EN 17479:2021

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

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.

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

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.
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.
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
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].
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.
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.
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.
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.
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);
— 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 min to 15 min;
— principle: measuring at the threshold of hearing.
4.4.3.3 Sound field generated by a loudspeaker (method 3b)
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 4.4.3.2.
Characteristics:
— method: subjective;
— test signals: 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: 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: measuring at the threshold of hearing.
4.4.4 Loudness balancing method (method 4)
In contrast to the laboratory test or the audiometric methods this test procedure works at sound levels
well above the threshold of hearing with sounds produced by a headset. The volume of the test sound
heard over headsets is adjusted by the test subject so that he/she experiences the sounds equally loudly
in both ears. This is conducted in three situations: once with open ears as a reference level, once with one
ear occluded to determine the attenuation of that particular earplug and once with either the other or
both ears occluded to determine the attenuation of the other earplug. From this, the attenuation value of
the earplug used for each ear can be calculated separately.
This method works for all types of earplugs that can be worn under a headset and does not need an
especially quiet environment.
Characteristics:
— method: subjective;
— test signals: pure tones or narrow-band noise;
— f: 125 Hz to 8 000 Hz;
— maximum background noise: 70 dB(A);
— sound field: headset;
— time required: 5 min to 15 min;
— principle: loudness balancing.
4.4.5 Acoustic leakage test (method 5)
This is an objective method only applicable to custom moulded and universal earplugs. A sound pressure
level is generated and measured by a loudspeaker and a microphone directly inside the earplug in the ear
canal. Leakages are visible in the frequency characteristics of the resulting sound level. A leakage is
identified as a reduced sound pressure level at low frequency (e.g. below 100 Hz) relative to higher
frequencies. Data evaluation at those two frequency ranges allows determination of the leakage and the
verification of the seal.
Characteristics:
— method: objective;
— test signals: low frequency tones;
— maximum background noise: 80 dB(A);
— sound field: sound source placed in earplug during testing;
— time required: 5 min;
— principle: measuring of leakage at low frequencies.
4.4.6 Air leakage test (method 6)
This is an objective method only applicable to custom moulded earplugs. It allows determination of
whether the individual custom moulded earplug is correctly adjusted to the ear canal, but does not
provide values for the sound attenuation of the hearing protector.
Through a channel in the earplug (e.g. after removal of the filter) a small static over- or under-pressure
(some mbar) is generated in the ear canal. Then either the maximum stable pressure is determined or
the pressure decay is observed over time. If the ear canal is sealed tightly, the maximum achievable
pressure is close to the maximum pressure of the pump, or when stopping the pump the pressure will
remain constant at least for several seconds. Looking at the pressure decay, for very accurate results the
pressure shall be monitored over quite a long time. Different designs of the measurement device are
available from simple mechanic types to electronic ones with automatic evaluation of the data.
Characteristics:
— method: objective;
— test signals: none;
— maximum background sound pressure level: no restriction (since method is non-acoustic);
— time required: 5 min;
— principle: measurement of pressure decay or of the maximum achievable overpressure.
4.4.7 Summary of different test methods
Table 1 provides a summary of the different test methods.
Table 1 — Summary of different test methods
Sound-level measurements
Loudness Acoustic
Method with microphone in real ear Audiometric method Audiometric-based method Air leakage test
balancing leakage test
(MIRE)
with with with
Sub method with headset with headset with headset
loudspeaker loudspeaker loudspeaker
Difference of Measurement of
Difference of Difference of Difference of Difference of Difference of Measuring low
sound Loudness pressure decay
Principle sound thresholds of thresholds of thresholds of thresholds of frequency
pressure balancing or maximum
pressure levels hearing hearing hearing hearing leakage
levels stable pressure
Involvement
Objective Objective Subjective Subjective Subjective Subjective Subjective Objective Objective
of subject
Pure tones or Pure tones or
Narrow-band Pure tones or Low frequency
Test signal Broadband Broadband narrow-band Narrow-band noise narrow-band None
noise narrow-band noise tones
noise noise
Sound source
Diffuse and Diffuse and quasi-
Sound field Headset Free field Headset Headset Headset placed in earplug None
quasi-free field free field
during testing
Maximum
background 70 dB(A) 70 dB(A) 40 dB(A) 25 dB(A) 40 dB(A) 25 dB(A) 70 dB(A) 80 dB(A) No restriction
noise
Single or multiple Single or multiple
125 Hz to 125 Hz to
frequencies or frequencies or
Measured 125 Hz to 125 Hz to 8 000 Hz or 8 000 Hz or 125 Hz to
narrow-band noise narrow-band noise Not applicable Not applicable
frequencies 8 000 Hz 8 000 Hz selected selected 8 000 Hz
in the range of in the range of
band(s) band(s)
125 Hz to 8 000 Hz 125 Hz to 8 000 Hz
Time
5 min to 5 min to 5 min to
5 min 5 min 5 min to 15 min 5 min to 10 min 5 min 5 min
a
20 min 10 min 15 min
required
a
See 4.1 for description of time required.
5 Test procedure of the fit testing methods
5.1 General
This clause describes the most important aspects of the actual execution of the different fit testing
methods. The assessment criteria shall be defined by the manufacturer of the hearing protectors.
5.2 Sound-level measurements with microphone in real ear (MIRE) (method 1)
5.2.1 Sound field generated by a headset (method 1a)
This method is only applicable to earplugs. To measure the sound pressure level under the earplug,
samples with a sound bore are necessary. This requires for foam and flanged earplugs in most cases
surrogate samples. For custom moulded earplugs an access for the measurement of internal sound
pressure shall be available (dual channel earplug).
For the test the two microphones (mostly in one unit) shall be connected to the earplug under test. Then
the earplug can be inserted into the ear of the user. Care should be taken that the connection between the
microphone and the earplug is not disrupted. If surrogate earplugs are used care should be taken to
ensure the same fitting is achieved compared to the standard version of the earplug.
The headset shall be placed carefully on the head without changing the fitting of the earplug. The cable
from the microphones should not create a leakage at the headset cushions. The actual measurement time
should be less than a minute using a broadband signal and analysing the single frequency bands. If two
microphone units are available for left and right earplugs the measurement can be done binaurally.
NOTE MIRE measurements as insertion loss (sequentially with and without the hearing protector using one
microphone only) are not covered here.
Results can be displayed in frequency bands and in a single number quantity as the PAR (personal
attenuation rating). Care shall be taken to which attenuation value of EN ISO 4869-2:2018 [8] this
individual result corresponds. Measurement uncertainty shall be taken into account for the comparison
of the individual attenuation with the target value.
The following Figure 1 shows the process in a schematic way.
Figure 1 — Flowchart for method 1a
5.2.2 Sound field generated by a loudspeaker (method 1b)
This method is applicable to both earmuffs and earplugs. In both cases surrogate samples can be used
with an inserted microphone for a measurement under the hearing protector. The procedure itself is very
similar to the one described in the section above for MIRE with a headset. For earplugs, the use of a
loudspeaker avoids the necessity to place the headset correctly. Care should be taken to position the test
subject at the correct distance to the loudspeaker and with the test subject facing the loudspeaker.
The following Figure 2 shows the process in a schematic way.
NOTE In case of measuring earmuffs, this flowchart is an example using surrogate earmuff samples.
Figure 2 — Flowchart for method 1b
5.3 Audiometric method (method 2)
5.3.1 Sound field generated by a headset (method 2a)
This method is only applicable to earplugs. Two thresholds of hearing – one with earplug and one without
– are to be measured. The order of the two can be chosen freely. If the fitting of the earplugs as during
everyday use is to be tested and the test subject can come directly from the work place, the occluded
threshold should be measured first.
Suitable headsets are necessary with the free volume between pinna and the headset cups being large
enough not to make contact with the earplug or interfere with the fitting of the earplug. Care is to be taken
not to touch the earplugs while fitting the headset. Depending on the headset cups some types of bulky
custom moulded earplugs (concha type) or flanged earplugs with a long stem/handle have possibly to be
excluded from the test.
The determination of the threshold of hearing should be done by trained personnel to ensure the
reproducibility of the results. Most audiometers require manual handling. Also the test subjects should
be familiar with the test procedure. The threshold can be determined by different techniques: ascending
(increasing the sound level until the test sound is heard), descending (decreasing the sound level until
the test sound is not heard any more) or bracketing (e.g. Békésy, the sound level is increased and
decreased alternately; the mean value of the summit and valley points is the threshold of hearing).
The method is sensitive to background noise. This will especially affect the open threshold and shift it to
higher values, thus the resulting sound attenuation of the earplug will be lower than in reality. For a
headset, the effect is strongest for the low frequencies where the sound attenuation of the headset is the
lowest. Thus, the results for these frequencies shall be checked thoroughly.
In principle, it is possible to measure only one frequency (often 500 Hz) to assess the fit of the earplug.
However, such a measurement is susceptible to errors in the threshold determination. Only if the results
of several frequencies are available, outliers can be identified. Better results are to be expected by the
measurement of two or three frequencies. Often combinations of 250 Hz and 500 Hz or 500 Hz, 1 000 Hz
and 2 000 Hz are used.
NOTE The single frequency measurement could provide limited information in predicting the overall achieved
attenuation.
The basic results are the attenuation values at the measured frequencies. From these, additional values
like a PAR can be calculated. Software based audiometers allow the automatic comparison with sound
attenuation values of the type examination entered into the software.
For stand-alone audiometers, the test can be performed without additional IT equipment.
The following Figure 3 shows the process in a schematic way.
NOTE The order of the two sections for “open” and “occluded” measurements is interchangeable.
Figure 3 — Flowchart for method 2a and 3a
5.3.2 Sound field generated by a loudspeaker (method 2b)
This method can be applied to earplugs and earmuffs (see also 5.4.2). When a setup for free-field
audiometry is used, background noise is a critical issue. The open threshold is very sensitive to external
noise. This applies to all frequencies tested, but the highest background levels are to be expected in the
low frequency range due to the limited sound attenuation of buildings, walls, doors etc.
Another difference to method 2a is the binaural approach due to the free sound field. For each threshold
(open and occluded) the respective ear with the lower threshold will determine the result. This can be
different ears for the two measurements. This means that the attenuation cannot be determined for each
ear separately and the result is less accurate than a monaural measurement with a headset.
The following Figure 4 shows the process in a schematic way.

NOTE The order of the two sections for “open” and “occluded” measurements is interchangeable.
Figure 4 — Flowchart for method 2b and 3b
5.4 Audiometric-based method (method 3)
5.4.1 Sound field generated by a headset (method 3a)
This method is only applicable to earplugs. Similar as with audiometers the threshold of hearing of the
test subject is determined twice, with and without earplug. The device for the threshold determination is
custom-built and in some cases can be designed only for products of one manufacturer. The difference to
audiometers can lie in the test sounds (pure tones, narrow-band), the measurable frequencies and the
headset.
The remarks from 5.3 on headset fitting, number of frequencies and background noise apply here as well.
The handling for threshold determination may be more automated or pre-determined. Additionally, such
devices do not require an annual calibration as a medical product, unlike audiometer
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