Acoustics - Reference zero for the calibration of audiometric equipment - Part 3: Reference equivalent threshold vibratory force levels for pure tones and bone vibrators (ISO 389-3:2016)

ISO 389-1:2016 specifies the following data applicable to the calibration of bone vibrators for pure-tone bone-conduction audiometry:
a) reference equivalent threshold vibratory force levels (RETVFL), corresponding to the threshold of hearing of young otologically normal persons by bone-conduction audiometry;
b) essential characteristics of the bone vibrator and the method of coupling to the test subject, and to the mechanical coupler;
c) essential characteristics of the masking noise and the baseline masking noise level applied to the ear not under test.
Guidance on the practical application of this part of ISO 389 in the calibration of audiometers is given in Annex B.
RETVFL is the vibratory force level transmitted to a mechanical coupler of specified characteristics by a vibrator when applied to the mechanical coupler under stated conditions of test and when energized at the voltage level corresponding to the normal threshold of hearing for location on the mastoid prominence.
NOTE 1 Values for the differences in reference equivalent threshold vibratory force levels between location on the forehead and mastoid are included for information in Annex C.
NOTE 2 Recommended procedures for carrying out bone-conduction audiometry are specified in ISO 8253‑1.

Akustik - Standard-Bezugspegel für die Kalibrierung audiometrischer Geräte - Teil 3: Äquivalente Bezugs-Schwellenkraftpegel für reine Töne und Knochenleitungshörer (ISO 389-3:2016)

Dieser Teil von ISO 389 legt die folgenden, für die Kalibrierung von Knochenleitungshörern in der Reinton-Knochenleitungs-Audiometrie anwendbaren Daten fest:
a)   Äquivalente Bezugs-Schwellenkraftpegel (RETVFL), die den durch Knochenleitungs-Audiometrie bestimmten Hörschwellenpegeln von jungen, otologisch normalen Personen entsprechen;
b)   Wesentliche Eigenschaften des Knochenleitungshörers sowie die Methode zur Ankopplung an den Probanden und an den mechanischen Kuppler;
c)   Wesentliche Eigenschaften und der Grundpegel des Verdeckungsgeräuschs, mit dem das nicht geprüfte Ohr beschallt wird.
Anleitung zur praktische Anwendung dieses Teils von ISO 389 bei der Kalibrierung von Audiometer ist im Anhang B enthalten.
Der Bezugs-Schwellenpegel der periodischen Kraft ist der vibratorische Wert der Kraft auf einen mechanischen Kuppler mit festgelegten Eigenschaften, die über einen Vibrator, wenn ein mechanischen Kuppler mit festgelegten Prüfbedingungen verwendet wird, auf diesen wirkt und dieser mit einer Spannung, die den üblichen Hörschwellen für die Stelle entspricht, betrieben, am vorstehenden Teil des Mastoids angewendet wird.
ANMERKUNG 1   Werte für die Unterschiede zwischen den äquivalenten Bezugs-Schwellenkraftpegeln bei Stirnankopplung und bei Mastoidankopplung sind zur Information in Anhang C angegeben.
ANMERKUNG 2   Empfohlene Verfahren zur Durchführung der Knochenleitungs-Audiometrie sind in ISO 8253 1 beschrieben.

Acoustique - Zéro de référence pour l'étalonnage d'équipements audiométriques - Partie 3: Niveaux de référence équivalents de force vibratoire liminaire pour les vibrateurs à sons purs et les ossivibrateurs (ISO 389-3:2016)

ISO 389-3:2016 fournit les spécifications suivantes, qui sont applicables à l'étalonnage des ossivibrateurs pour l'audiométrie à sons purs en conduction osseuse:
a) les niveaux de référence équivalents de force vibratoire liminaire, correspondant au seuil d'audition de sujets jeunes otologiquement normaux déterminé par audiométrie en conduction osseuse;
b) les caractéristiques principales de l'ossivibrateur et la méthode permettant de l'installer sur le sujet soumis à l'essai et de le raccorder au coupleur mécanique;
c) les caractéristiques principales du bruit de masque et le niveau de base du masquage appliqué à l'oreille non soumise à l'essai.
Des préconisations concernant l'application pratique de la présente partie de I'ISO 389 à l'étalonnage des audiomètres sont données en Annexe B.
Le niveau de référence équivalent de force vibratoire liminaire (RETVFL) est le niveau de la force vibratoire transmise à un coupleur mécanique de caractéristiques spécifiées par un vibrateur lorsque ce dernier est appliqué sur le coupleur mécanique dans des conditions d'essai spécifiées et lorsqu'il est excité à un niveau de tension correspondant au seuil normal d'audition pour un emplacement sur l'apophyse mastoïde.
NOTE 1 Les valeurs correspondant à la différence de niveau de référence équivalent de force vibratoire liminaire entre l'emplacement sur le front et l'emplacement sur l'apophyse mastoïde de l'ossivibrateur sont données à titre d'information en Annexe C.
NOTE 2 L'ISO 8253‑1 spécifie des modes opératoires recommandés pour réaliser les essais audiométriques en conduction osseuse.

Akustika - Referenčna ničla za umerjanje avdiometrov - 3. del: Referenčne ekvivalentne ravni za prag vibracijske sile za čiste tone in za kostne vibratorje (vzbujevalnike kostnih vibracij) (ISO 389-3:2016)

Ta del standarda ISO 389 določa naslednje podatke, ki se uporabljajo za umerjanje kostnih vibratorjev za avdiometrijo s kostno prevodnostjo čistih tonov:
a) referenčne ekvivalentne ravni za prag vibracijske sile (RETVFL), ki ustrezajo pragu sluha pri mladostnikih brez težav s sluhom na podlagi avdiometrije s kostno prevodnostjo;
b) bistvene lastnosti kostnega vibratorja ter metode pritrjevanja na preskušanca in na mehanski spojnik;
c) bistvene lastnosti maskirnega hrupa in izhodiščne ravni maskirnega hrupa, ki mu je izpostavljeno uho v nepreskusnih pogojih.
Napotki za praktično uporabo tega dela standarda ISO 389 pri umerjanju avdiometrov so
podani v dodatku B.
RETVFL je raven vibracijske sile, prenesene na mehanski spojnik s podanimi karakteristikami prek vibratorja, pri uporabi z mehanskim spojnikom v navedenih preskusnih pogojih in napajanju prek napetostne ravni, ki ustreza običajnemu pragu sluha za lokacijo na mastoidnem odrastku.
OPOMBA 1: Vrednosti razlik pri referenčnih ekvivalentnih ravneh za prag vibracijske sile med lokacijama ob čelu in na mastoidu so vključene kot informativne vrednosti v dodatku C.
OPOMBA 2: Priporočeni postopki za opravljanje avdiometrije s kostno prevodnostjo so podani v standardu ISO 8253 1.

General Information

Status
Published
Publication Date
16-Feb-2016
Technical Committee
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
17-Feb-2016
Completion Date
17-Feb-2016

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SLOVENSKI STANDARD
SIST EN ISO 389-3:2016
01-junij-2016
1DGRPHãþD
SIST EN ISO 389-3:1999
$NXVWLND5HIHUHQþQDQLþOD]DXPHUMDQMHDYGLRPHWURYGHO5HIHUHQþQH

HNYLYDOHQWQHUDYQL]DSUDJYLEUDFLMVNHVLOH]DþLVWHWRQHLQ]DNRVWQHYLEUDWRUMH

Y]EXMHYDOQLNHNRVWQLKYLEUDFLM  ,62

Acoustics - Reference zero for the calibration of audiometric equipment - Part 3:

Reference equivalent threshold vibratory force levels for pure tones and bone vibrators

(ISO 389-3:2016)

Akustik - Standard-Bezugspegel für die Kalibrierung audiometrischer Geräte - Teil 3:

Äquivalente Bezugs-Schwellenkraftpegel für reine Töne und Knochenleitungshörer (ISO

389-3:2016)

Acoustique - Zéro de référence pour l'étalonnage d'équipements audiométriques - Partie

3: Niveaux de référence équivalents de force vibratoire liminaire pour les vibrateurs à

sons purs et les ossivibrateurs (ISO 389-3:2016)
Ta slovenski standard je istoveten z: EN ISO 389-3:2016
ICS:
13.140 Vpliv hrupa na ljudi Noise with respect to human
beings
17.140.01 $NXVWLþQDPHUMHQMDLQ Acoustic measurements and
EODåHQMHKUXSDQDVSORãQR noise abatement in general
SIST EN ISO 389-3:2016 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 389-3:2016
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SIST EN ISO 389-3:2016
EN ISO 389-3
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2016
EUROPÄISCHE NORM
ICS 13.140 Supersedes EN ISO 389-3:1998
English Version
Acoustics - Reference zero for the calibration of
audiometric equipment - Part 3: Reference equivalent
threshold vibratory force levels for pure tones and bone
vibrators (ISO 389-3:2016)

Acoustique - Zéro de référence pour l'étalonnage Akustik - Standard-Bezugspegel für die Kalibrierung

d'équipements audiométriques - Partie 3: Niveaux de audiometrischer Geräte - Teil 3: Äquivalente Bezugs-

référence équivalents de force vibratoire liminaire Schwellenkraftpegel für reine Töne und

pour les vibrateurs à sons purs et les ossivibrateurs Knochenleitungshörer (ISO 389-3:2016)

(ISO 389-3:2016)
This European Standard was approved by CEN on 2 January 2016.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this

European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by

translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 389-3:2016 E

worldwide for CEN national Members.
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SIST EN ISO 389-3:2016
EN ISO 389-3:2016 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 389-3:2016
EN ISO 389-3:2016 (E)
European foreword

This document (EN ISO 389-3:2016) has been prepared by Technical Committee ISO/TC 43 "Acoustics"

in collaboration with Technical Committee CEN/TC 211 “Acoustics” the secretariat of which is held by

DIN.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by August 2016, and conflicting national standards shall

be withdrawn at the latest by August 2016.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent

rights.
This document supersedes EN ISO 389-3:1998.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,

France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,

Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
Endorsement notice

The text of ISO 389-3:2016 has been approved by CEN as EN ISO 389-3:2016 without any modification.

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SIST EN ISO 389-3:2016
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SIST EN ISO 389-3:2016
INTERNATIONAL ISO
STANDARD 389-3
Second edition
2016-02-01
Acoustics — Reference zero for
the calibration of audiometric
equipment —
Part 3:
Reference equivalent threshold
vibratory force levels for pure tones
and bone vibrators
Acoustique — Zéro de référence pour l’étalonnage d’équipements
audiométriques —
Partie 3: Niveaux de référence équivalents de force vibratoire
liminaire pour les vibrateurs à sons purs et les ossivibrateurs
Reference number
ISO 389-3:2016(E)
ISO 2016
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SIST EN ISO 389-3:2016
ISO 389-3:2016(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2016, Published in Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form

or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior

written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of

the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
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Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2016 – All rights reserved
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SIST EN ISO 389-3:2016
ISO 389-3:2016(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 2

4 Reference equivalent threshold vibratory force levels (RETVFL) .................................................................... 3

5 Test conditions and requirements ..................................................................................................................................................... 4

5.1 General ........................................................................................................................................................................................................... 4

5.2 Bone vibrator ......... ................................................................................................................................................................................... 4

5.3 Fitting of the bone vibrator .......................................................................................................................................................... 4

5.4 Mechanical coupler ............................................................................................................................................................................. 5

5.5 Test signal .................................................................................................................................................................................................... 5

5.6 Masking noise .......................................................................................................................................................................................... 5

5.7 Masking transducer ............................................................................................................................................................................ 5

5.8 Fitting of masking transducer .................................................................................................................................................... 5

5.9 Baseline masking level ..................................................................................................................................................................... 6

Annex A (informative) Note on the derivation of RETVFL values ........................................................................................... 7

Annex B (informative) Guidance on the application of the reference zero to the calibration

of bone-conduction audiometers ........................................................................................................................................................ 8

Annex C (informative) Differences in reference equivalent threshold vibratory force levels

between forehead and mastoid location of vibrator ...................................................................................................10

Annex D (informative) Bone-conduction threshold of hearing for frequencies below 250 Hz ............12

Bibliography .............................................................................................................................................................................................................................13

© ISO 2016 – All rights reserved iii
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SIST EN ISO 389-3:2016
ISO 389-3:2016(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the meaning of ISO specific terms and expressions related to conformity

assessment, as well as information about ISO’s adherence to the WTO principles in the Technical

Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information

The committee responsible for this document is ISO/TC 43, Acoustics.

This second edition cancels and replaces the first edition (ISO 389-3:1994), which has been technically

revised. It also incorporates the Technical Corrigendum ISO 389-3:1994/Cor 1:1995.

ISO 389 consists of the following parts, under the general title Acoustics — Reference zero for the

calibration of audiometric equipment:

— Part 1: Reference equivalent threshold sound pressure levels for pure tones and supra-aural earphones

— Part 2: Reference equivalent threshold sound pressure levels for pure tones and insert earphones

— Part 3: Reference equivalent threshold vibratory force levels for pure tones and bone vibrators

— Part 4: Reference levels for narrow-band masking noise

— Part 5: Reference equivalent threshold sound pressure levels for pure tones in the frequency range

8 kHz to 16 kHz
— Part 6: Reference threshold of hearing for test signals of short duration

— Part 7: Reference threshold of hearing under free-field and diffuse-field listening conditions

— Part 8: Reference equivalent threshold sound pressure levels for pure tones and circumaural earphones

— Part 9: Preferred test conditions for the determination of reference hearing threshold levels

iv © ISO 2016 – All rights reserved
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SIST EN ISO 389-3:2016
ISO 389-3:2016(E)
Introduction

Each part of ISO 389 specifies a specific reference zero for the calibration of audiometric equipment.

ISO 389-1, ISO 389-2 and ISO 389-8 are applicable to audiometric equipment for the transmission of

pure tones by air conduction.

For clinical diagnostic and other audiometric purposes, it is often necessary to compare the measured

hearing threshold levels of a person for sound transmitted to the inner ear by the air-conduction and

bone-conduction pathways, respectively. Bone-conducted sound is provided for this purpose by an

electromechanical vibrator applied to the mastoid prominence or to the forehead of the person under test.

The reference zero for the calibration of audiometric equipment for air conduction is defined in

ISO 389-1, ISO 389-2 and ISO 389-8 in terms of reference equivalent threshold sound pressure levels

(RETSPL), i.e. threshold sound pressure levels produced in an ear simulator or acoustic coupler of

specified characteristics by supra-aural, circumaural or insert earphones of various patterns, when

excited electrically at a level corresponding to the threshold of hearing of young otologically normal

persons. Similarly, this part of ISO 389 provides a reference zero for bone-conduction audiometry in

terms of reference equivalent threshold vibratory force levels (RETVFL), i.e. the vibratory force levels

produced by a bone vibrator on a specified mechanical coupler when the vibrator is excited electrically

at a level corresponding to the threshold of hearing of young otologically normal persons. In some

countries, the preferred location is the mastoid prominence; in other countries, the forehead location

is used in addition to the mastoid prominence. Different RETVFL values are valid for each of the two

positions (see Annex C).

For bone-conduction measurements, it is necessary to specify the static force of application of the

vibrator to the test subject and to the mechanical coupler, as well as certain geometrical features of the

vibrator tip. In addition, it is usually necessary to apply masking noise to the ear not under test, since

excitation of the cranial bones by the vibrator may be heard by that ear instead of (or in addition to) the

ear intended for the test. An appropriate specification of the masking noise is, therefore, required as an

adjunct to the reference equivalent threshold vibratory force levels, and such a specification is given

in this part of ISO 389. Due to the so-called “occlusion effect” whereby the wearing of the transducer

needed to provide the (air-conducted) masking noise causes a lowering of the bone-conduction

threshold of hearing of the ear receiving the masking signal, it is necessary for the level of masking

noise to be raised to cancel out the occlusion effect and provide adequate masking of the ear not under

test. The specification of masking noise given in this part of ISO 389 is based on the procedures used in

the experimental investigations from which the reference zero of this part of ISO 389 is derived.

Use of this reference zero to calibrate audiometers will ensure that measured bone-conduction hearing

threshold levels of persons with unimpaired hearing or with hearing losses of purely sensorineural

type (i.e. having unimpaired outer and middle ear function) will be compatible with the air-conduction

hearing threshold levels of the same persons when using the reference zero of ISO 389-1, ISO 389-2 or

ISO 389-8, respectively. Although exact equivalence of air-conduction and bone-conduction thresholds

for any individual in these classes cannot be expected, due to biological variability of sound transmission

through the external and middle ear and through the cranial bones, this part of ISO 389 will ensure

that systematic deviations averaged over groups of such persons are reduced to a practical minimum.

This part of ISO 389 is based on an assessment of technical data provided by laboratories in three

countries using methods of threshold testing which, in the respects described, were essentially uniform.

Examination of the data showed that the experimental results were consistent. It has, therefore, been

possible to standardize a reference zero by means of RETVFL values which are to be used for all bone

vibrators used in audiometry having similar characteristics to those used by the laboratories. The

systematic uncertainties introduced by this deliberate simplification will be small in comparison to the

usual step size of hearing level controls in clinical audiometers (5 dB).
© ISO 2016 – All rights reserved v
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SIST EN ISO 389-3:2016
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SIST EN ISO 389-3:2016
INTERNATIONAL STANDARD ISO 389-3:2016(E)
Acoustics — Reference zero for the calibration of
audiometric equipment —
Part 3:
Reference equivalent threshold vibratory force levels for
pure tones and bone vibrators
1 Scope

This part of ISO 389 specifies the following data applicable to the calibration of bone vibrators for pure-

tone bone-conduction audiometry:

a) reference equivalent threshold vibratory force levels (RETVFL), corresponding to the threshold of

hearing of young otologically normal persons by bone-conduction audiometry;

b) essential characteristics of the bone vibrator and the method of coupling to the test subject, and to

the mechanical coupler;

c) essential characteristics of the masking noise and the baseline masking noise level applied to the

ear not under test.

Guidance on the practical application of this part of ISO 389 in the calibration of audiometers is

given in Annex B.

RETVFL is the vibratory force level transmitted to a mechanical coupler of specified characteristics by a

vibrator when applied to the mechanical coupler under stated conditions of test and when energized at the

voltage level corresponding to the normal threshold of hearing for location on the mastoid prominence.

NOTE 1 Values for the differences in reference equivalent threshold vibratory force levels between location on

the forehead and mastoid are included for information in Annex C.

NOTE 2 Recommended procedures for carrying out bone-conduction audiometry are specified in ISO 8253-1.

2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 389-1, Acoustics — Reference zero for the calibration of audiometric equipment — Part 1: Reference

equivalent threshold sound pressure levels for pure tones and supra-aural earphones

ISO 389-2, Acoustics — Reference zero for the calibration of audiometric equipment — Part 2: Reference

equivalent threshold sound pressure levels for pure tones and insert earphones

ISO 389-4, Acoustics — Reference zero for the calibration of audiometric equipment — Part 4: Reference

levels for narrow-band masking noise

IEC 60318-6, Electroacoustics — Simulators of human head and ear — Part 6: Mechanical coupler for the

measurement of bone vibrators
© ISO 2016 – All rights reserved 1
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SIST EN ISO 389-3:2016
ISO 389-3:2016(E)
3 Terms and definitions

For the purposes of this document, the definitions given in ISO 389-1 and ISO 389-2, and the following

terms and definitions apply.
3.1
bone conduction

transmission of sound to the inner ear primarily by means of mechanical vibration of the cranial bones

3.2
bone vibrator

electromechanical transducer intended to produce the sensation of hearing by vibrating the cranial bones

3.3
vibratory force level

ten times the logarithm to base ten of the ratio of the mean square vibratory force by the square of the

reference force, 1 μN
Note 1 to entry: The vibratory force level is expressed in decibels (dB).
3.4
mechanical coupler

device for calibrating bone vibrators, designed to present a specified mechanical impedance to a bone

vibrator applied with a specified static force, and equipped with an electromechanical transducer to

enable the vibratory force level at the surface contact between a bone vibrator and mechanical coupler

to be determined
Note 1 to entry: A mechanical coupler is specified in IEC 60318–6.
3.5
equivalent threshold vibratory force level

vibratory force level for a given ear, at a specified frequency, for a specified configuration of bone

vibrator and for a stated force of application of the bone vibrator to the human mastoid prominence, set

up by the bone vibrator on a specified mechanical coupler when the bone vibrator is actuated by that

voltage which, with the bone vibrator applied to the mastoid prominence concerned, would correspond

to the threshold of hearing
Note 1 to entry: The term is relevant for monaural listening only.
3.6
reference equivalent threshold vibratory force level
RETVFL

mean value of the equivalent threshold vibratory force levels at a specified frequency, of a sufficiently

large number of ears of otologically normal persons, of both sexes, aged between 18 years and 25

years inclusive, expressing the threshold of hearing in a specified mechanical coupler for a specified

configuration of bone vibrator
Note 1 to entry: The term was formerly referred to by the acronym RETFL.
3.7
hearing level

vibratory force level (or sound pressure level) at a specified frequency, for a specified model of

transducer and for a specified manner of application, produced by the transducer in a specified

mechanical coupler (or ear simulator or acoustic coupler) minus the appropriate reference equivalent

threshold vibratory force level (or reference equivalent threshold sound pressure level) for bone

conduction or air conduction, as applicable

Note 1 to entry: By extension, this definition may be applied to a narrow band of noise.

2 © ISO 2016 – All rights reserved
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SIST EN ISO 389-3:2016
ISO 389-3:2016(E)
3.8
occlusion effect

increase in level of a bone-conducted signal reaching the inner ear when an earphone or earplug is placed

over, or at the entrance to the ear canal, thereby forming an enclosed air volume in the external ear

Note 1 to entry: The effect depends on the type of earphone or earplug used and is greatest at low frequencies.

Note 2 to entry: This is expressed in decibels (dB).
3.9
masking

process by which the threshold of hearing of a sound is raised by the presence of another

(masking) sound
3.10
masking
amount by which the hearing threshold level is so raised
Note 1 to entry: This is expressed in decibels.
3.11
baseline masking level

level, expressed as hearing level of a band of noise delivered by air conduction for the purpose of

masking, in the presence of which a pure tone at the centre frequency of the noise band and at a hearing

level of 35 dB is just audible, on the basis of 50 % detection in repeated trials by an otologically normal

person, having a hearing threshold level of 0 dB by air conduction for that pure tone

Note 1 to entry: The value of 35 dB for the pure-tone test stimulus has been adopted arbitrarily as lying within the

range used in experimental studies on which this part of ISO 389 is based. It does not imply a recommendation to

adopt this level of masking noise in clinical practice.

Note 2 to entry: The relationship between the levels of a masking noise and a pure tone just masked by the

presence of this noise is specified in ISO 389-4.

Note 3 to entry: The term was formerly called “datum level of masking noise” in the earlier edition of this

part of ISO 389.

Note 4 to entry: By extension, this definition may be applied to a narrow band of noise.

3.12
critical bandwidth

bandwidth of a frequency band of sound, being a portion of a continuous noise spectrum of wider

bandwidth, which effectively masks a tone coinciding with the centre frequency of the band

3.13
vibrotactile threshold level

vibratory force level at which a person gives a predetermined percentage of correct detection responses

on repeated trials due to the sensation of vibration on the skin
Note 1 to entry: A 50 % correct detection rate is often used.
3.14
white noise

noise, having a power spectral density that is essentially independent of frequency

4 Reference equivalent threshold vibratory force levels (RETVFL)

Reference equivalent threshold vibratory force levels for location of the bone vibrator on the mastoid

prominence are given in Table 1. They are derived from determinations of the threshold of hearing by

© ISO 2016 – All rights reserved 3
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SIST EN ISO 389-3:2016
ISO 389-3:2016(E)

bone conduction of otologically normal persons as measured on the mastoid prominence, under the

conditions described in Clause 5 (see Annex A).

NOTE 1 It is emphasized that the data given in Table 1 are derived from results obtained with different types

of bone vibrators having different electromechanical properties, applied to the head in the specified manner.

The procedures used to compensate for differences in the masking levels used in the three studies may also have

contributed to differences among studies.

NOTE 2 Values for frequencies below 250 Hz are not specified in this part of ISO 389. Results from one

laboratory are given for information in Annex D.
5 Test conditions and requirements
5.1 General

The reference equivalent threshold vibratory force levels apply when the conditions and requirements

specified in this Clause are met.
5.2 Bone vibrator

The vibrator shall have a plane, circular tip, of nominal area 175 mm . Any airborne sound which it

radiates when in contact with the head of a test subject having unimpaired external and middle ear

function shall be low enough in level to provide a margin of 10 dB or more between the true bone-

conduction hearing threshold level and a false air-conduction hearing threshold level evoked by the

bone vibrator. A method to show conformity with this requirement is given in Annex B.

If this condition is not met directly at all frequencies, the unwanted sound radiation is excluded by

inserting an earplug into the external canal of the ear under test at the frequencies which are affected.

Due to the occlusion effect, use of the earplug is confined to frequencies above 2 000 Hz.

5.3 Fitting of the bone vibrator

A headband shall be used to hold the vibrator on the mastoid prominence with a nominal static force of

5,4 N. The vibrator shall be placed on the mastoid prominence, not touching the pinna, and adjusted so

as to remain in a stable position.

Table 1 — Reference equivalent threshold vibratory force levels (RETVFL) for location of the

vibrator on the mastoid prominence
Frequency RETVFL
Hz (reference: 1 μN)
250 67,0
315 64,0
400 61,0
500 58,0
630 52,5
750 48,5
800 47,0
1 000 42,5
1 250 39,0
Values rounded to the nearest 0,5 dB.
Values for these frequencies are derived by interpolation.

Values for these frequencies are derived from the results from one laboratory only.

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