IEC 60118-15:2012

IEC 60118-15 ®
Edition 1.0 2012-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electroacoustics – Hearing aids –
Part 15: Methods for characterising signal processing in hearing aids with a
speech-like signal
Électroacoustique – Appareils de correction auditive –
Partie 15: Méthodes de caractérisation du traitement des signaux dans les
appareils de correction auditive avec un signal de type parole

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IEC 60118-15 ®
Edition 1.0 2012-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electroacoustics – Hearing aids –

Part 15: Methods for characterising signal processing in hearing aids with a

speech-like signal
Électroacoustique – Appareils de correction auditive –

Partie 15: Méthodes de caractérisation du traitement des signaux dans les

appareils de correction auditive avec un signal de type parole

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX V
ICS 17.140.50 ISBN 978-2-88912-932-4

– 2 – 60118-15  IEC:2012
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 8
4 Limitations . 9
5 Setup . 9
5.1 System overview . 9
5.2 Estimated insertion gain . 11
5.3 Coupler gain . 12
6 Test equipment . 12
6.1 Acoustical requirements . 12
6.2 Test signal . 13
6.2.1 Specification of ISTS . 13
6.2.2 Shaping of the test signal for determining the EIG . 14
6.3 Earphone coupler and attachments . 15
6.3.1 Estimated insertion gain . 15
6.3.2 Coupler gain . 15
7 Test conditions . 15
7.1 Programming of hearing aid . 15
7.2 End user settings for programming . 16
7.2.1 Hearing aid features . 16
7.2.2 Vent selection for programming . 16
7.2.3 Directionality . 16
7.3 Audiograms for a typical end-user . 16
8 Measurements and analysis . 18
8.1 Measurements . 18
8.1.1 General . 18
8.1.2 Estimated insertion gain (EIG) . 19
8.1.3 Coupler gain (optional for 2 cm coupler) . 19
8.2 Analysis . 19
8.2.1 General . 19
8.2.2 Compensating for hearing aid processing delay . 21
8.2.3 Correction for use of 2 cm coupler for EIG determination . 21
8.2.4 Calculation of the estimated insertion gain for the LTASS of the ISTS
(LTASS EIG) . 21
8.2.5 Calculation of the coupler gain for the LTASS of the ISTS (LTASS
coupler gain) (optional) . 22
8.2.6 Sectioning of recorded signals for percentile calculations . 22
th th th
8.2.7 Calculation of the EIG for the 30 , 65 and 99 percentiles of the
ISTS (percentile EIG) . 23
th th th
8.2.8 Calculation of the coupler gain for the 30 , 65 and 99 percentiles
of the ISTS (Percentile coupler gain) (optional) . 23
9 Data presentation . 24
9.1 LTASS gain (LTASS EIG or LTASS coupler gain) . 24
9.2 Percentile gain (percentile EIG or percentile coupler gain) . 25

60118-15  IEC:2012 – 3 –
9.3 Interpretation of gain views . 26
9.3.1 LTASS gain view . 26
9.3.2 Percentile gain view . 26
9.4 Mandatory data . 27
Annex A (informative) International speech test signal (ISTS) . 28
Bibliography . 32

Figure 1 – Measurement setup for the estimated insertion gain . 11
Figure 2 – Measurement setup for the coupler gain. 12
th th th
Figure 3 – ISTS 30 , 65 , 99 percentiles and LTASS in dB versus one-third-octave
bands . 14
Figure 4 – Standard audiograms for the flat and moderately sloping group . 17
Figure 5 – Standard audiograms for the steep sloping group . 18
Figure 6 – Overview of analysis . 20
Figure 7 – Time alignment of output signal (y) relative to the input signal (x) . 21
Figure 8 – Sectioning of recorded signals . 22
th
Figure 9 – Illustration of the method for obtaining "time aligned gain" for the 65
percentile . 24
Figure 10 – LTASS gain at 3 input sound pressure levels . 24
Figure 11 – LTASS gain at 3 input levels relative the LTASS gain at 65 dB input sound
pressure level . 25
Figure 12 – Percentile gain for 3 percentiles and corresponding LTASS gain . 25
Figure A.1 – ISTS level distributions for five third-octave bands as measured from
50 % overlapping 125 ms sections of the ISTS . 31

th th th
Table 1 – ISTS 30 , 65 , 99 percentiles and LTASS in dB at one-third-octave bands . 14
Table 2 – Standard audiograms for the flat and moderately sloping group. 17
Table 3 – Standard audiograms for the steep sloping group . 18
Table 4 – Recommended coupler correction values when using the 2 cm coupler . 21

– 4 – 60118-15  IEC:2012
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROACOUSTICS –
HEARING AIDS –
Part 15: Methods for characterising signal processing
in hearing aids with a speech-like signal

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-
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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
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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
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services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
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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 60118-15 has been prepared by IEC technical committee 29:
Electroacoustics.
The text of this standard is based on the following documents:
CDV Report on voting
29/719/CDV 29/730A/RVC
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.

60118-15  IEC:2012 – 5 –
A list of all parts of IEC 60118 series, published under the general title Electroacoustics –
Hearing aids, can be found on the IEC website.
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.
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 – 60118-15  IEC:2012
INTRODUCTION
The characterisation of hearing aids in actual use can differ significantly from those
determined in accordance with standards such as IEC 60118-0 and IEC 60118-7. These
standards use non speech-like test signals with the hearing aid set to specific settings which
are, in general, not comparable with typical user settings.
This standard describes a recommended speech-like test signal, the International Speech
Test Signal (ISTS), and a method for the characterisation of hearing aids using this signal
with the hearing aid set to actual user settings or to the manufacturers' recommended settings
for one of a range of audiograms. For the purposes of this standard the hearing aid is
considered to be a combination of the physical hearing aid and the fitting software which
accompanies it.
60118-15  IEC:2012 – 7 –
ELECTROACOUSTICS –
HEARING AIDS –
Part 15: Methods for characterising signal processing
in hearing aids with a speech-like signal

1 Scope
This part of IEC 60118 specifies a test signal designed to represent normal speech, the
International Speech Test Signal (ISTS), together with the procedures and the requirements
for measuring the characteristics of signal processing in air-conduction hearing aids. The
measurements are used to derive the estimated insertion gain (EIG). For the purposes of
characterizing a hearing aid for production, supply and delivery, the procedures and
requirements to derive the coupler gain on a 2 cm coupler as defined in IEC 60318-5 are
also specified.
The procedure uses a speech-like test signal and the hearing aid settings are set to those
programmed for an individual end-user or those recommended by the manufacturer for a
typical end-user for a range of flat, moderately sloping or steep sloping audiograms, so that
the measured characteristics are comparable to those which may be obtained by a wearer at
typical user settings.
The purpose of this standard is to ensure that the same measurements made on a hearing aid
following the procedures described, and using equipment complying with these requirements,
give substantially the same results.
Measurements of the characteristics of signal processing in hearing aids which apply non-
linear processing techniques are valid only for the test signal used. Measurements which
require a different test signal or test conditions are outside the scope of this standard.
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 as given by the values
given in 6.1.
Measurement methods that take into account the acoustic coupling of a hearing aid to the
individual ear and the acoustic influence of the individual anatomical variations of an end-user
on the acoustical performance of the hearing aid, known as real-ear measurements, are
outside the scope of this particular standard.
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 60118-7, Electroacoustics – Hearing aids – Part 7: Measurement of the performance
characteristics of hearing aids for production, supply and delivery quality assurance purposes
IEC 60118-8:2005, Electroacoustics – Hearing aids – Part 8: Methods of measurement of
performance characteristics of hearing aids under simulated in situ working conditions

– 8 – 60118-15  IEC:2012
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 61260, Electroacoustics – Octave-band and fractional-octave-band filters
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply:
3.1
sound pressure level
all sound pressure levels specified are measured in decibels (dB) referenced to 20 μPa
3.2
percentile sound pressure level
sound pressure level, in dB, below which a certain percentage of the measured sound
pressure levels fall, measured in a 125 ms time interval, over a stated measurement period
Note 1 to entry: As an example: The 30th percentile sound pressure level is the sound pressure level below which
30 % of the measured sound pressure levels are found, and the remaining 70 % of the measured sound pressure
levels are higher.
Note 2 to entry: The 99th percentile may be interpreted as a peak sound pressure level indicator.
Note 3 to entry: The definition of percentile used here is according to general statistics. This definition may differ
from other sciences such as acoustics.
3.3
international speech test signal
ISTS
speech-like test signal as defined in this standard
3.4
long term average speech spectrum
LTASS
sound pressure level measured in one-third-octave bands averaged over a long time period of
speech
Note 1 to entry: For this standard a time period of 45 s is chosen.
3.5
occluded ear simulator
OES
ear simulator as defined in IEC 60318-4
3.6
estimated insertion gain of a hearing aid
EIG
estimate of the real-ear insertion gain as may be obtained across a group of persons
Note 1 to entry: This estimate is based on measurements of hearing aid gain using an occluded ear simulator or a
2 cm coupler, as defined in IEC 60318-5.

60118-15  IEC:2012 – 9 –
3.7
coupler gain of a hearing aid
hearing aid gain measured by means of a 2 cm coupler, as defined in IEC 60318-5
3.8
LTASS gain of a hearing aid
estimated insertion gain or coupler gain provided for the long-term average speech spectrum
of the international speech test signal
3.9
percentile gain of a hearing aid
estimated insertion gain or the coupler gain provided for a given percentile of the distribution
of sound pressure levels in a one-third-octave band of the international speech test signal
4 Limitations
This standard provides a technical characterisation of hearing aids and is not defining a
clinical procedure for insertion gain measurements. However, results are shown as estimated
insertion gain in order to improve the understanding of the results in relation to in situ
conditions.
The estimated insertion gain may differ substantially from in situ results obtained on an
individual person, due to differences between in situ conditions and the use of ear simulator
or coupler as well as anatomical variation of head, torso, pinna, ear canal, and eardrum. Care
should be taken when interpreting the results.
5 Setup
5.1 System overview
The goal of the test method is to provide an estimate of the insertion gain as may be obtained
across a group of persons. For the purpose of characterizing a hearing aid for production,
supply and delivery also the coupler gain on a 2 cm coupler as defined in IEC 60318-5 is
provided.
This standard employs the international speech test signal (ISTS) for the measurement of
hearing aid gain in one-third-octave bands and introduces the concept of gain for the long
term average speech spectrum (LTASS gain) and the concept of time-aligned gain for a given
percentile of the distribution of one-third-octave band sound pressure level of the ISTS
(percentile gain) in 125 ms sections. Within each band, the LTASS gain is the gain averaged
over the test duration. Within each band, the percentile gain for a given percentile is
determined for each 125 ms section in the ISTS distribution which has the sound pressure
level of the given percentile, and these gains are averaged over the duration of the test.
The methods of this standard yield an estimated insertion gain (EIG) (preferred) and a 2 cm
th th th
coupler gain (optional) for the LTASS and the 30 , 65 and 99 percentiles of the ISTS.
For the EIG measurement, the ISTS is spectrally shaped by the free-field to the hearing-aid-
microphone transformation for the type of hearing aid being tested. The output of the hearing
aid is preferably measured in an occluded ear simulator but may also be estimated from
3 3
2 cm coupler sound pressure level by adding the occluded ear simulator to 2 cm coupler
difference. The EIG (calculated as the LTASS gain or as the speech gain at various percentile
sound pressure levels) is derived by subtracting the relevant ISTS band level and the manikin
unoccluded ear gain (IEC 60118-8:2005, Annex B) from the hearing aid output band level.
For the 2 cm coupler gain measurements, the input to the hearing aid is the ISTS and its
output is the 2 cm coupler sound pressure level.

– 10 – 60118-15  IEC:2012
Figure 1 and Figure 2 show an overview of the method.
• Figure 1 shows the measurement procedure for the hearing aid response for
determining the estimated insertion gain using an occluded ear simulator in
accordance with IEC 60318-4 or a 2 cm coupler in accordance with IEC 60318-5 and
applying a free-field to hearing-aid-microphone transform of IEC 60118-8.
• Figure 2 shows the measurement procedure for the hearing aid response for
determining the coupler gain using a 2 cm coupler in accordance with IEC 60318-5.

60118-15  IEC:2012 – 11 –
5.2 Estimated insertion gain
International International
speech test speech test
signal signal
Chamber Chamber
equalization equalization
MLE
IEC 60118-8
Sound
Sound
chamber chamber
loudspeaker
loudspeaker
Chamber Chamber
loudspeaker loudspeaker
to hearing aid to reference
microphone microphone
Hearing aid in
chamber
Ear simulator
or 2 cm³
coupler
Coupler Reference
microphone microphone
Output signal for Input signal for
analysis analysis
IEC  221/12
NOTE 1 The ear simulator complies with IEC 60318-4; the 2 cm coupler is in accordance with IEC 60318-5.
NOTE 2 Blocks with vertical lines are actual physical parts of the measurement setup. Blocks with horizontal lines
are pre- and post-processing steps in software.
Figure 1 – Measurement setup for the estimated insertion gain

– 12 – 60118-15  IEC:2012
5.3 Coupler gain
International International
speech test speech test
signal signal
Chamber Chamber
equalization equalization
Sound Sound
chamber chamber
loudspeaker loudspeaker
Chamber Chamber
loudspeaker loudspeaker
to hearing aid to reference
microphone microphone
Hearing aid in
chamber
2 cm³ coupler
Coupler Reference
microphone microphone
Output signal for Input signal for
analysis analysis
IEC  222/122
NOTE 1 The 2 cm coupler complies with IEC 60318-5.
NOTE 2 Blocks with vertical lines are actual physical parts of the measurement setup. Blocks with horizontal lines
are pre- and post-processing steps in software.
Figure 2 – Measurement setup for the coupler gain
6 Test equipment
6.1 Acoustical requirements
For the acoustical measurements the requirements for test equipment, test conditions and the
acoustic test box as listed in IEC 60118-7 shall be followed. In particular, the following
requirements apply:
60118-15  IEC:2012 – 13 –
a) The test box used shall provide essentially free field conditions in the frequency range
200 Hz to 8 kHz.
b) The hearing aid shall be positioned to reflect a frontal sound incidence (0 degrees azimuth
and elevation as defined in IEC 61669). If this is not appropriate for the type of hearing
aid, the actual incidence should be stated.
c) The input sound pressure level at the hearing aid reference point is kept constant by
means of a reference microphone (pressure method) or by using the substitution method.
d) One-third-octave-band filters with nominal centre frequencies from 250 Hz to 6,3 kHz shall
be used. The filters shall conform to the class 2 requirements of IEC 61260.
e) Unwanted stimuli in the acoustic test box, such as ambient noise and mechanical
vibrations shall be sufficiently low so as not to affect the test results by more than 0,5 dB.
This can be verified if the output level of the hearing aid falls at least 10 dB when the
signal source is switched off.
f) The sound pressure level at the hearing aid reference point shall be accurate within
± 1,5 dB over the frequency range from 200 Hz to 2 kHz and within ± 2,5 dB from 2 kHz to
8 kHz.
g) The free-field response level of the reference microphone used to measure the test signal,
along with its associated amplifier and readout device, shall be frequency independent
within ± 1 dB in the frequency range 200 Hz to 5 kHz and within ± 2 dB in the frequency
range 5 kHz to 8 kHz relative to the free-field response level at 1 kHz. The pressure
response level calibration of the reference microphone system shall be known by
calibration at one frequency between 250 Hz and 1 250 Hz, preferably at 1 kHz. The
expanded uncertainty of the calibration shall not exceed 1 dB.
h) The relative pressure response level of the coupler microphone, along with its associated
amplifier and readout device, shall be frequency-independent within ± 1 dB in the
frequency range 200 Hz to 5 kHz and within ± 2 dB in the range 5 kHz to 8 kHz relative to
the pressure sensitivity at 1 kHz. The pressure response level calibration of the coupler
microphone system shall be known by calibration at one frequency between 250 Hz and
1 250 Hz, preferably at 1 kHz. The expanded uncertainty of the calibration shall not
exceed 1 dB.
6.2 Test signal
6.2.1 Specification of ISTS
The international speech test signal (ISTS) shall be used as the test signal for the
measurements of this standard. This signal is developed by the European Hearing Instrument
Manufacturers Association which holds the copyright. It is available from this organization free
of charge as a 16 bit or 24 bit file of type .wav.
The ISTS has been produced from recordings of female speakers of Arabic, English, French,
German, Mandarin and Spanish. The recordings were cut into short segments and
recomposed in random order. A description of the ISTS is given in Annex A and in [1] . The
ISTS has the following essential characteristics:
a) The signal bandwidth is from 100 Hz to 16 kHz. For the measurements in this standard
only the bandwidth is relevant that includes all one-third-octave bands with nominal
centre frequencies from 0,25 kHz to 6,3 kHz.
b) The long term average speech spectrum (LTASS) is given in Table 1 and in Figure 3. It
is the average LTASS for female talkers reported in [2]. For acoustical reproduction the
accuracy shall be within ± 3 dB for all one-third-octave bands with nominal centre
frequencies from 0,25 kHz to 6,3 kHz.
th th th
c) The 30 , 65 and 99 percentiles of the distribution of the sound pressure level in
125 ms time blocks in one-third-octave-octave bands are given in Table 1 and in
___________
Figures in brackets refer to the Bibliography.

– 14 – 60118-15  IEC:2012
Figure 3. For acoustical reproduction the accuracy shall be within ± 3 dB for all one-
third-octave bands with nominal centre frequencies from 0,25 kHz to 6,3 kHz.
d) The total duration is 60 s. Longer durations are possible in multiples of 60 s by
concatenating 60 s signals. End and start transitions of the signal are made to match.
e) The nominal overall sound pressure level is defined over the band from 200 Hz to
5 kHz. This level is 65 dB which is considered to be the level of normal conversational
speech at 1 m distance.
NOTE When the ISTS is used at other levels than 65 dB sound pressure level, the signal will not be fully
representative for real soft or loud speech as vocal effort will not correspond to these different levels.

99 %
LTASS
65 %
30 %
0,25 0,5 1 2 4 8 16
Frequency  (kHz)
IEC  223/12
th th th
, 65 , 99 percentiles and LTASS in dB
Figure 3 – ISTS 30
versus one-third-octave bands
th th th
Table 1 – ISTS 30 , 65 , 99 percentiles and LTASS in dB at one-third-octave bands
INTERNATIONAL SPEECH TEST SIGNAL: SOUND PRESSURE LEVEL IN dB FOR ONE-THIRD-OCTAVE BANDS
kHz 0,25 0,315 0,40 0,50 0,63 0,80 1,00 1,25 1,60 2,00 2,50 3,15 4,00 5,00 6,30 8,00 10,00 12,50 16,00
th
68,8 65,7 66,5 67,5 67,4 64,4 60,3 59,1 58,1 55,8 53,9 54,0 51,6 51,1 53,2 51,5 50,1 49,7 48,0
percentile
th
47,9 48,2 55,3 53,4 52,6 47,6 43,7 41,8 42,8 40,6 39,5 38,6 37,0 35,5 30,9 33,5 36 33,6 32,3
percentile
th
34,7 37,7 40,6 42,7 37,2 32,6 30,9 29,9 29,7 28,4 29,6 28,3 27,7 24,2 20,8 23,3 26,1 25,0 22,6
percentile
LTASS 55,9 53,1 56,7 56,7 55,4 53,0 49,3 47,3 46,7 43,8 42,3 41,7 40,3 39,6 40,2 39,9 40,0 37,8 36,1

6.2.2 Shaping of the test signal for determining the EIG
The input sound signal accompanying traditional measurement methods is usually specified
under free-field conditions. As described in the scope, the EIG method shall give
measurement results which are comparable to results which would be obtained when
measuring on a person. I.e. when the hearing aid is positioned on a person the free-field
condition no longer applies.
Sound pressure level  (dB)
60118-15  IEC:2012 – 15 –
For the measurement of the EIG a free-field to hearing-aid-microphone transformation shall
be applied to the test signal. Data for the free-field to hearing-aid-microphone transformation
applicable to most typical hearing aid constructions are specified in IEC 60118-8:2005,
Table A.1. If the test signal is not shaped according to these data, the actually used data sets
shall be stated. Only transform data appropriate for the actual hearing aid shall be used. Note
that the specified overall sound pressure level of the input sound signal shall be established
prior to shaping.
For the measurement of the coupler gain a free field input signal is directly applied to the
hearing aid. Hence no transformations on the test signal are needed.
6.3 Earphone coupler and attachments
6.3.1 Estimated insertion gain
For the measurement of the hearing aid output, the occluded ear simulator according to
IEC 60318-4 is the preferred coupler. The IEC 60318-4 occluded ear simulator will provide an
impedance termination of the hearing aid under test which is comparable to a real ear.
To connect the hearing aid to the occluded ear simulator an appropriate occluded ear
simulator adaptor should be used according to IEC 60318-4.
If the occluded ear simulator is not used, instead the 2 cm coupler in accordance with
IEC 60318-5 is to be used. The HA-1 coupler is used for ITE hearing aids. The HA-2 coupler
is used for BTE hearing aids. The HA-1 coupler is also used for BTE hearing aids with the
receiver in the canal or using thin coupling tubes.
Results comparing 2 cm coupler and OES measurements will differ from each other and a
correction will therefore have to be applied for the 2 cm coupler, see 8.2.3. The remaining
differences are mainly due to differences caused by the receiver load of the hearing aid.
The used coupler and adaptor shall be clearly stated. The used setup shall be specified in
sufficient detail to reproduce the complete measurement setup.
6.3.2 Coupler gain
For the coupler gain option, a 2 cm coupler in accordance with IEC 60318-5 is to be used.
The HA-1 coupler is used for ITE hearing aids. The HA-2 coupler is used for BTE hearing
aids. The HA-1 coupler is also used for BTE hearing aids with the receiver in the canal or
using thin coupling tubes.
The used coupler shall be clearly stated. The used setup shall be specified in sufficient detail
to reproduce the complete measurement setup.
7 Test conditions
7.1 Programming of hearing aid
The hearing aid settings are programmed as for an individual end-user, so as to characterise
hearing aid performance for that individual end-user.
Alternatively, the hearing aid settings are programmed as for a typical end-user with an
audiogram as selected from a range of audiograms as defined in 7.3, that falls within the
fitting range of the hearing aid. All relevant information shall be supplied that defines the
typical end-user. The programming shall be a typical best fit for that typical end-user using the
supplied software from the manufacturer.

– 16 – 60118-15  IEC:2012
All relevant parameters, features and end-user settings that influence the programming using
the specified fitting software should be supplied to reproduce the setting in which the hearing
aid was measured.
If, for the purpose of the measurements, a deviation on the end-user settings is considered
necessary, this deviation shall be specified.
7.2 End user settings for programming
7.2.1 Hearing aid features
All settings of the hearing aid should be set to end-user settings, including noise reduction
algorithms, feedback suppression systems, echo cancellation, etc.
In some cases a special hearing aid setting may be used. Those cases may occur when the
test set-up influences the normal operation of the hearing aid. For instance: hearing aid
settings that relate to venting, directionality or when features or parameters vary automatically
depending on an acoustical environment. A special setting may also be used to demonstrate
the effect of a specific setting option, for instance related to gain compression characteristics,
noise reduction parameters, maximum gain settings, or other. Features like frequency
transposition should be disabled as that may give measurement results that are difficult to
interpret. In all cases the special setting(s) shall be clearly specified.
7.2.2 Vent selection for programming
To programme the hearing aid the programming software may require to specify the size of an
end-user venting. In these cases, it is recommended that the programming of the hearing aid
be based on a closed venting.
When the hearing aid is programmed for an open vent, it is noted that the actual
measurements will have no venting. If a hearing aid is programmed for an open vent, the
measurement results may not correspond fully to the programmed fitting.
7.2.3 Directionality
Hearing aids with directional microphones should be set to omni-directional mode, if possible.
When it is not possible to select the omni-directional mode this should be clearly stated. Care
should be taken to interpret the measurements as these may depend on the directional
system of the hearing aid.
7.3 Audiograms for a typical end-user
To programme the hearing aid as for a typical end-user, an audiogram that falls within the
fitting range of the hearing aid should be selected from the group of audiograms as defined
below.
The set of standard audiograms for the flat and moderately sloping group is shown in Table 2
and Figure 4. The set of standard audiograms for the steep sloping group is shown in Table 3
and Figure 5.
The Hearing Loss (HL) is calculated as HL = (HL0,5k+HL1k+HL2k+HL4k)/4, where HLxk
means hearing loss at x kHz.
The derivation of the group of audiograms is described in [3].

60118-15  IEC:2012 – 17 –
No other type audiograms have been specified as these have variations that occur only very
seldom (e.g., reverse slope, cookie-bite, mixed, conductive). If none of the above specified
audiograms is suitable, the manufacturer may specify another audiogram provided it has been
clearly defined.
Table 2 – Standard audiograms for the flat and moderately sloping group
No HL 0,25 kHz 0,375 kHz 0,5 kHz 0,75 kHz 1 kHz 1,5 kHz 2 kHz 3 kHz 4 kHz 6 kHz
N1 16 10 10 10 10 10 10 15 20 30 40
N2 31 20 20 20 22,5 25 30 35 40 45 50
N3
46 35 35 35 35 40 45 50 55 60 65
N4 63 55 55 55 55 55 60 65 70 75 80
N5 76 65 67,5 70 72,5 75 80 80 80 80 80
N6 89 75 77,5 80 82,5 85 90 90 95 100 100
N7 103 90 92,5 95 100 105 105 105 105 105 105

Standard audiograms – Flat and moderately stopping

Frequency  (kHz)
0,25 0,375 0,5 0,75 1 1,5 2 3 4 6
N1
N2
N3
N4
N5
N6
N7
IEC  224/12
Figure 4 – Standard audiograms for the flat and moderately sloping group
Hearing level  (dB)
– 18 – 60118-15  IEC:2012
Table 3 – Standard audiograms for the steep sloping group
No HL 0,25 kHz 0,375 kHz 0,5 kHz 0,75 kHz 1 kHz 1,5 kHz 2 kHz 3 kHz 4 kHz 6 kHz
S1 23 10 10 10 10 10 10 15 30 55 70
S2
49 20 20 20 22,5 25 35 55 75 95 95
S3 63 30 30 35 47,5 60 70 75 80 80 85

Standard audiograms – Steep stoping
Frequency  (kHz)
0,25 0,375 0,5 0,75 1 1,5 2 3 4 6
S1
S2
S3
IEC  225/12
Figure 5 – Standard audiograms for the steep sloping group
8 Measurements and analysis
8.1 Measurements
8.1.1 General
Sixty seconds of the ISTS test signal as specified in 6.2 shall
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