation of the audiometer controls during the actual listening test, radiation from
the audiometer, or radiation from any part of a computer system used in conjunction wi
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