SIST HD 450.9 S1:2004

SLOVENSKI STANDARD
SIST HD 450.9 S1:2004
01-januar-2004
[Not translated]
Hearing aids - Part 9: Methods of measurement of characteristics of hearing aids with
bone vibrator output
Hörgeräte - Teil 9: Verfahren zur Messung der Übertragungseigenschaften von
Knochenleitungshörgeräten
Appareils de correction auditive - Partie 9: Méthodes de mesure des caractéristiques des
appareils de correction auditive à sortie par ossivibrateur
Ta slovenski standard je istoveten z: HD 450.9 S1:1987
ICS:
11.180.15 3ULSRPRþNL]DJOXKHRVHEHLQ Aids for deaf and hearing
RVHEH]RNYDURVOXKD impaired people
17.140.50 Elektroakustika Electroacoustics
SIST HD 450.9 S1:2004 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST HD 450.9 S1:2004

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SIST HD 450.9 S1:2004

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SIST HD 450.9 S1:2004

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SIST HD 450.9 S1:2004
NORME CEI
INTERNATIONALE IEC
60118-9
INTERNATIONAL
Première
édition
STANDARD
First edition
1985-01
Appareils
de correction auditive
Neuvième partie:
Méthodes de mesure des caractéristiques
des appareils de correction auditive à sortie
par ossivibrateur
Hearing aids
Part 9:
Methods of measurement of characteristics
of hearing aids with bone vibrator output
© IEC 1985
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
utilisée quelque forme
sous que ce soit et par aucun any form or by any means, electronic or mechanical,
procédé, électronique ou mécanique, y compris la photo- including photocopying and microfilm, without permission in
copie
et les microfilms, sans l'accord écrit de l'éditeur. writing from the publisher.
International Electrotechnical Commission 3, rue de Varembé Geneva, Switzerland
Telefax: +41 22 919 0300 e-mail: inmail@iec.ch IEC web site http: //www.iec.ch
CODE PRIX
Commission Electrotechnique Internationale
L
PRICE CODE
International Electrotechnical Commission
IEC
MemayHapogwaa 3neKrporexHH4ecnaa HoMHCCHc
Pour prix, voir catalogue en vigueur
• • For price, see current catalogue

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SIST HD 450.9 S1:2004
118-9 © I E C 1985 — 3 —
CONTENTS
Pages
5
FOREWORD
PREFACE 5
INTRODUCTION 7
Clause
7
1. Scope
7 2. Object
9
3. General
9
4. Explanation of terms
13
Test equipment 5.
13
6. Test conditions
17
7. Measurements
21
8. Frequency response recording chart
APPENDIX A – Examples of test assemblies 22

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INTERNATIONAL ELECTROTECHNICAL COMMISSION
HEARING AIDS
Part 9: Methods of measurement of characteristics of hearing aids with bone vibrator output
FOREWORD
1) The formal decisions or agreements of the IEC on technical matters, prepared by Technical Committees on which all the
National Committees having a special interest therein are represented, express, as nearly as possible, an international
consensus of opinion on the subjects dealt with.
2)
They have the form of recommendations for international use and they are accepted by the National Committees in that sense.
3)
In order to promote international unification, the IEC expresses the wish that all National Committees should adopt the text
of the IEC recommendation for their national rules in so far as national conditions will permit. Any divergence between the
IEC recommendation and the corresponding national rules should, as far as possible, be clearly indicated in the latter.
PREFACE
This standard has been prepared by IEC Technical Committee No.29: Electroacoustics.
The text of this standard is based on the following documents:
Six Months' Rule Report on Voting
29(CO)133 29(CO)137
Further information can be found in the Report on Voting, indicated in the table above.

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118-9 © IEC 1985 — 7 —
HEARING AIDS
Part 9: Methods of measurement of characteristics of hearing aids with bone vibrator output
INTRODUCTION
IEC Publication 118-0: Hearing Aids, Part 0: Measurement of Electroacoustical Characteristics, gives
information on methods of test for air conduction hearing aids. The majority of hearing aids in use are of this
type but a small percentage use a bone vibrator instead of an earphone. The use of a bone vibrator requires a
different method of measuring the output from the hearing aid and also makes it impractical to measure
amplification directly in terms of acoustic gain.
Amplification in the case of an air conduction hearing aid is expressed as the difference between the output
sound pressure level in an acoustic coupler or ear simulator and the input sound pressure level measured in a
specified manner. However, with bone conduction hearing aids the input is in terms of sound pressure level
but the output will be in terms of mechanical vibration measured as an alternating force or force level.
This standard defines a method of expressing the input/output ratio as an acousto-mechanical sensitivity
level measured .on a mechanical coupler according to the second edition of IEC Publication 373: Mechanical
Coupler for Measurements on Bone Vibrators.
By means of information provided in this standard the performance of hearing aids with bone vibrator
outputs which do not form an integral part of the hearing aid for example body worn hearing aids, may be
measured in a similar manner to aids with air conduction outputs as described in IEC Publication 118-0.
Where the bone vibrator forms an integral part of the hearing aid, or where it is attached in some fixed
manner to the hearing aid (e.g. a headband type bone conduction hearing aid), performance cannot be
measured in the same way as for body-worn aids, due to the large dimensions of the mechanical coupler
having to be in contact with the spectacle arm. This standard recommends a pressure method of controlling
the input sound pressure level, to the hearing aid microphone.
The second edition of IEC Publication 373, describes the means of measuring the output from a bone
vibrator.
1. Scope
This standard specifies methods of measurement of the characteristics of hearing aids using bone
vibrator output.
2. Object
The methods described will produce a suitable basis for the exchange of information or for direct
comparison of the electroacoustical characteristics of hearing aids using bone vibrator output. These
methods are chosen to be practical and reproducible and are based on selected fixed parameters.

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The results obtained by the methods specified herein express the performance under the conditions
of the test, but will not necessarily agree exactly with the performance of the hearing aid under practical
conditions of use.
General
3.
3.1 Throughout this standard all sound pressure levels specified are referred to 20 µPa. When appropriate,
sound pressure level will be abbreviated to SPL.
3.2 In this standard, reference is made to the following IEC publications:
Publication 68: Basic Environmental Testing Procedures.
Publication 118-0 (1983): Hearing Aids, Part 0: Measurement of Electroacoustical Characteristics.
Publication 118-7 (1983): Hearing Aids, Part 7: Measurement of the Performance Characteristics of
Hearing Aids for Quality Inspection for Delivery Purposes.
Publication 263 (1982): Scales and Sizes for Plotting Frequency Characteristics and Polar Diagrams.
Publication 373 (–): Mechanical Coupler for Measurements on Bone Vibrators.
4. Explanation of terms
Terms other than those used in IEC Publication 118-0 are given below.
4.1 Bone vibrator
An electromechanical transducer intended to produce the sensation of hearing by vibrating the
cranial bones.
4.2
Mechanical coupler
A device designed to present a specified mechanical impedance to a vibrator applied with a specified
static force and equipped with a mechano-electric transducer to enable the alternating force level at the
surface of contact between vibrator and mechanical coupler to be determined.
4.3 Vibratory force level (force level)
Twenty times the logarithm to the base 10 of the ratio of the r.m.s. value of the force transmitting the
vibration to the reference value of 1 micronewton (1 RN), expressed in decibels.
4.4 Output force level (OFL)
The vibratory force level produced at a specified frequency on a mechanical coupler by the bone
vibrator of the hearing aid under test.

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4.5 Output force level frequency response (force level curve)
The OFL produced on the mechanical coupler by the hearing aid expressed as a function of fre-
quency under specified test conditions for constant input sound pressure level.
4.6
Output force level for an input sound pressure level of 90 dB (0FL90)
The OFL at a specified frequency produced with an input sound pressure level of 90 dB and the
hearing aid gain control in the full-on position.
4.7
Reference point (of a hearing aid)
A point on the hearing aid chosen for the purpose of defining its position, normally the centre of the
main sound entry to the aid.
4.8
Acousto-mechanical sensitivity
At a specified frequency and under specified operating conditions the quotient of the vibratory force
produced on the mechanical coupler by the hearing aid and the sound pressure at the reference point of
the hearing aid.
4.9
Acousto-mechanical sensitivity level (AMSL)
Twenty times the logarithm to the base 10 of the ratio of the acousto-mechanical sensitivity to the
a
reference sensitivity of 2 1 µP ; expressed in decibels.
Note. -
To calculate the acousto-mechanical sensitivity level (AMSL) from measurements made in this standard the
following formula may be used:
AMSL = OFL – INPUT SPL
where OFL is expressed in decibels ref. 1 µN and sound pressure level to the hearing aid microphone in decibels
ref. 20 µPa.
4.10
Reference test gain control position
The setting of the hearing aid gain control that provides an output force level on the mechanical
coupler 15 ± 1 dB less than OFL 90 for an input sound pressure level of 60 dB at the reference test
frequency of 1600 Hz. For certain hearing aids for which a higher reference test frequency is more
appropriate (so called high-tone hearing aids) 2500 Hz shall be used. If 2500 Hz is used this shall be
clearly stated. If the acousto-mechanical sensitivity level available will not permit this, the full on gain
control position of the hearing aid shall be used.
4.11 Basic force level frequency response curve
The output force level frequency response curve obtained with the gain control in the reference test
gain position and with an input SPL of 60 dB.

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5.
Test equipment
5.1 Equipment for the measurement of the output force level
The equipment used for measurement of OFL on the mechanical coupler produced by the hearing
aid, shall comply with the following requirements:
5.1.1 For all measurements a mechanical coupler in accordance with the second edition of IEC Publication
373 shall be used.
5.1.2 The output force level corresponding to hum, vibration, thermal agitation and other noise sources
shall be sufficiently low to ensure that the reading shall drop at least 10 dB when the test signal is
switched off.
For this purpose a high-pass filter not affecting frequencies of 200 Hz and above may be employed.
5.1.3 The output indicator used shall give the r.m.s. indication within a tolerance of ±0.5 dB at a signal
crest factor of not more than 3.
Notes 1. –
Under certain conditions it is necessary to use a selective measuring system in order to ensure that the response
of the hearing aid to the signal can be differentiated from inherent noise in the hearing aid. The use of the
selective system should be stated in the report on test results.
2. –
It is well known that the type of output indicator employed may influence the test results significantly if a non-
sinusoidal voltage is being measured. Such non-sinusoidal voltages may be present when making measurements
with high input levels.
5.1.4 The overall accuracy of the electronic measuring system following the mechanical coupler shall be
within ± 0.5 dB at a specified frequency.
5.1.5 The calibration of the mechanical coupler shall be in accordance with the second edition of IEC
Publication 373.
Note. –
The calibration of the mechanical coupler should be repeated sufficiently often, preferably at least once a year, to
ensure that it remains wi
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