SIST EN 17479:2022
(Main)Hearing protectors - Guidance on selection of individual fit testing methods
Hearing protectors - Guidance on selection of individual fit testing methods
This document gives guidance on the appropriate selection of fit testing methods and measurement, and provides practical guidance on fit testing methods, their uses and limitations.
This document does not specify the technical requirements for manufacturing fit testing equipment.
Gehörschützer - Leitfaden zur Auswahl von Prüfverfahren für die individuelle Passung
Dieses Dokument enthält einen Leitfaden für die geeignete Auswahl von Methoden zur Prüfung der Anpassung und -messungen und enthält praktische Hinweise zu Methoden zur Prüfung der Anpassung sowie deren Anwendungen und Einschränkungen.
Dieses Dokument legt nicht die technischen Anforderungen für die Herstellung von Geräten zur Prüfung der Anpassung fest.
Protecteurs individuels contre le bruit - Recommandations relatives au choix des méthodes individuelles de contrôle de l'ajustement
Le présent document fournit des recommandations pour un choix approprié des méthodes et mesurages de contrôle de l'ajustement et donne des recommandations pratiques sur les méthodes de contrôle de l'ajustement, leurs applications et leurs limites.
Le présent document ne spécifie pas les exigences techniques pour la fabrication d'équipements de contrôle d'ajustement.
Varovala sluha - Navodila za izbiro ustreznih preskusnih metod za individualno prilagajanje
Ta dokument podaja navodila za izbiro ustreznih preskusnih metod za prilagajanje in merjenje ter praktične smernice v zvezi s preskusnimi metodami za prilagajanje in njihovo uporabo oziroma omejitvami.
Ta dokument ne določa tehničnih zahtev za proizvodnjo preskusne opreme za prilagajanje.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 17479:2022
01-januar-2022
Varovala sluha - Navodila za izbiro ustreznih preskusnih metod za individualno
prilagajanje
Hearing protectors - Guidance on selection of individual fit testing methods
Gehörschützer - Leitfaden zur Auswahl von Prüfverfahren für die individuelle Passung
Protecteurs individuels contre le bruit - Recommandations relatives au choix des
méthodes individuelles de contrôle de l'ajustement
Ta slovenski standard je istoveten z: EN 17479:2021
ICS:
13.340.20 Varovalna oprema za glavo Head protective equipment
SIST EN 17479:2022 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 17479:2022
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SIST EN 17479:2022
EN 17479
EUROPEAN STANDARD
NORME EUROPÉENNE
November 2021
EUROPÄISCHE NORM
ICS 13.340.20
English Version
Hearing protectors - Guidance on selection of individual fit
testing methods
Protecteurs individuels contre le bruit - Gehörschützer - Leitfaden zur Auswahl von
Recommandations relatives au choix des méthodes Prüfverfahren für den individuellen Sitz
individuelles de contrôle de l'ajustement
This European Standard was approved by CEN on 13 September 2021.
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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, 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: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 17479:2021 E
worldwide for CEN national Members.
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SIST EN 17479:2022
EN 17479:2021 (E)
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Individual fit testing methods . 7
4.1 General . 7
4.2 Test methods . 8
4.3 Reference method for sound attenuation measurements of hearing protectors . 9
4.4 Description of different fit testing methods . 9
5 Test procedure of the fit testing methods . 16
5.1 General . 16
5.2 Sound-level measurements with microphone in real ear (MIRE) (method 1) . 16
5.3 Audiometric method (method 2) . 18
5.4 Audiometric-based method (method 3) . 21
5.5 Loudness balancing (method 4) . 22
5.6 Acoustic leakage test (method 5) . 23
5.7 Air leakage test (method 6) . 24
6 Evaluation criteria . 25
6.1 Application field of the different methods . 25
6.2 Selection according to ease of use . 27
6.3 Individual care for workers with hearing impairment . 28
6.4 Applicability of methods to the different types of hearing protectors . 29
7 Frequency of fit testing . 30
8 Uncertainty . 30
8.1 General factors for the uncertainty of fit testing . 30
8.2 Particular factors regarding the uncertainty for the different fit testing methods . 31
8.3 Quantitative approach. 33
9 Test report . 34
Annex A (informative) Comparison to target values . 36
Annex B (informative) Example of a protocol for the determination of measurement
uncertainty . 40
Bibliography . 41
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EN 17479:2021 (E)
European foreword
This document (EN 17479:2021) has been prepared by Technical Committee CEN/TC 159 “Hearing
protectors”, 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 May 2022, and conflicting national standards shall be
withdrawn at the latest by May 2022.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland,
Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North
Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United
Kingdom.
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Introduction
The need for the use of hearing protectors is obvious nowadays. Appropriate hearing protection is chosen
based on different selection criteria such as required sound attenuation, comfort, workplace environment
and a possible need for communication, audibility of important sounds etc. Different selection criteria for
hearing protector selection are given in EN 458:2016 “Hearing protectors — Recommendations for
selection, use, care and maintenance — Guidance document” [4].
As appropriate sound attenuation should be key in this selection process, this should be compared to the
user’s need in two steps. Firstly, appropriate hearing protection should be selected based on the
attenuation data from the REAT test according to EN ISO 4869-1:2018 [7] and EN ISO 4869-2:2018 [8],
as provided by the manufacturer. Secondly, by using individual fit testing methods the effective
attenuation can be assessed (e.g. acoustic or pressure sealing, personal attenuation rating, etc.).
In addition, the effective attenuation can be estimated and compared to the required sound attenuation.
Whilst fit testing can play a valuable role in the selection and usage, it is no substitute for conformity
testing.
Fit testing can also be used to increase the awareness of the user on the importance of a proper fit. It can
help the user achieve a fit that maximizes the likelihood of that user receiving the expected level of
protection. It could also form part of the training for safety engineers, healthcare specialists and
supervisors, to provide a good understanding of the importance of a proper fitting and it can also be a
helpful training aid for the user.
This document gives practical guidance for the appropriate selection of fit testing methods, their uses and
limitations.
This document does not specify the technical requirements for manufacturing fit testing equipment.
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EN 17479:2021 (E)
1 Scope
This document gives guidelines for the appropriate selection of fit testing methods and measurement,
and provides practical guidelines on fit testing methods, their uses and limitations.
This document does not specify the technical requirements for manufacturing fit testing equipment.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/
3.1
fit testing
procedure for checking that a specific hearing protector is suitable for use by a
specific individual by assessing the physical fit, seal, sound attenuation or other properties of the hearing
protector
3.2
repeatability
closeness of the agreement between the results of successive measurements of the same test item carried
out under the same conditions of measurement
Note 1 to entry: These conditions are called repeatability conditions.
Note 2 to entry: Repeatability conditions include:
— the same measurement procedure;
— the same observer;
— the same measuring instrument, used under the same conditions;
— the same location;
— repetition over a short period of time.
Note 3 to entry: Repeatability may be expressed quantitatively in terms of the dispersion characteristics of the
results.
[SOURCE: ISO/IEC Guide 98-3:2008, B.2.15, modified: “(of results of measurements)” deleted in term
designation and “measurand” replaced by “test item”.]
3.3
reproducibility
closeness of the agreement between the results of measurements of the same test item carried out under
changed conditions of measurement
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Note 1 to entry: A valid statement of reproducibility requires specification of the conditions changed.
Note 2 to entry: The changed conditions may include:
— principle of measurement;
— method of measurement;
— observer;
— measuring instrument;
— reference standard;
— location;
— provision of suitable facility (e.g. sound booth);
— conditions of use;
— time.
Note 3 to entry: Reproducibility may be expressed quantitatively in terms of the dispersion characteristics of the
results.
Note 4 to entry: Results are here usually understood to be corrected results.
[SOURCE: ISO/IEC Guide 98-3:2008, B.2.16, modified: “(of results of measurements)” deleted in term
designation and “measurand” replaced by “test item”.]
3.4
personal attenuation rating
PAR
individual attenuation given as a single value in dB that a user obtains for the fit of the hearing protector
that was tested
Note 1 to entry: The PAR can be either the combined left-right (binaural) or separate left-right ear value.
Note 2 to entry: The calculation procedure is not standardized and is specified by the manufacturer for a specific
fit testing method.
3.5
real-ear attenuation at threshold method
REAT method
test procedure for determination of the sound attenuation of a hearing protector
Note 1 to entry: The measurement of sound attenuation is described in EN ISO 4869-1 [7].
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3.6
threshold of hearing
lowest sound pressure level at which, under specified conditions, a person gives a predetermined
percentage of correct detection responses on repeated trials
Note 1 to entry: For the purpose of this document, the threshold of hearing is measured with the hearing
protector (occluded threshold of hearing) and without the hearing protector (open threshold of hearing).
[SOURCE: EN ISO 4869-1:2018, 3.7, modified: “ISO 4869-1” replaced by “this document” in Note 1 to
entry. “the hearing protector (occluded threshold of hearing)” and “(open threshold of hearing)” added
in Note 1 to entry. Last sentence of Note 1 to entry of EN ISO 4869-1:2018, 3.7 deleted.]
3.7
surrogate hearing protector
hearing protector modified by the manufacturer of the fit testing system that has been demonstrated
when used in the fit testing system to yield attenuation equivalent to the standard hearing protectors that
it represents
Note 1 to entry: Surrogate hearing protectors include surrogate samples, surrogate earplugs and surrogate
earmuffs.
[SOURCE: ANSI S12.71-2018, 3.20, modified: “FAES for estimates using its system” replaced by “fit testing
system” and “estimation system” replaced by “fit testing system”. Note 1 to entry added.]
3.8
insertion loss
algebraic difference, in decibels, between the one-third-octave-band sound pressure level measured by
the microphone of the acoustic test fixture with the hearing protector absent and the sound pressure
level with the hearing protector present
[SOURCE: EN ISO 4869-3:2007, 3.5]
3.9
noise reduction
difference between sound pressure levels external to and under the hearing protector, generally
measured simultaneously
[SOURCE: ANSI S12.42-2010, 3.20, modified: “The arithmetic” at the beginning of the definition deleted,
“in decibels” deleted, “external to and under the hearing protector” moved forward after “sound pressure
level” and “generally” added.]
4 Individual fit testing methods
4.1 General
The fit testing methods can be categorized in three different ways:
— mechanical or acoustic tests according to a physical principle;
— subjective (sound detection at the threshold of hearing or loudness balancing) or objective
(measuring) tests;
— tests for one specified product only or for a range of different hearing protectors.
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Each test method will have a different pass/fail criterion. Refer to the manufacturer for further
information.
In this document, the wording “time required” takes into consideration:
— fitting of the hearing protector on the user;
— fitting of the appropriate test equipment;
— measurement of both ears;
— data analysis.
NOTE The initial setup of the test apparatus is not included.
4.2 Test methods
Currently available tests comprise:
Method 1: Sound-level measurements with microphone in real ear (MIRE)
This is an objective acoustic test method where a sound field is generated. With two microphones the
sound pressure levels outside of the hearing protector and underneath the hearing protector are
measured under noise load, usually simultaneously (noise reduction). With specifically determined
correction factors it is possible to derive sound attenuation values in correspondence with REAT.
— Method 1a: Sound field generated by a headset.
— Method 1b: Sound field generated by a loudspeaker (free field).
Method 2: Audiometric method (determination of the threshold of hearing with and without
hearing protector)
This is an acoustic test method. The thresholds of hearing with and without hearing protector are
determined in a subjective measurement. The difference of the two measured thresholds of hearing is the
sound attenuation.
— Method 2a: Sound field generated by a headset.
— Method 2b: Sound field generated by a loudspeaker.
Method 3: Audiometric-based method (determination of the threshold of hearing with and
without hearing protector)
This is an acoustic test method. The thresholds of hearing with and without hearing protector are
determined in a subjective measurement. The principle is similar to method 2, but instead of an
audiometer a custom-built device especially for fit testing is used.
— Method 3a: Sound field generated by a headset.
— Method 3b: Sound field generated by a loudspeaker.
NOTE The thresholds determined are not the thresholds of hearing measured by audiometric method.
Method 4: Loudness balancing method
This is an acoustic test method. The test subject balances the loudness between the two ears with one or
two earplugs and without any earplug in a subjective measurement.
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Method 5: Acoustic leakage test
This is an acoustic test method. A sound pressure level is generated and measured by a loudspeaker and
a microphone directly inside the earplug in the ear canal. The frequency characteristics of the sound in
the ear canal contains objective information on the fitting of the earplug.
Method 6: Air leakage test
This is a non-acoustic test method, based on an air pressure measurement. The leakage of a custom
moulded earplug in the ear canal is objectively determined by the decay of a small over-pressure behind
the earplug or by measuring the maximum achievable over-pressure for a given maximum pressure of
the pump.
4.3 Reference method for sound attenuation measurements of hearing protectors
The reference method for determining the sound attenuation of hearing protectors is the so-called REAT
method (”real-ear attenuation at threshold”) in accordance with EN ISO 4869-1:2018 [7]. It is also used
in the type examination test as specified in EN 352-1:2020 [1], EN 352-2:2020 [2] and EN 352-3:2020
[3]. Here, the threshold of hearing of the subject is measured twice in a diffuse sound field: once with and
once without hearing protector. The measurement is performed with one-third-octave-band noise at the
octave band centre frequencies between 125 Hz (optionally 63 Hz) and 8 000 Hz. The threshold of
hearing is usually determined via a bracketing method (e.g. by the Békésy method as described in
ANSI S3.20 [15]). The REAT method provides information on a sample of 16 subjects (mean, standard
deviation) and requires according to the specifications of the standard very low ambient noise levels and
a diffuse sound field.
NOTE The methods described in 4.2 that give sound attenuation data can have results that differ from the
values obtained in the laboratory tests. These numbers are the mean values of subjective, binaural tests at the
threshold of hearing. For each product, it is necessary to define limits of the sound attenuation from the individual
fit testing that are in accordance with the REAT data.
4.4 Description of different fit testing methods
4.4.1 Sound-level measurements with microphone in real ear (MIRE) (method 1)
4.4.1.1 General
The MIRE method involves measurement of sound pressure levels inside and outside of the protected
ear. The sound field is generated either by a headset or by a loudspeaker.
The difference between the level in the ear underneath the hearing protector and outside the protected
ear is determined directly in one measurement with the use of two microphones (noise reduction). The
sound attenuation of a hearing protector can be determined from the difference of the two sound
pressure levels. The first microphone is inserted in the hearing protector from the outside (e.g. a tube
microphone) and the second one is placed outside of the ear (if applicable, under the headset that
generates the test sounds). If the result of the MIRE measurement needs to be equated to the labelled
data, the whole system (including the sound field) shall be calibrated in relation to REAT (labelled)
subjective attenuation data.
NOTE 1 The basic method of taking measurements in the ear canal is described in EN ISO 11904-1:2002 [12].
NOTE 2 ‘Noise reduction’ as measured by MIRE does not correspond directly to ‘insertion loss’ as measured by
REAT (labelled sound attenuation values). REAT measurements are based on the subjective difference in threshold
of hearing (with and without hearing protector), while MIRE measurements are based on the objective difference
in sound pressure levels (outside the protected ear and underneath the hearing protector). If correction values for
calibration of ‘noise reduction’ to REAT values are used, they need to be adjusted per product.
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If a tube microphone or an electrically connected microphone is inserted in the ear canal and a wire or
tube is placed alongside the earplug, there is a possibility of a leak. This could compromise the seal of the
earplug and result in inaccurate measurements.
NOTE 3 It is also possible to measure ‘insertion loss’ using MIRE by using one microphone only placed in front
of the eardrum and measuring sequentially with and without the hearing protector in place.
If, in case of a single-channel earplug with filter, the filter is removed for the measurement to insert the
microphone into the earplug and the ear canal, only the fit of the earpiece alone is measured not the sound
attenuation of the product as a whole. In that case, the filter should be measured in a separate
measurement. For earplugs with no channel (foam, flanged and banded earplugs), surrogate earplugs can
be used to perform the measurement.
4.4.1.2 Sound field generated by a headset (method 1a)
In principle, it is possible to test any earplug that can be worn under a headset. However, this method
requires earplugs with a separate channel to incorporate the microphone for the measurement under the
earplug.
Characteristics:
— method: objective;
— test signals: broadband noise (e.g. 80 dB(A), maximum level 95 dB(A) for safety reasons);
— f: 125 Hz to 8 000 Hz;
— maximum background noise: 70 dB(A);
— sound field: headset;
— time required: 5 min;
— principle: sound level difference.
4.4.1.3 Sound field generated by a loudspeaker (free field) (method 1b)
The sound attenuation of a hearing protector can be determined in the sound field of a loudspeaker.
Corrections for the microphone positions and the sound field are incorporated. This method has the
advantage that earmuffs and all types of earplugs can be tested, also bulky types that would not fit under
a headset. As described in 4.4.1.2 sometimes only specially modified hearing protectors with an inserted
microphone can be used.
Characteristics:
— method: objective;
— test signals: broadband noise (e.g. 80 dB(A), maximum level 95 dB(A) for safety reasons);
— f: 125 Hz to 8 000 Hz;
— maximum background noise: 70 dB(A);
— sound field: free field;
— time required: 5 min;
— principle: sound level difference.
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4.4.2 Audiometric method (determination of the threshold of hearing with and without hearing
protector) (method 2)
4.4.2.1 General
This method is similar in principle to the REAT method (see 4.3) and can be realized with the help of an
audiometer. Here as well, the threshold of hearing of the test subject is measured with and without
hearing protectors. This method requires a quiet environment since it works at the threshold of hearing.
Two aspects of the measurement procedure that can vary are described below:
— The test sounds can be narrow-band noise or pure tones. Since the sound field and (for pure tones)
the test noise are different to the laboratory conditions the thresholds of hearing can be expected to
have other values. Thus, also the calculated sound attenuation could be different.
— The threshold of hearing can be determined either with ascending levels or by means of an up-and-
down (bracketing) method. In the latter, the level is by turns increased and reduced several times,
and the threshold of hearing level is narrowed down by the upward and downward excursions.
4.4.2.2 Sound field generated by a headset (method 2a)
It can be used for all types of earplugs that can be worn under a headset.
Characteristics:
— method: subjective;
— test signals: pure tones or narrow-band noise;
— f: 125 Hz to 8 000 Hz or selected band(s);
— maximum background noise: 40 dB(A) (based on EN ISO 8253-1:2010);
NOTE See EN ISO 8253-1:2010 [10] for more information on requirements on background noise level in one-
third-octave-bands.
— sound field: headset;
— time required: 5 min to 20 min;
— principle: measurement at the threshold of hearing.
4.4.2.3 Sound field generated by a loudspeaker (method 2b)
This method has the advantage that earmuffs and all kinds of earplugs can be tested, also bulky types that
would not fit under a headset. The threshold of hearing (open and occluded) is simultaneously measured
for both ears. This results in only one attenuation value representing both ears and a shorter measuring
time than measuring according to 4.4.2.2.
Characteristics:
— method: subjective;
— test signals: narrow-band noise;
— f: 125 Hz to 8 000 Hz or selected band(s);
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— maximum background noise: 25 dB(A) (based on EN ISO 8253-2:2009);
NOTE See EN ISO 8253-2:2009 [11] for more information on requirements on background noise level in
1/3 octave bands.
— sound field: diffuse and quasi-free field;
— time required: 5 min to 10 min;
— principle: measurement at the threshold of hearing.
4.4.3 Audiometric-based method (determination of the threshold of hearing with and without
hearing protector) (method 3)
4.4.3.1 General
This acoustic method is similar to the audiometric method. The test sounds can be narrow-band noise
(similar to the procedure in EN ISO 4869-1:2018 [7]) or pure tones (used in audiometry). The threshold
of hearing is determined twice, with and without hearing protector. The difference between these two
values for each test signal gives the sound attenuation.
The use of a custom-built device instead of an audiometer could restrict the use on selected hearing
protectors but gives more flexibility with regard to the experimenter and the maintenance of the system
(no special audiometric education and annual calibration are necessary).
On the other hand, the values of the single thresholds cannot be used because the devices are not
calibrated on absolute levels. Only the difference of the two thresholds gives realistic values.
4.4.3.2 Sound field generated by a headset (method 3a)
It can be used for all types of earplugs that can be worn under a headset.
Characteristics:
— method: subjective;
— test signals: pure tones or narrow-band noise;
— f: single or multiple frequencies or narrow-band noise in the range of 125 Hz to 8 000 Hz;
— maximum background noise: 40 dB(A) (based on EN ISO 8253-1:2010);
NOTE See EN ISO 8253-1:2010 [10] for more information on requirements on background noise level in
1/3 octave bands.
— sound field: headset;
— time required: 5
...
SLOVENSKI STANDARD
oSIST prEN 17479:2020
01-marec-2020
Varovala sluha - Navodila za izbiro ustreznih individualnih preskusnih metod
Hearing protectors - Guidance on selection of individual fit testing methods
Gehörschützer - Leitfaden zur Auswahl von Prüfverfahren für den individuellen Sitz
Protecteurs individuels contre le bruit - Recommandations relatives au choix des
méthodes individuelles de contrôle de l'ajustement
Ta slovenski standard je istoveten z: prEN 17479
ICS:
13.340.20 Varovalna oprema za glavo Head protective equipment
oSIST prEN 17479:2020 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN 17479:2020
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oSIST prEN 17479:2020
DRAFT
EUROPEAN STANDARD
prEN 17479
NORME EUROPÉENNE
EUROPÄISCHE NORM
January 2020
ICS 13.340.20
English Version
Hearing protectors - Guidance on selection of individual fit
testing methods
Protecteurs individuels contre le bruit - Gehörschützer - Leitfaden zur Auswahl von
Recommandations relatives au choix des méthodes Prüfverfahren für den individuellen Sitz
individuelles de contrôle de l'ajustement
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 159.
If this draft becomes a European Standard, 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.
This draft European Standard was established by CEN 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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 17479:2020 E
worldwide for CEN national Members.
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oSIST prEN 17479:2020
prEN 17479:2020 (E)
Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Individual fit testing methods . 8
4.1 General . 8
4.2 Test methods . 8
4.3 Reference method for sound attenuation measurements of hearing protectors . 9
4.4 Different methods for the individual quality fit of hearing protectors . 10
4.4.1 Sound-level measurements with microphone in real ear (MIRE) . 10
4.4.2 Audiometric method (determination of the threshold of hearing with and without
hearing protector) . 11
4.4.3 Audiometric based method (determination of a threshold of hearing with and
without hearing protector) . 12
4.4.4 Loudness balancing method . 13
4.4.5 Acoustic Leakage test . 14
4.4.6 Air leakage test . 14
4.4.7 Summary of different test methods . 15
5 Test procedure of the fit testing methods . 17
5.1 General . 17
5.2 Sound-level measurements with microphone in real ear (MIRE) . 17
5.2.1 Sound field generated by a headset (method 1a) . 17
5.2.2 Sound field generated by a loudspeaker (method 1b) . 18
5.3 Audiometric method . 19
5.3.1 Sound field generated by a headset (method 2a) . 19
5.3.2 Sound field generated by a loudspeaker (method 2b) . 21
5.4 Audiometric-based method . 22
5.4.1 Sound field generated by a headset (method 3a) . 22
5.4.2 Sound field generated by a loudspeaker (method 3b) . 23
5.5 Loudness balancing . 23
5.6 Acoustic leakage test . 24
5.7 Air leakage test . 25
6 Evaluation criteria . 26
6.1 Application field of the different methods . 26
6.1.1 General . 26
6.1.2 Select an appropriate hearing protector . 27
6.1.3 End user training . 28
6.1.4 Training for trainers and supervisors . 28
6.1.5 Health surveillance . 28
6.1.6 Verify adequacy of attenuation to noise level at workplace . 28
6.1.7 Fitting for custom moulded earplugs . 28
6.1.8 Awareness increase . 28
6.2 Selection according to ease of use . 29
6.3 Individual care for workers with hearing impairment . 29
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6.4 Applicability of methods to the different types of hearing protectors . 30
7 Frequency of fit testing . 31
8 Uncertainty . 31
8.1 General factors for the uncertainty of fit testing . 31
8.2 Particular factors regarding the uncertainty for the different fit testing methods . 32
8.2.1 MIRE techniques . 32
8.2.2 Audiometric methods. 32
8.2.3 Audiometric based methods . 33
8.2.4 Loudness balancing . 33
8.2.5 Acoustic leakage test . 33
8.2.6 Air leakage test . 34
8.3 Quantitative approach . 34
8.3.1 MIRE techniques . 34
8.3.2 Audiometric systems . 34
8.3.3 Audiometric based systems . 34
8.3.4 Loudness balancing . 35
8.3.5 Acoustic leakage test . 35
8.3.6 Air leakage test . 35
9 Test Report . 35
Annex A (informative) Comparison to target values . 37
A.1 General . 37
A.2 Sound attenuation values from type examination . 37
A.2.1 General . 37
A.2.2 Octave band values . 37
A.2.3 HML and SNR values . 38
A.3 Residual levels at the ear . 39
Annex B (informative) Example of a protocol for the determination of measurement
uncertainty . 40
Bibliography . 41
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European foreword
This document (prEN 17479:2020) has been prepared by Technical Committee CEN/TC 159 “Hearing
protectors”, the secretariat of which is held by DIN.
This document is currently submitted to the CEN Enquiry.
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Introduction
The need for the use of hearing protectors is obvious nowadays. Appropriate hearing protection is
chosen based on different selection criteria such as required sound attenuation, comfort, workplace
environment and a possible need for communication, audibility of important sounds etc. Reference to
different selection criteria for hearing protector selection are given in EN 458:2016 “Hearing protectors
— Recommendations for selection, use, care and maintenance — Guidance document”.
As appropriate sound attenuation should be key in this selection process, this should be compared to
the user’s need in two steps. Firstly, appropriate hearing protection should be selected based on the
attenuation data from the REAT test according to EN 352, as provided by the manufacturer. Secondly,
using fit testing methods, the individual protective properties of the hearing protector should be
assessed. Especially, since no ear is similar, what gives a certain protection to one, might give a non-
appropriate protection to another. The attenuation of the hearing protector is roughly maximized by
the mean attenuation values from the REAT test, but the real attenuation is determined by how well the
hearing protector fits to the ear (acoustical sealing, insertion depth, etc.). Hence it is very important that
the acoustic seal be checked. In addition, the real attenuation can be estimated and compared to the
required sound attenuation. While allowing a test on site and on the end user, the lack of precision of fit
testing methods cannot be a substitute for selection but these methods are the necessary complement
to this selection. Therefore, comparison to selection data are expected to be accounted for in this lack of
precision. If no acceptable fit can be reached after carefully following the manufacturer’s instructions,
i.e. if the comparison is not satisfactory, the user should consider another size of that type of hearing
protection or select a suitable alternative.
Fit testing can also be used to increase the awareness of the user on the importance of a proper fit. It
will help the user in achieving the right level of protection against the noise hazard and the workplace
environment. It could also form part of the training for safety engineers, healthcare specialists and
supervisors, to provide a good understanding of the importance of a proper fitting and it can also be a
helpful training aid for the user.
This document gives guidance for appropriate selection of fit testing methods and measurement,
providing practical guidance on fit testing methods, their uses and limitations. The uncertainty of fit
testing methods is one of those limitations, which should be taken into account. There is the uncertainty
that is inherent to the way the fit testing system works. Furthermore, there is the repeatability of the
measurement due to differences in positioning of the hearing protector that leads to an increase of the
uncertainty of the system as a whole.
This document does not specify the technical requirements for manufacturing fit testing equipment as
they do not fall within the scope of this document.
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1 Scope
This document gives guidance on the appropriate selection of fit testing methods and measurement,
and provides practical guidance on fit testing methods, their uses and limitations.
This document does not specify the technical requirements for manufacturing fit testing equipment.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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.
EN ISO 4869-1:2018, Acoustics — Hearing protectors — Part 1: Subjective method for the measurement
of sound attenuation (ISO 4869-1:2018)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
3.1
fit testing
procedure for checking the individual protective properties of a hearing
protection device
Note 1 to entry: Individual protective properties can be evaluated by using different measurement procedures.
3.2
repeatability
closeness of the agreement between the results of successive measurements of the same test item
carried out under the same conditions of measurement
Note 1 to entry: These conditions are called repeatability conditions.
Note 2 to entry: Repeatability conditions include:
— the same measurement procedure;
— the same observer;
— the same measuring instrument, used under the same conditions;
— the same location;
— repetition over a short period of time.
Note 3 to entry: Repeatability may be expressed quantitatively in terms of the dispersion characteristics of the
results.
[SOURCE: ISO/IEC Guide 98-3:2008, B.2.15, modified]
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3.3
reproducibility
closeness of the agreement between the results of measurements of the same test item carried out
under changed conditions of measurement
Note 1 to entry: A valid statement of reproducibility requires specification of the conditions changed.
Note 2 to entry: The changed conditions may include:
— principle of measurement;
— method of measurement;
— observer;
— measuring instrument;
— reference standard;
— location;
— provision of suitable facility (e.g. sound booth);
— conditions of use;
— time.
Note 3 to entry: Reproducibility may be expressed quantitatively in terms of the dispersion characteristics of
the results.
Note 4 to entry: Results are here usually understood to be corrected results.
[SOURCE: ISO/IEC Guide 98-3:2008, B.2.16, modified]
3.4
personal attenuation rating
PAR
individual attenuation given as a single value in dB that a user obtains for the fit of the hearing
protector that was tested
Note 1 to entry: The PAR can be either the combined left-right (binaural) or separate left-right ear value.
Note 2 to entry: The calculation procedure is not standardized and is specified by the manufacturer for a
specific fit testing method.
3.5
real-ear attenuation at threshold method
REAT method
test procedure for determination of the sound attenuation of a hearing protector
Note 1 to entry: The measurement of sound attenuation is described in EN ISO 4869-1.
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3.6
threshold of hearing
lowest sound pressure level at which, under specified conditions, a person gives a predetermined
percentage of correct detection responses on repeated trials
Note 1 to entry: For the purpose of this document, the threshold of hearing is measured with (occluded
threshold of hearing) and without (open threshold of hearing) the hearing protector.
[SOURCE: EN ISO 4869-1:2018, 3.7, modified: “(occluded threshold of hearing)” and “(open threshold of
hearing)” added in Note 1 to entry. Last sentence of Note 1 to entry of EN ISO 4869-1:2018, 3.7 deleted.]
3.7
surrogate hearing protector
hearing protector modified by the manufacturer of the fit testing system that has been demonstrated
when used in the fit testing system to yield attenuation equivalent to the standard hearing protectors
that it represents
Note 1 to entry: Surrogate hearing protectors include surrogate samples, surrogate earplugs and surrogate
earmuffs.
4 Individual fit testing methods
4.1 General
The fit testing methods can be categorized in three different ways:
— mechanical or acoustical tests according to the physical principle;
— subjective (sound recognition at the threshold of hearing or loudness balancing) or objective
(measuring) tests;
— tests for one specified product only or for a range of different hearing protectors.
Each test method will have a different pass/fail criterion. Refer to the manufacturer for further
information.
In this document, the term “timeframe” takes into consideration:
— fitting of the hearing protector on the user;
— fitting of the appropriate test equipment;
— measurement of both ears;
— data analysis.
NOTE The initial setup of the test apparatus is not included.
4.2 Test methods
Currently available tests comprise:
Method 1: Sound-level measurements with microphone in real ear (MIRE)
This is an acoustic test method where a sound field is generated. With two microphones the sound
pressure levels outside of the hearing protector and behind or under the hearing protector are
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measured, usually simultaneously. With some corrections the sound attenuation can be calculated from
these values.
— Method 1a: Sound field generated by a headset
— Method 1b: Sound field generated by a loudspeaker
Method 2: Audiometric method (determination of the threshold of hearing with and without
hearing protector)
This is an acoustic test method. The thresholds of hearing with and without hearing protector are
determined in a subjective measurement. The difference of the two measured thresholds of hearing is
the sound attenuation.
— Method 2a: Sound field generated by a headset
— Method 2b: Sound field generated by a loudspeaker
Method 3: Audiometric based method (determination of a threshold of hearing with and without
hearing protector)
This is an acoustic test method. Thresholds of hearing with and without hearing protector are
determined in a subjective measurement. The principle is similar to method 2, but instead of an
audiometer a custom-built device especially for fit testing is used.
— Method 3a: Sound field generated by a headset
— Method 3b: Sound field generated by a loudspeaker
NOTE The thresholds determined are not the audiometric thresholds of hearing.
Method 4: Loudness balancing method
This is an acoustical test method. The test subject balances the loudness between the two ears with one
or two earplugs and without any earplug in a subjective measurement.
Method 5: Acoustic leakage test
This is an acoustic test method. A sound pressure level is generated and measured by both a
loudspeaker and a microphone directly inside the earplug in the ear canal. The frequency characteristic
of the sound in the ear canal contains objective information on the fitting of the earplug.
Method 6: Air leakage test
This is a non-acoustic test method, based on an air pressure measurement. The leakage of a custom
moulded earplug in the ear canal is objectively determined by the decay of a small over-pressure behind
the earplug or by measuring the maximum achievable over-pressure for a given maximum pressure of
the pump.
4.3 Reference method for sound attenuation measurements of hearing protectors
The reference method for determining the sound attenuation of hearing protectors is the so-called
REAT method (”Real Ear Attenuation at Threshold”) in accordance with EN ISO 4869-1:2018. It is also
used in the type examination test as specified in EN 352-1, EN 352-2 and EN 352-3. Here the threshold
of hearing of the subject is measured twice in a diffuse sound field: once with and once without hearing
protector. The measurement is performed with one-third octave band noise at the octave band centre
frequencies between 125 Hz (optionally 63 Hz) and 8 000 Hz. The threshold of hearing is usually
determined via a bracketing method (e.g. by the Békésy method). The REAT method provides
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information on a sample of 16 subjects (mean, standard deviation) and requires according to the
specifications of the standard very low ambient noise levels and a diffuse sound field.
NOTE The sound attenuation determined by the methods described in 4.2 generally will differ from the
values obtained in the laboratory tests. These numbers are the mean values of subjective, binaural tests at the
threshold of hearing. For each product it is necessary to define limits of the sound attenuation from the individual
fit testing that are in accordance with the laboratory data.
4.4 Different methods for the individual quality fit of hearing protectors
4.4.1 Sound-level measurements with microphone in real ear (MIRE)
4.4.1.1 General
The MIRE method involves measurement of sound pressure levels inside and outside of the ear. The
sound field is generated either by a headset or a loudspeaker.
The difference between the level in the ear under the hearing protector and outside the ear (called
noise reduction) is determined directly with the use of two microphones. The sound attenuation of an
earplug can be determined from the difference of the two sound pressure levels. In order to get both
values in one measurement two microphones are used: the first one inserted in the earplug from the
outside (e.g. a tube microphone) and the second one outside of the ear (if applicable, under the headset
that generates the test sounds). The sound pressure level in the open ear canal cannot be measured
directly, but will be deduced from the level outside of the occluded ear. Therefore, it is necessary to take
into account correction factors that describe the effect of the ear on the sound field. Moreover the
influence of the measuring position in the occluded ear canal (typically not at the tympanic membrane
but in the earplug or at its end) shall be considered. The whole system (including the sound field) shall
be calibrated in relation to validated subjective attenuation data.
In this connection, it should be noted that the noise reduction does not correspond directly to the sound
attenuation of a hearing protector (“insertion loss”). To determine the insertion loss, measurements
shall be taken twice in the same ear canal, with and without a hearing protector in place. This difference
between noise reduction and insertion loss shall be taken into account when the attenuation is
reported.
NOTE The basic method of taking measurements in the ear canal is described in the standard
EN ISO 11904-1.
4.4.1.2 Sound field generated by a headset (method 1a)
In principle, it is possible to test any earplug that can be worn under a headset, but probably the
correction values discussed above need to be adjusted for every product. Moreover, the earplugs shall
be modified in order to incorporate the microphone for the measurement under the earplug (e.g. a tube
microphone).
Characteristics:
— method: objective;
— test signals: broadband noise;
— f = 125 Hz to 8000 Hz;
— maximal background noise: 80 dB(A);
— sound field: hea
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