Electroacoustics - Hearing aids - Part 15: Methods for characterising signal processing in hearing aids with a speech-like signal

IEC 60118-15:2012 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 cm3 coupler as defined in IEC 60318-5 are also specified. 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. 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.

Akustik - Hörgeräte - Teil 15: Methoden zur Charakterisierung der Hörgeräte-Signalverarbeitung

Electroacoustique - 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

La CEI 60118-15:2012 spécifie un signal d'essai conçu pour représenter la parole normale, le signal vocal international de test (ISTS), ainsi que les procédures et les exigences relatives à la mesure des caractéristiques de traitement des signaux dans les appareils de correction auditive à conduction aérienne. Les mesures sont utilisées pour obtenir le gain d'insertion estimé (EIG, estimated insertion gain). Pour les besoins de la caractérisation d'un appareil de correction auditive aux fins de production, de livraison et d'approvisionnements, les procédures et exigences pour obtenir le gain de coupleur à l'aide d'un coupleur de 2 cm3 tel que défini dans la CEI 60318-5 sont également spécifiées. Le but de la présente norme est de garantir que les mêmes mesures effectuées sur un appareil de correction auditive en suivant les procédures décrites, et en utilisant l'appareillage conformément à ces exigences, donnent pratiquement les mêmes résultats. Les méthodes de mesure qui tiennent compte du couplage acoustique d'un appareil de correction auditive à l'oreille individuelle et de l'influence acoustique des variations anatomiques individuelles d'un utilisateur final sur les performances acoustiques de l'appareil de correction auditive, connues sous le nom de mesures d'oreille réelle, sont en dehors du domaine d'application de la présente norme particulière.

Elektroakustika - Slušni pripomočki - 15. del: Metode za ugotavljanje lastnosti obdelave signalov v slušnih pripomočkih s signali, podobnimi govoru

Akustične meritve, akustične značilnosti in pojavi, akustično preskušanje, akustika, akustično-električne naprave, avdiometri, slušni prag, podatki, definicije, ušesa, elektroakustika, frekvence, meritev frekvence, funkcionalne značilnosti, slušna sposobnost, slušni pripomočki, sluh (slušno zaznavanje), izmenjava informacij, meritev, merilni pogoji, merilni instrumenti, merilne tehnike, hrup, hrup (okoljski), nominalne vrednosti, natančnost, značilnosti, preskušanje kakovosti, ocene, občutljivost, obdelava signala, signali, zvok, zvočna polja, raven zvočnega tlaka, zvočni viri, specifikacija (odobritev), razumljivost govora, preskusni signali, preskušanje, preskusni pogoji, prenos, značilnosti prenosa

General Information

Status
Published
Publication Date
14-May-2012
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
07-May-2012
Due Date
12-Jul-2012
Completion Date
15-May-2012

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SLOVENSKI STANDARD
SIST EN 60118-15:2012
01-julij-2012
(OHNWURDNXVWLND6OXãQLSULSRPRþNLGHO0HWRGH]DXJRWDYOMDQMHODVWQRVWL
REGHODYHVLJQDORYYVOXãQLKSULSRPRþNLKVVLJQDOLSRGREQLPLJRYRUX

Electroacoustics - Hearing aids - Part 15: Methods for characterising signal processing in

hearing aids with a speech-like signal
Akustik - Hörgeräte - Teil 15: Methoden zur Charakterisierung der Hörgeräte-
Signalverarbeitung
Electroacoustique - 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
Ta slovenski standard je istoveten z: EN 60118-15:2012
ICS:
11.180.15 3ULSRPRþNL]DJOXKHRVHEHLQ Aids for deaf and hearing
RVHEH]RNYDURVOXKD impaired people
17.140.50 Elektroakustika Electroacoustics
SIST EN 60118-15:2012 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN 60118-15:2012
---------------------- Page: 2 ----------------------
SIST EN 60118-15:2012
EUROPEAN STANDARD
EN 60118-15
NORME EUROPÉENNE
April 2012
EUROPÄISCHE NORM
ICS 17.140.50
English version
Electroacoustics -
Hearing aids -
Part 15: Methods for characterising signal processing in hearing aids with
a speech-like signal
(IEC 60118-15:2012)
Electroacoustique - Akustik -
Appareils de correction auditive - Hörgeräte -

Partie 15: Méthodes de caractérisation du Teil 15: Methoden zur Charakterisierung

traitement des signaux dans les appareils der Hörgeräte-Signalverarbeitung
de correction auditive avec un signal de (IEC 60118-15:2012)
type parole
(CEI 60118-15:2012)

This European Standard was approved by CENELEC on 2012-03-27. CENELEC members are bound to comply

with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard

the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on

application to the CEN-CENELEC Management Centre or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other

language made by translation under the responsibility of a CENELEC member into its own language and notified

to the CEN-CENELEC Management Centre has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus,

the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,

Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia,

Spain, Sweden, Switzerland, Turkey and the United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Management Centre: Avenue Marnix 17, B - 1000 Brussels

© 2012 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 60118-15:2012 E
---------------------- Page: 3 ----------------------
SIST EN 60118-15:2012
EN 60118-15:2012 - 2 -
Foreword

The text of document 29/719/CDV, future edition 1 of IEC 60118-15, prepared by IEC/TC 29

"Electroacoustics" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as

EN 60118-15:2012.
The following dates are fixed:
(dop) 2012-12-27
• latest date by which the document has
to be implemented at national level by
publication of an identical national
standard or by endorsement
(dow) 2015-03-27
• latest date by which the national
standards conflicting with the
document have to be withdrawn

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such patent

rights.
Endorsement notice

The text of the International Standard IEC 60118-15:2012 was approved by CENELEC as a European

Standard without any modification.

In the official version, for Bibliography, the following notes have to be added for the standards indicated:

IEC 61669 NOTE Harmonized as EN 61669.
IEC 60118-0:1983 NOTE Harmonized as EN 60118-0:1993 + A1:1994 (not modified).
+ A1:1994
---------------------- Page: 4 ----------------------
SIST EN 60118-15:2012
- 3 - EN 60118-15:2012
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

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.

NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD

applies.
Publication Year Title EN/HD Year
IEC 60118-7 - Electroacoustics - Hearing aids - EN 60118-7 -
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 - EN 60118-8 2005
Part 8: Methods of measurement of
performance characteristics of hearing aids
under simulated in situ working conditions
IEC 60318-4 - Electroacoustics - Simulators of human head EN 60318-4 -
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 EN 60318-5 -
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 61260 - Electroacoustics - Octave-band and EN 61260 -
fractional-octave-band filters
---------------------- Page: 5 ----------------------
SIST EN 60118-15:2012
---------------------- Page: 6 ----------------------
SIST EN 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
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX V
ICS 17.140.50 ISBN 978-2-88912-932-4

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 7 ----------------------
SIST EN 60118-15:2012
– 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

---------------------- Page: 8 ----------------------
SIST EN 60118-15:2012
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

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

---------------------- Page: 9 ----------------------
SIST EN 60118-15:2012
– 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-

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 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.

---------------------- Page: 10 ----------------------
SIST EN 60118-15:2012
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.
---------------------- Page: 11 ----------------------
SIST EN 60118-15:2012
– 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.
---------------------- Page: 12 ----------------------
SIST EN 60118-15:2012
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

---------------------- Page: 13 ----------------------
SIST EN 60118-15:2012
– 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.
---------------------- Page: 14 ----------------------
SIST EN 60118-15:2012
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
...

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