SIST EN ISO 8253-3:2022

Acoustics - Audiometric test methods - Part 3: Speech audiometry (ISO 8253-3:2022)

This document specifies basic methods for speech recognition tests for audiological applications.
NOTE       Examples of speech materials are given in Annex A.
In order to ensure minimum requirements of precision and comparability between different test procedures including speech recognition tests in different languages, this document specifies requirements for the composition, validation and evaluation of speech test materials, and the realization of speech recognition tests. This document does not specify the contents of the speech material because of the variety of languages.
Furthermore, this document also specifies the determination of reference values and requirements for the realization and manner of presentation. In addition, there are features of speech tests described which are important to be specified, but which are not understood as a requirement.
This document specifies procedures and requirements for speech audiometry with the recorded test material being presented by an audiometer through a transducer, e.g., an earphone, bone vibrator, or loudspeaker arrangement for sound field audiometry. Methods for using noise either for masking the non-test ear or as a competing sound are described.
Some test subjects, for example children, can require modified test procedures not specified in this document.
Specialized tests, such as those used for evaluating directional hearing and dichotic hearing, are outside the scope of this document.

Akustik - Audiometrische Prüfverfahren - Teil 3: Sprachaudiometrie (ISO 8253-3:2022)

Dieses Dokument beschreibt grundlegende Verfahren für in der Audiologie angewandte Sprachverständlich-keits¬tests.
ANMERKUNG Beispiele für Sprachmaterialien sind in Anhang A angegeben.
Um sicherzustellen, dass Mindestanforderungen hinsichtlich der Genauigkeit und der Vergleichbarkeit zwischen verschiedenen Testverfahren, einschließlich Sprachverständlichkeitstests in verschiedenen Sprachen, eingehalten werden, legt dieses Dokument Anforderungen an die Zusammensetzung, Validierung und Auswertung von Sprachtestmaterialien und an die Realisierung von Sprachverständlichkeitstests fest. Im Hinblick auf die Vielzahl der Sprachen legt dieses Dokument nicht die Inhalte der einzelnen Sprachmaterialien fest.
Weiterhin beschreibt dieses Dokument die Bestimmung der Bezugswerte und die Anforderungen an die Realisierung und die Art der Darbietung. Außerdem sind die Merkmale von Sprachtests beschrieben, deren Festlegung wichtig ist, die aber nicht als Anforderung aufgefasst werden
Dieses Dokument legt Verfahren und Anforderungen für die Sprachaudiometrie mit aufgezeichnetem Sprachtestmaterial fest, das von einem Audiometer über einen Wandler, z. B. Kopfhörer, Knochenleitungshörer oder Lautsprecheranordnung für die Schallfeldaudiometrie, angeboten wird. Die Verfahren für den Einsatz von Rauschen, entweder zur Verdeckung am nichtgeprüften Ohr oder als Zusatzschall, werden beschrieben.
Einige Versuchspersonen, z. B. Kinder, können geänderte Prüfabläufe erfordern, die nicht in diesem Dokument festgelegt sind.
Spezielle Prüfverfahren, wie sie für die Bestimmung des Richtungshörens und des dichotischen Hörens verwendet werden, liegen außerhalb des Anwendungsbereiches dieses Dokuments.

Acoustique - Méthodes d'essais audiométriques - Partie 3: Audiométrie vocale (ISO 8253-3:2022)

Le présent document spécifie les méthodes fondamentales d'essais de reconnaissance vocale pour les applications audiologiques.
NOTE            Des exemples de matériels vocaux sont donnés à l'Annexe A.
Afin de garantir l'existence d'exigences minimales de précision et de comparabilité entre différents modes opératoires d'essai, y compris pour des essais de reconnaissance vocale dans différentes langues, le présent document spécifie les exigences relatives à la composition, à la validation et à l'évaluation des matériels vocaux d'essai, ainsi qu'à la réalisation des essais de reconnaissance vocale. Le présent document ne spécifie pas le contenu du matériel vocal, en raison de la multiplicité des langues.
De plus, le présent document spécifie également la détermination de valeurs de référence et les exigences relatives à celle-ci, ainsi que le mode de présentation. Il existe en outre des caractéristiques des essais vocaux décrits qu'il est important de spécifier, mais qui ne sont pas considérées comme des exigences.
Le présent document spécifie des modes opératoires et des exigences applicables à l'audiométrie vocale, la présentation du matériel vocal d’essai enregistré s'effectuant au moyen d'un audiomètre, à l'aide d'un transducteur, par exemple, un écouteur ou un ossivibrateur, ou à l'aide de haut-parleurs pour l'audiométrie en champ acoustique. Il décrit des méthodes d'utilisation de bruits, soit comme bruits de masquage appliqués à l'oreille non testée, soit comme bruits de fond.
Pour certains sujets d’essai, par exemple les enfants, le recours à des modes opératoires d'essai modifiés, non spécifiés dans le présent document, peut se révéler nécessaire.
Les essais spécialisés, tels que ceux qui servent à évaluer l'audition directionnelle et l'audition dichotique, ne relèvent pas du domaine d'application du présent document.

Akustika - Avdiometrijske preskusne metode - 3. del: Govorna avdiometrija (ISO 8253-3:2022)

General Information

• Status: Published
• Public Enquiry End Date: 19-Feb-2021
• Publication Date: 15-Jun-2022
• ICS: 13.140 - Noise with respect to human beings
• ICS: 17.140.01 - Acoustic measurements and noise abatement in general
• Technical Committee: AKU - Acoustics
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 19-May-2022
• Due Date: 24-Jul-2022
• Completion Date: 16-Jun-2022
• Ref Project: EN ISO 8253-3:2022 - Acoustics - Audiometric test methods - Part 3: Speech audiometry (ISO 8253-3:2022)

Relations

• Replaces: SIST EN ISO 8253-3:2012 - Acoustics - Audiometric test methods - Part 3: Speech audiometry (ISO 8253-3:2012)
• Effective Date: 01-Jul-2022

Overview

EN ISO 8253-3:2022 - Acoustics: Audiometric test methods - Part 3: Speech audiometry (ISO 8253-3:2022) establishes standardized procedures for speech recognition tests used in audiological applications. Published by CEN/ISO in 2022 (superseding the 2012 edition), the document specifies requirements for the composition, validation and evaluation of recorded speech test materials and for conducting speech audiometry using an audiometer and transducers (earphones, bone vibrator or loudspeaker sound-field systems). The standard intentionally does not prescribe the linguistic content of speech materials because of language variability; examples are given in Annex A.

Key topics and technical requirements

• Speech material recording and calibration
  • Requirements for recording environment, setup and calibration signals.
  • Reference recordings and signal level specifications for speech, announcing and competing sounds.
• Validation and equivalence
  • Procedures to determine a reference speech recognition curve, phonemic and perceptual equivalence across test lists, and test–retest reliability.
  • Documentation requirements for validated materials.
• Test methods and measurement
  • Procedures for determining speech detection threshold (SDT), speech recognition threshold (SRT) and speech recognition scores.
  • Use of recorded material presented through an audiometer and choice of transducer (earphones, bone vibrator, sound field).
• Masking and competing sounds
  • Methods for contralateral masking and for presenting competing sounds (masking noise or competing speech), including guidance on signal‑to‑noise ratio (SNR) and presentation.
• Instrumentation, calibration and uncertainty
  • Requirements for audiometric equipment, ambient sound levels in test rooms and stages of maintenance/calibration (Stage A routine checks, Stage B periodic electroacoustic tests, Stage C basic calibration).
  • Guidance on measurement uncertainty and intervals between tests.
• Scope limitations
  • Specialized procedures (e.g., directional‑hearing or dichotic tests) and some modified protocols (for certain children) are outside the scope.

Practical applications and users

This standard is essential for:

• Clinical audiologists and hearing clinics implementing standardized speech audiometry for diagnosis and monitoring.
• Hearing‑aid and cochlear‑implant centers validating speech recognition outcomes.
• Occupational health services conducting hearing assessments.
• Manufacturers of audiometers, transducers and test materials ensuring compliance and interoperability.
• Researchers designing speech recognition studies and cross‑language material validation. Using EN ISO 8253-3:2022 helps ensure comparability, repeatability and traceability of speech audiometry results across clinics, languages and devices.

Related standards

• Other parts of ISO 8253 (pure‑tone audiometry and objective measures) and national CEN/ISO documentation on acoustics and audiometry are commonly used alongside this part.

Keywords: EN ISO 8253-3:2022, speech audiometry, audiometric test methods, speech recognition tests, calibration, masking, sound field audiometry, speech recognition threshold, speech detection threshold.

Standards Content (Sample)

SLOVENSKI STANDARD
01-julij-2022
Nadomešča:
SIST EN ISO 8253-3:2012
Akustika - Avdiometrijske preskusne metode - 3. del: Govorna avdiometrija (ISO
8253-3:2022)
Acoustics - Audiometric test methods - Part 3: Speech audiometry (ISO 8253-3:2022)
Akustik - Audiometrische Prüfverfahren - Teil 3: Sprachaudiometrie (ISO 8253-3:2022)
Acoustique - Méthodes d'essais audiométriques - Partie 3: Audiométrie vocale (ISO
8253-3:2022)
Ta slovenski standard je istoveten z: EN ISO 8253-3:2022
ICS:
13.140 Vpliv hrupa na ljudi Noise with respect to human
beings
17.140.01 Akustična merjenja in Acoustic measurements and
blaženje hrupa na splošno noise abatement in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 8253-3
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2022
EUROPÄISCHE NORM
ICS 13.140 Supersedes EN ISO 8253-3:2012
English Version
Acoustics - Audiometric test methods - Part 3: Speech
audiometry (ISO 8253-3:2022)
Acoustique - Méthodes d'essais audiométriques - Akustik - Audiometrische Prüfverfahren - Teil 3:
Partie 3: Audiométrie vocale (ISO 8253-3:2022) Sprachaudiometrie (ISO 8253-3:2022)
This European Standard was approved by CEN on 18 January 2022.

CEN 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 CEN
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 CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 8253-3:2022 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 8253-3:2022) has been prepared by Technical Committee ISO/TC 43
"Acoustics" in collaboration with Technical Committee CEN/TC 211 “Acoustics” the secretariat of which
is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by August 2022, and conflicting national standards shall
be withdrawn at the latest by August 2022.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 8253-3:2012.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 8253-3:2022 has been approved by CEN as EN ISO 8253-3:2022 without any
modification.
INTERNATIONAL ISO
STANDARD 8253-3
Third edition
2022-01
Acoustics — Audiometric test
methods —
Part 3:
Speech audiometry
Acoustique — Méthodes d'essais audiométriques —
Partie 3: Audiométrie vocale
Reference number
ISO 8253-3:2022(E)
ISO 8253-3:2022(E)
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO 8253-3:2022(E)
Contents Page
Foreword .v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Requirements for recording of speech material . 5
4.1 General requirements . 5
4.2 Calibration signal . 5
4.3 Reference recording . . 5
4.4 Recording environment . 6
4.5 Recording setup . 6
4.6 Signals and levels . 6
4.6.1 Calibration signals . 6
4.6.2 Speech signals . 7
4.6.3 Announcing signals . 7
4.6.4 Competing sound signals . 7
4.7 Phonemic equivalence across test lists . 7
4.8 Perceptual equivalence across test lists . 7
5 Validation of speech material recordings . 8
5.1 General . 8
5.2 Determination of reference speech recognition curve . 8
5.3 Determination of perceptual equivalence of test lists . 9
5.4 Determination of test-retest reliability . 9
5.5 Documentation . 9
6 Requirements for speech audiometry .10
6.1 Audiometric equipment . 10
6.2 Ambient sound pressure levels in test room for speech audiometry . 10
6.3 Sound field speech audiometry . 10
7 Preparation and instruction of test subject .11
7.1 General . 11
7.2 Preparation of test subject . . 11
7.3 Instruction of test subject . 11
8 Subject's response mode .11
9 Determination of speech detection threshold level .12
10 Determination of speech recognition threshold level .13
11 Determination of speech recognition scores.14
12 Contralateral masking .14
13 Speech audiometry with competing sound .15
13.1 Type of competing sound .15
13.2 Presentation of competing sound . 15
13.3 Speech and competing sound levels . 15
13.4 Test procedure . 16
13.4.1 General . 16
13.4.2 Speech recognition score at fixed SNR . 16
13.4.3 Speech recognition threshold level with a competing sound . 16
14 Format of speech audiogram .16
15 Measurement uncertainty .17
iii
ISO 8253-3:2022(E)
16 Maintenance and calibration of equipment .17
16.1 General . 17
16.2 Stage A: Routine checking and listening tests . 17
16.3 Stage B: Periodic electroacoustic tests . 18
16.4 Stage C: Basic calibration tests . 18
16.5 Intervals between tests . 18
Annex A (informative) Example of speech materials .20
Annex B (informative) Examples of competing sound .21
Annex C (informative) Typical results .22
Annex D (informative) Optimization of perceptual equivalence of test lists .26
Annex E (informative) Measurement uncertainty .27
Annex F (informative) Determination of minimum number of subjects .32
Annex G (informative) Determination of test-retest reliability .34
Bibliography .39
iv
ISO 8253-3:2022(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 43, Acoustics, in collaboration with
the European Committee for Standardization (CEN) Technical Committee CEN/TC 211, Acoustics, in
accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This third edition cancels and replaces the second edition (ISO 8253-3:2012), which has been technically
revised. The main changes compared to the previous edition are as follows:
— The technical requirements for recording of speech material were adapted to recent equipment and
technology.
— The determination of reference speech recognition curves was revised. An annex that gives advices
on how to determine the minimum number of subjects was introduced.
— The determination of speech recognition threshold levels is described in a more general manner.
— Symbols for the graphical representation of speech audiometry results were introduced.
A list of all the parts in the ISO 8253 series can be found on the ISO website.
v
ISO 8253-3:2022(E)
Introduction
Speech audiometry is used for the assessment of hearing in connection with diagnostic evaluation and
audiological rehabilitation.
The results of speech audiometry depend on the speech material and test method used. This document
sets conditions for speech materials in order to ensure minimum requirements of precision and
comparability between different tests using different speech materials including materials in different
languages. It also specifies procedures to be used when testing speech recognition.
vi
INTERNATIONAL STANDARD ISO 8253-3:2022(E)
Acoustics — Audiometric test methods —
Part 3:
Speech audiometry
1 Scope
This document specifies basic methods for speech recognition tests for audiological applications.
NOTE Examples of speech materials are given in Annex A.
In order to ensure minimum requirements of precision and comparability between different test
procedures including speech recognition tests in different languages, this document specifies
requirements for the composition, validation and evaluation of speech test materials, and the realization
of speech recognition tests. This document does not specify the contents of the speech material because
of the variety of languages.
Furthermore, this document also specifies the determination of reference values and requirements for
the realization and manner of presentation. In addition, there are features of speech tests described
which are important to be specified, but which are not understood as a requirement.
This document specifies procedures and requirements for speech audiometry with the recorded test
material being presented by an audiometer through a transducer, e.g., an earphone, bone vibrator, or
loudspeaker arrangement for sound field audiometry. Methods for using noise either for masking the
non-test ear or as a competing sound are described.
Some test subjects, for example children, can require modified test procedures not specified in this
document.
Specialized tests, such as those used for evaluating directional hearing and dichotic hearing, are outside
the scope of this document.
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.
ISO 8253-1, Acoustics — Audiometric test methods — Part 1: Pure-tone air and bone conduction audiometry
ISO 8253-2, Acoustics — Audiometric test methods — Part 2: Sound field audiometry with pure-tone and
narrow-band test signals
ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
me a s ur ement (GUM: 1995)
IEC 60645-1:2017, Electroacoustics — Audiometric equipment — Part 1: Equipment for pure-tone and
speech audiometry
IEC 61672-1, Electroacoustics — Sound level meters — Part 1: Specifications
ISO 8253-3:2022(E)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 8253-1 and ISO 8253-2 and
the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
speech signal
acoustic signal which carries information in a given language
Note 1 to entry: A speech signal can be a voice signal or an acoustic signal simulating a voice signal.
3.2
test item
particular monosyllabic or polysyllabic word, or logatom (3.12), or spondee, or sentence, or time-limited
segment of connected speech, used in accordance with defined rules of presentation and scoring in a
speech audiometric procedure
Note 1 to entry: Scoring may be based on a complete test item or parts thereof being correctly recognized.
3.3
test list
number of selected test items (3.2), presented and scored as a single unit
3.4
set of test items
selected number of test items (3.2) from a test list
3.5
speech material
entire set of test items (3.4) which is used for speech recognition tests
Note 1 to entry: Usually the speech material is subdivided into several test lists.
3.6
open-set test
test in which the number of alternative responses to each test item (3.2) is unlimited
3.7
closed-set test
test in which the number of alternative responses to each test item (3.2) is limited
3.8
phoneme
the smallest phonetic unit that distinguishes one word from another in a particular language
3.9
phoneme class
subdivision of phonemes that show characteristic similarities in vocal production mode as well as in
acoustical signal properties
3.10
phoneme distribution
relative distribution of the various phonemes within a given speech material (3.5)
ISO 8253-3:2022(E)
3.11
syllable
segment of speech consisting of an (optional) onset, a nucleus, and an (optional) coda, where the
nucleus most often consists of a vowel sound and the onset and coda most often consist of one or more
consonant sounds
3.12
logatom
syllabic unit that has no verbal meaning to the listener
Note 1 to entry: A logatom is sometimes called a “nonsense syllable”.
3.13
carrier phrase
sentence or phrase in which a test item (3.2) is embedded such that the correct recognition of the test
item (3.2) is not dependent upon the context or meaning of the sentence or phrase
3.14
connected speech
continuous speech with natural intonation, consisting of consecutive sentences with logical connections
3.15
reference recording
master recording
well-defined recording that represents the speech material (3.5) and that is used for validation and
application of the speech material (3.5)
3.16
speech level
sound pressure level of a specified speech material (3.5) as measured in an appropriate acoustic coupler,
ear simulator or in a sound field, with a specified frequency and time weighting
Note 1 to entry: The frequency and the time weighting should be according to IEC 61672-1.
3.17
speech detection threshold level
for a given test subject, for a specified speech material (3.5) and a specified manner of signal
presentation, the speech level at which it is detected as sound (not necessarily understood) in 50 % of
the trials
Note 1 to entry: Is synonymous with the expression “speech awareness threshold”.
3.18
speech recognition score
for a given test subject, for a specified speech material (3.5), a specified manner of signal presentation
and at a specified speech level, the percentage of correctly recognized test items (3.2) or scorable items
if the scoring method is not based on whole test items (3.2)
3.19
speech audiogram
graphical representation of the results of speech audiometry, where the speech recognition score is
plotted as percentage along the ordinate and speech level, in dB, or hearing level for speech, in dB, or
speech-to-noise level difference, in dB, along the abscissa
3.20
maximum speech recognition score
for a given test subject, for a specified speech material (3.5) and a specified manner of signal
presentation, the maximum speech recognition score obtained regardless of the speech level
ISO 8253-3:2022(E)
3.21
speech recognition threshold level
for a given test subject, for a specified speech material (3.5) and a specified manner of signal
presentation, the lowest speech level at which the speech recognition score is equal to 50 % or another
specified value
Note 1 to entry: Speech recognition threshold has been called “speech reception threshold”.
3.22
reference speech recognition threshold level
for a specified speech material (3.5) and a specified manner of signal presentation, the median value of
the speech recognition threshold levels of a sufficiently large number of otologically normal persons, of
both sexes, between 18 years and 25 years inclusive for whom the speech material (3.5) is appropriate
3.23
hearing level for speech
for a specified speech material (3.5) and a specified manner of signal presentation, the speech level
minus the appropriate reference speech recognition threshold level
3.24
optimum speech level
for a given test subject, for a specified speech material and a specified manner of signal presentation,
the speech level or range of speech levels at which maximum speech recognition score is obtained
3.25
half-optimum speech level
for a given test subject, for a specified speech material and a specified manner of signal presentation,
the speech level at which half of the maximum speech recognition score is obtained
3.26
most comfortable level for speech
for a given test subject, a specific speech material (3.5) and a specified manner of presentation, the
speech level at which the loudness of the speech signal (3.1) is judged by the test subject to be most
comfortable
3.27
speech recognition curve
for a given test subject, for a specified speech material (3.5) and a specified manner of signal
presentation, a curve that describes the speech recognition score as a function of speech level
3.28
reference speech recognition curve
for a specified speech material (3.5) and a specified manner of presentation, a curve that describes the
speech recognition score as a function of speech level for a sufficiently large number of otologically
normal persons of both sexes, aged between 18 years and 25 years inclusive and for whom the speech
material (3.5) is appropriate
3.29
competing sound
additional sound that is presented during speech recognition tests
3.30
competing sound level
sound pressure level of a competing sound as measured in an appropriate acoustic coupler, ear
simulator or in a sound field, with a specified frequency and time weighting
Note 1 to entry: The frequency and the time weighting should be according to IEC 61672-1.
ISO 8253-3:2022(E)
3.31
SNR
speech-to-noise ratio
speech-to-noise level difference
difference between the speech level and the competing sound level
3.32
effective masking level for speech
level of a specified masking sound equivalent to that hearing level for speech to which the speech
recognition threshold level for a specified speech signal (3.1) would be raised by the presence of that
masking sound
4 Requirements for recording of speech material
4.1 General requirements
Each recording shall contain the following signals:
a) the speech material;
b) a signal for the calibration of the equipment for speech audiometry.
4.2 Calibration signal
The calibration signal shall meet the following requirements:
a) A minimum duration of 60 s.
b) The calibration signal for sound-field speech audiometry shall be a weighted random noise, e.g., as
specified in IEC 60645-1:2017, 6.5.3, a band of noise centred at 1 kHz and having a bandwidth of
one-third octave, or a frequency-modulated tone at 1 kHz having a bandwidth of at least one-third
octave — the modulating signal shall be either sinusoidal or triangular with a repetition rate in the
range from 4 Hz to 20 Hz.
c) The calibration signal for earphones or bone vibrators shall be as specified in b). Alternatively, a
pure-tone signal may be used.
4.3 Reference recording
The voice characteristics of the speaker influence the test results. For general-use tests, a suitable
speaker, either male or female, shall have a normal and clear articulation and should speak with a
generally well understood dialect. The speaker shall be instructed to maintain clarity, natural pace, and
vocal effort and avoid emphasis on keywords.
NOTE 1 Tests with representative speech facilitate the comparison of results.
NOTE 2 For some applications, e.g., localized speech tests, a specific dialect can be required.
A reference recording mainly consists of the elements specified in 4.1. The reference recording shall not
be modified. All speech materials used for testing shall be equivalent copies of the reference recording.
Any changes of the reference recording (e.g., a new recording or changes of levels or frequency content)
require a new validation (see Clause 5).
For speech audiometry intended to be performed in noise, the reference recording shall also include the
associated competing sound or sounds, either on the same or on separate channels.
ISO 8253-3:2022(E)
4.4 Recording environment
The room in which the speech is recorded shall be sufficiently quiet to provide a signal-to-noise ratio of
at least 40 dB and should have a reverberation time of less than 0,5 s at any frequency in the range from
125 Hz to 8 000 Hz.
4.5 Recording setup
The frequency response of the recording setup, including the microphone used, shall be documented
along with the recording setup at least in the frequency range from 125 Hz to 8 000 Hz.
NOTE The quality of the recording and negligible loss of quality after repeated use make digital recordings
superior.
The signal-to-noise ratio of the recording shall be at least 40 dB when measured using the same
frequency weighting as for measuring the speech level.
4.6 Signals and levels
A speech test may comprise different types of signals. Common signals are calibration signals, speech
signals, announcing signals and competing sound signals.
NOTE 1 Not all speech tests comprise all of these signal types. The minimum type expected to be comprised is
speech signals.
NOTE 2 Speech signals can be logatomes, syllables, words, or sentences.
4.6.1 Calibration signals
Calibration signals may comprise a signal used to determine the sound pressure level (referred to as
the calibration signal) and additional signals used to check, for instance, the frequency response of the
equipment. A speech test should not comprise more than one calibration signal to determine the sound
pressure level.
NOTE 1 A common calibration procedure is to play the calibration signal in a defined state of the audiometry
software and to adjust the equipment until a particular sound pressure level is reported by a suitable level meter.
After that, the software is able to set the output to any required sound pressure level by adjusting either the
signal amplitude or the audiometer level (attenuator or amplifier level).
If a speech test comprises a calibration signal, the calibration signal level shall be stated and measured
as equivalent continuous sound pressure level (L ) with one of the frequency weightings specified
eq
in IEC 61672-1. For digital calibration signals, its root mean square (RMS) level re. full scale shall be
documented within the speech test.
NOTE 2 Due to common speech spectra shapes, frequency weighting Z (linear) is expected to yield the same
levels as weighting C. However, weighting C can be preferred in order to avoid influences of unheard interfering
noise (with very low or very high frequencies).
NOTE 3 Not all sound level meters allow to determine L , but instead provide particular time weightings (e.g.,
eq
exponential “FAST” or “SLOW”). For an unmodulated or little modulated calibration signal, a slow time weighting
can be a good approximation of L .
eq
If a speech test does not comprise a calibration signal, a particular part (subset) of the speech signals
shall be specified which is to be used to determine the speech level in a calibration procedure. In this
case, the speech level shall be stated and measured in the same way as defined above for the calibration
signal level.
NOTE 4 When speech signals are used for calibration, a time weighting of the sound level meter is not a good
approximation of L .
eq
ISO 8253-3:2022(E)
4.6.2 Speech signals
The relation (amplitude ratio or level difference in dB, respectively) of all speech signals to the signal
used for the calibration shall be documented within the speech test. The nominal speech level is given
by the level of the calibration signal when played at a nominal level difference of 0 dB.
EXAMPLE If a speech signal has a level difference of −3 dB with respect to the calibration signal and the
speech signal is to be presented at a level of 60 dB, the equipment is adjusted to yield a calibration signal level of
63 dB while playing the speech signal.
NOTE 1 Speech signals might be adjusted in their level in order to adjust their intelligibility. Hence, the L of a
eq
speech signal cannot be equal to the L of the calibration signal even when their nominal level difference is 0 dB.
eq
NOTE 2 For speech test lists based on single test items separated by silent intervals, the integration does not
include these intervals. For test lists based on single test items with a carrier phrase, the integration includes the
test items only. In a digital recording, the silent intervals can be removed by editing. Numerical correction may
also be made by determination of the total duration of the test items and the total duration of the silent intervals.
4.6.3 Announcing signals
Announcing signals are optionally employed to be played in advance of a particular speech signal, e.g.
to increase the attention. Their level might differ from the speech level, e.g., might be higher in order to
be better understandable.
4.6.4 Competing sound signals
Competing sound signals are employed to determine the score (e.g., intelligibility) in a speech test at a
particular speech-to-noise ratio (SNR), also referred to as speech test in noise. The relation (amplitude
ratio or level difference in dB, respectively) of all competing sound signals to the signal used for the
calibration shall be documented within the speech test. The nominal competing sound level is given by
the level of the calibration signal when played at a nominal level difference of 0 dB.
NOTE Due to historical or other reasons, different competing sound signals may yield different L values
eq
even when their nominal level difference is 0 dB.
4.7 Phonemic equivalence across test lists
The phoneme distribution shall be equal across test lists.
NOTE This does not require all phonemes be equally distributed within the test lists.
In some cases, it may not be possible to achieve perfect phonemic equivalence. In such cases, the test
lists shall be phonemically equivalent based on phoneme classes, e.g., voiced and unvoiced plosives and
fricatives, nasals, long and short vowels.
4.8 Perceptual equivalence across test lists
All test lists of a specific speech material shall be perceptually equivalent, i.e., the result of the speech
recognition test shall be independent of the choice of test list.
The speech recognition curves for all test lists shall have been determined in such a way that the speech
recognition threshold level can be determined. All speech recognition curves measured as given in 5.3
shall be within a range to be documented (see 5.5 k).
NOTE In order to increase the perceptual homogeneity of the speech material, speech recognition differences
between the particular speech test items can be minimized (see Annex D).
ISO 8253-3:2022(E)
5 Validation of speech material recordings
5.1 General
For the validation, equipment fulfilling the requirements of IEC 60645-1 shall be used. Testing shall
be performed monaurally for earphone or bone vibrator presentation. For sound field audiometry, the
loudspeaker arrangement specified for the intended use of the speech material shall be applied. Only
complete test lists shall be used.
5.2 Determination of reference speech recognition curve
The reference speech recognition curve for each speech material and manner of presentation shall
be determined by performing speech recognition tests using a sufficiently large group of otologically
normal persons of both sexes, between 18 years and 25 years inclusive, whose first language is the
language of the speech material. The hearing threshold levels of the test subjects should be at or below
10 dB at the frequencies 250 Hz, 500 Hz, 750 Hz, 1 000 Hz, 1 500 Hz, 2 000 Hz, 3 000 Hz, 4 000 Hz,
6 000 Hz, and 8 000 Hz. At a maximum of two frequencies the hearing threshold level may be at or
below 15 dB. If this criterion is not met, the minimum requirements for the pure-tone hearing threshold
levels of test subjects shall be specified by the laboratory carrying out the validation.
NOTE The necessary minimum number of subjects can be determined according to Annex F.
If the speech recognition test is intended to be performed with children, the reference speech
recognition curve shall be determined using a sufficiently large group of otologically normal children of
the same age range as the speech material is intended to be used for.
To achieve the reference speech recognition curve, speech recognition measurements shall be
performed at different presentation levels (or SNRs in case of a speech recognition test in competing
sound). The speech recognition measurements shall be performed within the normal context of the
speech stimulus (e.g., presentation of sentences when using a sentence test). The speech recognition
of each particular test item shall then be scored and analysed independently (e.g., scoring of particular
words of the sentences).
If the speech recognition test is intended to be used in silence, the reference speech recognition curve
shall be determined in silence.
If the speech recognition test is intended to be used with a competing sound, the reference speech
recognition curve shall be determined using this competing sound. If the test is intended to be used
with different competing sounds, the reference speech recognition curve shall be determined using
each particular competing sound.
The reference speech recognition curve shall be given as a table which describes the relation between
speech level (or SNR) and speech recognition score. The speech levels (or SNRs) which are required to
achieve the speech recognition scores 30 %, 40 %, 50 %, 60 %, 70 %, 80 %, and 90 % shall be specified.
Usually, the measurements are carried out at predefined speech levels (or SNRs) so that the values
for the required recognition scores are not directly available. Therefore, it shall be specified how the
speech levels (or SNRs) for the recognition scores 30 %, 40 %, 50 %, 60 %, 70 %, 80 %, and 90 % are
calculated form the measurement data. One possibility is computing the median for each speech level
(or SNR), and fit a discrimination function to these median values. In this case, the objective function
and the parameters fitted shall be provided.
If it is difficult to determine the whole reference speech recognition curve from 0 % to 100 %, ensure
that the speech recognition curve is determined in the range of interest. If the speech recognition
test is intended to be used for the determination of speech recognition threshold levels, the reference
speech recognition curve should be measured at values near the speech recognition threshold level
(including values above and below this value) using a sufficient number of measurements. If the speech
recognition test is intended to be used for the determination of the optimum speech level, the reference
ISO 8253-3:2022(E)
speech recognition curve should be measured at values from 50 % (or less) to values near to 100 %
using a sufficient number of measurements.
NOTE Typical results are shown in Annex C.
5.3 Determination of perceptual equivalence
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