SIST EN ISO 11690-1:2021

Acoustics - Recommended practice for the design of low-noise workplaces containing machinery - Part 1: Noise control strategies (ISO 11690-1:2020)

This document outlines strategies to be used in dealing with noise problems in existing and planned
workplaces by describing basic concepts in noise control (noise reduction, noise emission, noise
immission and noise exposure). It is applicable to all types of workplaces and all types of sources of
sound which are met in workplaces, including human activities.
It includes those important strategies to adopt when buying a new machine or equipment.
This document deals only with audible sound.

Akustik - Richtlinien für die Gestaltung lärmarmer maschinenbestückter Arbeitsstätten - Teil 1: Allgemeine Grundlagen (ISO 11690-1:2020)

Ausgehend von der Beschreibung der grundlegenden Konzepte des Schallschutzes (Lärmminderung, Geräuschemission, Geräuschimmission und Geräuschexposition), beschreibt dieses Dokument Strategien für die Behandlung von Lärmproblemen in bestehenden und geplanten Arbeitsstätten. Es ist anwendbar auf alle Arten von Arbeitsstätten und alle Arten von Schall, die in Arbeitsräumen vorkommen können, wobei auch menschliche Tätigkeiten eingeschlossen sind.
Sie enthält wichtige Hinweise, die beim Kauf einer neuen Maschine oder Anlage anzuwenden sind.
Dieses Dokument befasst sich ausschließlich mit Hörschall.

Acoustique - Pratique recommandée pour la conception de lieux de travail à bruit réduit contenant des machines - Partie 1: Stratégies de maîtrise du bruit (ISO 11690-1:2020)

Le présent document présente les stratégies à mettre en œuvre pour traiter les problèmes de bruit sur les lieux de travail existants ou en projet, en s'appuyant sur des concepts de base liés à la maîtrise du bruit (maîtrise du bruit, émission sonore, bruit ambiant et exposition au bruit). Il s'applique à tous les types de lieux de travail et de sources de bruit rencontrées sur les lieux de travail, activités humaines comprises.
Il inclut les stratégies importantes à adopter lors de l'achat d'une nouvelle machine ou d'un nouvel équipement.
Le présent document ne traite que des sons audibles.

Akustika - Priporočena praksa za oblikovanje tihih delovnih mest - 1. del: Strategija obvladovanja hrupa (ISO 11690-1:2020)

General Information

• Status: Published
• Public Enquiry End Date: 09-Sep-2020
• Publication Date: 26-Jan-2021
• ICS: 13.140 - Noise with respect to human beings
• ICS: 17.140.20 - Noise emitted by machines and equipment
• Technical Committee: AKU - Acoustics
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 30-Nov-2020
• Due Date: 04-Feb-2021
• Completion Date: 27-Jan-2021
• Ref Project: EN ISO 11690-1:2020 - Acoustics - Recommended practice for the design of low-noise workplaces containing machinery - Part 1: Noise control strategies (ISO 11690-1:2020)

Relations

• Replaces: SIST EN ISO 11690-1:1997 - Acoustics - Recommended practice for the design of low-noise workplaces containing machinery - Part 1: Noise control strategies (ISO 11690-1:1996)
• Effective Date: 01-Mar-2021

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 11690-1:2021
01-marec-2021
Nadomešča:
SIST EN ISO 11690-1:1997
Akustika - Priporočena praksa za oblikovanje tihih delovnih mest - 1. del:
Strategija obvladovanja hrupa (ISO 11690-1:2020)

Acoustics - Recommended practice for the design of low-noise workplaces containing

machinery - Part 1: Noise control strategies (ISO 11690-1:2020)

Akustik - Richtlinien für die Gestaltung lärmarmer maschinenbestückter Arbeitsstätten -

Teil 1: Allgemeine Grundlagen (ISO 11690-1:2020)

Acoustique - Pratique recommandée pour la conception de lieux de travail à bruit réduit

contenant des machines - Partie 1: Stratégies de maîtrise du bruit (ISO 11690-1:2020)

Ta slovenski standard je istoveten z: EN ISO 11690-1:2020
ICS:
13.140 Vpliv hrupa na ljudi Noise with respect to human
beings
17.140.20 Emisija hrupa naprav in Noise emitted by machines
opreme and equipment
SIST EN ISO 11690-1:2021 en,fr,de

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

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SIST EN ISO 11690-1:2021
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SIST EN ISO 11690-1:2021
EN ISO 11690-1
EUROPEAN STANDARD
NORME EUROPÉENNE
November 2020
EUROPÄISCHE NORM
ICS 13.140 Supersedes EN ISO 11690-1:1996
English Version
Acoustics - Recommended practice for the design of low-
noise workplaces containing machinery - Part 1: Noise
control strategies (ISO 11690-1:2020)

Acoustique - Pratique recommandée pour la Akustik - Richtlinien für die Gestaltung lärmarmer

conception de lieux de travail à bruit réduit contenant maschinenbestückter Arbeitsstätten - Teil 1:

des machines - Partie 1: Stratégies de maîtrise du bruit Allgemeine Grundlagen (ISO 11690-1:2020)

(ISO 11690-1:2020)
This European Standard was approved by CEN on 17 October 2020.

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

© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 11690-1:2020 E

worldwide for CEN national Members.
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SIST EN ISO 11690-1:2021
EN ISO 11690-1:2020 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 11690-1:2021
EN ISO 11690-1:2020 (E)
European foreword

This document (EN ISO 11690-1:2020) 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 2021, and conflicting national standards shall be

withdrawn at the latest by May 2021.

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 11690-1:1996.

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, 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.
Endorsement notice

The text of ISO 11690-1:2020 has been approved by CEN as EN ISO 11690-1:2020 without any

modification.
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SIST EN ISO 11690-1:2021
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SIST EN ISO 11690-1:2021
INTERNATIONAL ISO
STANDARD 11690-1
Second edition
2020-10
Acoustics — Recommended practice
for the design of low-noise workplaces
containing machinery —
Part 1:
Noise control strategies
Acoustique — Pratique recommandée pour la conception de lieux de
travail à bruit réduit contenant des machines —
Partie 1: Stratégies de maîtrise du bruit
Reference number
ISO 11690-1:2020(E)
ISO 2020
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SIST EN ISO 11690-1:2021
ISO 11690-1:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

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]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
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SIST EN ISO 11690-1:2021
ISO 11690-1:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

3.1 General noise descriptors .............................................................................................................................................................. 1

3.2 Noise emission descriptors .......................................................................................................................................................... 2

3.3 Noise immission and noise exposure .................................................................................................................................. 4

3.4 Noise reduction ...................................................................................................................................................................................... 6

4 Basic concepts in noise control ..........................................................................................................................................................11

4.1 Basic noise control strategy ......................................................................................................................................................11

4.2 Concept of noise reduction ........................................................................................................................................................11

5 Assessment of the noise situation ...................................................................................................................................................12

5.1 Quantities for noise emission, noise immission and noise exposure ...................................................12

5.1.1 Noise emission quantities [see 3.2 and Figure 1 a)] ......................................................................12

5.1.2 Noise immission and noise exposure quantities [see 3.3 and Figures 1 b),

1 c) and 2] ...........................................................................................................................................................................12

5.2 Description of the noise situation .......................................................................................................................................13

5.3 Use of noise information sheets and noise maps ...................................................................................................14

6 Parties involved ..................................................................................................................................................................................................15

7 How to tackle noise problems in workplaces ......................................................................................................................15

7.1 Noise control objectives ...............................................................................................................................................................15

7.2 Principles of noise control planning for new and existing workplaces ..............................................16

7.2.1 General...................................................................................................................................................................................16

7.2.2 Preliminary planning and design stage .....................................................................................................17

7.2.3 Planning and design stage ....................................................................................................................................17

7.2.4 Implementation stage...............................................................................................................................................18

7.2.5 Assessment and acceptance stage .................................................................................................................19

7.3 Dealing with existing noise problems ..............................................................................................................................19

8 What to do before buying a new machine ...............................................................................................................................19

8.1 Questions that a potential buyer should consider ................................................................................................19

8.2 What information to request from potential suppliers ....................................................................................20

8.3 Declared and additional noise emission values ......... ..............................................................................................22

8.4 Meaning and use of noise emission values ..................................................................................................................22

8.5 Requirements for noise immission levels .....................................................................................................................23

8.6 Verification of declared noise emission and/or noise immission levels ............................................23

8.7 Developments .......................................................................................................................................................................................23

9 Noise prediction as a planning tool................................................................................................................................................24

10 Long-term noise control programme ...........................................................................................................................................24

Bibliography .............................................................................................................................................................................................................................27

© ISO 2020 – All rights reserved iii
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SIST EN ISO 11690-1:2021
ISO 11690-1:2020(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 .org/ 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 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, Subcommittee SC 1, Noise,

in collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/

TC 211, Acoustics, in accordance with the Agreement on technical cooperation between ISO and CEN

(Vienna Agreement).

This second edition cancels and replaces the first edition (ISO 11690-1:1996), of which it constitutes a

minor revision. The changes compared to the previous edition are editorial.
A list of all parts in the ISO 11690 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 2020 – All rights reserved
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SIST EN ISO 11690-1:2021
ISO 11690-1:2020(E)
Introduction

Several standards specify methods for measurement and/or evaluation of noise. The final objective of

the ISO 11690 series is noise reduction.

A number of noise control measures are offered. However, in order to be effective, the most appropriate

noise control measure(s) should be chosen for a given situation.

It is important when non-acoustic engineers are involved in noise control practice for these engineers

to have a basic knowledge of noise emission and propagation characteristics and to understand the

basic principles of noise control.

To assist in the development of noise control in the workplace, it is essential that the information

contained in these recommended practices is disseminated through International Standards.

In order to reduce noise as a hazard in the workplace, individual countries have produced national

legislation. Generally, such national legislation requires noise control measures to be carried out in

order to achieve the lowest reasonable levels of noise emission, noise immission and noise exposure,

taking into account:
— known available measures;
— the state of the art regarding technical progress;
— the treatment of noise at source;
— appropriate planning, procurement and installation of machines and equipment.

This part of ISO 11690, together with the two other parts in the series, outlines procedures to be

considered when dealing with noise control at workplaces, within workrooms and in the open. These

recommended practices give in relatively simple terms the basic information necessary for all parties

involved in noise control in workplaces and in the design of low-noise workplaces to promote the

understanding of the desired noise control requirements.

The purpose of the ISO 11690 series is to bridge the gap between existing literature on noise control and

the practical implementation of noise control measures. In principle, the series applies to all workplaces

and its main function is:

— to provide simple, brief information on some aspects of noise control in workplaces;

— to act as a guide to help in the understanding of requirements in standards, directives, text books,

manuals, reports and other specialized technical documents;

— to provide assistance in decision making when assessing the various measures available.

The ISO 11690 series should be useful to persons such as plant personnel, health and safety officers,

engineers, managers, staff in planning and purchasing departments, architects and suppliers of plants,

machines and equipment. However, the above-mentioned parties should keep in mind that adherence

to the recommendations of the ISO 11690 series is not all that is necessary to create a safe workplace.

The effects of noise on health, well-being and human activity are many. By giving guidelines for noise

control strategies and measures, the ISO 11690 series aims at a reduction of the impact of noise on

human beings at workplaces. Assessment of the impact of noise on human beings is dealt with in other

documents.
© ISO 2020 – All rights reserved v
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SIST EN ISO 11690-1:2021
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SIST EN ISO 11690-1:2021
INTERNATIONAL STANDARD ISO 11690-1:2020(E)
Acoustics — Recommended practice for the design of low-
noise workplaces containing machinery —
Part 1:
Noise control strategies
1 Scope

This document outlines strategies to be used in dealing with noise problems in existing and planned

workplaces by describing basic concepts in noise control (noise reduction, noise emission, noise

immission and noise exposure). It is applicable to all types of workplaces and all types of sources of

sound which are met in workplaces, including human activities.

It includes those important strategies to adopt when buying a new machine or equipment.

This document deals only with audible sound.
2 Normative references

The following documents are referred to in the text in such 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 4871, Acoustics — Declaration and verification of noise emission values of machinery and equipment

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 http:// www .electropedia .org/
3.1 General noise descriptors
3.1.1
sound pressure level

ten times the logarithm to the base 10 of the ratio of the mean-square sound pressure p, in pascals, to

the square of a reference value, p
 
L =10lg dB
 
 2 
 
where the reference value, p , is 20 µPa

Note 1 to entry: The sound pressure level is the main quantity to describe the noise at a given point. It is expressed

in decibels and should be measured with a standardized sound level meter (see IEC 61672-1).

Note 2 to entry: The frequency weighting (A or C) or the width of the frequency band and the time weighting

(S [slow], F [fast], I [impulse] or peak) used should be indicated.
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SIST EN ISO 11690-1:2021
ISO 11690-1:2020(E)

Note 3 to entry: For example, the C-weighted sound pressure level with time weighting peak is L .

pC,peak

Note 4 to entry: The notation L is used whether the sound pressure level refers to emission (see 3.2), immission

or exposure (see 3.3).
3.1.2
equivalent continuous sound pressure level
peq,T

sound pressure level of a continuous steady sound that within a measurement time interval, T, has the

same mean square sound pressure as a sound under consideration which varies with time, and is the

level of the mean square sound pressure over a time interval
 
01, Lt()
 
L =10lg 10 ddt B
pTeq, ∫
 
 0 

Note 1 to entry: Equivalent continuous sound pressure level is expressed in decibels.

Note 2 to entry: The equivalent continuous sound pressure level is the main quantity to assess the immission at

work stations and the exposure of persons.

Note 3 to entry: When immission or exposure is considered, impulse and tone adjustments, DL and DL , in

I T

decibels, may be used to take into account the influence of impulsive and tonal components (L + DL + DL )

pA,eq,T I T
(see ISO 1996-1, ISO 1996-2 and ISO 1999).

Note 4 to entry: Subscript “eq,T” is often omitted because in all cases considered in this document the sound

pressure is determined over a certain measurement time interval (see IEC 61672-1).

3.1.3
work station

position, in the vicinity of a machine, which can be occupied by the operator or a position where a task

is carried out
3.2 Noise emission descriptors
3.2.1
noise emission

airborne sound radiated into the environment from a defined source (machine or equipment)

[see Figure 1 a)]
3.2.2
sound power level

ten times the logarithm to the base 10 of the ratio of the sound power P, in watts, radiated by the sound

source under test to the reference sound power P = 1 pW

Note 1 to entry: Sound power level is expressed in decibels and is a descriptor of the emission of a sound source

(see the ISO 3740 and ISO 9614 series). The frequency weighting or the width of the frequency band used should

be indicated.
Note 2 to entry: For example, the A-weighted sound power level is L .
3.2.3
emission sound pressure level

sound pressure level caused by a sound source under test at its work station or at any other specified

position

Note 1 to entry: Emission sound pressure level is expressed in decibels (dB) and is an additional descriptor of the

emission of a sound source (see ISO 11200 to ISO 11204).
2 © ISO 2020 – All rights reserved
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SIST EN ISO 11690-1:2021
ISO 11690-1:2020(E)

Note 2 to entry: The frequency weighting and/or the time weighting or the width of the frequency band used

shall be indicated.

Note 3 to entry: For example, the C-weighted peak emission sound pressure level is L .

pC,peak

Note 4 to entry: The A-weighted emission sound pressure level is often averaged over an operational period of a

sound source; it is denoted L .
3.2.4
surface sound pressure level
pA,d

A-weighted sound pressure level averaged on an energy basis over a measurement surface at a distance

d from the sound source
Note 1 to entry: When d = 1 m, it is usually noted L .
pA,1m
3.2.5
measured noise emission value

any of the A-weighted sound power level, the A-weighted time-averaged emission sound pressure level,

or the C-weighted peak emission sound pressure level, determined from measurements

Note 1 to entry: Measured values may be determined either for a single machine or from the average of a number

of machines.

Note 2 to entry: Measured noise emission value is expressed in decibels and is not rounded.

3.2.6
noise emission declaration

information on the noise emitted by the machine, given by the manufacturer or the supplier in technical

documents or other literature, concerning noise emission values

Note 1 to entry: The noise emission declaration may take the form of either the declared single-number noise

emission value or the declared dual-number noise emission value.
3.2.7
uncertainty

value of the measurement uncertainty associated with a measured noise emission value

Note 1 to entry: Uncertainty is expressed in decibels and is not rounded.
3.2.8
declared single-number noise emission value

sum of a measured noise emission value, L, and the associated uncertainty, K, rounded to the nearest

decibel (dB)
L = L + K
3.2.9
declared dual-number noise emission value
L and K

measured noise emission value, L, and its associated uncertainty, K, both rounded to the nearest decibel

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SIST EN ISO 11690-1:2021
ISO 11690-1:2020(E)
3.3 Noise immission and noise exposure
3.3.1
noise immission at a work station

all noises that arrive, whether or not a worker is present, over a specific time period T, at a measuring

point (work station) in the actual situation; i.e. noise coming from the machine, noise coming from the

other sound sources and noise reflected by the ceiling, the walls and any fittings [see Figure 1 b)]

Note 1 to entry: T can be the duration of a measurement, an operating cycle of a machine, a process, the duration

a worker is usually present at or near the measurement point, or the duration of the workshift.

3.3.2
noise exposure of a person

all noises that arrive, over a specific time period T, at a person’s ear in the actual situation [see Figure 1 c)

and Figure 2]
3.3.3
noise immission and noise exposure descriptors

equivalent continuous A-weighted sound pressure level normalized to a nominal working day, L

pTAe,,q
in decibels
LL=+10lg TT/ dB
pTAe,,qApT,,eq e 0
0 e

where T is the reference duration (e.g. 8 h) and T is the duration of the workshift

0 e

Note 1 to entry: Immission is measured at the work station. Exposure is measured at the ear of the person.

Note 2 to entry: L can result from the energetic summation of immission or exposure values, L ,

pTAe,,q pTAe,,q
0 i
measured over individual time periods T , with ∑=TT .
i e
Note 3 to entry: In some countries, a rating level L is used:
pAr,
LL=+DL +DL dB
ppAr,,AeqI,T T
where DL and DL describe impulsive and tonal components.
I T
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SIST EN ISO 11690-1:2021
ISO 11690-1:2020(E)
a) Noise emission; sound radiation of a machine:
— machine related
— specified operating conditions
— independent of environment
b) Noise immission: sound impact at the work
station:
— work station related
— real operation
— dependendent on immission time
— contribution from all sound sources
c) Noise exposure; sound impact on human beings:
— person related [at one or several work stations
or for a person moving around (see Figure 2)]
— real operation
— dependent on exposure time
— contribution from all sound sources

Figure 1 — Illustration of the difference between noise emission, noise immission and noise

exposure (see also Figure 2)
Figure 2 — Illustration of noise exposure for a person moving around
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SIST EN ISO 11690-1:2021
ISO 11690-1:2020(E)
3.4 Noise reduction
3.4.1
sound reduction index

descriptor of transmission loss defined as ten times the logarithm to the base 10 of the ratio of the sound

power incident on a test specimen to the sound transmitted through the test specimen (see Figure 3.)

Note 1 to entry: It is expressed in decibels and is frequency dependent.

Note 2 to entry: Methods for determining the insulation of walls, doors, ceilings and windows are described in

ISO 10140 (all parts) and in ISO 717-1.
Key
1 reflection
2 absorption
3 transmission

NOTE A proportion of the sound which is incident on a partition or wall is reflected, a proportion is

transformed into heat (i.e. is absorbed) and a proportion goes through the wall to the other side (i.e. is

tran
...