oSIST prEN 17479:2020

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 den individuellen Sitz

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 individualnih preskusnih metod

General Information

• Status: Not Published
• Public Enquiry End Date: 19-Mar-2020
• ICS: 13.340.20 - Head protective equipment
• Technical Committee: OVP - Personal protecting equipment
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 04-Feb-2020
• Due Date: 23-Jun-2020
• Completion Date: 01-Apr-2020
• Ref Project: FprEN 17479 - Hearing protectors - Guidance on selection of individual fit testing methods

Standards Content (sample)

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.

---------------------- Page: 1 ----------------------
oSIST prEN 17479:2020
---------------------- Page: 2 ----------------------
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.
---------------------- Page: 3 ----------------------
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

---------------------- Page: 4 ----------------------
oSIST prEN 17479:2020
prEN 17479:2020 (E)

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

---------------------- Page: 5 ----------------------
oSIST prEN 17479:2020
prEN 17479:2020 (E)
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.
---------------------- Page: 6 ----------------------
oSIST prEN 17479:2020
prEN 17479:2020 (E)
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.
---------------------- Page: 7 ----------------------
oSIST prEN 17479:2020
prEN 17479:2020 (E)
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]
---------------------- Page: 8 ----------------------
oSIST prEN 17479:2020
prEN 17479:2020 (E)
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.

---------------------- Page: 9 ----------------------
oSIST prEN 17479:2020
prEN 17479:2020 (E)
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

---------------------- Page: 10 ----------------------
oSIST prEN 17479:2020
prEN 17479:2020 (E)

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

---------------------- Page: 11 ----------------------
oSIST prEN 17479:2020
prEN 17479:2020 (E)

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
...