IEC 60118-16:2022

IEC 60118-16 ®
Edition 1.0 2022-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electroacoustics – Hearing aids –
Part 16: Definition and verification of hearing aid features

Électroacoustique – Appareils de correction auditive –
Partie 16: Définition et vérification des caractéristiques des appareils de
correction auditive
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IEC 60118-16 ®
Edition 1.0 2022-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electroacoustics – Hearing aids –

Part 16: Definition and verification of hearing aid features

Électroacoustique – Appareils de correction auditive –

Partie 16: Définition et vérification des caractéristiques des appareils de

correction auditive
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.140.50 ISBN 978-2-8322-1088-7

– 2 – IEC 60118-16:2022 © IEC 2022
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Application to non-air-conduction hearing aids . 10
5 Test equipment . 10
5.1 Acoustical requirements . 10
5.2 Examples of test signals for common listening situations . 11
6 Verification of noise reduction. 11
6.1 Noise reduction for speech enhancement . 11
6.2 Gain reduction for noise . 12
7 Strategies of hearing aid programs and their verification. 13
7.1 General . 13
7.2 User-selected hearing aid programs . 13
7.2.1 Description . 13
7.2.2 Verification . 13
7.3 Automatically-selected hearing aid programs depending on listening
situation . 14
7.3.1 Description . 14
7.3.2 Verification by setting a marker . 15
7.3.3 Verification using a linear gain configuration . 15
8 Verification of feedback reduction . 16
8.1 General . 16
8.2 Coupling of the hearing aid . 16
8.3 Measurement procedure . 16
8.4 Post processing . 17
9 Verification of the number of hearing aid channels . 18
9.1 Visualization of the effect of multichannel signal processing . 18
9.2 Evaluation of the number of independent channels . 19
10 Verification of an output limiter . 20
Annex A (informative) Coupling of the hearing aid to the measurement coupler in
order to provoke feedback . 21
A.1 Simplified coupling of air-conduction hearing aids to the 2 cm acoustic
coupler . 21
A.2 Head and torso simulator with vented ear canal extension . 22
Annex B (informative) Particular guidance . 24
B.1 Verification of user selected hearing aid programs . 24
B.2 Automatically-selected hearing aid programs depending on listening
situation . 25
B.2.1 Verification by setting a marker . 25
B.2.2 Verification by using a linear gain configuration . 27
Bibliography . 29

Figure 1 – Visualization of user selected HAPs . 13
Figure 2 – Visualization of automatically-selected HAPs depending on listening
situation . 14

Figure 3 – Example of the plot of the results of the feedback reduction measurement . 18
Figure A.1 – Simplified coupling of air-conduction hearing aids with one microphone to
the 2 cm acoustic coupler to provoke feedback . 21
Figure A.2 – Simplified coupling of air-conduction hearing aids with two microphones to
the 2 cm acoustic coupler to provoke feedback . 22
Figure A.3 – Head and torso simulator for the measurement of air-conduction hearing
aids according to IEC/TS 60318-7 together with an ear simulator according to
IEC 60318-4 and a vented ear canal extension . 22
Figure A.4 – Example for a vented ear canal extension with medium flow (left) and high
flow (right) . 23
Figure B.1 – Visualization of the verification of user-selected hearing aid programs . 24
Figure B.2 – Visualization of the measurement of the reference data for the verification
of automatically-selected hearing aid programs by setting a marker . 25
Figure B.3 – Visualization of the measurement for the verification of
automatically-selected hearing aid programs by setting a marker where a marker is set
to the hearing aid program 1 . 26
Figure B.4 – Visualization of the measurement for the verification of
automatically-selected hearing aid programs by using a linear gain configuration . 28

Table 1 – Examples of test signals for different listening situations . 11
Table 2 – Symbols used for the evaluation and results of the feedback reduction
measurement . 17
Table 3 – Example results of the procedure for the verification of multichannel signal
processing . 19
Table B.1 – Example results for the verification of user selected hearing aid programs . 24
Table B.2 – Example results for the verification of automatically-selected hearing aid
programs by setting a marker . 27
Table B.3 – Example for the evaluation of the results for the verification of
automatically-selected hearing aid programs by setting a marker . 27

– 4 – IEC 60118-16:2022 © IEC 2022
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROACOUSTICS – HEARING AIDS –

Part 16: Definition and verification of hearing aid features

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
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preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
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Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
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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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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.
IEC 60118-16 has been prepared by technical committee 29: Electroacoustics. It is an
International Standard.
The text of this International Standard is based on the following documents:
Draft Report on voting
29/1110/FDIS 29/1116/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 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 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 document 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 60118-16:2022 © IEC 2022
ELECTROACOUSTICS – HEARING AIDS –

Part 16: Definition and verification of hearing aid features

1 Scope
This part of IEC 60118 gives definitions for common hearing aid features such as noise
reduction or feedback reduction, etc. Only acoustical inputs are considered. Binaural features
are currently not covered in this document. In addition, measurement procedures are described
to verify hearing aid features. The objective is not to evaluate the performance of features but
to verify their existence and functionality.
Furthermore, definitions and procedures are kept as general as possible so that this document
can be applied to various types of hearing aids, for example, air-conduction hearing aids or
bone conduction hearing aids. To this end, the general definition for the term "hearing aid" given
in IEC 60118-0 is adopted, and this document does not refer to any specific ear simulator or
acoustic coupler but uses a general definition of a coupler. However, if a general view is not
applicable or leads to unclear or complex wording, the situation for an air-conduction hearing
aid only is considered. Nevertheless, an explanation is given on how this document can be
applied to hearing aids which do not use air conduction.
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 60118-0:— , Electroacoustics – Hearing aids – Part 0: Measurement of the performance
characteristics of hearing aids
IEC 60118-15, Electroacoustics – Hearing aids – Part 15: Methods for characterising signal
processing in hearing aids with a speech-like signal
IEC 61260-1, Electroacoustics – Octave-band and fractional-octave-band filters – Part 1:
Specifications
ISO 21748, Guidance for the use of repeatability, reproducibility and trueness estimates in
measurement uncertainty evaluation
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
___________
Fourth edition under preparation. Stage at the time of publication: IEC FDIS 60118-0:2022

3.1
sound pressure level
SPL
ten times the logarithm to the base 10 of the ratio of the square of the sound pressure, p, to the
square of a reference value, p expressed in decibels, where the reference value, p , is 20 µPa
0 0
[SOURCE: ISO/TR 25417:2007, 2.2, modified – The abbreviated term has been added and the
symbol, formula and notes to entry have been omitted.]
3.2
1/f noise
pink noise
random noise having a continuous spectrum and such that the power spectral density is
proportional to the reciprocal of the frequency in the frequency range considered
3.3
signal-to-noise ratio
SNR
difference in sound pressure level between the target signal, usually speech, and the
interference signal, usually noise
3.4
hearing aid
wearable instrument intended to aid a person with impaired hearing
[SOURCE: IEC 60118-0:—, 3.2]
3.5
reference point
point related to the hearing aid sound inlet port(s) for the purpose of defining the position of the
hearing aid
3.6
hearing aid user
person wearing a hearing aid to alleviate hearing impairment
3.7
measurement coupler
device through which the output of a hearing aid can be measured
Note 1 to entry: For an air-conduction hearing aid, usually the acoustic coupler according to IEC 60318-5 or the
occluded-ear simulator according to IEC 60318-4 is used as a measurement coupler and for a bone conduction
hearing aid, the coupler according to IEC 60318-6 or a skull simulator is used.
3.8
hearing aid program
HAP
set of parameters, defining at least the frequency characteristic and possibly other parameters
of the signal processing of a hearing aid that can be selected by the hearing aid user or that
are automatically selected by the hearing aid to adapt the signal processing to specific listening
situations
– 8 – IEC 60118-16:2022 © IEC 2022
3.9
configurable hearing aid program
configurable HAP
hearing aid program with an adjustable set of parameters, which can be configured and
reconfigured to meet the individual needs of the hearing aid user without influencing the
processing in other programs
Note 1 to entry: Usually fitting software provided by the hearing aid manufacturer, a computer and a programming
interface are used to configure the set of parameters.
Note 2 to entry: The fact that a hearing aid program is configurable has the benefit that the signal processing can
be optimized to the individual needs, for example, for a specific listening situation for this specific user.
3.10
non-configurable hearing aid program
non-configurable HAP
hearing aid program configured by the manufacturer or automatically by the hearing aid
depending on the listening situation, which cannot be reconfigured either by the hearing aid
user or by using the fitting software without influencing the processing in other programs
3.11
listening situation
situation in which a hearing aid user requires a specific signal processing
Note 1 to entry: This definition is intentionally different from the term "acoustic environment" in ISO 12913-1:2014,
2.2 and 3.4.
3.12
noise reduction
feature of the signal processing of a hearing aid intended to reduce noise with respect to the
absolute level or relative to the level of a target signal
3.13
noise reduction for speech enhancement
feature of the signal processing of a hearing aid intended to increase the signal-to-noise ratio
even if speech and noise are presented simultaneously from the same direction and have the
same long-term average spectrum
Note 1 to entry: It is possible that the increase in signal-to-noise ratio will not increase speech intelligibility.
3.14
gain reduction for noise
feature of the signal processing of a hearing aid intended to decrease the gain for noise
compared to the gain for speech even if speech and noise are presented successively from the
same direction and have the same long-term average spectrum
3.15
feedback
return of some of the energy of the output signal from the hearing aid to the input of the same
hearing aid
3.16
critical feedback condition
situation where feedback causes a whistling noise at the output of the hearing aid

3.17
feedback reduction
feature of the signal processing of a hearing aid to reduce or completely avoid the occurrence
of the critical feedback condition without reducing gain
Note 1 to entry: Changing the feedback path, by, for example, increasing the sealing of the earmold, is not a part
of the signal processing and therefore not understood as feedback reduction.
3.18
hearing aid channel
feature of the signal processing of a hearing aid that enables individual adjustment of the gain
and the parameters of an automatic gain control for a certain frequency range
Note 1 to entry: A hearing aid channel can consist of multiple hearing aid bands.
3.19
hearing aid band
feature of the signal processing of a hearing aid that enables individual adjustment of the gain
for a certain frequency range
3.20
maximum power output
MPO
maximum level at the output of the hearing aid which is adjustable by the output limiter
3.21
output limiter
feature of a hearing aid that allows one to define and redefine a limit for maximum power output
(MPO)
3.22
fitted maximum output sound pressure level
fitted OSPL90
maximum output SPL of a hearing aid when measured after fitting with 90 dB input SPL
[SOURCE: IEC 60601-2-66:2019, 201.3.206, modified – Note to entry has been omitted.]
3.23
functional test setting
FTS
setting of the hearing aid where all accessible features in the fitting software are manually
disabled and a linear gain is applied equally to the reference test setting of the gain control
according to IEC 60118-0
Note 1 to entry: The difference between reference test setting (RTS) as defined in IEC 60118-0 and the functional
test setting (FTS) is due to the fact that not always all features are accessible in the fitting software and can be
disabled.
3.24
rank
number of singular values of a matrix A that are equal to or exceed 0,95 which is
written as rank(A)
3.25
singular values
number of positive real values in linear algebra which can be computed for a
matrix as a result of a singular value decomposition (SVD)

– 10 – IEC 60118-16:2022 © IEC 2022
4 Application to non-air-conduction hearing aids
Definitions and procedures in this document are kept as general as possible so that this
document can be applied to various types of hearing aids, for example, air-conduction hearing
aids or bone conduction hearing aids. However, in some subclauses and definitions, a general
view is not applicable or leads to an unclear or complex wording so that only air-conduction
hearing aids are considered.
NOTE For example, a sound pressure level is considered for the output signal of the hearing aid. However, this
holds for air-conduction hearing aids only. For bone conduction, the output is a force, and for other devices the output
can be any other physical quantity.
To apply this document to devices other than air-conduction hearing aids, it is required that:
• the input signal is an acoustic sound pressure,
• the output signal can be quantified by another physical quantity,
• and a measurement coupler exists that enables the measurement of this physical quantity
at the output of the hearing aid.
For bone conduction hearing aids, the output sound pressure level shall be replaced by an
output force level. In addition, for bone conduction hearing aids, references to IEC 60118-0
shall be understood as references to IEC 60118-9.
5 Test equipment
5.1 Acoustical requirements
For the presentation of acoustical input signals, as the test space a test room or a test box can
be used and the following requirements apply.
a) The input sound pressure level at the hearing aid reference point shall be controlled and
monitored by means of a reference microphone (pressure method) or by using the
substitution method according to IEC 60118-0.
b) The sound pressure level indicated by the reference microphone shall be accurate within
±2 dB for sinusoidal input signals with sound pressure levels between 40 dB SPL to 90 dB
SPL over the frequency range from 100 Hz to 10 kHz. A reduced frequency range from
200 Hz to 8 000 Hz or from 200 Hz to 5 kHz may be used and shall be stated.
c) The measurement of sound pressure levels with the reference microphone shall be accurate
within ±0,5 dB at the frequency of calibration.
d) The measurement of sound pressure levels with the reference microphone shall be accurate
within ±1,5 dB in the range from 200 Hz to 4 000 Hz and ±2 dB in the range from 4 000 Hz
to 10 000 Hz for frequencies that are not calibrated (see list item c)).
e) The accuracy of measurements with the measurement coupler shall be stated for the
frequency of calibration.
f) For the measurement coupler, the expanded uncertainty for the indication of output level
relative to the indication at the frequency of calibration shall be stated for a frequency range
of 200 Hz to 5 000 Hz, 200 Hz to 8 000 Hz, and 100 Hz to 10 000 Hz, if possible. A
frequency specific uncertainty or the greatest uncertainty within the frequency range can be
stated.
g) Octave-band and fractional-octave-band filters according to class 1 or class 2 of
IEC 61260‑1 shall be used.
h) Unwanted stimuli in the acoustic test space, 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 by at least 10 dB when the
signal source is switched off.

5.2 Examples of test signals for common listening situations
In Table 1, a list of test signals is provided that can be used for the different listening situations.
As speech signal, the international speech test signal (ISTS) as defined in IEC 60118-15 is
used (see also [8] ). In addition, as a speech shaped noise the international female masking
noise (IFnoise) with the same long-term average spectrum as the ISTS is considered [9]. All
examples of test signals listed in Table 1 have a crest factor < 20 dB. If other signals are used,
these signals shall also have a crest factor < 20 dB.
Table 1 – Examples of test signals for different listening situations
Listening situation Test signal
Speech in quiet ISTS at 55 dB SPL
Speech in quiet ISTS at 65 dB SPL
Speech in noise ISTS at 70 dB SPL mixed with IFnoise at 68 dB SPL
Speech in babble noise ISTS at 70 dB SPL mixed with ICRA noise track 7 at 65 dB SPL
Noise IFnoise at 70 dB SPL
Noise Traffic noise car motorway at 70 dB SPL
Noise 1/f noise at a 1/3-octave-band-level of 50 dB and with a frequency range
of 100 Hz to 10 000 Hz
1/f noise at a 1/3-octave-band-level of 50 dB and with a frequency range
Noise
of 200 Hz to 8 000 Hz
Noise 1/f noise at a 1/3-octave-band-level of 50 dB and with a frequency range
of 200 Hz to 5 000 Hz
Noise 1/f noise at a 1/3-octave-band-level of 50 dB and with a frequency range
of 1 000 Hz to 5 000 Hz
Music Orchestra at 75 dB SPL
Music Piano at 75 dB SPL
6 Verification of noise reduction
6.1 Noise reduction for speech enhancement
The following procedure describes a method to verify the existence and functionality of the
noise reduction for speech enhancement according to the phase inversion method described in
[10] or [11]. All signals are presented acoustically from the same sound source. Moreover, the
frequency range of the output signals should be limited to a frequency range of 200 Hz to
5 000 Hz.
a) Program the device to FTS and reduce the gain additionally by 10 dB or as defined by the
manufacturer.
b) Activate the noise reduction for speech enhancement.
c) Present a sequence containing the following signals to the hearing aid and record the output
signals:
);
• 5 s; pause (part 1, resulting in the recorded output signal y
• 60 s; ISTS at 70 dB SPL mixed with IFnoise at 68 dB SPL or at levels as defined by the
manufacturer (part 2, resulting in the recorded output signal y );
);
• 5 s; pause (part 3, resulting in the recorded output signal y
___________
Numbers in square brackets refer to the Bibliography.

– 12 – IEC 60118-16:2022 © IEC 2022
• 60 s; ISTS at 70 dB SPL mixed with IFnoise with inverted phase at 68 dB SPL or at
levels as defined by the manufacturer (part 4, resulting in the recorded output signal y );
• 5 s; pause (part 5, resulting in the recorded output signal y );
• 60 s; ISTS with inverted phase at 70 dB SPL mixed with IFnoise with inverted phase at
68 dB SPL or at levels as defined by the manufacturer (part 6, optional, resulting in the
recorded output signal y );
• 5 s; pause (part 7, optional, resulting in the recorded output signal y ).
d) Superpose the recordings in the following way:
s yy+ (1)
( )  processed speech signal
n yy− (2)
( )  processed noise signal
v y+ y (3)
( )  verification signal (optional)
NOTE The relative time alignment of the output signals is critical for this post-processing. An appropriate time
alignment can usually be reached for instance by presenting all parts of the signal within one signal and cutting
the recorded signal according to the corresponding number of samples.
e) Compute the sound pressure level L of the processed speech signal s, L of the processed
s n
noise signal n, and L of the test signal v. For each signal, the interval between 15 s to 60 s
v
is considered only.
f) As an optional verification of the measurement setup, L shall be 10 dB lower than L and
v s
L .
n
g) The difference L − L is the SNR at the output of the hearing aid. If this output SNR is at
s n
least 1 dB higher than the SNR of the input signal, the existence and functionality of the
noise reduction for speech enhancement have been verified.
6.2 Gain reduction for noise
The following procedure describes a method to verify the existence and functionality of a noise
reduction, which reduces the gain if only noise is available. All signals are presented
acoustically from the same sound source. Moreover, the frequency range of the output signals
should be limited to a frequency range of 200 Hz to 5 000 Hz.
a) Program the device to FTS and additionally reduce the gain by 10 dB or as defined by the
manufacturer.
b) Activate the gain reduction for noise.
c) Present a sequence containing the following signals to the hearing aid and record the output
signals:
• 5 s; pause (part 1, resulting in the recorded output signal y );
• 60 s; ISTS at 70 dB SPL or as defined by the manufacturer but equal to the level of the
IFnoise in part 4 (part 2, resulting in the recorded output signal y );
• 5 s; pause (part 3, resulting in the recorded output signal y );
• 60 s; IFnoise at 70 dB SPL or as defined by the manufacturer but equal to the level of
the ISTS in part 2 (part 4, resulting in the recorded output signal y );
=
=
=
• 5 s; pause (part 5, resulting in the recorded output signal y ).
d) Compute the sound pressure level of y and y for the interval of 15 s to 60 s which results
2 4
in L , L .
2 4
e) If the difference L − L is higher than 2 dB, the existence and functionality of the gain
2 4
reduction for noise have been verified.
7 Strategies of hearing aid programs and their verification
7.1 General
Clause 7 describes how to verify the existence of the different types of HAPs – user selected
HAPs and automatically-selected HAPs depending on the listening situation – which are
configurable or non-configurable. HAPs not related to acoustical input are not included in this
document. Each of the following test procedures distinguishes between a number of hearing
aid programs, which should be considered independently and cannot be directly summed up to
a total number of programs. In addition, Annex B includes particular guidance and examples for
all of the following test procedures.
7.2 User-selected hearing aid programs
7.2.1 Description
For this strategy, a specific number of hearing aid programs can be selected by the hearing aid
user. To this end, the user has to classify the listening situation and choose the appropriate
HAP accordingly (see Figure 1).

Figure 1 – Visualization of user selected HAPs
7.2.2 Verification
For the verification of user-selected HAPs, each of the programs shall be defined by a different
signal processing strategy or set of parameters. If any two HAPs are defined by the same
strategy or parameters, they will be regarded as being the same program. In the case of
configurable HAPs, it shall be ensured that different programs provide different output
characteristics.
If the change of a HAP affects the directional characteristics of the hearing aid only, this shall
be considered in the signal presentation, for example, by presenting signals from different
directions.
– 14 – IEC 60118-16:2022 © IEC 2022
Before the verification, one shall choose an input signal, for example, ISTS with 65 dB. Then,
the verification consists of the following steps.
a) Fill the memory slots in the hearing aid with the required number n of different user-selected
HAPs using the fitting software.
b) Switch to each HAP and measure the corresponding output signal. The switching between
programs shall be as performed by the user; a switching with the fitting software is not valid.
c) Compute the difference in 1/3-octave-band levels from 800 Hz to 5 kHz pairwise between
all output signals and calculate the root mean square of these 1/3-octave-band level
differences in decibels. Record the calculated difference with a precision of one decimal
point.
d) Build a matrix A of pairwise comparisons where the entries are 1 (unity), if the 1/3-octave-
band gain differences is 2 dB larger than the relative measurement uncertainty between
multiple measurements according to ISO 21748, and 0 (zero) otherwise (see Clause B.1).
NOTE A is a n x n symmetric matrix with a main diagonal of zeros.
e) The number of different HAPs selectable by the user n computes as
meas
 1
if rank A = 0
 ( )
n = (4)

meas
rank A
( )
otherwise


7.3 Automatically-selected hearing aid programs depending on listening situation
7.3.1 Description
For the automatic selection of HAPs, the hearing aid shall include a signal classification that is
able to distinguish between different listening situations. Using this classification, the hearing
aid then selects or blends the appropriate program (see Figure 2).

Figure 2 – Visualization of automatically-selected HAPs
depending on listening situation
In 7.3.2 and 7.3.3, two procedures are described to verify the existence of
automatically-selected HAPs. The procedure of 7.3.2 gives a deeper insight into the
functionality since confusions during the automatic selection are also noticeable. Nevertheless,
this procedure is only applicable to configurable HAPs so that non-configurable HAPs should
be verified with the procedure of 7.3.3.

7.3.2 Verification by setting a marker
If the automatic selection of HAPs is considered, the switching to a specific HAP is triggered by
a specific listening situation [12]. Thus, a different input signal representing a specific listening
situation is required for each HAP. Here, the signals of Clause 5 can be used. For reasons of
clarity, the order of presentation shall be equal to the order of the HAPs, i.e., input signal 1
shall aim to trigger hearing aid program 1, etc.
If the change of a hearing aid program affects the directional characteristics of the hearing aid
only or it is triggered by sound direction, this shall be considered in the signal presentation, for
example, by presenting signals from different directions.
The verification consists of the following steps.
a) Present each input signal for 60 s, measure the corresponding output signal, and save this
output signal as reference. For the following evaluation, only the output signal in the interval
of 15 s to 60 s or as specified by the manufacturer shall be considered.
NOTE For this step, no requirements have to be defined for the adjustment of the hearing aid programs.
In contrast to 7.1, the different hearing aid programs may also be programmed with the
same set of parameters.
b) Adjust the first HAP so that the root mean square of the 1/3-octave-band-levels from 800 Hz
to 5 kHz shows a difference of at least 2 dB compared to the results obtained in step a).
This is understood as setting a marker to the first HAP. All other HAPs shall be adjusted as
in step a). Present each input signal, measure and save the corresponding output signal.
Repeat this step successively for all other HAPs until each of the HAPs has been marked
once.
c) Compute the root mean square of the difference in 1/3-octave-band-levels from 800 Hz to
5 kHz between the output signals of step b) and the corresponding reference signals of
step a) and record the calculated difference with a precision of one decimal point. If this
difference is 2 dB larger than the relative measurement uncertainty between multiple
measurements according to ISO 21748, a marker has been detected.
d) For the verification, each listening situation is considered separately. If a marker can be
detected for the corresponding input signal only, the functionality of a HAP is verified. This
procedure shall be repeated for all listening situations. The total number of HAPs
corresponds to the number of HAPs where the functionality has been verified (see B.2.1).
7.3.3 Verification using a linear gain configuration
During the following procedure, all signals shall be presented from the same direction with a
length of 60 s and, for the evaluation, the interval between 15 s and 60 s shall be considered
only. If the sound direction has an influence on which hearing aid programs are triggered, all
the following steps shall be repeated for other directions of the sound source.
a) Program
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