ISO/DIS 1996-2

Acoustics -- Description, assessment and measurement of environmental noise

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

Standards Content (sample)

DRAFT INTERNATIONAL STANDARD ISO/DIS 1996-2
ISO/TC 43/SC 1 Secretariat: DS
Voting begins on: Voting terminates on:
2003-05-29 2003-10-29

INTERNATIONAL ORGANIZATION FOR STANDARDIZATION • МЕЖДУНАРОДНАЯ ОРГАНИЗАЦИЯ ПО СТАНДАРТИЗАЦИИ • ORGANISATION INTERNATIONALE DE NORMALISATION

Acoustics — Description, assessment and measurement of
environmental noise —
Part 2:
Determination of environmental noise levels
Acoustique — Description, évaluation et mesurage du bruit de l'environnement —
Partie 2: Détermination des niveaux de bruit de l'environnement

[Revision of first edition (ISO 1996-2:1987), its Amendment 1:1998 and ISO 1996-3:1987]

ICS 13.140

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ISO/DIS 1996-2
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ISO/DIS 1996-2
Contents Page

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

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

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

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

4 Measurement uncertainty.....................................................................................................................2

5 Instrumentation .....................................................................................................................................3

5.1 Instrumentation system........................................................................................................................3

5.2 Calibration..............................................................................................................................................3

6 Operation of the source........................................................................................................................4

6.1 General ...................................................................................................................................................4

6.2 Road traffic.............................................................................................................................................4

6.3 Rail traffic ...............................................................................................................................................4

6.4 Air traffic.................................................................................................................................................5

6.5 Industrial plants.....................................................................................................................................5

7 Weather conditions ...............................................................................................................................5

7.1 General ...................................................................................................................................................5

7.2 Weather characterisation......................................................................................................................6

7.3 Favourable downwind conditions .......................................................................................................6

7.4 Average weather conditions ................................................................................................................7

8 Test procedure.......................................................................................................................................7

8.1 Principle .................................................................................................................................................7

8.2 Selection of measurement time interval .............................................................................................7

8.3 Microphone location .............................................................................................................................7

8.3.1 Outdoors ................................................................................................................................................7

8.3.2 Indoors....................................................................................................................................................8

8.4 Measurements .......................................................................................................................................9

8.4.1 L ..........................................................................................................................................................9

eqT

8.4.2 L ..........................................................................................................................................................9

max

8.4.3 L ............................................................................................................................................................9

8.4.4 L ...........................................................................................................................................................9

N,T

8.4.5 L ........................................................................................................................................................9

Cpeak

8.4.6 Tonal sound ...........................................................................................................................................9

8.4.7 Impulse sound .......................................................................................................................................9

8.4.8 Low frequency noise (frequency < 200 Hz) ........................................................................................9

8.4.9 Residual sound....................................................................................................................................10

8.4.10 Frequency range of measurements...................................................................................................10

9 Evaluation of the measurement result ..............................................................................................10

9.1 General .................................................................................................................................................10

9.2 L , L .................................................................................................................................................10

ET eqT

9.3 L ......................................................................................................................................................10

Fmax

9.4 L ...........................................................................................................................................................11

9.5 Indoor measurements.........................................................................................................................11

9.6 Residual sound....................................................................................................................................11

10 Extrapolation to other conditions......................................................................................................12

10.1 Location................................................................................................................................................12

10.2 Other time and operating conditions ................................................................................................12

11 Calculation...........................................................................................................................................13

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ISO/DIS 1996-2

11.1 General................................................................................................................................................. 13

11.2 Calculation methods .......................................................................................................................... 13

11.2.1 General................................................................................................................................................. 13

11.2.2 Specific procedures ........................................................................................................................... 13

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

Annex A (informative) Meteo-window and uncertainty due to weather...................................................... 15

A.1 Favourable sound propagation conditions...................................................................................... 15

A.2 Guidance on curvature requirements for favourable sound propagation and associated

weather induced uncertainty............................................................................................................. 15

A.3 Guidance on when the sound path curvature k > - 0,1 and k > 0,1 ............................................... 17

Annex B (informative) Microphone positions relative to reflecting surfaces ............................................ 20

B.1 Free field position............................................................................................................................... 20

B.2 Microphone directly on the surface (+6 dB measurement)............................................................ 20

B.3 Microphone near reflecting surface (+3 dB measurement)............................................................ 21

Annex C (informative) Objective method for assessing the audibility of tones in noise -

Engineering method ........................................................................................................................... 23

C.1 Introduction......................................................................................................................................... 23

C.2 Objective method................................................................................................................................ 23

C.2.1 General................................................................................................................................................. 23

C.2.2 Frequency analysis ............................................................................................................................ 23

C.2.3 Determination of sound pressure levels .......................................................................................... 24

C.2.4 Calculation of the tonal audibility, ∆L , and the adjustment, K ................................................... 25

ta T

C.3 Documentation.................................................................................................................................... 26

C.4 Detailed definitions of tone and masking noise levels................................................................... 26

C.4.1 Noise pauses....................................................................................................................................... 28

C.4.2 Tones................................................................................................................................................... 28

C.4.3 Masking Noise..................................................................................................................................... 29

C.5 Examples............................................................................................................................................. 29

Annex D (informative) Objective method for assessing the audibility of tones in noise - Survey

method................................................................................................................................................. 32

Annex E (informative) National, source specific calculation models ......................................................... 33

E.1 Road traffic.......................................................................................................................................... 33

E.2 Rail traffic ............................................................................................................................................ 33

E.3 Air traffic.............................................................................................................................................. 34

E.4 Industrial noise ................................................................................................................................... 34

Bibliography..................................................................................................................................................... 35

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ISO/DIS 1996-2
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.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standards

adopted by the technical committees are circulated to the member bodies for voting. Publication as an

International Standard requires approval by at least 75 % of the member bodies casting a vote.

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.

ISO 1996-2 was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 1, Noise.

This part of ISO 1996 is the second in a series of two parts replacing ISO 1996 parts 1, 2 and 3 dating from

1982 and 1997.

ISO 1996 consists of the following parts, under the general title Acoustics — Description, measurement and

assessment of environmental noise:
 Part 1: Basic quantities and assessment procedures
 Part 2: Determination of sound pressure levels
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DRAFT INTERNATIONAL STANDARD ISO/DIS 1996-2
Acoustics — Description, assessment and measurement of
environmental noise —
Part 2:
Determination of environmental noise levels
1 Scope

This part of ISO 1996 describes how sound pressure levels can be determined by direct measurement, by

extrapolation of measurement results by means of calculation or exclusively by calculation, intended as a

basis for assessing environmental noise. Recommendations are given regarding preferable conditions for

measurement or calculation to be applied in cases where other regulations do not apply.

2 Normative references

The following referenced documents are indispensable for the application 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, Acoustics - Description, assessment and measurement of environmental noise - Part 1: Basic

quantities and assessment of procedures.

ISO 5725, Accuracy (trueness and precision) of measurement methods and results – Part 1-6

ISO 9613-1, Acoustics - Attenuation of sound during propagation outdoors - Part 1: Calculation of the

absorption of sound by the atmosphere.

ISO 9613-2, Acoustics - Attenuation of sound during propagation outdoors - Part 2: A general method of

calculation.

ISO 10843, Acoustics - Methods for the physical measurement of single impulses or bursts of noise

ISO/DTS 13474, Acoustics - Impulse sound propagation for environmental noise assessment.

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
ISO, Guide for the expression of uncertainty in measurement (GUM)
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 1996-1 and the following apply.

3.1
receiver location
location at which the noise is assessed
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ISO/DIS 1996-2
3.2
calculation method

set of algorithms to calculate the sound immission level from measured or predicted sound emission and

sound attenuation data
3.3
prediction method

sub-set of a calculation method, intended for the calculation of future noise levels

3.4
measurement time interval
time interval during which single measurements is conducted
3.5
observation time interval
time interval during which a series of measurements is conducted
3.6
meteo-window

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

measurement results due to weather variation
3.7
sound path radius of curvature

R, in m, radius approximating the curvature of the sound paths, due to atmospheric refraction.

3.8
normalised sound path curvature

k, in , the inverse of the sound path radius of curvature multiplied by 1 000, with R expressed in m

4 Measurement uncertainty

The uncertainty of sound pressure levels determined as described in this International Standard depends on

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

and the measurement instrumentation and its method of operation at the chosen measurement site. The

measurement uncertainty shall be determined in compliance with the ISO Guide to Uncertainty in

Measurements (GUM). Some guidelines on how to estimate the measurement uncertainty are given in

Table 1 where the measurement uncertainty is expressed as an expanded uncertainty based on a combined

standard uncertainty multiplied by a coverage factor of 1,65 providing a level of confidence of approximately

90 %. Table 1 refers to A-weighted equivalent-continuous sound pressure levels only. Higher uncertainties are

to be expected on maximum levels, frequency band levels and tonal levels.

NOTE Competent authorities may set other levels of confidence. A coverage factor of 1,3 will, e.g., provide a level of

confidence of 80 % and one of 2 a level of confidence of 95 %.
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ISO/DIS 1996-2
Table 1 — Overview of the measurement uncertainty
Standard Standard Standard Standard Combined standard Expanded
deviation of deviation deviation due deviation due uncertainty measurement
reproducibility due to to weather to residual uncertainty
operating and ground sound
2) 3)
conditions conditions in dB
in dB
in dB
in dB in dB
in dB
1,0 X Y Z + 1,65 σ
2 2 2 2
1,0 + X +Y +Z

Different operator, different equipment, same place but everything else constant, see ISO 5725. If

type 2 sound level meters or directional microphones are used the value will be larger.

To be determined from at least 3, and preferably 5 measurements under repeatability conditions (the

same measurement procedure, the same instruments, the same operator, the same place) and at a

position where variations in meteorological conditions have little influence on the results. For long-term

measurements more measurements will be required to determine the repeatability standard deviation.

For road traffic some guidance on the value of X is given in 6.2.

The value will vary depending upon the measurement distance and the prevailing meteorology. A

method using a simplified meteorological window is provided in Annex A (in this case Y= σ ). For

long-term measurements different weather categories will have to be dealt with separately and then

combined together. For short-term measurements variations in ground conditions will be small.

However, for long-term measurements, these variations may add considerably to the measurement

uncertainty.

The value will vary depending on the difference between measured values and the residual sound.

This value refers to L -measurements.
Aeq
5 Instrumentation
5.1 Instrumentation system

The instrumentation system, including the microphone, cable and recorders if any, shall meet the

requirements for a type 1 instrument laid down in IEC 61672-1. A wind shield shall always be used during

outdoor measurements.

For measurements in octave or one-third-octave bands the instrumentation system shall meet the

requirements of IEC 61260.

NOTE If directional microphones, e.g. cardioid microphones, are used they have to be calibrated properly.

5.2 Calibration

Immediately before and after each series of measurements, apply a class 1 sound calibrator according to

IEC 60942 to the microphone for checking the calibration of the entire measuring system at one or more

frequencies.

NOTE If measurements take place over longer periods of time, e.g. over a daytime period or more, then the

measurement system should be checked either acoustically or electrically at regular periods, e.g. once or twice a day.

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ISO/DIS 1996-2

Verify the compliance of the calibrator with the requirements of IEC 60942 once a year and the compliance of

the instrumentation system with the requirements of IEC 61672-1 at least every two years in a laboratory with

traceability to a primary or national standard laboratory.

Record the date of the last check and confirmation of the compliance with the relevant IEC standard.

6 Operation of the source
6.1 General

The source operating conditions shall be statistically representative of the noise environment under

consideration. To obtain a reliable estimate of the equivalent-continuous sound pressure level as well as the

maximum sound pressure level the measurement time interval shall encompass a minimum number of noise

events. For the most common types of noise sources guidance is given in 6.2 to 6.5. The number of vehicle

pass-bys (vehicle, train, aircraft) needed to average the variation in individual vehicle noise emission depend

on the required accuracy. The level of confidence and confidence interval shall be noticed.

6.2 Road traffic

When measuring L the number of vehicle pass-bys shall be counted during the measurement time interval.

At least the two categories of vehicles ‘heavy’ and ‘light’ shall be distinguished between if the measurement

result shall be converted to other traffic conditions. In order to be able to determine the representativity of the

conditions the speed has to be measured and the type of road surface has to be recorded.

The number of vehicle pass-bys needed to average the variation in individual vehicle noise emission depend

on the required accuracy. The standard deviation denoted X in Table 1 to be expected as a function of the

number of pass-bys, n, can, if no better information is available, be calculated by means of Equation (1)

X ≅ dB (1)

When L from individual vehicle pass-bys are registered and used together with traffic statistics to calculate

L over the reference time interval, the minimum number of vehicles per category shall be 30 and vehicles

deviating extremely from the average (e.g. due to a defect exhaust silencer) shall be disregarded.

The maximum sound pressure levels differ between vehicle categories. Within each vehicle category a certain

spread of maximum sound pressure levels is encountered due to individual differences between vehicles and

due to variation in speed or driving pattern. The maximum sound pressure level should be determined based

on the sound pressure level measured during at least 30 pass-bys of vehicles of the category considered.

6.3 Rail traffic

L measurements shall comprise the pass-by noise from 10 or more of each category of train potentially

contributing significantly to the overall L . For freight trains a minimum number of 15 is recommended. If only

one category of trains contributes to L at least 20 pass-bys of that category shall be recorded. If necessary

measurements shall be continued another day.

To determine the maximum sound pressure level for a certain category of train category record the maximum

noise level during at least 20 pass-bys.

NOTE If it is not possible to obtain so many recordings it shall be stated in the report how many train pass-bys were

analysed and the influence on the uncertainty shall be assessed.
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6.4 Air traffic

When measuring L , measure pass-by noise from 5 or more of each relevant type of aircraft. Ensure that

traffic pattern (runway use, take-off and landing procedures, air fleet mix, time-of-day distribution of the traffic)

is relevant for the issue under consideration.

If the purpose is to measure the maximum sound pressure level from air traffic in a specific residential area,

ensure that the measurement period contains the aircraft types with the highest noise emission using the flight

tracks of nearest proximity. Maximum sound pressure levels shall be determined from at least 5 and

preferably 20 or more occurrences of the most noisy relevant aircraft operation. To estimate percentiles of the

distribution of maximum sound pressure levels record at least 20 relevant events.

NOTE If it is not possible to obtain so many recordings it shall be stated in the report how many aircraft pass-bys

were analysed and the influence on the uncertainty shall be assessed.
6.5 Industrial plants

The source operating conditions shall be divided into classes: For each class the time variation of the sound

emission from the plant shall be reasonabl
...