Electroacoustics - Audiometric equipment - Part 5: Instruments for the measurement of aural acoustic impedance/admittance

Applies to instruments designed primarily for the measurement of acoustic impedance/admittance in the human external acoustic meatus using a stated probe tone. It is recognized that other probe signals may also be used. The standard defines the characteristics to be specified by the manufacturer, lays down performance specifications for three types of instruments and specifies the facilities to be provided on these types. This standard describes methods of test to be used for approval testing and guidance on methods for undertaking routine calibration. The purpose of this standard is to ensure that measurements made under comparable test conditions with different instruments complying with the standard will be consistent. The standard is not intended to restrict development or incorporation of new features, nor to discourage innovative approaches. This first edition of EN 60645-5 cancels and replaces the first edition of EN 61027, published in 1991, and constitutes a technical revision.

Akustik - Audiometer - Teil 5: Geräte zur Messung der akustischen Impedanzen/Admittanzen des Gehörs

Electroacoustique - Appareillage audiométrique - Partie 5: Instruments pour la mesure de l'impédance ou de l'admittance aurale (impédancemètres ou admittancemètres)

S'applique aux instruments conçus principalement pour la mesure de l'impédance ou de l'admittance acoustiques dans le conduit auditif humain en utilisant une sonde dont le signal présente une fréquence spécifiée. Il est admis que d'autres signaux de sonde peuvent également être utilisés. La norme définit les caractéristiques qui doivent être spécifiées par le fabricant, donne des spécifications concernant trois classes d'instruments et spécifie les possibilités qui doivent être offertes pour ces classes. La présente norme décrit des méthodes d'essai qui doivent être utilisées pour les essais d'approbation de modèle et donne un guide concernant les méthodes à utiliser pour entreprendre l'étalonnage périodique. L'objet de cette norme est de s'assurer que les mesures effectuées dans des conditions d'essais comparables, avec différents instruments satisfaisant à la norme, sont cohérentes. Il n'est pas dans les intentions de cette norme d'empêcher le développement de nouvelles possibilités ni de décourager les innovations. Cette première édition de la EN 60645-5 annule et remplace la première édition de la EN 61027, publiée en 1991, et constitue une révision technique.

Elektroakustika – Avdiometrična oprema – 5. del: Instrumenti za merjenje ušesne akustične impedance/admitance (IEC 60645-5:2004)

General Information

Status
Published
Publication Date
06-Jan-2005
Technical Committee
Drafting Committee
Parallel Committee
Current Stage
6060 - Document made available
Due Date
07-Jan-2005
Completion Date
07-Jan-2005

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SLOVENSKI SIST EN 60645-5:2005
STANDARD
december 2005
Elektroakustika – Avdiometrična oprema – 5. del: Instrumenti za merjenje
ušesne akustične impedance/admitance (IEC 60645-5:2004)
Electroacoustics – Audiometric equipment – Part 5: Instruments for the
measurement of aural acoustic impedance/admittance (IEC 60645-5:2004)
ICS 17.140.50 Referenčna številka
SIST EN 60645-5:2005(en)

© Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

---------------------- Page: 1 ----------------------
EUROPEAN STANDARD EN 60645-5
NORME EUROPÉENNE
EUROPÄISCHE NORM January 2005
ICS 17.140.50 Supersedes EN 61027:1993
English version
Electroacoustics –
Audiometric equipment
Part 5: Instruments for the measurement
of aural acoustic impedance/admittance
(IEC 60645-5:2004)
Electroacoustique – Akustik –
Appareillage audiométrique Audiometer
Partie 5: Instruments pour la mesure Teil 5: Geräte zur Messung der
de l'impédance ou de l'admittance aurale akustischen Impedanzen/Admittanzen
(impédancemètres ou admittancemètres) des Gehörs
(CEI 60645-5:2004) (IEC 60645-5:2004)

This European Standard was approved by CENELEC on 2004-12-01. 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, Cyprus, Czech

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

Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden,

Switzerland and United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2005 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 60645-5:2005 E
---------------------- Page: 2 ----------------------
EN 60645-5:2005 - 2 -
Foreword

The text of document 29/563/FDIS, future edition 1 of IEC 60645-5, prepared by IEC TC 29,

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

as EN 60645-5 on 2004-12-01.
This European Standard supersedes EN 61027:1993.
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) 2005-09-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2007-12-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice

The text of the International Standard IEC 60645-5:2004 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:

ISO 389-1 NOTE Harmonized as EN ISO 389-1:2000 (not modified).
ISO 389-2 NOTE Harmonized as EN ISO 389-2:1996 (not modified).
__________
---------------------- Page: 3 ----------------------
- 3 - EN 60645-5:2005
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 Where an international publication has been modified by common modifications, indicated by (mod), the relevant

EN/HD applies.
Publication Year Title EN/HD Year
1) 2)
IEC 60126 - IEC reference coupler for the HD 305 S1 1977
measurement of hearing aids using
earphones coupled to the ear by means
of ear inserts
1) 2)
IEC 60601-1 - Medical electrical equipment EN 60601-1 1990
Part 1: General requirements for safety
1) 2)
IEC 60601-1-2 - Medical electrical equipment EN 60601-1-2 2001
Part 1-2: General requirements for safety
- Collateral standard: Electromagnetic
compatibility - Requirements and tests
1) 2)
IEC 60601-1-4 - Medical electrical equipment EN 60601-1-4 1996
Part 1-4: General requirements for safety
- Collateral standard: Programmable
electrical medical systems
IEC 60645-1 2001 Electroacoustics - Audiological equipment EN 60645-1 2001
Part 1: Pure-tone audiometers
BIPM/IEC/IFCC/ - Guide to the expression of uncertainty in - -
ISO/IUPAP/OIML measurement (GUM)
Undated reference.
Valid edition at date of issue.
---------------------- Page: 4 ----------------------
NORME CEI
INTERNATIONALE
IEC
60645-5
INTERNATIONAL
Première édition
STANDARD
First edition
2004-11
Electroacoustique –
Appareillage audiométrique –
Partie 5:
Instruments pour la mesure de l'impédance
ou de l'admittance aurale (impédancemètres
ou admittancemètres)
Electroacoustics –
Audiometric equipment –
Part 5:
Instruments for the measurement
of aural acoustic impedance/admittance
 IEC 2004 Droits de reproduction réservés  Copyright - all rights reserved

Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in any

utilisée sous quelque forme que ce soit et par aucun procédé, form or by any means, electronic or mechanical, including

électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from

microfilms, sans l'accord écrit de l'éditeur. the publisher.

International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland

Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch

CODE PRIX
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Commission Electrotechnique Internationale
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
Pour prix, voir catalogue en vigueur
For price, see current catalogue
---------------------- Page: 5 ----------------------
60645-5  IEC:2004 – 3 –
CONTENTS

FOREWORD...........................................................................................................................5

INTRODUCTION.....................................................................................................................9

1 Scope.............................................................................................................................11

2 Normative references.....................................................................................................11

3 Terms and definitions .....................................................................................................13

4 Requirements for specific instruments ............................................................................19

5 General specifications....................................................................................................21

5.1 Measuring system.................................................................................................21

5.2 Pneumatic system.................................................................................................23

5.3 Acoustic reflex activating stimulus system .............................................................25

6 Demonstration of conformity with specifications..............................................................29

6.1 General.................................................................................................................29

6.2 Impedance/admittance measuring system .............................................................29

6.3 Probe signal..........................................................................................................29

6.4 Pneumatic system.................................................................................................31

6.5 Acoustic reflex activating stimulus signals .............................................................31

6.6 Maximum permitted expanded uncertainty of measurements .................................33

7 Calibration cavities.........................................................................................................35

7.1 General.................................................................................................................35

7.2 Dimensions of calibration cavities..........................................................................35

7.3 Material of calibration cavity walls .........................................................................35

7.4 Connection of probe to a calibration cavity ............................................................35

8 General requirements.....................................................................................................35

8.1 Marking.................................................................................................................35

8.2 Instruction manual.................................................................................................35

8.3 Safety requirements..............................................................................................35

8.4 Warm-up time........................................................................................................37

8.5 Supply variation and environmental conditions ......................................................37

8.6 Unwanted acoustic signals and radiation ...............................................................37

9 Symbols, forms and formats for acoustic impedance/admittance data.............................39

9.1 Symbols for indicating measured quantities...........................................................39

9.2 Tympanogram format............................................................................................39

9.3 Acoustic reflex test format .....................................................................................39

9.4 Eustachian tube function test format......................................................................41

10 Additional characteristics to be specified by the manufacturer ........................................41

10.1 Aural impedance/admittance measurement system ...............................................41

10.2 Pneumatic system.................................................................................................43

10.3 Acoustic reflex activating stimulus system .............................................................45

10.4 Analogue electrical output .....................................................................................45

Annex A (informative) Routine calibration ............................................................................47

Annex B (informative) Units and terms.................................................................................49

Annex C (informative) Overall temporal characteristics ........................................................53

Bibliography..........................................................................................................................57

---------------------- Page: 6 ----------------------
60645-5  IEC:2004 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROACOUSTICS –
AUDIOMETRIC EQUIPMENT –
Part 5: Instruments for the measurement
of aural acoustic impedance/admittance
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 provides no marking procedure to indicate its approval and cannot be rendered responsible for any

equipment declared to be in conformity with an IEC Publication.

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 60645-5 has been prepared by IEC technical committee 29:

Electroacoustics.

This first edition of IEC 60645-5 cancels and replaces the first edition of IEC 61027, published

in 1991, and constitutes a technical revision.
---------------------- Page: 7 ----------------------
60645-5  IEC:2004 – 7 –
The text of this standard is based on the following documents:
FDIS Report on voting
29/563/FDIS 29/567/RVD

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.

IEC 60645 consists of the following parts:
Part 1: Pure tone audiometers
Part 2: Equipment for speech audiometry

Part 3: Auditory test signals of short duration for audiometric and neuro-otological purposes

Part 4: Equipment for extended high-frequency audiometry
Part 5: Instruments for the measurement of aural acoustic impedance/admittance

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.
___________

Future editions of all parts of this series will appear under the new general title Electroacoustics – Audiometric

equipment.
---------------------- Page: 8 ----------------------
60645-5  IEC:2004 – 9 –
INTRODUCTION

Developments in the field of diagnostic hearing measurement have resulted in a number of

instruments designed to evaluate the acoustic impedance/admittance of the human ear by

means of acoustic probe signals having different frequencies and temporal characteristics.

The practical use of such instruments concerns to a large extent the measurement of changes

in acoustic impedance/admittance caused either by varying the air pressure in the external

acoustic meatus or by activating the middle ear muscle reflex.
---------------------- Page: 9 ----------------------
60645-5  IEC:2004 – 11 –
ELECTROACOUSTICS –
AUDIOMETRIC EQUIPMENT –
Part 5: Instruments for the measurement
of aural acoustic impedance/admittance
1 Scope

This part of IEC 60645 applies to instruments designed primarily for the measurement of

acoustic impedance/admittance in the human external acoustic meatus using a stated probe

tone. It is recognized that other probe signals may also be used. The standard defines the

characteristics to be specified by the manufacturer, lays down performance specifications for

three types of instruments and specifies the facilities to be provided on these types. This

standard describes methods of test to be used for approval testing and guidance on methods

for undertaking routine calibration.

The purpose of this standard is to ensure that measurements made under comparable test

conditions with different instruments complying with the standard will be consistent. The

standard is not intended to restrict development or incorporation of new features, nor to

discourage innovative approaches.
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 60126, IEC reference coupler for the measurement of hearing aids using earphones

coupled to the ear by means of ear inserts

IEC 60601-1, Medical electrical equipment – Part 1: General requirements for safety

IEC 60601-1-2, Medical electrical equipment – Part 1-2: General requirements for safety –

Collateral standard: Electromagnetic compatibility – Requirements and tests

IEC 60601-1-4, Medical electrical equipment – Part 1: General requirements for safety –

Collateral standard: Programmable electrical medical systems

IEC 60645-1:2001, Electroacoustics – Audiological equipment – Part 1: Pure-tone audio-

meters
BIPM/IEC/IFCC/ISO/IUPAC/IUPAP/OIML, Guide to the expression of uncertainty in
measurement (GUM)
___________
To be revised as IEC 60318-5.
---------------------- Page: 10 ----------------------
60645-5  IEC:2004 – 13 –
3 Terms and definitions
For the purposes of this document the following terms and definitions apply.

NOTE The units in this standard conform to the International System of Units (SI). However, for audiological

measurements test results have traditionally often been reported in other units. To provide information on the

conversion from such units to SI units, Annex B has been compiled.
3.1
aural impedance/admittance
general term covering all aspects of acoustic impedance/admittance of the ear

NOTE Throughout this standard the term aural impedance/admittance will be employed as a general term

covering all aspects of acoustic impedance/admittance of the ear, except where reference is made to specific

derivatives.
3.2
acoustic impedance

at a specified surface, quotient of sound pressure by volume velocity through the surface

NOTE 1 The symbol is Z and the unit is the pascal second per metre to the third power (Pa⋅s/m )

NOTE 2 The quantity usually measured is the modulus.
3.3
acoustic resistance
real component of complex acoustic impedance

NOTE The symbol is R and the unit is the pascal second per metre to the third power (Pa⋅s/m ).

3.4
acoustic reactance
imaginary component of complex acoustic impedance

NOTE The symbol is X and the unit is the pascal second per metre to the third power (Pa⋅s/m ).

3.5
acoustic admittance
at a given surface, the reciprocal of acoustic impedance at the same surface

NOTE 1 The symbol is Y and the unit is the metre to the third power per pascal second (m /Pa⋅s).

NOTE 2 Thus, the acoustic admittance at a given surface is the complex ratio of the volume velocity through the

surface of the sound pressure averaged over the surface. The quantity usually measured is the modulus.

3.6
acoustic conductance
real component of complex acoustic admittance

NOTE The symbol is G and the unit is the metre to the third power per pascal second (m /Pa⋅s).

3.7
acoustic susceptance
imaginary component of complex acoustic admittance

NOTE The symbol is B and the unit is the metre to the third power per pascal second (m /Pa⋅s).

3.8
acoustic inertance

ratio of the driving sound pressure to the resulting rate of change in volume velocity

NOTE The symbol is M and the unit is the pascal second to the second power per metre to the third power

2 3
(Pa⋅s /m ).
---------------------- Page: 11 ----------------------
60645-5  IEC:2004 – 15 –
3.9
acoustic compliance
ratio of volume displacement to sound pressure

NOTE The symbol is C and the unit is the metre to third power per pascal (m /Pa).

3.10
equivalent volume

volume of an air-filled hard-walled cylindrical cavity that offers the equivalent acoustic

impedance/admittance
NOTE 1 The volume is given by the formula:
V = γ ⋅ p ⋅ C = ρ ⋅ c ⋅ C
e s a a
where
V is the equivalent volume in m ;

γ is the ratio of specific heat for air at constant pressure to that at constant volume (approximately 1,40);

p is the barometric air pressure in Pa;

ρ is the ambient density of air in kg/m , at the temperature and pressure of the measurement;

c is the speed of sound in m/s at the temperature and pressure of the measurement;

C is the acoustic compliance in m /Pa.

NOTE 2 It has been practice to refer to aural impedance/admittance at the probe tone frequency of 226 Hz as an

equivalent volume of air.

NOTE 3 For a probe tone frequency of 226 Hz, the equivalent volume of air is equal to its physical volume

provided the latter does not exceed 5 cm .
3.11
relative pressure in the external acoustic meatus

difference between the pressure in the external acoustic meatus and the ambient barometric

pressure in daPa
3.12
probe

coupling device that is inserted into the external acoustic meatus to connect the instrument to

the ear
3.13
ear tip
device used to provide a seal between the probe and the external acoustic meatus
3.14
probe signal

acoustic signal that is emitted into the external auditory meatus by means of a probe

NOTE The signal is used to measure acoustic impedance/admittance.
3.15
probe ear
ear into which the probe in inserted
3.16
measurement plane

plane located at the frontal surface of the probe perpendicular to the volume velocity vector

---------------------- Page: 12 ----------------------
60645-5  IEC:2004 – 17 –
3.17
tympanometry

measurement of change of aural impedance/admittance as a function of air pressure in the

external acoustic meatus

NOTE The measured acoustic impedance/admittance values may depend on rate and direction of change of air

pressure as well as time spent with a certain constant air pressure in the external acoustic meatus.

3.17.1
measurement plane tympanometry

measurement of change of the aural impedance/admittance at the measurement plane,

comprising the combined impedance/admittance of the middle ear and part of the external

acoustic meatus
3.17.2
meatus-compensated tympanometry

measurement of the vector difference between the aural impedance/admittance obtained at

the test pressure and that obtained at a specific reference pressure in the external acoustic

meatus for a given fitting of the probe

NOTE 1 The reference pressure should be such as to effectively eliminate the influence of the middle ear.

NOTE 2 The reference pressure will normally be 200 daPa different from the indicated pressure, which gives

maximum admittance or minimum impedance indication, or fixed at 200 daPa relative to ambient pressure.

3.18
tympanogram

graphical display of some quantity related to aural impedance/admittance as a function of air

pressure in the external acoustic meatus
3.19
middle-ear muscle reflex
change in tonus of muscles of the middle ear in response to stimulation

NOTE The change may be measured as a variation in the acoustic impedance/admittance within the external

auditory meatus
3.19.1
acoustic reflex
middle-ear muscle reflex elicited by an acoustic stimulus
3.19.2
non-acoustic reflex
middle-ear muscle reflex elicited by a non-acoustic stimulus
3.20
acoustic reflex activating stimulus
acoustic stimulus that is used to elicit an acoustic reflex
3.21
stimulus ear

ear to which a reflex activating stimulus is presented in order to elicit a middle ear muscle

reflex
3.22
ipsilateral reflex
middle ear muscle reflex elicited in the stimulus ear
---------------------- Page: 13 ----------------------
60645-5  IEC:2004 – 19 –
3.23
contralateral reflex
middle ear muscle reflex elicited in the ear contralateral to the stimulus ear
4 Requirements for specific instruments

Three different types of aural acoustic impedance/admittance instruments are specified by the

requirements for minimum mandatory facilities (see Table 1). Other facilities are not

precluded. The three types relate to their presumed primary application.
Table 1 – Mandatory functions for aural impedance/admittance instruments
Type
1 2 3
Diagnostic/ clinical Tympanometry/ Tympanometry
reflex screening screening
Probe signal frequency 226 Hz x x x
Aural impedance/admittance measuring system
a a a
Measurement plane tympanometry x x x
a a a
Meatus compensated tympanometry x x x
Pneumatic system
Manual change of pressure x
Automatic change of pressure x x x
Acoustic reflex activating system
Contralateral routing x
Ipsilateral routing x x
Acoustic stimuli:
Pure tones x x
Broad-band noise x
Stimulus level control x
Presentation of results
Display or visual indicator x x x
Printout x
Data interface x
Indicating that either of the two alternatives shall be provided.
---------------------- Page: 14 ----------------------
60645-5  IEC:2004 – 21 –
5 General specifications
5.1 Measuring system
5.1.1 Units of measurement
The instruments may be designated to measure one or more components of aural

impedance/admittance. SI units or derived SI units shall be used. The units of measurement

shall be indicated on the front panel of the instrument.
5.1.2 Probe signal

A probe signal in the form of a pure tone with a frequency of 226 Hz shall be provided in

instruments of Types 1, 2 and 3. The actual frequency shall differ from its nominal frequency

by less than ±1 % for Type 1 instruments and by less than ± 2 % for Types 2 and 3. The total

harmonic distortion shall be less than 1 % for Type 1 and less than 3 % for Types 2 and 3,

when measured as specified in Clause 6. If pure tones of frequencies other than 226 Hz are

available, the same requirements with regard to frequency accuracy and harmonic distortion

shall apply.

NOTE When tests such as multi-frequency tympanometry are performed which require frequency accuracy better

than the 1 % specified, the manufacturer should state the accuracy of the frequency used for that test.

5.1.3 Probe signal level

For pure tones of any frequency, for stationary broadband and for non-stationary probe

signals the level shall be such that the probability of activating the middle ear muscle reflex by

the probe signal is acceptably small. For a 226 Hz pure tone probe signal, the sound pressure

level shall be 90 dB or less as measured according to Clause 6.

NOTE This requires a level less than the mean value minus two standard deviations for the threshold level of the

acoustic middle ear reflex in a sufficiently large otologically normal young adult population when the probe signal is

used as a reflex activating stimulus. A population of 25 persons is considered to be sufficiently large. ISO 389-1

defines an "otologically normal person" as "a person in a normal state of health who is free from all signs or

symptoms of ear disease and from obstructing wax in the ear canals and who has no history of undue exposure to

noise, exposure to potentially ototoxic drugs or familial hearing loss".
5.1.4 Measurement range

For a 226 Hz probe tone the minimum ranges expressed as equivalent volume of air shall be:

3 3
for measurement plane tympanometry, from 0,2 cm to 5 cm ; for meatus compensated
3 3 3 3
tympan
...

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