SIST EN ISO 4869-2:2019

Acoustics - Hearing protectors - Part 2: Estimation of effective A-weighted sound pressure levels when hearing protectors are worn (ISO 4869-2:2018)

This document specifies three methods (the octave-band, HML and SNR methods) of estimating
the A-weighted sound pressure levels effective when hearing protectors are worn. The methods are
applicable to either the sound pressure level or the equivalent continuous sound pressure level of the
noise. Although primarily intended for steady noise exposures, the methods are also applicable to
noises containing impulsive components. It is possible that these methods could not be suitable for use
with peak sound pressure level measurements.
The octave-band, H, M, L or SNR values are suitable for establishing sound attenuation criteria for
selecting or comparing hearing protectors, and/or setting minimum acceptable sound attenuation
requirements.

Akustik - Gehörschützer - Teil 2: Abschätzung der beim Tragen von Gehörschützern wirksamen A-bewerteten Schalldruckpegel (ISO 4869-2:2018)

Dieses Dokument legt drei Verfahren zur Abschätzung des beim Tragen von Gehörschützern wirksamen A bewerteten Schalldruckpegels (das Oktavband , das HML  und das SNR Verfahren) fest. Die Verfahren sind entweder auf den Schalldruckpegel des Lärms oder dessen äquivalenten Dauerschalldruckpegel an-wendbar. Obwohl sie primär für die Exposition gegenüber stationären Lärms bestimmt sind, sind sie auch auf impulshaltige Geräusche anwendbar. Es ist möglich, dass diese Verfahren nicht für Messungen des Spitzenschalldruckpegels geeignet  sein könnten.
Die Oktavband , H , M , L  oder SNR-Werte sind für die Festlegung von Kriterien bezüglich der Schalldämmung für die Auswahl oder den Vergleich von Gehörschützern und/oder zur Festsetzung von Mindestanforderun¬gen an die Schalldämmung geeignet.

Acoustique - Protecteurs individuels contre le bruit - Partie 2: Estimation des niveaux de pression acoustique pondérés A en cas d'utilisation de protecteurs individuels contre le bruit (ISO 4869-2:2018)

Le présent document spécifie trois méthodes (la méthode par bande d'octave, la méthode HML et la méthode SNR) pour estimer les niveaux de pression acoustique effectifs pondérés A en cas d'utilisation de protecteurs individuels contre le bruit. Ces méthodes s'appliquent soit au niveau de pression acoustique, soit au niveau de pression acoustique continu équivalent du bruit. Bien que ces méthodes soient essentiellement prévues pour des expositions à un bruit continu, elles s'appliquent également à des bruits comportant des composantes impulsives. Il est possible que ces méthodes ne soint pas appropriées pour des mesures de niveau de pression acoustique de crête.
Les valeurs par bandes d'octave, H, M, L ou SNR conviennent pour établir des critères d'affaiblissement acoustique qui serviront à sélectionner ou à comparer les protecteurs individuels contre le bruit et/ou à établir des exigences minimales acceptables pour l'affaiblissement acoustique.

Akustika - Oprema za varovanje sluha - 2. del: Ocena efektivne A-vrednotene ravni zvočnega tlaka pri nošenju osebne varovalne opreme pred hrupom (ISO 4869-2:2018)

Ta dokument določa tri metode (oktavno metodo, metodo HML in metodo SNR) za ocenjevanje efektivne A-vrednotene ravni zvočnega tlaka pri nošenju osebne varovalne opreme pred hrupom. Metode se uporabljajo za raven zvočnega tlaka ali enakovredno neprekinjeno raven zvočnega tlaka hrupa. Čeprav so metode primarno namenjene izpostavljenosti stalnemu hrupu, se uporabljajo tudi pri hrupu z impulzivnimi komponentami. Te metode morda niso primerne za uporabo pri merjenju vršne ravni zvočnega tlaka.
Oktavne vrednosti, vrednosti H, M, L ali SNR so primerne za vzpostavljanje meril dušenja zvoka pri izbiri ali primerjavi opreme za varovanje sluha in/ali določitvi zahtev glede minimalnega sprejemljivega dušenja zvoka.

General Information

• Status: Published
• Public Enquiry End Date: 04-Mar-2015
• Publication Date: 09-Dec-2018
• ICS: 13.340.20 - Head protective equipment
• ICS: 17.140.01 - Acoustic measurements and noise abatement in general
• Technical Committee: AKU - Acoustics
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 04-Dec-2018
• Due Date: 08-Feb-2019
• Completion Date: 10-Dec-2018
• Directive: 89/686/EEC - Council Directive 89/686/EEC of 21 December 1989 on the approximation of the laws of the Member States relating to personal protective equipment
• Ref Project: EN ISO 4869-2:2018 - Acoustics - Hearing protectors - Part 2: Estimation of effective A-weighted sound pressure levels when hearing protectors are worn (ISO 4869-2:2018)

Relations

• Replaces: SIST EN ISO 4869-2:1999 - Acoustics - Hearing protectors - Part 2: Estimation of effective A-weighted sound pressure levels when hearing protectors are worn (ISO 4869-2:1994)
• Effective Date: 01-Jan-2019
• Replaces: SIST EN ISO 4869-2:1999/AC:2007 - Acoustics - Hearing protectors - Part 2: Estimation of effective A-weighted sound pressure levels when hearing protectors are worn (ISO 4869-2:1994/Cor 1:2006)
• Effective Date: 01-Jan-2019
• Replaces: SIST EN ISO 4869-2:1999 - Acoustics - Hearing protectors - Part 2: Estimation of effective A-weighted sound pressure levels when hearing protectors are worn (ISO 4869-2:1994)
• Effective Date: 08-Jun-2022

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 4869-2:2019
01-januar-2019
1DGRPHãþD
SIST EN ISO 4869-2:1999
SIST EN ISO 4869-2:1999/AC:2007
$NXVWLND2SUHPD]DYDURYDQMHVOXKDGHO2FHQDHIHNWLYQH$YUHGQRWHQHUDYQL
]YRþQHJDWODNDSULQRãHQMXRVHEQHYDURYDOQHRSUHPHSUHGKUXSRP,62

Acoustics - Hearing protectors - Part 2: Estimation of effective A-weighted sound
pressure levels when hearing protectors are worn (ISO 4869-2:2018)
Akustik - Gehörschützer - Teil 2: Abschätzung der beim Tragen von Gehörschützern
wirksamen A-bewerteten Schalldruckpegel (ISO 4869-2:2018)
Acoustique - Protecteurs individuels contre le bruit - Partie 2: Estimation des niveaux de
pression acoustique pondérés A en cas d'utilisation de protecteurs individuels contre le
bruit (ISO 4869-2:2018)
Ta slovenski standard je istoveten z: EN ISO 4869-2:2018
ICS:
13.340.20 Varovalna oprema za glavo Head protective equipment
17.140.01 $NXVWLþQDPHUMHQMDLQ Acoustic measurements and
EODåHQMHKUXSDQDVSORãQR noise abatement in general
SIST EN ISO 4869-2:2019 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------

SIST EN ISO 4869-2:2019

---------------------- Page: 2 ----------------------

SIST EN ISO 4869-2:2019


EN ISO 4869-2
EUROPEAN STANDARD

NORME EUROPÉENNE

November 2018
EUROPÄISCHE NORM
ICS 13.340.20 Supersedes EN ISO 4869-2:1995
English Version

Acoustics - Hearing protectors - Part 2: Estimation of
effective A-weighted sound pressure levels when hearing
protectors are worn (ISO 4869-2:2018)
Acoustique - Protecteurs individuels contre le bruit - Akustik - Gehörschützer - Teil 2: Abschätzung der beim
Partie 2: Estimation des niveaux de pression Tragen von Gehörschützern wirksamen A-bewerteten
acoustique pondérés A en cas d'utilisation de Schalldruckpegel (ISO 4869-2:2018)
protecteurs individuels contre le bruit (ISO 4869-
2:2018)
This European Standard was approved by CEN on 23 April 2018.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, 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
© 2018 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 4869-2:2018 E
worldwide for CEN national Members.

---------------------- Page: 3 ----------------------

SIST EN ISO 4869-2:2019
EN ISO 4869-2:2018 (E)
Contents Page
European foreword . 3

2

---------------------- Page: 4 ----------------------

SIST EN ISO 4869-2:2019
EN ISO 4869-2:2018 (E)
European foreword
This document (EN ISO 4869-2:2018) has been prepared by Technical Committee ISO/TC 43
"Acoustics" in collaboration with Technical Committee CEN/TC 211 “Acoustics” the secretariat of which
is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by May 2019, and conflicting national standards shall be
withdrawn at the latest by May 2019.
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.
This document supersedes EN ISO 4869-2:1995.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Endorsement notice
The text of ISO 4869-2:2018 has been approved by CEN as EN ISO 4869-2:2018 without any
modification.

3

---------------------- Page: 5 ----------------------

SIST EN ISO 4869-2:2019

---------------------- Page: 6 ----------------------

SIST EN ISO 4869-2:2019
INTERNATIONAL ISO
STANDARD 4869-2
Second edition
2018-10
Acoustics — Hearing protectors —
Part 2:
Estimation of effective A-weighted
sound pressure levels when hearing
protectors are worn
Acoustique — Protecteurs individuels contre le bruit —
Partie 2: Estimation des niveaux de pression acoustique pondérés A en
cas d'utilisation de protecteurs individuels contre le bruit
Reference number
ISO 4869-2:2018(E)
©
ISO 2018

---------------------- Page: 7 ----------------------

SIST EN ISO 4869-2:2019
ISO 4869-2:2018(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2018
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved

---------------------- Page: 8 ----------------------

SIST EN ISO 4869-2:2019
ISO 4869-2:2018(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Measurement of sound attenuation of hearing protectors . 2
5 Calculation of the assumed protection value, APV , of a hearing protector for a
fx
selected protection performance . 2
6 Octave-band method. 3
7 HML method . 4
7.1 General . 4
7.2 Calculation of H, M and L values . 4
7.3 Application of HML method for estimation of the effective A-weighted sound
pressure level . 6
8 SNR method . 6
8.1 General . 6
8.2 Calculation of SNR values . 6
8.3 Application of SNR method for estimation of the effective A-weighted sound
pressure level . 7
Annex A (informative) Example of the calculation of the assumed protection values, APV .9
fx
Annex B (informative) Example of the calculation of L′ according to the octave-band method .10
p,Ax
Annex C (informative) Example of the calculation and use of H, M and L values .11
Annex D (informative) Example of the calculation and use of SNR values .14
Annex E (informative) Uncertainty of attenuation values and ratings .16
Bibliography .18
© ISO 2018 – All rights reserved iii

---------------------- Page: 9 ----------------------

SIST EN ISO 4869-2:2019
ISO 4869-2:2018(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www. iso. org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www. iso.o rg/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www. iso. org/iso/foreword. html.
This document was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 1, Noise.
This second edition cancels and replaces the first edition (ISO 4869-2:1994) which has been technically
revised. It also incorporates the corrected version ISO 4869-2:1994/Cor.1:2006.
The main technical changes are:
In the prior edition of the standard the H, M, L, and SNR values were computed from the group average
data by frequency. In this edition, the values are computed subject by subject and then combined
to provide both a mean value and a standard deviation value so that population distribution can be
estimated. The sound attenuation values for the frequency 63 Hz have been excluded from the H, M, L
and SNR calculation methods since this test frequency is optional in ISO 4869-1. Prior to rounding to
the nearest integer, values derived using this edition deviate from those derived using the previous
edition by less than 1 dB.
A list of all parts in the ISO 4869 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www. iso. org/members. html.
iv © ISO 2018 – All rights reserved

---------------------- Page: 10 ----------------------

SIST EN ISO 4869-2:2019
ISO 4869-2:2018(E)

Introduction
This document estimates an “effective” level, i.e. the A-weighted sound pressure level at the head centre
with the listener absent, minus the attenuation of the hearing protection devices. Effective values are
estimated since those are required to assess noise hazard with respect to permissible noise exposure
limits. An effective level differs from that in the ear canal since it has been converted to a sound-field
value via the transfer function of the open ear. Effective levels are typically 5 dB to 10 dB less than ear
canal levels depending on the spectrum of the incident noise.
Ideally, the A-weighted sound pressure level effective when a hearing protector is worn should be
estimated on the basis of both the octave-band sound attenuation data of the hearing protector
(measured in accordance with ISO 4869-1) and the octave-band sound pressure levels of the noise. It
is recognized, however, that in many situations information on the octave-band sound pressure levels
of the noise might not be available. Therefore, for many practical purposes, there is a need for simpler
methods to determine the effective A-weighted sound pressure levels which are only based on the A-
and C-weighted sound pressure levels of the noise. This document addresses both of these situations
by specifying an octave-band calculation method as well as two alternative simplified procedures, the
HML method and the SNR method.
The octave-band method is a calculation method involving the workplace octave-band sound pressure
levels and the octave-band sound attenuation data for the hearing protector that is being assessed.
Although it can be thought of as an "exact" reference method, it has its own inherent inaccuracies, since
it is based upon mean sound attenuation values and standard deviations for a group of test subjects,
and not the specific sound attenuation values for the individual person in question.
The HML method specifies three attenuation values, H, M and L, determined from the octave-band
sound attenuation data of a hearing protector. These values, when combined with the C- and A-weighted
sound pressure levels of the noise, are used to calculate the effective A-weighted sound pressure level
when the hearing protector is worn.
The SNR method specifies a single attenuation value, the single number rating, determined from the
octave-band sound attenuation data of a hearing protector. This value is subtracted from the C-weighted
sound pressure level of the noise to calculate the effective A-weighted sound pressure level when the
hearing protector is worn.
Due to the large spread of the sound attenuation provided by hearing protectors when worn by
individual persons, all three methods are nearly equivalent in their accuracy in the majority of noise
situations. Even the simplest method, the SNR method, will provide a reasonably accurate estimate
of the effective A-weighted sound pressure level to aid in the selection and specification of hearing
protectors. In special situations, for example especially high- or low-frequency noises, it is necessary to
use either the HML or the octave-band method.
Depending on the choice of a certain parameter in the calculation process, various protection
performances can be obtained. It should be noted that the protection performance values for all three
methods are only valid when:
— the hearing protectors are worn correctly and in the same manner as they were worn by subjects
when carrying out the ISO 4869-1 test;
— the hearing protectors are properly maintained;
— the anatomical characteristics of the subjects involved in the ISO 4869-1 test are a reasonable match
for the population of actual wearers.
Thus, the principal source of potential inaccuracy in use of the three methods described in this document
is the basic ISO 4869-1 input data. If the input data do not accurately describe the degree of protection
achieved by the target population, then no calculation method will provide sufficient accuracy.
© ISO 2018 – All rights reserved v

---------------------- Page: 11 ----------------------

SIST EN ISO 4869-2:2019
ISO 4869-2:2018(E)

The uncertainty of the attenuation values and ratings is described in Annex E.
NOTE Differences of 3 dB or less in the determination of the effective sound pressure level for comparable
hearing protectors are generally insignificant.
vi © ISO 2018 – All rights reserved

---------------------- Page: 12 ----------------------

SIST EN ISO 4869-2:2019
INTERNATIONAL STANDARD ISO 4869-2:2018(E)
Acoustics — Hearing protectors —
Part 2:
Estimation of effective A-weighted sound pressure levels
when hearing protectors are worn
1 Scope
This document specifies three methods (the octave-band, HML and SNR methods) of estimating
the A-weighted sound pressure levels effective when hearing protectors are worn. The methods are
applicable to either the sound pressure level or the equivalent continuous sound pressure level of the
noise. Although primarily intended for steady noise exposures, the methods are also applicable to
noises containing impulsive components. It is possible that these methods could not be suitable for use
with peak sound pressure level measurements.
The octave-band, H, M, L or SNR values are suitable for establishing sound attenuation criteria for
selecting or comparing hearing protectors, and/or setting minimum acceptable sound attenuation
requirements.
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.
ISO 4869-1, Acoustics — Hearing protectors — Part 1: Subjective method for the measurement of sound
attenuation
ISO 9612:2009, Acoustics — Determination of occupational noise exposure — Engineering method
IEC 61672-1, Electroacoustics — Sound level meters — Part 1: Specifications
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 4869-1 and the following 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 http: //www .electropedia .org/
3.1
protection performance
x
percentage of individuals for which the achieved protection is equal to or greater than the designated
value, where the percentage is indicated by adding a subscript to the symbols representing the different
methods, e.g. APV H , M , L , SNR
fx, x x x x
Note 1 to entry: The value of protection performance is often chosen to be 84 % [corresponding to the constant
α = 1 (see Clause 5)].
© ISO 2018 – All rights reserved 1

---------------------- Page: 13 ----------------------

SIST EN ISO 4869-2:2019
ISO 4869-2:2018(E)

3.2
effective A-weighted sound pressure level
L′
p,Ax
A-weighted sound pressure level effective when a given hearing protector is worn for a specified
protection performance, x, and a specific noise situation
Note 1 to entry: It is calculated in accordance with any of the three methods specified in ISO 4869-2.
3.3
predicted noise level reduction
PNR
x
difference between the A-weighted sound pressure level of the noise, L , and the effective A-weighted
p,A
sound pressure level, L′ when a given hearing protector is worn for a specified protection
p,Ax
performance, x, and a specific noise situation
3.4
assumed protection value
APV
fx
value representing the attenuation in that octave band for a particular octave band, f, a specified
protection performance, x, and a given hearing protector
3.5
high-frequency attenuation value
H
x
value representing the predicted noise level reduction, PNR , for noises with (L − L ) = −2 dB for a
x p,C p,A
specified protection performance, x, and a given hearing protector
3.6
medium-frequency attenuation value
M
x
value representing the predicted noise level reduction, PNR , for noises with (L − L ) = +2 dB for a
x p,C p,A
specified protection performance, x, and a given hearing protector
3.7
low-frequency attenuation value
L
x
value representing the predicted noise level reduction, PNR , for noises with (L − L ) = +10 dB for a
x p,C p,A
specified protection performance, x, and a given hearing protector
3.8
single number rating
SNR
x
value that is subtracted from the measured C-weighted sound pressure level, L , in order to estimate
p,C
the effective A-weighted sound pressure level, L′ for a specified protection performance, x, and a
p,Ax
given hearing protector
4 Measurement of sound attenuation of hearing protectors
The one-third-octave-band attenuation values of the hearing protector to be used in the calculation
methods specified in this part of ISO 4869 shall be measured in accordance with ISO 4869-1.
5 Calculation of the assumed protection value, APV , of a hearing protector for a
fx
selected protection performance
The calculation begins with the selection of the desired protection performance, x, and the associated
constant α (see Table 1). When α = 1 and x = 84 %, the subscripts to the attenuation values may be
omitted.
2 © ISO 2018 – All rights reserved

---------------------- Page: 14 ----------------------

SIST EN ISO 4869-2:2019
ISO 4869-2:2018(E)

The assumed protection value, APV , of the hearing protector is calculated for each octave band using
fx
the following formula:
APV = m − α s (1)
fx f f
where
subscript f represents the centre frequency of the octave band;
subscript x represents the selected protection performance;
m is the mean sound attenuation determined in accordance with ISO 4869-1;
f
s is the standard deviation determined in accordance with ISO 4869-1;
f
α is the inverse of the standard normal cumulative distribution for a specific protection
performance, having the values given in Table 1.
Table 1 — Values of α for various protection performances x
Protection performance x Value of α
%
50 0,00
75 0,67
80 0,84
84 1,00
90 1,28
95 1,64
98 2,00
An example of the calculation of the assumed protection values, APV , is given in Annex A.
fx
6 Octave-band method
This method requires octave-band sound pressure levels of the noise and assumed protection values,
APV . Since the method is noise specific, the calculation shall be made for each noise situation.
fx
The A-weighted sound pressure level effective when the hearing protector is worn, L′ , is calculated
p,Ax
using the following formula:
8
01,(LA+−A PV )
pf,(kf)(kf) ()kx
L′ =10lg 10 dB (2)
p,Ax
∑
k=1
where
subscripts f(k) represent the octave-band mid-frequency; f(1) = 63 Hz; f(2) = 125 Hz;
f(3) = 250 Hz; …; f(8) = 8 000 Hz;
L is the sound pressure level of the noise in the octave band;
p,f(k)
A is the frequency weighting A in accordance with IEC 61672-1 at the octave-band
f(k)
mid-frequencies (see Table B.1).
If 63 Hz octave-band data for either the noise or the hearing protector are not available, then the
summation in Formula (2) begins at 125 Hz. For the subsequent HML and SNR methods the computations
© ISO 2018 – All rights reserved 3

---------------------- Page: 15 ----------------------

SIST EN ISO 4869-2:2019
ISO 4869-2:2018(E)

always begin at 125 Hz regardless of the availability of the data at 63 Hz. The resulting L′ value shall
p,Ax
be rounded to the nearest integer.
An example of the estimation of the effective A-weighted sound pressure level when a given hearing
protector is worn in a specific noise situation is given in Annex B.
7 HML method
7.1 General
This method requires C- and A-weighted sound pressure levels of the noise and H, M and L values.
7.2 Calculation of H, M and L values
Calculation of the H , M and L values in dB is based on eight reference noise spectra with different
x x x
(L − L ) values (see Table 2) and the individual sound attenuation values, a , of the hearing
p,C p,A jf(k)
protector. The values are independent of the actual noise situation to which they are applied, and are
calculated using the following formulae, where H , M , and L , refer to the mean values of the indices,
m m m
and H , M and L refer to the standard deviations of those indices:
s s, s
H = H − αH (3)
x m s
M = M − αM (4)
x m s
L = L − αL (5)
x m s
where
subscript x represents the selected protection performance;
α is a constant specified in Table 1.
N
1
H = H (6)
mj∑
N
j=1
N
1
M = M (7)
mj∑
N
j=1
N
1
L = L (8)
mj∑
N
j=1
N
1
2
H = ()HH− (9)
sj m
∑
N−1
j=1
N
1
2
M = ()MM− (10)
sj∑ m
N−1
j=1
N
1
2
L = ()LL− (11)
sj m
∑
N−1
j=1
4 © ISO 2018 – All rights reserved

---------------------- Page: 16 ----------------------

SIST EN ISO 4869-2:2019
ISO 4869-2:2018(E)

4 4
HP=−02,,50NR 48 dPNR (12)
jj∑ ii∑ ji
i=1 i=1
8 8
MP=−02,,50NR 16 dPNR (13)
jj∑ ii∑ ji
i=5 i=5
8 8
LP=+02,,50NR 23 dPNR (14)
jj∑ ii∑ ji
i=5 i=5
8
01,(L −a )
pf,(A ()ki jf k)
PNR =−100dB 10lg 10 dB (15)
ji ∑
k=2
where
N is the number of subjects;
a is the sound attenuation value in dB for subject j and frequency f(k) determined in
jf(k)
accordance with ISO 4869-1;
subscript j represents the number of the test subject;
subscript i represents the number of the reference noise spectrum;
L and d values are given in Table 2.
p,Af(k)i i
NOTE In Formula (15), the value of 100 dB represents the total A-weighted sound pressure level of each of
the noises in Table 2 specified for the octave bands from 125 Hz to 8 000 Hz.
The resulting H , M and L values shall be rounded to the nearest integer.
x x x
An example of the calculation of the H, M and L values is given in Annex C.
Table 2 — A-weighted octave-band sound pressure levels, L , of eight reference noises, i,
p,Af(k)i
normalized to an A-weighted sound pressure level of 100 dB, (L − L ) values and constants d
p,C p,A i
A-weighted octave-band sound pressure levels, L , dB
p,Af(k)i
Octave-band centre frequency, f, Hz
(L − L )
p,C p,A
i k d
i
dB
125 250 500 1 000 2 000 4 000 8 000
k = 2 … … … … … k = 8
1 62,6 70,8 81,0 90,4 96,2 94,7 92,3 −1,2 −1,20
2 68,9 78,3 84,3 92,8 96,3 94,0 90,0 −0,5 −0,49
3 71,1 80,8 88,0 95,0 94,4 94,1 89,0 0,1 0,14
4 77,2 84,5 89,8 95,5 94,3 92,5 88,8 1,6 1,56
5 77,4 86,5 92,5 96,4 93,0 90,4 83,7 2,3 −2,98
6 82,0 89,3 93,3 95,6 93,0 90,1 83,0 4,3 −1,01
7 84,2 90,1 93,6 96,2 91,3 87,9 81,9 6,1 0,85
8 88,0 93,4 93,8 94,2 91,4 87,9 79,9 8,4 3,14
[1][2]
NOTE 1  d is an empirically derived number .
i
NOTE 2  The value of 100 dB for the total A-weighted sound pressure level, L , is arbitrary and was chosen for
p,A
computational simplicity.
© ISO 2018 – All rights reserved 5

---------------------- Page: 17 ----------------------

SIST EN ISO 4869-2:2019
ISO 4869-2:2018(E)

7.3 Application of HML method for estimation of the effective A-weighted sound
pressure level
The effective A-weighted sound pressure level, L′ , is calculated in two steps as follows.
p,Ax
a) The predicted noise level reduction, PNR , is calculated from the H , M and L values and the C- and
x x x x
A-weighted sound pressure levels of the noise. The calculations are as follows.
For noises with (L − L ) ≤ 2 dB
p,C p,A
HM−
xx
PNRM=− ()LL−−2dB (16)
xx pp,,CA
4
For noises with (L  − L ) > 2 dB
p,C p,A
ML−
xx
PNRM=− ()LL−−2dB (17)
xx pp,,CA
8
b)
...