ISO/DTS 1999

Acoustics — Estimation of noise-induced hearing loss

See Annex.

Acoustique — Estimation de la perte auditive induite par le bruit

General Information

• Status: Not Published
• ICS: 13.140 - Noise with respect to human beings
• Technical Committee: ISO/TC 43 - Acoustics
• Drafting Committee: ISO/TC 43 - Acoustics
• Current Stage: 5092 - FDIS referred back to TC or SC
• Start Date: 23-Jul-2025
• Completion Date: 26-Jul-2025

Relations

• Revises: ISO 1999:2013 - Acoustics — Estimation of noise-induced hearing loss
• Effective Date: 06-Jun-2022

Standards Content (Sample)

FINAL DRAFT
Technical
Specification
ISO/TC 43
Acoustics — Estimation of noise-
Secretariat: DIN
induced hearing loss
Voting begins on:
Acoustique — Estimation de la perte auditive induite par le bruit 2025-04-30
Voting terminates on:
2025-06-25
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WITH THEIR COMMENTS, NOTIFICATION OF ANY
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INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
FINAL DRAFT
Technical
Specification
ISO/TC 43
Acoustics — Estimation of noise-
Secretariat: DIN
induced hearing loss
Voting begins on:
Acoustique — Estimation de la perte auditive induite par le bruit
Voting terminates on:
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 SUPPOR TING DOCUMENTATION.
© ISO 2025
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 2
3 Terms and definitions . 2
4 Principle . 3
5 Description and measurement of noise exposure . 4
6 Prediction of the effects of noise on hearing threshold . 4
6.1 Statistical distribution of hearing threshold levels of a noise-exposed population .4
6.2 Databases for hearing threshold levels associated with age (HTLA) .4
6.2.1 General .4
6.2.2 Database A .5
6.2.3 Database B.5
6.2.4 Choice of database.5
6.3 Calculation of effect of noise, N .5
7 Assessment of noise-induced hearing loss and impairment .10
7.1 Hearing loss due to noise .10
7.2 Hearing impairment .10
7.3 Risk of hearing impairment due to noise .10
Annex A (informative) Database A, selected values of the statistical distribution of hearing
threshold deviations as a function of age (HTLA) for an otologically normal population
(highly screened) .11
Annex B (informative) Examples for database B .13
Annex C (informative) Examples of calculations of effect of noise, N .23
Annex D (informative) Example of the calculation of risk of hearing impairment due to noise
exposure .25
Annex E (informative) Kurtosis-adjusted noise exposure level normalized to an 8 h working
day, L’ .29
p,A,8 h
Annex F (informative) Derivation of values of effect of noise, N.32
Bibliography .34

iii
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of 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 www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 43, Acoustics.
This fourth edition cancels and replaces the third edition (ISO 1999:2013), which has been technically
revised.
The main changes are as follows:
— The second and third editions of this standard were based on estimates of effect of noise, N, developed
using the empirical models of two databases (see References [2] and [22]). However, traceability
of the derivation of those estimates has been lost and the Working Group of Technical Committee
43, ISO/TC43/WG1 “Threshold of Hearing,” has been unable to assess its validity. The values of N in
this technical specification were derived from the hearing threshold levels calculated from the same
empirical models as the previous versions (see Annex F).
— In this edition, a recommendation for an adjustment is made to the noise exposure level to improve
prediction of hearing threshold levels for people exposed to noise with substantial impulse/impact
components (see Annex E).
— This revised version introduces a tabular representation of the effect of noise, N, with interpolation
between tabled values to replace the formulae presented by previous editions.
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
Introduction
This document presents, in statistical terms, the relationship between noise exposure, unprotected unless
otherwise stated, and its effect on hearing threshold levels in people of various ages. This document provides
procedures for estimating the hearing loss due to noise exposure in populations by comparison to various
non-noise exposed populations. For any given noise exposure, effect of noise, N, has a range of positive values
reflecting the variability of susceptibility to noise-induced hearing loss among individuals.
Persons regularly exposed to noise can develop hearing loss of varying severity. Due to hearing loss, their
understanding of speech, perception of everyday acoustic signals, or appreciation of music can be impaired.
With the exception of traumatic damage to the ear caused by exposure to blast, high-impulse noise and
extremely high levels of steady-state noise, permanent impairment of the hearing organ takes time and
is progressive over months, years, or decades of exposure. For a single individual, it is not possible to
determine precisely which changes in hearing threshold level are caused by noise and which changes are
caused by other factors. However, for a sufficiently large population exposed to a specific noise, changes in
the statistical distributions of hearing threshold levels can be determined. Predictions from this technical
specification can be used to describe differences in hearing threshold levels between two populations that
are similar in all relevant respects except that one population has had a well-defined (usually occupational)
noise exposure.
Researchers have for many years found that noise with substantial impulse/impact components is more
hazardous to hearing than noise at similar sound pressure levels without substantial impulse/impact
components. In this edition, an adjustment is made to the noise exposure level to improve prediction of
hearing threshold levels for people exposed to noise with substantial impulse/impact components. The
adjustment is based on the distribution of values in the sound pressure waveform using the statistical
measure kurtosis (see Annex E).
This document was derived from the hearing threshold levels calculated from the same empirical models as
the previous versions (References [2] and [22]; see Annex F). document uses the formula H’ = H + N – (H x N
/120) to calculate expected hearing threshold level (H’) from the combination of components due to noise
(N) and other factors, principally age (H). In order to derive the noise-induced component, this formula was
rearranged to calculate the values of N shown in Tables 1 and 2of this revision: N = (H’ – H)/(1- H/120),
where each value of N was calculated using the unweighted arithmetic mean, or average, of the two values of
H’ and the two values of H in the two databases at each frequency, noise level, duration and percentile value
shown in the table. Interpolation between values of N in Tables 1 and 2 enables calculation of values of N
not included in the table. The formulation was validated by comparison with a broader set of published data
on noise-induced hearing loss, as compiled in Reference [26]. A Hearing Th
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Acoustics — Estimation of noise-induced hearing loss
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Commented [eXtyles1]: The reference "ISO 2025" is to a
withdrawn standard
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
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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 Formatted: Default Paragraph Font
at the address below or ISO’s member body in the country of the requester.
Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
Formatted: French (France)
EmailE-mail: [e-mail]
Formatted: French (France)
Website: www.iso.orgwww.iso.org
Formatted: French (France)
Published in Switzerland
Formatted: Font: 10 pt
Formatted: Font: 10 pt
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Formatted: FooterPageRomanNumber, Space After: 0
pt, Line spacing: single
ii © ISO 2025 – All rights reserved
ii
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Contents
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Foreword . v
Adjust space between Asian text and numbers
Introduction . vi
1 Scope . 1
2 Normative references . 2
3 Terms and definitions . 2
4 Principle . 4
5 Description and measurement of noise exposure . 4
6 Prediction of the effects of noise on hearing threshold . 5
6.1 Statistical distribution of hearing threshold levels of a noise-exposed population . 5
6.2 Databases for hearing threshold levels associated with age (HTLA) . 5
6.3 Calculation of effect of noise, N . 6
7 Assessment of noise-induced hearing loss and impairment . 11
7.1 Hearing loss due to noise . 11
7.2 Hearing impairment . 11
7.3 Risk of hearing impairment due to noise . 12
Annex A (informative) Database A, selected values of the statistical distribution of hearing
threshold deviations as a function of age (HTLA) for an otologically normal population
(highly screened) . 13
Annex B (informative) Examples for database B . 15
Annex C (informative) Examples of calculations of effect of noise, N . 25
Annex D (informative) Example of the calculation of risk of hearing impairment due to noise
exposure . 28
Annex E (informative) Kurtosis-adjusted noise exposure level normalized to an 8 h working
day, L’p,A,8 h . 33
Annex F (informative) Derivation of values of effect of noise, N . 36
Bibliography . 38

Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Principle . 5
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5 Description and measurement of noise exposure . 5
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6 Prediction of the effects of noise on hearing threshold . 5
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6.1 Statistical distribution of hearing threshold levels of a noise-exposed population . 5
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Tab stops: Not at 17.2 cm
6.2 Databases for hearing threshold levels associated with age (HTLA) . 5
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6.2.1 General. 5
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6.2.2 Database A . 6
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© ISO 2025 – All rights reserved
iii
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6.2.3 Database B . 6
6.2.4 Choice of database . 6
6.3 Calculation of effect of noise, N
7 Assessment of noise-induced hearing loss and impairment . 12
7.1 Hearing loss due to noise . 12
7.2 Hearing impairment . 12
7.3 Risk of hearing impairment due to noise
Annex A (informative) Database A, selected values of the statistical distribution of hearing
threshold deviations as a function of age (HTLA) for an otologically normal population
(highly screened) . 1313
Annex B (informative) Examples for database B . 215
B.1 Selected values from database B.1 . 215
B.2 Selected values from database B.2 . 417
B.3 Selected values from database B.3 . 619
B.4 Selected values from database B.4 . 821
B.5 Selected values from database B.5 . 1023
Annex C (informative) Examples of calculations of effect of noise, N
Annex D (informative) Example of the calculation of risk of hearing impairment due to noise
exposure . 1326
Annex E (informative) Kurtosis-adjusted noise exposure level normalized to an 8 h working day,
'
L
p,A,8h
Annex F (informative) Derivation of values of effect of noise, N
Bibliography . 1831
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iv © ISO 2025 – All rights reserved
iv
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Formatted: Font: Bold
Foreword
Formatted: HeaderCentered, Left
ISO (the International Organization for Standardization) is a worldwide federation of national standards Formatted: Adjust space between Latin and Asian text,
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through Adjust space between Asian text and numbers
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 document 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).
Formatted: English (United Kingdom)
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents.www.iso.org/patents. ISO shall not be held responsible for identifying any or all such
patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of 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
www.iso.org/iso/foreword.htmlwww.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 43, Acoustics.
Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers
This fourth edition cancels and replaces the third edition (ISO 1999:2013), which has been technically revised.
Formatted: Default Paragraph Font
Formatted: Default Paragraph Font
The main changes ar
...