SIST EN 60318-4:2010

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 60318-4:2010)

IEC 60318-4:2010 describes an occluded-ear simulator intended for the measurement of insert earphones in the frequency range from 100 Hz to 10 000 Hz. It is suitable for air conduction hearing aids and earphones, coupled to the ear by means of ear inserts e.g. ear moulds or similar devices. The occluded-ear simulator is also suitable as the basis for an extension intended to simulate the complete ear canal and the outer ear (for instance in head simulators). The occluded-ear simulator simulates the acoustic transfer impedance for the occluded normal adult human ear. However, it does not simulate the leakage between an earmould and a human ear canal; therefore, the results obtained with the occluded-ear simulator may deviate from the performance of an insert earphone on a real ear, especially at low frequencies. Moreover, large performance variations among individual ears will occur which should be considered when using the ear simulator. Above 10 kHz the device does not simulate a human ear, but can be used as an acoustic coupler at additional frequencies up to 16 kHz. Below 100 Hz, the device has not been verified to simulate a human ear, but can be used as an acoustic coupler at additional frequencies down to 20 Hz. IEC 60318-4:2010 cancels and replaces IEC 60711, published in 1981 and constitutes a technical revision. The main changes with respect to the previous edition are listed below:  - extension of the usable frequency range to 100 Hz - 16 000 Hz;  - addition of values of maximum permitted expanded uncertainties to all tolerances.

Akustik - Simulatoren des menschlichen Kopfes und Ohres - Teil 4: Simulator für den abgeschlossenen Gehörgang zur Messung an mittels Ohreinsätzen an das Ohr angekoppelten Ohrhörern (IEC 60318-4:2010)

Electroacoustique - Simulateurs de tête et d'oreille humaines - Partie 4: Simulateur d'oreille occluse pour la mesure des écouteurs couplés à l'oreille par des embouts (CEI 60318-4:2010)

La CEI 60318-4:2010 décrit un simulateur d'oreille occluse, destiné à la mesure des écouteurs internes, dans la plage de fréquences comprise entre 100 Hz et 10 000 Hz. Ce simulateur est adapté aux appareils de correction auditive et écouteurs en conduction aérienne, couplés à l'oreille au moyen d'embouts, par exemple embouts moulés ou dispositifs similaires. Le simulateur d'oreille occluse peut aussi être utilisé comme appareil destiné à simuler le canal auditif complet et l'oreille externe (par exemple, dans les simulateurs de tête). Le simulateur d'oreille occluse simule l'impédance acoustique de transfert pour l'oreille occluse humaine normale d'adulte. Il ne simule cependant pas la fuite entre l'embout moulé et le canal auditif humain; par conséquent, les résultats obtenus avec le simulateur d'oreille occluse peuvent s'écarter des résultats fournis par un écouteur interne couplé à une oreille réelle, particulièrement aux fréquences basses. De plus, de grandes variations des résultats existent pour différentes oreilles, ce qu'il convient de prendre en compte lors de l'utilisation du simulateur d'oreille. Au-delà d'une fréquence de 10 kHz, le dispositif ne simule pas l'oreille humaine, mais peut en revanche être utilisé comme coupleur acoustique à des fréquences supplémentaires jusqu'à 16 kHz. En dessous d'une fréquence de 100 Hz, il n'a pas été vérifié que le dispositif simule l'oreille humaine, ce dernier pouvant en revanche être utilisé comme coupleur acoustique à des fréquences supplémentaires jusqu'à 20 Hz. La CEI 60318-4:2010 annule et remplace la CEI 60711, parue en 1981, dont elle constitue une révision technique. La liste des principales modifications par rapport à l'édition précédente est la suivante:  - élargissement du domaine de fréquence utile de 100 Hz à 16 000 Hz;  - ajout des valeurs d'incertitude élargie maximale admise à toutes les tolérances.

Elektroakustika - Simulatorji človeške glave in ušes - 4. del: Simulator zamašenega ušesa za merjenje ušesnih slušalk, spojenih z ušesom prek ušesnih vstavkov (IEC 60318-4:2010)

Ta del IEC 60318 opisuje simulator zamašenega ušesa, namenjen za merjenje vstavljivih slušalk v frekvenčnem razponu med 100 Hz in 10 000 Hz. Primeren je za slušne pripomočke in slušalke, ki prevajajo zrak, spojene z ušesom prek ušesnih vstavkov, npr. ušesnih odlitkov ali podobnih pripomočkov. Simulator zamašenega ušesa je primeren tudi kot osnova za razširitev, ki je namenjena za simulacijo celotnega ušesnega kanala in zunanjega ušesa (na primer pri simulatorjih glave). Simulator zamašenega ušesa posnema impedanco zvočnega prenosa za zamašeno človeško uho normalnega odraslega. Vendar pa ne posnema uhajanja med ušesnim odlitkom in kanalom človeškega ušesa, zato se rezultati, dobljeni s simulatorjem zamašenega ušesa, lahko razlikujejo od delovanja vstavljive slušalke v pravem ušesu, predvsem pri nizkih frekvencah.  Poleg tega med posameznimi ušesi prihaja do velikih odstopanj v delovanju, ki jih je treba upoštevati pri uporabi ušesnih simulatorjev. Pripomoček nad 10 kHz ne posnema človeškega ušesa, vendar se lahko uporabi kot akustični spojnik pri dodatnih frekvencah do 16 kHz. Ni preverjeno, ali pripomoček posnema človeško uho pri frekvencah pod 100 Hz, vendar se lahko uporabi kot akustični spojnik pri dodatnih frekvencah do 20 Hz.

General Information

• Status: Published
• Publication Date: 21-Jul-2010
• ICS: 13.140 - Noise with respect to human beings
• ICS: 17.140.50 - Electroacoustics
• Technical Committee: I11 - Imaginarni 11
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 07-Jul-2010
• Due Date: 11-Sep-2010
• Completion Date: 22-Jul-2010
• Ref Project: EN 60318-4:2010 - 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

Relations

• Replaces: SIST HD 443 S1:2004 - Occluded-ear simulator for the measurement of earphones coupled to the ear by ear inserts
• Effective Date: 29-Jan-2023
• Revised: SIST HD 443 S1:2004 - Occluded-ear simulator for the measurement of earphones coupled to the ear by ear inserts
• Effective Date: 07-May-2013

Overview

EN 60318-4:2010 (adoption of IEC 60318-4:2010) specifies an occluded-ear simulator used for electroacoustic measurements of insert earphones and air‑conduction hearing aids coupled to the ear by means of ear inserts (e.g., ear moulds). The standard defines the simulator’s purpose, construction principles, calibration method and coupling arrangements. It is intended to simulate the acoustic transfer impedance of a normal occluded adult human ear primarily in the frequency band 100 Hz to 10 000 Hz and can be used as an acoustic coupler up to 16 kHz or down to 20 Hz under limited conditions.

Key topics and requirements

• Scope and limitations
  • Simulates the occluded normal adult human ear’s acoustic transfer impedance (100 Hz–10 kHz).
  • Does not simulate leakage between an earmould and a real ear; results may deviate, especially at low frequencies.
  • Above 10 kHz the device is not representative of the human ear (usable as coupler up to 16 kHz); below 100 Hz not verified for ear simulation.
• Construction and dimensions
  • Defines principal cavity geometry and an example design to achieve the target transfer impedance.
  • Specifies use of a calibrated pressure‑type microphone and pressure equalization arrangements where required.
• Calibration and measurement
  • Specifies atmospheric reference conditions and a calibration method for reproducible sound pressure measurements.
  • Adds maximum permitted expanded uncertainties to tolerances, improving traceability and repeatability of results.
• Coupling procedures
  • Details recommended coupling practices for insert earphones, in‑the‑ear and behind‑the‑ear hearing aids, and modular devices to ensure consistent measurements.
• Uncertainty and reporting
  • Tables and annexes list permitted uncertainties and procedures for characterizing level versus frequency for the nominal simulator volume.

Applications and users

EN 60318-4:2010 is used by:

• Earphone and hearing‑aid manufacturers for R&D, design validation and production testing of insert earphones and earmould‑coupled devices.
• Acoustic test laboratories and certification bodies performing standardized electroacoustic measurements and type‑approval testing.
• Standards and regulatory authorities referencing repeatable coupler measurements in specifications and conformity assessments.
• Audiology equipment developers and researchers conducting comparative measurements or extended high‑frequency audiometry studies.

Practical uses include acoustic output verification, frequency response comparison, type approval testing and baseline characterization of insert transducers.

Related standards

• IEC 60318 series (other head/ear simulators)
• IEC 60711 (superseded by IEC 60318-4)
• IEC 61094-4 (measurement microphone specifications)
• ISO/IEC Guide 98-3 (GUM: uncertainty of measurement)
• Relevant audiometric standards such as ISO 389‑6 (extended high‑frequency earphones)

Standards Content (Sample)

SLOVENSKI STANDARD
01-september-2010
1DGRPHãþD
SIST HD 443 S1:2004
(OHNWURDNXVWLND6LPXODWRUMLþORYHãNHJODYHLQXãHVGHO6LPXODWRU]DPDãHQHJD
XãHVD]DPHUMHQMHXãHVQLKVOXãDONVSRMHQLK]XãHVRPSUHNXãHVQLKYVWDYNRY,(&

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-
4:2010)
Akustik - Simulatoren des menschlichen Kopfes und Ohres - Teil 4: Simulator für den
abgeschlossenen Gehörgang zur Messung an mittels Ohreinsätzen an das Ohr
angekoppelten Ohrhörern (IEC 60318-4:2010)
Electroacoustique - Simulateurs de tête et d'oreille humaines - Partie 4: Simulateur
d'oreille occluse pour la mesure des écouteurs couplés à l'oreille par des embouts (CEI
60318-4:2010)
Ta slovenski standard je istoveten z: EN 60318-4:2010
ICS:
13.140 Vpliv hrupa na ljudi Noise with respect to human
beings
17.140.50 Elektroakustika Electroacoustics
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 60318-4
NORME EUROPÉENNE
May 2010
EUROPÄISCHE NORM
ICS 17.140.50 Supersedes HD 443 S1:1983

English version
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 60318-4:2010)
Electroacoustique -  Akustik -
Simulateurs de tête et d'oreille humaines - Simulatoren des menschlichen Kopfes
Partie 4: Simulateur d'oreille occluse und Ohres -
pour la mesure des écouteurs couplés Teil 4: Simulator für den abgeschlossenen
à l'oreille par des embouts Gehörgang zur Messung an mittels
(CEI 60318-4:2010) Ohreinsätzen an das Ohr angekoppelten
Ohrhörern
(IEC 60318-4:2010)
This European Standard was approved by CENELEC on 2010-05-01. 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 Central Secretariat 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 Central Secretariat 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 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

© 2010 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60318-4:2010 E
Foreword
The text of document 29/662/CDV, future edition 1 of IEC 60318-4, prepared by IEC TC 29,
Electroacoustics, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as
EN 60318-4 on 2010-05-01.
This standard supersedes HD 443 S1:1983.
The main changes with respect to the previous edition are listed below:
− extension of the usable frequency range to 100 Hz – 16 000 Hz;
− addition of values of maximum permitted expanded uncertainties to all tolerances.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN and CENELEC shall not be held responsible for identifying any or all such patent
rights.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2011-02-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2013-05-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 60318-4:2010 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:
[1]  ISO 389-2 NOTE  Harmonized as EN ISO 389-2.
[2]  ISO 389-5 NOTE  Harmonized as EN ISO 389-5.
[3]  ISO 389-6 NOTE  Harmonized as EN ISO 389-6.
__________
- 3 - EN 60318-4:2010
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following referenced documents are indispensable for the application 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.

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 61094-4 - Measurement microphones - EN 61094-4 -
Part 4: Specifications for working standard
microphones
ISO/IEC Guide 98-3 - Uncertainty of measurement - - -
Part 3: Guide to the expression of uncertainty
in measurement (GUM:1995)
IEC 60318-4 ®
Edition 1.0 2010-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
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

Électroacoustique – Simulateurs de tête et d’oreille humaines –
Partie 4: Simulateur d'oreille occluse pour la mesure des écouteurs couplés à
l'oreille par des embouts
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
R
CODE PRIX
ICS 17.140.50 ISBN 2-8318-1076-6
– 2 – 60318-4 © IEC:2010
CONTENTS
FOREWORD.3
1 Scope.5
2 Normative references .5
3 Terms and definitions .5
4 Construction .7
4.1 General .7
4.2 Principal cavity dimensions .7
4.3 Calibrated pressure-type microphone .7
4.4 Pressure equalization.8
4.5 Acoustic transfer impedance level .8
4.6 Example of design.8
5 Calibration.9
5.1 Atmospheric reference conditions.9
5.2 Calibration method .9
6 Coupling of earphones and hearing aids to the occluded-ear simulator.9
6.1 Audiometers with insert earphones.9
6.2 In-the-ear hearing aids (custom made) .9
6.3 Hearing aids with insert earphone .10
6.4 Behind-the-ear and spectacle hearing aids.11
6.5 Modular in-the-ear hearing aids.12
7 Maximum permitted expanded uncertainty of measurements .14
Annex A (informative) Example of one specific design of occluded-ear simulator .16
Annex B (informative) Principle of calibration for the occluded-ear simulator.17
Bibliography.19

Figure 1 – Connection of an in-the-ear hearing aid to the occluded-ear simulator .10
Figure 2 – Connection of an insert earphone to the occluded-ear simulator .11
Figure 3 – Connection of a behind-the-ear hearing aid to the occluded-ear simulator.13
Figure 4 – Connection of an in-the-ear hearing aid (modular type) to the occluded-ear
simulator.14
Figure A.1 – Example of one specific design of occluded-ear simulator.16

Table 1 – Level of the acoustic transfer impedance modulus and associated tolerances .8
Table 2 – Values of maximum permitted expanded uncertainty U for basic type
max
approval measurements.15
Table B.1 – Sound pressure level relative to that at the reference frequency 500 Hz
(L (f)– L (500)) for the nominal effective volume (1 260 mm ) of the occluded-ear
p p
simulator, and associated tolerances .18

60318-4 © IEC:2010 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
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

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
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with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
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 60318-4 has been prepared by IEC technical committee 29:
Electroacoustics.
This first edition of IEC 60318-4 cancels and replaces IEC 60711, published in 1981 and
constitutes a technical revision.
The main changes with respect to the previous edition are listed below:
– extension of the usable frequency range to 100 Hz – 16 000 Hz;
– addition of values of maximum permitted expanded uncertainties to all tolerances.

– 4 – 60318-4 © IEC:2010
The text of this standard is based on the following documents:
Enquiry draft Report on voting
29/662/CDV 29/685/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.
A list of all parts of the IEC 60318 series can be found on the IEC website under the title:
Electroacoustics – Simulators of human head and ear.
The committee has decided that the contents of this publication will remain unchanged until

the maintenance result 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.
60318-4 © IEC:2010 – 5 –
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

1 Scope
This part of IEC 60318 describes an occluded-ear simulator intended for the measurement of
insert earphones in the frequency range from 100 Hz to 10 000 Hz. It is suitable for air
conduction hearing aids and earphones, coupled to the ear by means of ear inserts e.g. ear
moulds or similar devices. The occluded-ear simulator is also suitable as the basis for an
extension intended to simulate the complete ear canal and the outer ear (for instance in head
simulators).
The occluded-ear simulator simulates the acoustic transfer impedance for the occluded
normal adult human ear. However, it does not simulate the leakage between an earmould and
a human ear canal; therefore, the results obtained with the occluded-ear simulator may
deviate from the performance of an insert earphone on a real ear, especially at low
frequencies. Moreover, large performance variations among individual ears will occur which
should be considered when using the ear simulator.
Above 10 kHz the device does not simulate a human ear, but can be used as an acoustic
coupler at additional frequencies up to 16 kHz. Below 100 Hz, the device has not been
verified to simulate a human ear, but can be used as an acoustic coupler at additional
frequencies down to 20 Hz.
NOTE Due to resonances in the acoustic transfer impedance of the occluded-ear simulator above 10 kHz, high
measurement uncertainties, e.g. in the order of 10 dB, can occur in earphone responses. Repeatable results mainly
are obtained for insert earphones with high acoustic damping (used for instance in the extended high-frequency
audiometry, see the earphones listed in ISO 389-6)[3] coupled to the occluded-ear simulator by means of a
simple, symmetrically designed and air tight coupling device.
2 Normative references
The following referenced documents are indispensable for the application 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 61094-4, Measurement microphones – Part 4: Specifications for working standard
microphones
ISO/IEC Guide 98-3, Uncertainty of measurement – Part 3: Guide to the expression of
uncertainty in measurement (GUM:1995)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
___________
Figures in square brackets refer to the Bibliography.

– 6 – 60318-4 © IEC:2010
3.1
ear insert
device used to provide the acoustic coupling between an earphone and the ear canal (e.g. an
earmould or a similar device with or without a connecting tube)
3.2
insert earphone
small earphone coupled to the ear canal by means of an ear insert or attached to a
connecting element which is inserted into the ear canal
NOTE This ear insert may be a part of the insert earphone.
3.3
ear-mould simulator
ear insert simulator
insert which terminates the entrance of the ear simulator and provides for passage of sound
into the occluded-ear simulator through an opening on its axis
3.4
ear simulator
device for measuring the acoustic output of sound sources where the sound pressure is
measured by a calibrated microphone coupled to the source so that the overall acoustic
impedance of the device approximates that of the normal human ear at a given location and in
a given frequency band
3.5
occluded-ear simulator
ear simulator which approximates the acoustic transfer impedance of the inner part of the ear
canal, from the tip of an ear insert to the eardrum
3.6
acoustic coupler
device for measuring the acoustic output of sound sources where the sound pressure is
measured by a calibrated microphone coupled to the source by a cavity of predetermined
shape and volume which does not necessarily approximate the acoustical impedance of the
normal human ear
3.7
reference plane of the occluded-ear simulator
plane perpendicular to the axis of the cavity of the simulator, chosen to pass through the
position normally occupied by the tip of an earmould in a human ear
3.8
acoustic transfer impedance of the occluded-ear simulator
quotient of the sound pressure at the diaphragm of its microphone by the volume velocity
through the reference plane
–3
unit: Pa⋅s⋅m
3.9
acoustic transfer impedance level of the occluded-ear simulator
ten times the logarithm to the base of ten of the quotient of the absolute value (modulus) of
the squared acoustic transfer impedance of the occluded-ear simulator by the squared
–3
reference acoustic transfer impedance of one pascal second per cubic metre (Pa⋅s⋅m )

unit: dB
60318-4 © IEC:2010 – 7 –
3.10
effective volume
equivalent volume of air of the acoustic compliance of the ear simulator formed by the cavity
and the microphone at a frequency of 500 Hz
unit: mm
4 Construction
4.1 General
The occluded-ear simulator shall be constructed of hard, dimensionally stable, non-porous
and non-magnetic material. The general construction of the occluded-ear simulator and
mounting of the microphone shall aim at minimizing the response of the microphone to
vibration (for example from an earphone) or to extraneous sound outside the cavity.
NOTE 1 The external diameter of the occluded-ear simulator should be kept as small as possible in order to
minimize diffractional errors which might affect the measurements when the occluded-ear simulator has to be
placed in a free sound field.
NOTE 2 In order to avoid a possible sound attenuation caused by the dust protector (see Figure A.1), an
earphone calibration should be performed above 10 kHz at least every two years with the occluded-ear simulator
equipped with and without its dust protector in place. The two results should not differ by more than 0,2 dB at
frequencies up to 16 kHz. If this is not the case at some frequencies, earphone measurements at those frequencies
should generally be performed without the dust protector.
The construction of the occluded-ear simulator shall permit the location of a transducer at the
reference plane for calibrating the simulator.
Where tolerances are specified in this part of IEC 6
...