Acoustics -- Description, measurement and assessment of environmental noise

ISO 1996-2:2017 describes how sound pressure levels intended as a basis for assessing environmental noise limits or comparison of scenarios in spatial studies can be determined. Determination can be done by direct measurement and by extrapolation of measurement results by means of calculation. This document is primarily intended to be used outdoors but some guidance is given for indoor measurements as well. It is flexible and to a large extent, the user determines the measurement effort and, accordingly, the measurement uncertainty, which is determined and reported in each case. Thus, no limits for allowable maximum uncertainty are set up. Often, the measurement results are combined with calculations to correct for reference operating or propagation conditions different from those during the actual measurement. This document can be applied on all kinds of environmental noise sources, such as road and rail traffic noise, aircraft noise and industrial noise.

Acoustique -- Description, évaluation et mesurage du bruit de l'environnement

Akustika - Opis, merjenje in ocena hrupa v okolju - 2. del: Določanje ravni zvočnega tlaka

Ta dokument opisuje, kako je mogoče določiti ravni zvočnega tlaka kot osnovo za ocenjevanje mejnih vrednosti hrupa v okolju ali primerjavo scenarijev v prostorskih študijah. Določanje se lahko izvede z neposrednim merjenjem in ekstrapolacijo rezultatov meritev s pomočjo izračuna.
Ta dokument je namenjen predvsem uporabi na prostem, vendar je podanih tudi nekaj smernic za merjenje v zaprtih prostorih. Je prilagodljiv in uporabnik lahko v veliki meri določa merjenje in ustrezno tudi merilne negotovosti, ki so določene in podane za vsak primer. Zato niso določene nobene mejne vrednosti dovoljene največje negotovosti. Pogosto so rezultati meritev kombinirani z izračuni za popravke pri referenčnih obratovalnih pogojih ali pogojih za razširjanje, ki se razlikujejo od pogojev med dejanskim merjenjem. Ta dokument se lahko uporablja za vse vire hrupa v okolju, kot so hrup cestnega in železniškega prometa, letalski hrup in industrijski hrup.

General Information

Status
Published
Publication Date
13-Jul-2017
Current Stage
6060 - International Standard published
Start Date
26-Apr-2017
Completion Date
14-Jul-2017

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INTERNATIONAL ISO
STANDARD 1996-2
Third edition
2017-07
Acoustics — Description,
measurement and assessment of
environmental noise —
Part 2:
Determination of sound pressure levels
Acoustique — Description, évaluation et mesurage du bruit de
l’environnement —
Partie 2: Détermination des niveaux de pression acoustique
Reference number
ISO 1996-2:2017(E)
ISO 2017
---------------------- Page: 1 ----------------------
ISO 1996-2:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland

All rights reserved. Unless otherwise specified, 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
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2017 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 1996-2:2017(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

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

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

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

4 Measurement uncertainty .......................................................................................................................................................................... 3

5 Instrumentation for acoustical measurements ................................................................................................................... 5

5.1 General ........................................................................................................................................................................................................... 5

5.2 Calibration .................................................................................................................................................................................................. 6

5.3 Verification ................................................................................................................................................................................................. 6

5.4 Long-term monitoring ...................................................................................................................................................................... 6

6 Principles ..................................................................................................................................................................................................................... 6

6.1 General ........................................................................................................................................................................................................... 6

6.2 Independent measurements ....................................................................................................................................................... 7

7 Operation of the source ................................................................................................................................................................................. 8

7.1 General ........................................................................................................................................................................................................... 8

7.2 Road traffic ................................................................................................................................................................................................. 8

7.2.1 L measurement ............................................................................................................................................................. 8

7.2.2 L measurement ......................................................................................................................................................... 9

max

7.3 Rail traffic .................................................................................................................................................................................................... 9

7.3.1 L measurement ............................................................................................................................................................. 9

7.3.2 L measurement ......................................................................................................................................................... 9

max

7.4 Air traffic ...................................................................................................................................................................................................10

7.4.1 L measurement ..........................................................................................................................................................10

7.4.2 L measurement ......................................................................................................................................................11

max

7.5 Industrial plants ......... .........................................................................................................................................................................11

7.5.1 L measurement ..........................................................................................................................................................11

7.5.2 L measurement ......................................................................................................................................................11

max

8 Meteorological conditions .......................................................................................................................................................................12

8.1 General ........................................................................................................................................................................................................12

8.2 Favourable propagation ...............................................................................................................................................................13

8.3 Effects of precipitation on measurements ...................................................................................................................13

9 Measurement procedures ........................................................................................................................................................................13

9.1 Selection of measurement time interval ........................................................................................................................13

9.1.1 Long-term measurements ....................................................................................................................................13

9.1.2 Short-term measurements ...................................................................................................................................14

9.2 Microphone location .......................................................................................................................................................................14

9.2.1 Outdoors ..............................................................................................................................................................................14

9.2.2 Indoors ..................................................................................................................................................................................15

9.3 Measurements ......................................................................................................................................................................................15

9.3.1 Long-term unattended measurements ......................................................................................................15

9.3.2 Short-term attended measurements ...........................................................................................................16

9.3.3 Residual sound ...............................................................................................................................................................17

9.3.4 Frequency range of measurements ..............................................................................................................17

9.3.5 Measurements of meteorological parameters ....................................................................................17

10 Evaluation of the measurement results .....................................................................................................................................18

10.1 General ........................................................................................................................................................................................................18

10.2 Determination of L , L and L ...................................................................................................................................

E,T eq,T N,T 18

10.2.1 L and L .......................................................................................................................................................................

E,T eq,T 18

10.2.2 L ..............................................................................................................................................................................................

N,T 18
© ISO 2017 – All rights reserved iii
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ISO 1996-2:2017(E)

10.3 Treatment of incomplete or corrupted data ...............................................................................................................19

10.3.1 General...................................................................................................................................................................................19

10.3.2 Wind sound .......................................................................................................................................................................19

10.4 Level correction for residual sound ...................................................................................................................................19

10.5 Determination of standard uncertainty .........................................................................................................................19

10.6 Determination of L .....................................................................................................................................................................

den 20

10.6.1 Determination from long-term L measurements ........................................................................20

10.6.2 Determination from long-term L measurements of individual events........................20

10.6.3 Determination from short-term measurements ...............................................................................21

10.7 Maximum level, L ........................................................................................................................................................................

max 22

11 Extrapolation to other locations .......................................................................................................................................................22

11.1 General ........................................................................................................................................................................................................22

11.2 Extrapolation by means of calculations..........................................................................................................................22

11.3 Extrapolation by means of measured attenuation functions .......................................................................23

12 Calculation ...............................................................................................................................................................................................................23

12.1 General ........................................................................................................................................................................................................23

12.2 Calculation methods ........................................................................................................................................................................24

12.2.1 General...................................................................................................................................................................................24

12.2.2 Specific procedures ....................................................................................................................................................24

13 Information to be recorded and reported ..............................................................................................................................24

Annex A (informative) Determination of radius of curvature .................................................................................................26

Annex B (informative) Microphone locations relative to reflecting surfaces .........................................................29

Annex C (informative) Selection of measurement/monitoring site ..................................................................................34

Annex D (informative) Correction to reference condition ..........................................................................................................36

Annex E (informative) Elimination of unwanted sound ................................................................................................................41

Annex F (informative) Measurement uncertainty ...............................................................................................................................42

Annex G (informative) Examples of uncertainty calculations .................................................................................................44

Annex H (informative) Maximum sound pressure levels .............................................................................................................49

Annex I (informative) Measurement of residual sound .................................................................................................................52

Annex J (informative) Objective method for assessing the audibility of tones in noise —

Engineering method ......................................................................................................................................................................................54

Annex K (informative) Objective method for assessing the audibility of tones in noise —

Survey method .....................................................................................................................................................................................................56

Annex L (informative) National and European source specific calculation models .........................................57

Bibliography .............................................................................................................................................................................................................................60

iv © ISO 2017 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 1996-2:2017(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 on 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 . i so .org/ iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 1, Noise.

This third edition cancels and replaces the second edition (ISO 1996-2:2007), which has been technically

revised.
A list of all the parts in the ISO 1996 series can be found on the ISO website.
© ISO 2017 – All rights reserved v
---------------------- Page: 5 ----------------------
ISO 1996-2:2017(E)
Introduction

Measurements of environmental noise are complicated because there is a great number of variables to

consider when planning and performing the measurements. As each measurement occasion is subject

to current source and meteorological conditions which cannot be controlled by the operator, it is often

not possible to control the resulting uncertainty of the measurements. Instead, the uncertainty is

determined after the measurements based on an analysis of the acoustic measurements and collected

data on source operating conditions and on meteorological parameters important for the sound

propagation.

Because this document has the ambition both to comply with new and stricter requirements on

measurement uncertainty calculations and to cover all kinds of sources and meteorological conditions,

it has become more complicated than what a standard covering a single, specific source and application

could have been. The best use of the standard is to use it as a basis for developing more dedicated

standards serving specific sources and aims.
vi © ISO 2017 – All rights reserved
---------------------- Page: 6 ----------------------
INTERNATIONAL STANDARD ISO 1996-2:2017(E)
Acoustics — Description, measurement and assessment of
environmental noise —
Part 2:
Determination of sound pressure levels
1 Scope

This document describes how sound pressure levels intended as a basis for assessing environmental

noise limits or comparison of scenarios in spatial studies can be determined. Determination can be

done by direct measurement and by extrapolation of measurement results by means of calculation.

This document is primarily intended to be used outdoors but some guidance is given for indoor

measurements as well. It is flexible and to a large extent, the user determines the measurement effort

and, accordingly, the measurement uncertainty, which is determined and reported in each case. Thus,

no limits for allowable maximum uncertainty are set up. Often, the measurement results are combined

with calculations to correct for reference operating or propagation conditions different from those

during the actual measurement. This document can be applied on all kinds of environmental noise

sources, such as road and rail traffic noise, aircraft noise and industrial noise.

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 1996-1:2016, Acoustics — Description, measurement and assessment of environmental noise — Part 1:

Basic quantities and assessment procedures

ISO 20906:2009/Amd 1:2013, Acoustics — Unattended monitoring of aircraft sound in the vicinity of

airports — Amendment 1

ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories

ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in

me a s ur ement (GUM: 1995)
IEC 60942, Electroacoustics — Sound calibrators
IEC 61260, Electroacoustics — Octave-band and fractional-octave-band filters
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 1996-1 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
© ISO 2017 – All rights reserved 1
---------------------- Page: 7 ----------------------
ISO 1996-2:2017(E)
3.1
measurement time interval
time interval during which measurements are conducted

Note 1 to entry: For measurements of sound exposure level or equivalent-continuous sound pressure level, the

measurement time interval is the time period of integration.

Note 2 to entry: For measurements of maximum sound pressure level or percent exceedance level, etc., the

measurement time interval is the observation time interval (3.2).
3.2
observation time interval
time interval during which a series of measurements is conducted
3.3
prediction time interval
time interval over which levels are predicted

Note 1 to entry: It is now perhaps more common to predict sound levels using computers than to measure

them for some sources such as transportation noise sources. The prediction time interval corresponds to the

measurement time interval (3.1) except, for the former, the levels are predicted, and for the latter, the levels are

measured.
3.4
long-term measurement

measurement sufficiently long to encompass all emission situations and meteorological conditions

which are needed to obtain a representative average
3.5
short-term measurement

measurement during measurement time intervals (3.1) with well-defined emission and meteorological

conditions
3.6
receiver location
location at which the noise is assessed
3.7
calculation method

set of algorithms to calculate the sound pressure level at a specified receiver location (3.6) from

measured or predicted sound power levels and sound attenuation data
3.8
prediction method

subset of a calculation method (3.7), intended for the calculation of future noise levels

3.9
meteorological window

set of weather conditions during which measurements can be performed with limited and known

variation in measurement results due to weather variation
3.10
emission window

set of emission conditions during which measurements can be performed with limited variation in

measurement results due to variations in operating conditions
3.11
sound path radius of curvature
cur

radius approximating the curvature of the sound paths due to atmospheric refraction

Note 1 to entry: R is given in metres.
cur
2 © ISO 2017 – All rights reserved
---------------------- Page: 8 ----------------------
ISO 1996-2:2017(E)

Note 2 to entry: Often, the parameter used is 1/R to avoid infinitely large values during straight ray

cur
propagation.
3.12
monitor

instrumentation used for a single automated continuous sound monitoring terminal which monitors

the A-weighted sound pressure levels, their spectra and all relevant meteorological quantities such as

wind speed, wind direction, rain, humidity, atmospheric stability, etc.

Note 1 to entry: Meteorological measurements need not be taken at each monitor provided such measurements

are taken within an appropriate distance from the monitors and such distance is given in the report.

3.13
automated sound monitoring system

entire automated continuous sound monitoring system including all monitors (3.12), the base or central

data collection position (host station) and all software and hardware involved in its operation

3.14
reference condition
condition to which the measurement results are to be referred (corrected)

Note 1 to entry: Examples of reference conditions are atmospheric sound absorption at yearly average

temperature and humidity and yearly average traffic flows for day, evening and night, respectively.

3.15
independent measurement

consecutive measurements carried out with a time space long enough to make both source operating

conditions and sound propagation conditions statistically independent of the same conditions of other

measurements in the series

Note 1 to entry: In order to achieve independent conditions for meteorological conditions, a time space of several

days is normally required.
3.16
low-frequency sound

sound containing frequency components of interest within the range covering the one-third octave

bands 16 Hz to 200 Hz

Note 1 to entry: This definition is specific for this document. Other definitions can apply in different national

regulations.
4 Measurement uncertainty

The uncertainty of sound pressure levels determined as described in this document depends on the

sound source and the measurement time interval, the meteorological conditions, the distance from

the source and the measurement method and instrumentation. The measurement uncertainty shall be

determined in compliance with ISO/IEC Guide 98-3 (GUM). Choose one of the following approaches that

are all GUM-compatible:

a) The modelling approach that consists in identifying and quantifying all major sources of uncertainty

(the so-called uncertainty budget). This is the preferred method.

b) The inter-laboratory approach that consists in carrying out a round-robin test in order to determine

the standard deviation of reproducibility of the measurement method.

NOTE 1 If more than one measurement method exists for a certain measurand, any systematic deviations

[1]
are taken into account, for example, by implementing ISO 21748 .

c) The hybrid approach that consists in using jointly the modelling approach and the inter-laboratory

approach. In this case, the inter-laboratory approach is used for components of the uncertainty

© ISO 2017 – All rights reserved 3
---------------------- Page: 9 ----------------------
ISO 1996-2:2017(E)

budget for which the contributions cannot be quantified using the mathematical model of the

modelling approach because of lack of technical knowledge.
NOTE 2 Note 1 equally applies.

According to the modelling approach, each significant source of uncertainty shall be identified.

Systematic effects shall be eliminated or reduced by the application of corrections wherever possible. If

the quantity to be measured is L, which is a function of the quantities x , the formula becomes:

Lf= xx,,xx,..., (1)
12 3 j

If each quantity has the standard uncertainty u , the combined standard uncertainty is given by

Formula (2):
uL()= cu (2)

assuming that the input quantities x are independent. Under the same assumptions, the sensitivity

coefficient c is given by Formula (3):
c = (3)

The measurement uncertainty to be reported is the uncertainty associated with a chosen coverage

probability, the so-called expanded uncertainty. By convention, a coverage probability of 95 % is usually

chosen, with an associated coverage factor of 2. This means that the result becomes L ± 2 u.

NOTE 3 Cognizant authorities can set other coverage probabilities. A coverage factor of 1,3 will, for example,

provide a coverage probability of 80 %.

For environmental noise measurements f(x ), it is extremely complicated and it is hardly feasible to

[2]

put up exact formulae for the function f. Following the principles given in ISO 3745, some important

sources of uncertainty can be identified. For an in
...

SLOVENSKI STANDARD
SIST ISO 1996-2:2017
01-september-2017
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SIST ISO 1996-2:2007
$NXVWLND2SLVPHUMHQMHLQRFHQDKUXSDYRNROMXGHO'RORþDQMHUDYQL
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Acoustics - Description, measurement and assessment of environmental noise - Part 2:

Determination of sound pressure levels

Acoustique - Description, évaluation et mesurage du bruit de l'environnement -- Partie 2:

Détermination des niveaux de pression acoustique
Ta slovenski standard je istoveten z: ISO 1996-2:2017
ICS:
13.140 Vpliv hrupa na ljudi Noise with respect to human
beings
17.140.01 $NXVWLþQDPHUMHQMDLQ Acoustic measurements and
EODåHQMHKUXSDQDVSORãQR noise abatement in general
SIST ISO 1996-2:2017 en

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

---------------------- Page: 1 ----------------------
SIST ISO 1996-2:2017
---------------------- Page: 2 ----------------------
SIST ISO 1996-2:2017
INTERNATIONAL ISO
STANDARD 1996-2
Third edition
2017-07
Acoustics — Description,
measurement and assessment of
environmental noise —
Part 2:
Determination of sound pressure levels
Acoustique — Description, évaluation et mesurage du bruit de
l’environnement —
Partie 2: Détermination des niveaux de pression acoustique
Reference number
ISO 1996-2:2017(E)
ISO 2017
---------------------- Page: 3 ----------------------
SIST ISO 1996-2:2017
ISO 1996-2:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland

All rights reserved. Unless otherwise specified, 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
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2017 – All rights reserved
---------------------- Page: 4 ----------------------
SIST ISO 1996-2:2017
ISO 1996-2:2017(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

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

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

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

4 Measurement uncertainty .......................................................................................................................................................................... 3

5 Instrumentation for acoustical measurements ................................................................................................................... 5

5.1 General ........................................................................................................................................................................................................... 5

5.2 Calibration .................................................................................................................................................................................................. 6

5.3 Verification ................................................................................................................................................................................................. 6

5.4 Long-term monitoring ...................................................................................................................................................................... 6

6 Principles ..................................................................................................................................................................................................................... 6

6.1 General ........................................................................................................................................................................................................... 6

6.2 Independent measurements ....................................................................................................................................................... 7

7 Operation of the source ................................................................................................................................................................................. 8

7.1 General ........................................................................................................................................................................................................... 8

7.2 Road traffic ................................................................................................................................................................................................. 8

7.2.1 L measurement ............................................................................................................................................................. 8

7.2.2 L measurement ......................................................................................................................................................... 9

max

7.3 Rail traffic .................................................................................................................................................................................................... 9

7.3.1 L measurement ............................................................................................................................................................. 9

7.3.2 L measurement ......................................................................................................................................................... 9

max

7.4 Air traffic ...................................................................................................................................................................................................10

7.4.1 L measurement ..........................................................................................................................................................10

7.4.2 L measurement ......................................................................................................................................................11

max

7.5 Industrial plants ......... .........................................................................................................................................................................11

7.5.1 L measurement ..........................................................................................................................................................11

7.5.2 L measurement ......................................................................................................................................................11

max

8 Meteorological conditions .......................................................................................................................................................................12

8.1 General ........................................................................................................................................................................................................12

8.2 Favourable propagation ...............................................................................................................................................................13

8.3 Effects of precipitation on measurements ...................................................................................................................13

9 Measurement procedures ........................................................................................................................................................................13

9.1 Selection of measurement time interval ........................................................................................................................13

9.1.1 Long-term measurements ....................................................................................................................................13

9.1.2 Short-term measurements ...................................................................................................................................14

9.2 Microphone location .......................................................................................................................................................................14

9.2.1 Outdoors ..............................................................................................................................................................................14

9.2.2 Indoors ..................................................................................................................................................................................15

9.3 Measurements ......................................................................................................................................................................................15

9.3.1 Long-term unattended measurements ......................................................................................................15

9.3.2 Short-term attended measurements ...........................................................................................................16

9.3.3 Residual sound ...............................................................................................................................................................17

9.3.4 Frequency range of measurements ..............................................................................................................17

9.3.5 Measurements of meteorological parameters ....................................................................................17

10 Evaluation of the measurement results .....................................................................................................................................18

10.1 General ........................................................................................................................................................................................................18

10.2 Determination of L , L and L ...................................................................................................................................

E,T eq,T N,T 18

10.2.1 L and L .......................................................................................................................................................................

E,T eq,T 18

10.2.2 L ..............................................................................................................................................................................................

N,T 18
© ISO 2017 – All rights reserved iii
---------------------- Page: 5 ----------------------
SIST ISO 1996-2:2017
ISO 1996-2:2017(E)

10.3 Treatment of incomplete or corrupted data ...............................................................................................................19

10.3.1 General...................................................................................................................................................................................19

10.3.2 Wind sound .......................................................................................................................................................................19

10.4 Level correction for residual sound ...................................................................................................................................19

10.5 Determination of standard uncertainty .........................................................................................................................19

10.6 Determination of L .....................................................................................................................................................................

den 20

10.6.1 Determination from long-term L measurements ........................................................................20

10.6.2 Determination from long-term L measurements of individual events........................20

10.6.3 Determination from short-term measurements ...............................................................................21

10.7 Maximum level, L ........................................................................................................................................................................

max 22

11 Extrapolation to other locations .......................................................................................................................................................22

11.1 General ........................................................................................................................................................................................................22

11.2 Extrapolation by means of calculations..........................................................................................................................22

11.3 Extrapolation by means of measured attenuation functions .......................................................................23

12 Calculation ...............................................................................................................................................................................................................23

12.1 General ........................................................................................................................................................................................................23

12.2 Calculation methods ........................................................................................................................................................................24

12.2.1 General...................................................................................................................................................................................24

12.2.2 Specific procedures ....................................................................................................................................................24

13 Information to be recorded and reported ..............................................................................................................................24

Annex A (informative) Determination of radius of curvature .................................................................................................26

Annex B (informative) Microphone locations relative to reflecting surfaces .........................................................29

Annex C (informative) Selection of measurement/monitoring site ..................................................................................34

Annex D (informative) Correction to reference condition ..........................................................................................................36

Annex E (informative) Elimination of unwanted sound ................................................................................................................41

Annex F (informative) Measurement uncertainty ...............................................................................................................................42

Annex G (informative) Examples of uncertainty calculations .................................................................................................44

Annex H (informative) Maximum sound pressure levels .............................................................................................................49

Annex I (informative) Measurement of residual sound .................................................................................................................52

Annex J (informative) Objective method for assessing the audibility of tones in noise —

Engineering method ......................................................................................................................................................................................54

Annex K (informative) Objective method for assessing the audibility of tones in noise —

Survey method .....................................................................................................................................................................................................56

Annex L (informative) National and European source specific calculation models .........................................57

Bibliography .............................................................................................................................................................................................................................60

iv © ISO 2017 – All rights reserved
---------------------- Page: 6 ----------------------
SIST ISO 1996-2:2017
ISO 1996-2:2017(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 on 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 . i so .org/ iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 1, Noise.

This third edition cancels and replaces the second edition (ISO 1996-2:2007), which has been technically

revised.
A list of all the parts in the ISO 1996 series can be found on the ISO website.
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Introduction

Measurements of environmental noise are complicated because there is a great number of variables to

consider when planning and performing the measurements. As each measurement occasion is subject

to current source and meteorological conditions which cannot be controlled by the operator, it is often

not possible to control the resulting uncertainty of the measurements. Instead, the uncertainty is

determined after the measurements based on an analysis of the acoustic measurements and collected

data on source operating conditions and on meteorological parameters important for the sound

propagation.

Because this document has the ambition both to comply with new and stricter requirements on

measurement uncertainty calculations and to cover all kinds of sources and meteorological conditions,

it has become more complicated than what a standard covering a single, specific source and application

could have been. The best use of the standard is to use it as a basis for developing more dedicated

standards serving specific sources and aims.
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INTERNATIONAL STANDARD ISO 1996-2:2017(E)
Acoustics — Description, measurement and assessment of
environmental noise —
Part 2:
Determination of sound pressure levels
1 Scope

This document describes how sound pressure levels intended as a basis for assessing environmental

noise limits or comparison of scenarios in spatial studies can be determined. Determination can be

done by direct measurement and by extrapolation of measurement results by means of calculation.

This document is primarily intended to be used outdoors but some guidance is given for indoor

measurements as well. It is flexible and to a large extent, the user determines the measurement effort

and, accordingly, the measurement uncertainty, which is determined and reported in each case. Thus,

no limits for allowable maximum uncertainty are set up. Often, the measurement results are combined

with calculations to correct for reference operating or propagation conditions different from those

during the actual measurement. This document can be applied on all kinds of environmental noise

sources, such as road and rail traffic noise, aircraft noise and industrial noise.

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 1996-1:2016, Acoustics — Description, measurement and assessment of environmental noise — Part 1:

Basic quantities and assessment procedures

ISO 20906:2009/Amd 1:2013, Acoustics — Unattended monitoring of aircraft sound in the vicinity of

airports — Amendment 1

ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories

ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in

me a s ur ement (GUM: 1995)
IEC 60942, Electroacoustics — Sound calibrators
IEC 61260, Electroacoustics — Octave-band and fractional-octave-band filters
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 1996-1 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
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3.1
measurement time interval
time interval during which measurements are conducted

Note 1 to entry: For measurements of sound exposure level or equivalent-continuous sound pressure level, the

measurement time interval is the time period of integration.

Note 2 to entry: For measurements of maximum sound pressure level or percent exceedance level, etc., the

measurement time interval is the observation time interval (3.2).
3.2
observation time interval
time interval during which a series of measurements is conducted
3.3
prediction time interval
time interval over which levels are predicted

Note 1 to entry: It is now perhaps more common to predict sound levels using computers than to measure

them for some sources such as transportation noise sources. The prediction time interval corresponds to the

measurement time interval (3.1) except, for the former, the levels are predicted, and for the latter, the levels are

measured.
3.4
long-term measurement

measurement sufficiently long to encompass all emission situations and meteorological conditions

which are needed to obtain a representative average
3.5
short-term measurement

measurement during measurement time intervals (3.1) with well-defined emission and meteorological

conditions
3.6
receiver location
location at which the noise is assessed
3.7
calculation method

set of algorithms to calculate the sound pressure level at a specified receiver location (3.6) from

measured or predicted sound power levels and sound attenuation data
3.8
prediction method

subset of a calculation method (3.7), intended for the calculation of future noise levels

3.9
meteorological window

set of weather conditions during which measurements can be performed with limited and known

variation in measurement results due to weather variation
3.10
emission window

set of emission conditions during which measurements can be performed with limited variation in

measurement results due to variations in operating conditions
3.11
sound path radius of curvature
cur

radius approximating the curvature of the sound paths due to atmospheric refraction

Note 1 to entry: R is given in metres.
cur
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Note 2 to entry: Often, the parameter used is 1/R to avoid infinitely large values during straight ray

cur
propagation.
3.12
monitor

instrumentation used for a single automated continuous sound monitoring terminal which monitors

the A-weighted sound pressure levels, their spectra and all relevant meteorological quantities such as

wind speed, wind direction, rain, humidity, atmospheric stability, etc.

Note 1 to entry: Meteorological measurements need not be taken at each monitor provided such measurements

are taken within an appropriate distance from the monitors and such distance is given in the report.

3.13
automated sound monitoring system

entire automated continuous sound monitoring system including all monitors (3.12), the base or central

data collection position (host station) and all software and hardware involved in its operation

3.14
reference condition
condition to which the measurement results are to be referred (corrected)

Note 1 to entry: Examples of reference conditions are atmospheric sound absorption at yearly average

temperature and humidity and yearly average traffic flows for day, evening and night, respectively.

3.15
independent measurement

consecutive measurements carried out with a time space long enough to make both source operating

conditions and sound propagation conditions statistically independent of the same conditions of other

measurements in the series

Note 1 to entry: In order to achieve independent conditions for meteorological conditions, a time space of several

days is normally required.
3.16
low-frequency sound

sound containing frequency components of interest within the range covering the one-third octave

bands 16 Hz to 200 Hz

Note 1 to entry: This definition is specific for this document. Other definitions can apply in different national

regulations.
4 Measurement uncertainty

The uncertainty of sound pressure levels determined as described in this document depends on the

sound source and the measurement time interval, the meteorological conditions, the distance from

the source and the measurement method and instrumentation. The measurement uncertainty shall be

determined in compliance with ISO/IEC Guide 98-3 (GUM). Choose one of the following approaches that

are all GUM-compatible:

a) The modelling approach that consists in identifying and quantifying all major sources of uncertainty

(the so-called uncertainty budget). This is the preferred method.

b) The inter-laboratory approach that consists in carrying out a round-robin test in order to determine

the standard deviation of reproducibility of the measurement method.

NOTE 1 If more than one measurement method exists for a certain measurand, any systematic deviations

[1]
are taken into account, for example, by implementing ISO 21748 .

c) The hybrid approach that consists in using jointly the modelling approach and the inter-laboratory

approach. In this case, the inter-laboratory approach is used for components of the uncertainty

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budget for which the contributions cannot be quantified using the mathematical model of the

modelling approach because of lack of technical knowledge.
NOTE 2 Note 1 equally applies.

According to the modelling approach, each significant source of uncertainty shall be identified.

Systematic effects shall be eliminated or reduced by the appl
...

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