SIST EN 60118-0:2002
(Main)Hearing aids -- Part 0: Measurement of electroacoustical characteristics
Hearing aids -- Part 0: Measurement of electroacoustical characteristics
Defines the measurement of physical performance characteristics of air-conduction hearing aids based on a free-field technique and measured with an ear simulator. Describes methods of measurement for evaluation of the electroacoustical characteristics of hearing aids.
Hörgeräte -- Teil 0: Messung der elektroakustischen Eigenschaften
Appareils de correction auditive -- Partie 0: Méthodes de mesure des caractéristiques électroacoustiques
Décrit la mesure des caractéristiques physiques des appareils de correction auditive à conduction aérienne, fondée sur une technique de champ acoustique libre et utilisant un simulateur d'oreille. Décrit des méthodes de mesure pour l'évaluation des caractéristiques électroacoustiques des appareils de correction auditive.
Hearing aids - Part 0: Measurement of electroacoustical characteristics (IEC 60118-0:1983)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 60118-0:2002
01-september-2002
Hearing aids - Part 0: Measurement of electroacoustical characteristics (IEC 60118-
0:1983)
Hearing aids -- Part 0: Measurement of electroacoustical characteristics
Hörgeräte -- Teil 0: Messung der elektroakustischen Eigenschaften
Appareils de correction auditive -- Partie 0: Méthodes de mesure des caractéristiques
électroacoustiques
Ta slovenski standard je istoveten z: EN 60118-0:1993
ICS:
11.180.15 3ULSRPRþNL]DJOXKHRVHEHLQ Aids for deaf and hearing
RVHEH]RNYDURVOXKD impaired people
17.140.50 Elektroakustika Electroacoustics
SIST EN 60118-0:2002 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 60118-0:2002
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SIST EN 60118-0:2002
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SIST EN 60118-0:2002
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SIST EN 60118-0:2002
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SIST EN 60118-0:2002
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SIST EN 60118-0:2002
NORME CEI
INTERNATIONALE IEC
118-0
INTERNATIONAL
Deuxième édition
STAN DARD
Second edition
1983
de correction auditive
Appareils
Partie zéro:
Méthodes de mesure des caractéristiques
électroacoustiques
Hearing aids
Part 0:
Measurement of electroacoustical
characteristics
de reproduction Copyright - all rights reserved
© CEI 1983 Droits réservés —
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in
utilisée sous quelque forme que ce soit et par aucun pro- any form or by any means, electronic or mechanical,
cédé, électronique ou mécanique, y compris la photocopie et including photocopying and microfilm, without permission
les microfilms, sans l'accord écrit de l'éditeur. in writing from the publisher.
Bureau Central de la Commission Electrotechnique Internationale 3, rue de Varembé Genève, Suisse
Commission Electrotechnique Internationale CODE PRIX
International Electrotechnical Commission PRICE CODE
MerkgyHapoaHaa 3neKrporexHHVecnaa HOMHCCHR
IEC
• Pour prix, voir catalogue en vigueur
•
For price, see current catalogue
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SIST EN 60118-0:2002
118-0 © IEC 1983 - 3 -
CONTENTS
Page
FOREWORD 7
PREFACE 7
Clause
11
1. Scope
2. Object 11
3. General conditions 13
4. Explanation of terms 13
4.1 Ear simulator 13
4.2 Substitution method 13
13
4.3 Comparison method
4.4 Pressure method 13
4.5 Simulated in situ method 13
4.6 13 Reference orientation (of a hearing aid)
15
4.7 Reference point (of a hearing aid)
4.8 Test point 15
4.9 Supply voltage 15
4.10 Acoustic gain 15
15
4.11 Full-on acoustic gain (frequency response curve)
15
4.12 Maximum acoustic gain at a specified frequency
4.13 Saturation sound pressure level (frequency response curve) 15
15
4.14 Maximum saturation sound pressure level
4.15 Output sound pressure level for an input sound pressure level of 90 dB (OSPL 90) at a specified frequency (or
frequencies) 15
15
4.16 Reference test frequency
4.17 Reference test gain control position 17
17
4.18 Reference test gain
17
4.19 Frequency response
4.20 Comprehensive frequency response curves 17
17
4.21 Basic frequency response curve
17
4.22 Steady state input-output graph
5. Test equipment 17
17
5.1 Acoustical requirements for the test enclosure
19
5.2 Sound field at the test point
5.3 Ear simulator 19
5.4 Equipment for the measurement of sound pressure level in the ear simulator 19
21
5.5 Equipment for automatic sweep frequency recording
5.6 Calibration of free-field sound pressure level 21
21
6. Test conditions
21
6.1 Choice of test point
6.2 Calibrating the sound field 23
23
6.3 Locating the hearing aid for tests
6.4 Normal operating conditions for the hearing aid 25
7. Measurements 27
27
7.1 Maximum saturation sound pressure level
7.2 Output sound pressure level frequency response for an input SPL of 90 dB 27
29
7.3 Full-on acoustic gain frequency response
29
7.4 Comprehensive frequency responses and basic frequency response
7.5 Effect of tone control position on the basic frequency response 31
7.6 Effect of gain control position on frequency response 31 .
7.7 Characteristics of the gain control 33
7.8 Effect on the full-on acoustic gain of va riation of battery or supply voltage 33
7.9 riation of internal resistance of battery or supply 33
Effect on the full-on acoustic gain of va
7.10 Effect on OSPL 90 of variation of battery or supply voltage 35
7.11 Battery current 35
7.12 Measurement of amplitude non-linearities in hearing aids 35
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Page
Clause
41
7.13 Effect on amplitude non-linearities of variation of battery or supply voltage and internal impedance
41
7.14 Internal noise generated in the hearing aid
43 7.15 Characteristics of hearing aid with induction pick-up coil input
47 7.16 Characteristics of hearing aids with automatic gain control circuits
47
8. Frequency response recording chart
49
APPENDIX A — Harmonic and intermodulation distortion
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SIST EN 60118-0:2002
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118-0 © I E C 1983
INTERNATIONAL ELECTROTECHNICAL COMMISSION
HEARING AIDS
Part 0: Measurement of electroacoustical characteristics
FOREWORD
1) The formal decisions or agreements of the I EC 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 inte rnational use and they are accepted by the National Committees in that
sense.
3) In order to promote international unification, the I EC expresses the wish that all National Committees should adopt the
text of the I EC recommendation for their national rules in so far as national conditions will permit. Any divergence
between the I EC recommendation and the corresponding national rules should, as far as possible, be clearly indicated in
the latter.
PREFACE
This standard has been prepared by I EC Technical Committee No. 29: Electroacoustics.
It forms Part 0 of the second edition of I EC Publication 118 which is currently under revision and which will be issued with
a modified generic title: Hearing Aids.
This second edition will comprise the following parts:
Publication 118-0 Part
0: Measurement of Electroacoustical Characteristics.
Publication 118-1 Part 1: Hearing Aids with Induction Pick-up Coil Input.
Publication 118-2 Pa rt 2: Hearing Aids with Automatic Gain Control Circuits.
Publication 118-3 Pa rt 3: Hearing Aid Equipment not Entirely Worn on the Listener.
Publication 118-4 Pa rt 4: Magnetic Field Strength in Audio-frequency Induction Loops for Hearing Aid Purposes.
Publication 118-5 Pa rt 5: Nipples for Insert Earphones.
Publication 118-6 Pa 6: External Electrical Inputs to Personal Hearing Aids. (In preparation.)
rt
Publication 118-7 Part 7: Measurement of Performance Characteristics of Hearing Aids for Quality Inspection for Delivery
Purposes.
Publication 118-8 Part 8: Methods of Measurement of Perform ance Characteristics of Hearing Aids under Simulated in situ
Working Conditions. (In preparation.)
Publication 118-9 Part 9: Method of Measurement of Characteristics of Hearing Aids with Bone Vibrator Outputs. (In
preparation.)
Publication 118-10 Part 10: Standard Practices for Hearing Aid Specification. (Under consideration.)
Publication 118-11 Pa
rt 11: Symbols and other Markings on Hearing Aids and Related Equipment.
A first draft was discussed at the meeting held in Sydney in 1980. As a result of this meeting, a draft, Document 29(Central
Office)122, was submitted to the Na tional Committees for approval under the Six Months' Rule in December 1980.
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SIST EN 60118-0:2002
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118-0 © I E C 1983
The National Committees of the following countries voted explicitly in favour of publication:
Romania
Austria Germany
South Africa
Hungary Belgium
(Republic of)
Canada Israel
Italy Spain
Czechoslovakia
Sweden
Denmark Japan
Turkey
Egypt Netherlands
Norway United Kingdom
German Democratic
United States of America
Republic Poland
Other I EC publications quoted in this standard:
68: Basic Environmental Testing Procedures.
Publications Nos.
118: Hearing Aids.
1: Hearing Aids with Induction Pick-up Coil.
118-1: Part
118-2: Part 2: Hearing Aids with Automatic Gain Control Circuits.
7: Measurement of the Performance Characteristics of Hearing Aids for Quality Inspection
118-7: Part
for Delivery Purposes.
8: Methods of Measurement of Performance Characteristics of Hearing Aids under
118-8: Part
Simulated in situ Working Conditions (in preparation).
126: I EC Reference Coupler for the Measurement of Hearing Aids Using Earphones Coupled to the
Ear by Means of Ear Inserts.
225: Octave, Half-octave and Third-octave Band Filters Intended for the Analysis of Sounds and
Vibrations.
263: Scales and Sizes for Plotting Frequency Characteristics and Polar Diagrams.
rts.
711: Occluded-ear Simulator for the Measurement of Earphones Coupled to the Ear by Ear Inse
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HEARING AIDS
Part 0: Measurement of electroacoustical characteristics
1. Scope
This standard describes the measurement of physical performance characteristics of air-
conduction hearing aids based on a free-field technique and measured with an ear simulator.
2. Object
2.1 The object of this standard is to describe methods of measurement for the evaluation of the
electroacoustical characteristics of hearing aids.
The methods are chosen first of all to be practical and reproducible, and consequently they
are based on fixed parameters chosen, to a ce rtain extent, arbitrarily. This should be taken into
consideration when comparisons are being made between test results for hearing aids of
different models and manufacture, and in each case it is advisable to examine to what extent
the arbitrarily chosen parameters will influence the comparison of such test results.
2.2 The test results obtained by the methods specified in this standard express the performance
under the conditions of the test and may deviate substantially from the performance of the
hearing aid under practical conditions of use.
2.3 It is not the purpose of this standard to restrict the variety of hearing aid performance and
characteristics available, nor to inhibit in any way advances in the state of the art.
2.4 The most significant change in this standard is the use of an ear simulator in accordance with
I E C Publication 711: Occluded-ear Simulator for the Measurement of Earphones Coupled to
the Ear by Ear Inserts, rather than an acoustic coupler, I E C Publication 126: I EC Reference
Coupler for the Measurement of Hearing Aids Using Earphones Coupled to the Ear by Means
of Ear Inserts. The effect of this change will be to give an apparent significant increase, at some
frequencies, of both gain and saturation output levels over the results obtained when
measurements are made with the acoustic coupler. Results obtained by using the methods
described in this standard cannot therefore be directly compared with those previously obtained
using the first edition of I E C Publication 118: Recommended Methods for Measurement of the
Electroacoustical Characteristics of Hearing Aids, or I E C Publication 118-7: Hearing Aids,
7: Measurement of Performance Characteristics of Hearing Aids for Quality Inspection for
Part
rt 8: Methods of Measurement of Performance
Delivery Purposes, or I E C Publication 118-8: Pa
in situ Working Conditions. (In preparation.)
Characteristics of Hearing Aids under Simulated
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SIST EN 60118-0:2002
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118-0 © IEC 1983
3. General conditions
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 Reference is made to IEC Publication 711 (1981): Occluded Ear Simulator for the
rts.
Measurement of Earphones Coupled to the Ear by Ear Inse
3.3 Test results obtained by the substitution method using point-by-point measurement shall be
considered basic and should be used as a reference when results from the comparison method
and the pressure method are being interpreted (see Sub-clauses 4.2, 4.3 and 4.9).
4. Explanation of terms
4.1 Ear simulator
An ear simulator is a device for measuring the output sound pressure of an earphone under
well-defined loading conditions in a specified frequency range. It consists essentially of a cavity
of specified volume, acoustic load networks, and a calibrated microphone. The location of the
microphone is chosen so that the sound pressure at the microphone corresponds approximately
to the sound pressure generated at the human eardrum (see I E C Publication 711).
4.2 Substitution method
A method of measurement in which the hearing aid and the microphone employed to
measure the free-field sound pressure are placed alternatively at the same point in the sound
field.
4.3 Comparison method
A method of measurement in which the hearing aid and the microphone employed to
measure the free-field sound pressure, are placed simultaneously at two acoustically equivalent
points in the sound field.
4.4 Pressure method
A method of measurement in which the input sound pressure level is controlled close to the
sound entry of the hearing aid by a pressure calibrated controlling microphone, thus substan-
tially eliminating diffraction effects from the hearing aid.
4.5 Simulated in situ method
A method of measurement in which the hearing aid is mounted upon an artificial head and
torso in order to simulate the acoustical effects of an average adult wearer.
4.6 Reference o rientation (of a hearing aid)
The orientation of a hearing aid in the test enclosure with respect to the sound source, which
corresponds to the o rientation of a hearing aid under actual use on a person facing the sound
source.
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4.7 Reference point (of a hearing aid)
A point on the hearing aid chosen for the purpose of defining its position.
4.8 Test point
A position in the test enclosure to which the measurements of the free-field sound pressure
level are referred and at which the reference point of the hearing aid is located for test purposes.
Supply voltage
4.9
The voltage at the battery terminals of the hearing aid with the hearing aid switched on.
Acoustic gain — at a specified frequency and under specified operating conditions.
4.10
The difference between the sound pressure level developed in the acoustic coupler by the
hearing aid and the sound pressure level measured at the test point.
(frequency response curve) — at a specified frequency or as a function of
4.11 Full-on acoustic gain
frequency. The acoustic gain under essentially linear input/output conditions obtainable from
the hearing aid measured with the gain control at maximum (full-on) and at stated settings of
the other hearing aid controls.
4.12 Maximum acoustic gain at a specified frequency
The highest possible acoustic gain that can be obtained from the hearing aid at the specified
frequency.
4.13 Saturation sound pressure level (frequency response curve)
The highest possible sound pressure level obtainable in the ear simulator from the hearing aid
at a specified frequency (or expressed as a function of frequency).
The saturation sound pressure level does not necessarily occur at the highest input level.
Note. —
4.14 Maximum saturation sound pressure level
The maximum value of a saturation sound pressure level frequency response curve.
9,9) at a specified
Output sound pressure level for an input sound pressure level of 90 dB (OSPL
4.15
frequency (or frequencies)
The sound pressure level produced in the ear simulator with an input sound pressure level of
90 dB at the specified frequency (or frequencies), the gain control being in the full-on position
and the other controls being set for maximum gain. The abbreviation for this term is OSPL 90 (or
OSPL 90 frequency response curve).
4.16 Reference test frequency
OSPL 90 to obtain
The frequency, at which the setting of the gain control is made in relation to
a reference test position of the gain control. The reference test frequency shall normally be
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1 600 Hz. For certain hearing aids for which a higher reference test frequency is more
appropriate (so called high-tone hearing aids) 2 500 Hz shall be used. If 2 500 Hz is used this
shall be clearly stated in the report.
4.17 Reference test gain control position
The setting of the hearing aid gain control which provides an output sound pressure level in
90 for an input sound pressure level of 60 dB at the
the ear simulator of 15 ± 1 dB less than OSPL
reference test frequency. If the gain available will not permit this, the full-on gain control
position of the hearing aid should be used.
4.18 Reference test gain
The acoustic gain of the hearing aid at the reference test frequency with the setting of the gain
control set to the reference test gain control position.
4.19 Frequency response
The sound pressure level developed in the ear simulator by the hearing aid expressed as a
function of frequency under specified test conditions.
4.20 Comprehensive frequency response curves
A family of frequency response curves obtained with the gain control in the reference test
gain position using a series of input sound pressure levels to exhibit the input-output character-
istics of the hearing aid over its full range of operation.
4.21 Basic frequency response curve
The frequency response curve obtained at the reference test gain setting with an input sound
pressure level of 60 dB.
4.22
Steady state input-output graph
At a stated frequency and gain control setting, the graph illustrating the output sound
pressure level as a function of the input sound pressure level, both expressed in decibels on.
identical linear scales.
5. Test equipment
5.1 Acoustical requirements for the test enclosure
5.1.1 The test enclosure shall, in the space to be used, provide essentially free-field conditions over
the frequency range 200 Hz to 8 000 Hz. Essentially free-field conditions are considered estab-
lished when the sound pressure level at points 100 mm in front of and behind the test point do
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118-0 © I EC 1983
law) by more than ±2 dB from 200 Hz to 400 Hz
not deviate from the inverse distance law ( 1
and ± 1 dB from 400 Hz to 8 000 Hz. At points 100 mm right, left, above and below the test
point, the SPL shall not deviate by more than ± 1 dB from the SPL at the test point in the
frequency range 200 Hz to 8 000 Hz. The hearing aid and any other obstacles shall not be
present in the test enclosure during the testing of the sound field.
5.1.2 The sound pressure level of the ambient noise in the free-field test enclosure in the frequency
range 200 Hz to 8 000 Hz shall be sufficiently low to ensure that the reading shall drop by at
least 10 dB when the test signal is switched off.
5.2 Sound field at the test point
The sound source shall be capable of producing at the test point sound pressure levels of
between 50 dB and 90 dB constant within the following tolerances:
a) When the substitution method is used: ± 1 dB over the frequency range 200 Hz to 5 000 Hz
and ± 1.5 dB over the frequency range 5 000 Hz to 8 000 Hz.
b) When the comparison method is used: ± 1.5 dB over the frequency range 200 Hz to
3 000 Hz and ± 2.5 dB over the frequency range 3 000 Hz to 8 000 Hz.
The frequency of the sound source shall be within ±2% of the indicated value.
The total harmonic distortion of the acoustic signal of the sound source shall not exceed 1%
up to and including an SPL of 70 dB and 2% for an SPL greater than 70 dB and up to 90 dB.
For distortion measurement the total harmonic distortion of the acoustic signal of the sound
source shall not exceed 0.5%.
5.3 Ear simulator
For all measurements the occluded-ear simulator according to I EC Publication 711 shall be
used.
If any measurements described in this standard are carried out with an acoustic coupler according to I EC
Note. —
Publication 126, this should clearly be stated with each relevant figure or graph in the test repo rt.
Equipment for the measurement of sound pressure level in the ear simulator
5.4
The equipment used for measurement of the sound pressure level produced by the hearing
aid in the ear simulator, shall comply with the following requirements:
5.4.1 The calibration of the sound pressure level measurement system, excluding the ear simulator,
shall be accurate to within ± 0.5 dB at a specified frequency.
Note. — The calibration of the microphone should be repeated sufficiently often to ensure that it remains within the
permitted limits during measurements.
5.4.2 The pressure sensitivity level of the measuring microphone shall be frequency-independent
within ± 1 dB in the frequency range 200 Hz to 3 000 Hz and within ±2 dB in the range
3 000 Hz to 8 000 Hz relative to the pressure sensitivity level at 1 000 Hz.
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5.4.3 Total harmonic distortion in the measuring equipment shall be less than 1% for sound pressure
levels up to 130 dB in the frequency range 200 Hz to 5 000 Hz and less than 3% for sound
pressure levels above 130 dB and up to and including 145 dB.
5.4.4 The sound pressure level corresponding to hum, thermal agitation and other noise sources
shall be sufficiently low to ensure that the reading shall drop by 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.
Note. — Noise level should be indicated on the response curve.
5.4.5 The output indicator used shall give an r.m.s. indication within a tolerance of ±0.5 dB at a
signal crest factor of not more than 3.
If under certain conditions it is necessary to use a selective measuring system in order to ensure that the
Notes 1. —
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 repo rt 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.
5.4.6 As the calibration of the ear simulator depends on ambient conditions, especially atmospheric
pressure, corrections for such a dependence shall be made when necessary (see Sub-
clause 6.4.5).
5.5 Equipment for automatic sweep frequency recording
The equipment shall be capable of maintaining at the test point all required sound pressure
levels between 50 dB to 90 dB within such tolerances as specified in Sub-clause 5.2.
The indicated frequency on a recorder chart shall be accurate within ± 5%. The automatically
recorded values shall not differ by more than 1 dB from the steady-state value over the
frequency range 200 Hz to 5 000 Hz and by not more than 2 dB above 5 000 Hz up to 8 000 Hz.
5.6 Calibration of free-field sound pressure level
The calibration of the free-field sound pressure level shall be accurate within ± 0.5 dB at a
specified frequency. The free-field sensitivity level of the measuring microphone shall be
frequency-independent within ± 1 dB in the frequency range 200 Hz to 5 000 Hz and within
± 1.5 dB in the range 5 000 Hz to 8 000 Hz relative to the free-field sensitivity level at a specified
frequency.
Note — For the comparison method it is recommended that a half-inch microphone should be used as the control
microphone.
6. Test conditions
Choice of test point
6.1
With the position of the sound source fixed in the test enclosure, a test point is chosen, so that
the requirements of Sub-clause 5.1 are fulfilled.
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The distance from the sound source to the test point shall be sufficient to prevent interaction
between the sound source and the hearing aid when the latter is located at the test point.
Usually a distance of 0.5 m to 1.5 m from the sound source is chosen.
The choice of the test point shall allow for a reproducible positioning of the test object within
± 10 mm.
6.2 Calibrating the sound field
The technique used for the calibration of the sound field differs according to whether the
substitution or comparison method is used.
6.2.1 Substitution method
The calibration of the sound field at the test point is made with the hearing aid absent, note
being made of the electrical input to the sound source required to provide the sound pressure
levels for a particular test.
6.2.2 Comparison method
The sound pressure at the test point is kept constant using a control microphone and the
equipment mentioned in Sub-clause 5.5.
Note. — A distance of 60 mm to 120 mm from the control microphone to the hearing aid using a symmetrical
arrangement with respect to the axis of the sound source is usually sufficient when both the hearing aid and
the control microphone have small physical dimensions.
Locating the hearing aid for tests
6.3
rientation of the hearing aid
6.3.1 Reference point and reference o
The reference point chosen for a particular hearing aid shall normally be the centre of the
main microphone opening area.
If another reference point is used it should be stated in the repo rt on test results.
The reference point of the hearing aid shall coincide with the test point (see Sub-clause 6.1).
The hearing aid is placed in the test enclosure in the reference o rientation.
A hearing aid for which the reference o rientation cannot be accurately defined shall be
placed with the surface in which the reference point is located facing towards the sound source
in such a way that the direction of the incident sound is perpendicular to the surface where the
reference point is located.
6.3.2 Mechanical support for the hearing aid
Care should be taken that neither the coupler nor the mechanical suppo
rt for the hearing aid
will appreciably disturb the sound field in the vicinity of the hearing aid at the test frequencies
used, and they should not introduce spurious effects arising from mechanical resonances or
mechanical vibrations, nor should they in any respect affect any mechanical or acoustical
property of the hearing aid under test.
The hearing aid shall be placed in the free-field without any baffle or other device simulating
the body or parts of the body of a wearer.
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When it is necessary to place the ear simulator in the sound field close to the hearing aid, it
shall be placed so as to produce minimum distortion of the sound field at the sound entry to the
hearing aid.
6.4 Normal operating conditions for the hearing aid
The normal operating conditions for the hearing aid which apply for measurement purposes,
when no other conditions are prescribed, are:
6.4.1 Battery or supply voltages
Either an actual battery of the type normally used in the hearing aid, partially discharged to
avoid typical high initial voltage, or a suitable power supply that simulates the voltage and
internal impedance of real batte ries of the type normally used, may be employed. The type of
power source used, the supply voltage and, in the case of a power supply, the internal
impedance shall be stated.
The battery voltage measurements shall be accurate within ± 50 mV from the value specified.
6.4.2 Gain control
Full-on gain control position, reference test gain position or other positions used, shall be
stated.
6.4.3 Other controls
The setting selected for the tone control shall be stated in the repo rt on test results. In general,
the basic setting, i.e. that giving the widest frequency range, shall be selected in preference to
settings in which the low or high frequencies are attenuated. If, however, there are reasons for
regarding some other settings more representative of the normal use of the hearing aid, these
as
settings may be adopted provided they are clearly described in the repo rt on test results.
All other control settings should be chosen. to give the highest OSPL J and the highest
acoustic gain. If the highest OSPL 90 is not associated with the highest acoustic gain, the setting
giving the highest OSPL 90 shall be used.
All controls settings selected shall be stated in the repo rt on test results.
6.4.4 Ambient conditions
Ambient conditions in the test space at the time of test shall be stated and kept within the
following tolerances:
23 ± 5 oC
temperature:
40% to 80%
relative humidity:
atmospheric pressure: 101.3 kPa
±20
Note. — If these conditions cannot be achieved, actual conditions shall be stated.
Reference is made to I EC Publication 68: Basic Environmental Testing Procedures.
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6.4.5 Sound outlet systems
Reference is made to IEC Publication 711. The particular system, i.e. inse rt earphone,
acoustic tu
...
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