ISO 1996-2:2007
(Main)Acoustics — Description, measurement and assessment of environmental noise — Part 2: Determination of environmental noise levels
Acoustics — Description, measurement and assessment of environmental noise — Part 2: Determination of environmental noise levels
ISO 1996-2:2007 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. ISO 1996-2:2007 can be used to measure with any frequency weighting or in any frequency band. Guidance is given to evaluate the uncertainty of the result of a noise assessment.
Acoustique — Description, évaluation et mesurage du bruit de l'environnement — Partie 2: Détermination des niveaux de bruit de l'environnement
Akustika - Opis, merjenje in ocena hrupa v okolju - 2. del: Določanje ravni hrupa v okolju
Ta del standarda ISO 1996 opisuje, kako je mogoče določiti zvočni tlak z neposrednim merjenjem, računsko z ekstrapolacijo merilnih rezultatov ali izključno računsko, in je namenjen kot podlaga za ocenjevanje hrupa v okolju. Podana so priporočila glede na preferenčne pogoje meritev ali izračunov, ki se uporabljajo v primerih, kadar ni v veljavi drugih predpisov. Ta del standarda ISO 1996 je mogoče uporabiti pri meritvah s katerim koli frekvenčnim vrednotenjem ali v katerem koli frekvenčnem pasu. Podane so smernice za določitev merilne negotovosti pri ocenjevanju hrupa.
OPOMBA 1: Ker ta del standarda ISO 1996 obravnava izvajanje meritev v dejanskih obratovalnih razmerah, ni nobene povezave tega dela ISO 1996 z drugimi standardi ISO, ki določajo merjenje emisij v točno določenih obratovalnih razmerah.
OPOMBA 2: Zaradi splošnosti sta opis frekvenčnega in časovnega vrednotenja v tem delu standarda ISO 1996 izpuščena.
General Information
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Buy Standard
Standards Content (Sample)
SLOVENSKI STANDARD
SIST ISO 1996-2:2007
01-september-2007
$NXVWLND2SLVPHUMHQMHLQRFHQDKUXSDYRNROMXGHO 'RORþDQMHUDYQLKUXSDY
RNROMX
Acoustics - Description, measurement and assessment of environmental noise - Part 2:
Determination of environmental noise levels
Ta slovenski standard je istoveten z:
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 1996-2:2007 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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INTERNATIONAL ISO
STANDARD 1996-2
Second edition
2007-03-15
Acoustics — Description, measurement
and assessment 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
Reference number
ISO 1996-2:2007(E)
©
ISO 2007
---------------------- Page: 2 ----------------------
ISO 1996-2:2007(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
© ISO 2007
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2007 – All rights reserved
---------------------- Page: 3 ----------------------
ISO 1996-2:2007(E)
Contents Page
Foreword. v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 2
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 . 5
6.4 Air traffic . 5
6.5 Industrial plants . 5
6.6 Low-frequency sound sources. 6
7 Weather conditions. 6
7.1 General. 6
7.2 Conditions favourable to sound propagation. 6
7.3 Average sound pressure levels under a range of weather conditions . 7
8 Measurement procedure . 7
8.1 Principle. 7
8.2 Selection of measurement time interval. 7
8.3 Microphone location. 7
8.4 Measurements. 9
9 Evaluation of the measurement result. 10
9.1 General. 10
9.2 Time-integrated levels, L and L . 11
E eqT
9.3 Maximum level, L . 11
max
9.4 Exceedance levels, L . 12
N,T
9.5 Indoor measurements . 12
9.6 Residual sound . 13
10 Extrapolation to other conditions . 13
10.1 Location . 13
10.2 Other time and operating conditions. 13
11 Calculation. 14
11.1 General. 14
11.2 Calculation methods. 14
12 Information to be recorded and reported.15
Annex A (informative) Meteorological window and measurement uncertainty due to weather . 16
Annex B (informative) Microphone positions relative to reflecting surfaces . 23
Annex C (informative) Objective method for assessing the audibility of tones in noise —
Reference method. 27
© ISO 2007 – All rights reserved iii
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ISO 1996-2:2007(E)
Annex D (informative) Objective method for assessing the audibility of tones in noise —
Simplified method . 36
Annex E (informative) National source-specific calculation methods. 37
Bibliography . 40
iv © ISO 2007 – All rights reserved
---------------------- Page: 5 ----------------------
ISO 1996-2:2007(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.
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 second edition of ISO 1996-2, together with ISO 1996-1:2003, cancels and replaces the first edition
(ISO 1996-2:1987), ISO 1996-1:1982 and ISO 1996-3:1987. It also incorporates the Amendment
ISO 1996-2:1987/Amd.1:1998.
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 environmental noise levels
© ISO 2007 – All rights reserved v
---------------------- Page: 6 ----------------------
INTERNATIONAL STANDARD ISO 1996-2:2007(E)
Acoustics — Description, measurement and assessment 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. This part of ISO 1996
can be used to measure with any frequency weighting or in any frequency band. Guidance is given to
evaluate the uncertainty of the result of a noise assessment.
NOTE 1 As this part of ISO 1996 deals with measurements under actual operating conditions, there is no relationship
between this part of ISO 1996 and other ISO standards specifying emission measurements under specified operating
conditions.
NOTE 2 For the sake of generality, the frequency and time weighting subscripts have been omitted throughout this part
of ISO 1996.
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 1996-1:2003, Acoustics — Description, measurement and assessment of environmental noise —
Part 1: Basic quantities and assessment procedures
ISO 7196, Acoustics — Frequency-weighting characteristic for infrasound measurements
IEC 60942:2003, Electroacoustics — Sound calibrators
IEC 61260:1995, Electroacoustics — Octave-band and fractional-octave band filters
IEC 61672-1:2002, Electroacoustics — Sound level meters — Part 1: Specifications
Guide to the expression of uncertainty in measurement (GUM), BIPM/IEC/IFCC/ISO/IUPAC/IUPAP/OIML,
1993 (corrected and reprinted, 1995)
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ISO 1996-2:2007(E)
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
3.2
calculation method
set of algorithms to calculate the sound pressure level at arbitrary locations from measured or predicted sound
emission and sound attenuation data
3.3
prediction method
subset of a calculation method, intended for the calculation of future noise levels
3.4
measurement time interval
time interval during which a single measurement is conducted
3.5
observation time interval
time interval during which a series of measurements is conducted
3.6
meteorological window
set of weather conditions during which measurements can be performed with limited and known variation in
measurement results due to weather variation
3.7
soundpath radius of curvature
R
radius approximating the curvature of the sound paths due to atmospheric refraction
NOTE R is expressed in kilometres.
3.8
low-frequency sound
sound containing frequencies of interest within the range covering the one-third octave bands from 16 Hz to
200 Hz
4 Measurement uncertainty
The uncertainty of sound pressure levels determined as described in this part of ISO 1996 depends on the
sound source and the measurement time interval, the weather conditions, the distance from the source and
the measurement method and instrumentation. The measurement uncertainty shall be determined in
accordance with the 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 2, providing a coverage probability of approximately
95 %. Table 1 refers to A-weighted equivalent continuous sound pressure levels only. Higher uncertainties
can be expected on maximum levels, frequency band levels and levels of tonal components in noise.
NOTE 1 Table 1 is not complete. When preparing this part of ISO 1996, insufficient information was available. In many
cases, it is appropriate to add more uncertainty contributions, e.g. the one associated with the selection of microphone
location.
NOTE 2 Cognizant authorities can set other levels of confidence. A coverage factor of 1,3, for example, provides a
level of confidence of 80 % and a coverage factor of 1,65, a level of confidence of 90 %.
2 © ISO 2007 – All rights reserved
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ISO 1996-2:2007(E)
In test reports, the coverage probability shall always be stated together with the expanded uncertainty.
Table 1 — Overview of the measurement uncertainty for L
Aeq
Standard uncertainty Combined standard Expanded
uncertainty measurement
Due to Due to Due to weather Due to residual
uncertainty
a d
σ
instrumentation operating and ground sound
t
b c
± 2,0 σ
conditions conditions
22 2 2 t
1, 0++X YZ+
1,0 Z
dB dB
X Y
dB dB
dB dB
a
For IEC 61672-1:2002 class 1 instrumentation. If other instrumentation (IEC 61672-1:2002 class 2 or IEC 60651:2001/
IEC 60804:2000 type 1 sound level meters) or directional microphones are used, the value will be larger.
b
To be determined from at least three, and preferably five, 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 are required to determine the repeatability
standard deviation. For road-traffic noise, some guidance on the value of X is given in 6.2.
c
The value varies depending upon the measurement distance and the prevailing meteorological conditions. A method using a
simplified meteorological window is provided in Annex A (in this case Y = σ ). For long-term measurements, it is necessary to deal with
m
different weather categories separately and then combined together. For short-term measurement, variations in ground conditions are
small. However, for long-term measurements, these variations can add considerably to the measurement uncertainty.
d
The value varies depending on the difference between measured total values and the residual sound.
5 Instrumentation
5.1 Instrumentation system
The instrumentation system, including the microphone, wind shield, cable and recorders, if any, shall conform
to the requirements of one of the following:
⎯ a class 1 instrument as specified in IEC 61672-1:2002,
⎯ a class 2 instrument as specified in IEC 61672-1:2002.
A wind shield shall always be used during outdoor measurements.
Cognizant authorities may require instruments conforming with IEC 61672-1:2002 class 1.
NOTE 1 IEC 61672-1:2002 class 1 instruments are specified over the range of air temperatures from − 10 °C to
+ 50 °C and IEC 61672-1:2002 class 2 instruments from 0 °C to + 40 °C.
NOTE 2 Most sound level meters that meet the requirements in IEC 60651 and IEC 60804 also meet the acoustic
requirements of IEC 61672-1.
For measurements in octave or one-third-octave bands, the class 1 and class 2 instrumentation systems shall
meet the requirements of a class 1 or class 2 filter, respectively, specified in IEC 61260:1995.
5.2 Calibration
Immediately before and after each series of measurements, a class 1, or, in the case of class 2 instruments, a
class 1 or a class 2 sound calibrator in accordance with IEC 60942:2003 shall be applied to the microphone to
check the calibration of the entire measuring system at one or more frequencies.
If measurements take place over longer periods of time, e.g. over a day or more, then the measurement
system should be checked either acoustically or electrically at regular intervals, e.g. once or twice a day.
© ISO 2007 – All rights reserved 3
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ISO 1996-2:2007(E)
It is recommended to verify the compliance of the calibrator with the requirements of IEC 60942 at least once
a year and the compliance of the instrumentation system with the requirements of the relevant IEC standards
at least every two years in a laboratory with traceability to national standards.
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.
NOTE The operating conditions of this part of ISO 1996 are always the actual ones. Accordingly, they normally differ
from the operating conditions stated in International Standards for noise emission measurements.
The equivalent continuous sound pressure level, L of noise from rail and air traffic can often be determined
eqT,
most efficiently by measuring a number of single event sound exposure levels, L , and calculating the
E
equivalent continuous sound pressure level based on these. Direct measurement of the equivalent continuous
sound pressure level, L , is possible when the noise is stationary or time varying, such as is the case with
eqT
noise from road traffic and industrial plants. Single-event sound exposure levels, L , from road vehicles can
E
be measured only at roads with a small traffic volume.
6.2 Road traffic
6.2.1 L measurement
eq
When measuring L , the number of vehicle pass-bys shall be counted during the measurement time interval.
eq
If the measurement result is converted to other traffic conditions, distinction shall be made between at least
the two categories of vehicles “heavy” and “light”. To determine if the traffic conditions are representative, the
average traffic speed shall be measured and the type of road surface noted.
NOTE A common definition of a heavy vehicle is one exceeding the mass 3 500 kg. Often heavy vehicles are divided
into several sub-categories depending on the number of wheel axles.
The number of vehicle pass-bys needed to average the variation in individual vehicle noise emission depends
on the required accuracy of the measured L . If no better information is available, the standard uncertainty
eq
denoted by X in Table 1 can be calculated by means of Equation (1):
10
X ≅ dB (1)
n
where n is the total number of vehicle pass-bys.
NOTE Equation (1) refers to mixed road traffic. If only one category of vehicles is involved, the standard uncertainty will
be smaller.
When L from individual vehicle pass-bys are registered and used together with traffic statistics to calculate
E
L over the reference time interval, the minimum number of vehicles per category shall be 30.
eq
6.2.2 L measurement
max
The maximum sound pressure levels as defined in ISO 1996-1 differ among vehicle categories. Within each
vehicle category, a certain spread of maximum sound pressure levels is encountered due to individual
differences among vehicles and variation in speed or driving patterns. 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.
4 © ISO 2007 – All rights reserved
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ISO 1996-2:2007(E)
6.3 Rail traffic
6.3.1 L measurement
eq
Measurements shall consist of the pass-by noise from at least 20 trains. Each category of train potentially
contributing significantly to the overall L shall be represented by at least five pass-bys. If necessary,
eq
measurements shall be continued on a subsequent day.
6.3.2 L measurement
max
To determine the maximum sound pressure level for a certain category of train, the maximum sound pressure
level during at least 20 pass-bys shall be recorded. If it is not possible to obtain this 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.
6.4 Air traffic
6.4.1 L measurement
eq
Measurements shall consist of the pass-by noise from five or more of each type of aircraft contributing
significantly to the sound pressure level to be determined. Ensure that traffic pattern (runway use, take-off and
landing procedures, airfleet mix, time-of-day distribution of the traffic) is relevant for the issue under
consideration.
6.4.2 L measurement
max
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 five 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. If it is not possible to obtain
this many recordings, it shall be stated in the report how many aircraft pass-bys are analysed and the
influence on the uncertainty shall be assessed.
NOTE Pass-by noise can be caused by aircraft in flight or on the ground, e.g. taxiing.
6.5 Industrial plants
6.5.1 L measurement
eq
The source operating conditions shall be divided into classes. For each class, the time variation of the sound
emission from the plant shall be reasonably stationary in a stochastical sense. The variation shall be less than
the variation in transmission-path attenuation due to varying weather conditions (see Clause 7). The time
variation of the sound emission from the plant shall be determined from 5 min to 10 min L values measured
eq
at a distance long enough to include noise contributions from all major sources and short enough to minimize
meteorological effects (see Clause 7) during a certain operating condition. If the source is cyclic, the
measurement time shall encompass a whole number of cycles. A new categorization of the operating
conditions shall be made if the criterion is exceeded. If the criterion is met, measure L during each class of
eq
operating condition and calculate the resulting L , taking into account the frequency and duration of each
eq
class of operating condition.
6.5.2 L measurement
max
If the purpose is to measure the maximum sound pressure level of noise from industrial plants, ensure that the
measurement period contains the plant operating condition with the highest noise emission occurring at the
nearest proximity to the receiver location. Maximum sound pressure levels shall be determined from at least
five events of the most noisy relevant operation condition.
NOTE The operating condition is defined by the activity as well as its location.
© ISO 2007 – All rights reserved 5
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ISO 1996-2:2007(E)
6.6 Low-frequency sound sources
Examples of low-frequency sound sources are helicopters, sound from bridge vibrations, subway trains,
stamping plants, pneumatic construction equipment, etc. ISO 1996-1:2003, Annex C, contains a further
discussion on low-frequency sound. Procedures to measure low-frequency noise are given in 8.3.2 and 8.4.9.
7 Weather conditions
7.1 General
The weather conditions shall be representative of the noise exposure situation under consideration.
The road or rail surface shall be dry and the ground surface shall not be covered with snow or ice and should
be neither frozen nor soaked by excessive amounts of water, unless such conditions are to be investigated.
Sound pressure levels vary with the weather conditions. For soft ground such variation is modest when
Equation (2) applies:
hh+
sr
W 0,1 (2)
r
where
h is the source height;
s
h is the receiver height;
r
r is the distance between the source and receiver.
If the ground is hard, larger distances are acceptable.
The meteorological conditions during measurement shall be described or, if necessary, monitored. When the
condition in Equation (2) is not fulfilled, the weather conditions can seriously affect the results of the
measurement. General guidance is given in 7.2 and 7.3, while more precise guidance is given in Annex A.
Upwind of the source, measurements have large uncertainties and such conditions are not usually suitable for
short-term environmental-noise measurements.
7.2 Conditions favourable to sound propagation
To facilitate the comparison of results, it is convenient to carry out measurements under selected
meteorological conditions, so that the results are reproducible. This is the case under rather stable sound
propagation conditions.
Such conditions exist when the sound paths are refracted downwards, for example during downwind, meaning
high sound pressure levels and moderate level variation. The sound path radius of curvature, R, is positive
and its value depends on the wind speed and temperature gradients near the ground, as expressed in
Equation (A.1).
With one dominant source, choose meteorological conditions with downward sound-ray curvature from the
source to the receiver and adopt measurement time intervals corresponding to the conditions given in
Annex A, for example R < 10 km.
As a guidance, the condition R < 10 km holds when
⎯ the wind is blowing from the dominant sound source to the receiver (daytime within an angle of ± 60°,
night-time within an angle of ± 90°),
6 © ISO 2007 – All rights reserved
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ISO 1996-2:2007(E)
⎯ the wind speed, measured at a height of 3 m to 11 m above the ground, is between 2 m/s and 5 m/s
during the daytime or more than 0,5 m/s at night-time,
⎯ no strong, negative temperature gradient occurs near the ground, e.g. when there is no bright sunshine
during the daytime.
7.3 Average sound pressure levels under a range of weather conditions
E
...
INTERNATIONAL ISO
STANDARD 1996-2
Second edition
2007-03-15
Acoustics — Description, measurement
and assessment 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
Reference number
ISO 1996-2:2007(E)
©
ISO 2007
---------------------- Page: 1 ----------------------
ISO 1996-2:2007(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
© ISO 2007
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2007 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 1996-2:2007(E)
Contents Page
Foreword. v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 2
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 . 5
6.4 Air traffic . 5
6.5 Industrial plants . 5
6.6 Low-frequency sound sources. 6
7 Weather conditions. 6
7.1 General. 6
7.2 Conditions favourable to sound propagation. 6
7.3 Average sound pressure levels under a range of weather conditions . 7
8 Measurement procedure . 7
8.1 Principle. 7
8.2 Selection of measurement time interval. 7
8.3 Microphone location. 7
8.4 Measurements. 9
9 Evaluation of the measurement result. 10
9.1 General. 10
9.2 Time-integrated levels, L and L . 11
E eqT
9.3 Maximum level, L . 11
max
9.4 Exceedance levels, L . 12
N,T
9.5 Indoor measurements . 12
9.6 Residual sound . 13
10 Extrapolation to other conditions . 13
10.1 Location . 13
10.2 Other time and operating conditions. 13
11 Calculation. 14
11.1 General. 14
11.2 Calculation methods. 14
12 Information to be recorded and reported.15
Annex A (informative) Meteorological window and measurement uncertainty due to weather . 16
Annex B (informative) Microphone positions relative to reflecting surfaces . 23
Annex C (informative) Objective method for assessing the audibility of tones in noise —
Reference method. 27
© ISO 2007 – All rights reserved iii
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ISO 1996-2:2007(E)
Annex D (informative) Objective method for assessing the audibility of tones in noise —
Simplified method . 36
Annex E (informative) National source-specific calculation methods. 37
Bibliography . 40
iv © ISO 2007 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 1996-2:2007(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.
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 second edition of ISO 1996-2, together with ISO 1996-1:2003, cancels and replaces the first edition
(ISO 1996-2:1987), ISO 1996-1:1982 and ISO 1996-3:1987. It also incorporates the Amendment
ISO 1996-2:1987/Amd.1:1998.
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 environmental noise levels
© ISO 2007 – All rights reserved v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 1996-2:2007(E)
Acoustics — Description, measurement and assessment 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. This part of ISO 1996
can be used to measure with any frequency weighting or in any frequency band. Guidance is given to
evaluate the uncertainty of the result of a noise assessment.
NOTE 1 As this part of ISO 1996 deals with measurements under actual operating conditions, there is no relationship
between this part of ISO 1996 and other ISO standards specifying emission measurements under specified operating
conditions.
NOTE 2 For the sake of generality, the frequency and time weighting subscripts have been omitted throughout this part
of ISO 1996.
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 1996-1:2003, Acoustics — Description, measurement and assessment of environmental noise —
Part 1: Basic quantities and assessment procedures
ISO 7196, Acoustics — Frequency-weighting characteristic for infrasound measurements
IEC 60942:2003, Electroacoustics — Sound calibrators
IEC 61260:1995, Electroacoustics — Octave-band and fractional-octave band filters
IEC 61672-1:2002, Electroacoustics — Sound level meters — Part 1: Specifications
Guide to the expression of uncertainty in measurement (GUM), BIPM/IEC/IFCC/ISO/IUPAC/IUPAP/OIML,
1993 (corrected and reprinted, 1995)
© ISO 2007 – All rights reserved 1
---------------------- Page: 6 ----------------------
ISO 1996-2:2007(E)
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
3.2
calculation method
set of algorithms to calculate the sound pressure level at arbitrary locations from measured or predicted sound
emission and sound attenuation data
3.3
prediction method
subset of a calculation method, intended for the calculation of future noise levels
3.4
measurement time interval
time interval during which a single measurement is conducted
3.5
observation time interval
time interval during which a series of measurements is conducted
3.6
meteorological window
set of weather conditions during which measurements can be performed with limited and known variation in
measurement results due to weather variation
3.7
soundpath radius of curvature
R
radius approximating the curvature of the sound paths due to atmospheric refraction
NOTE R is expressed in kilometres.
3.8
low-frequency sound
sound containing frequencies of interest within the range covering the one-third octave bands from 16 Hz to
200 Hz
4 Measurement uncertainty
The uncertainty of sound pressure levels determined as described in this part of ISO 1996 depends on the
sound source and the measurement time interval, the weather conditions, the distance from the source and
the measurement method and instrumentation. The measurement uncertainty shall be determined in
accordance with the 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 2, providing a coverage probability of approximately
95 %. Table 1 refers to A-weighted equivalent continuous sound pressure levels only. Higher uncertainties
can be expected on maximum levels, frequency band levels and levels of tonal components in noise.
NOTE 1 Table 1 is not complete. When preparing this part of ISO 1996, insufficient information was available. In many
cases, it is appropriate to add more uncertainty contributions, e.g. the one associated with the selection of microphone
location.
NOTE 2 Cognizant authorities can set other levels of confidence. A coverage factor of 1,3, for example, provides a
level of confidence of 80 % and a coverage factor of 1,65, a level of confidence of 90 %.
2 © ISO 2007 – All rights reserved
---------------------- Page: 7 ----------------------
ISO 1996-2:2007(E)
In test reports, the coverage probability shall always be stated together with the expanded uncertainty.
Table 1 — Overview of the measurement uncertainty for L
Aeq
Standard uncertainty Combined standard Expanded
uncertainty measurement
Due to Due to Due to weather Due to residual
uncertainty
a d
σ
instrumentation operating and ground sound
t
b c
± 2,0 σ
conditions conditions
22 2 2 t
1, 0++X YZ+
1,0 Z
dB dB
X Y
dB dB
dB dB
a
For IEC 61672-1:2002 class 1 instrumentation. If other instrumentation (IEC 61672-1:2002 class 2 or IEC 60651:2001/
IEC 60804:2000 type 1 sound level meters) or directional microphones are used, the value will be larger.
b
To be determined from at least three, and preferably five, 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 are required to determine the repeatability
standard deviation. For road-traffic noise, some guidance on the value of X is given in 6.2.
c
The value varies depending upon the measurement distance and the prevailing meteorological conditions. A method using a
simplified meteorological window is provided in Annex A (in this case Y = σ ). For long-term measurements, it is necessary to deal with
m
different weather categories separately and then combined together. For short-term measurement, variations in ground conditions are
small. However, for long-term measurements, these variations can add considerably to the measurement uncertainty.
d
The value varies depending on the difference between measured total values and the residual sound.
5 Instrumentation
5.1 Instrumentation system
The instrumentation system, including the microphone, wind shield, cable and recorders, if any, shall conform
to the requirements of one of the following:
⎯ a class 1 instrument as specified in IEC 61672-1:2002,
⎯ a class 2 instrument as specified in IEC 61672-1:2002.
A wind shield shall always be used during outdoor measurements.
Cognizant authorities may require instruments conforming with IEC 61672-1:2002 class 1.
NOTE 1 IEC 61672-1:2002 class 1 instruments are specified over the range of air temperatures from − 10 °C to
+ 50 °C and IEC 61672-1:2002 class 2 instruments from 0 °C to + 40 °C.
NOTE 2 Most sound level meters that meet the requirements in IEC 60651 and IEC 60804 also meet the acoustic
requirements of IEC 61672-1.
For measurements in octave or one-third-octave bands, the class 1 and class 2 instrumentation systems shall
meet the requirements of a class 1 or class 2 filter, respectively, specified in IEC 61260:1995.
5.2 Calibration
Immediately before and after each series of measurements, a class 1, or, in the case of class 2 instruments, a
class 1 or a class 2 sound calibrator in accordance with IEC 60942:2003 shall be applied to the microphone to
check the calibration of the entire measuring system at one or more frequencies.
If measurements take place over longer periods of time, e.g. over a day or more, then the measurement
system should be checked either acoustically or electrically at regular intervals, e.g. once or twice a day.
© ISO 2007 – All rights reserved 3
---------------------- Page: 8 ----------------------
ISO 1996-2:2007(E)
It is recommended to verify the compliance of the calibrator with the requirements of IEC 60942 at least once
a year and the compliance of the instrumentation system with the requirements of the relevant IEC standards
at least every two years in a laboratory with traceability to national standards.
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.
NOTE The operating conditions of this part of ISO 1996 are always the actual ones. Accordingly, they normally differ
from the operating conditions stated in International Standards for noise emission measurements.
The equivalent continuous sound pressure level, L of noise from rail and air traffic can often be determined
eqT,
most efficiently by measuring a number of single event sound exposure levels, L , and calculating the
E
equivalent continuous sound pressure level based on these. Direct measurement of the equivalent continuous
sound pressure level, L , is possible when the noise is stationary or time varying, such as is the case with
eqT
noise from road traffic and industrial plants. Single-event sound exposure levels, L , from road vehicles can
E
be measured only at roads with a small traffic volume.
6.2 Road traffic
6.2.1 L measurement
eq
When measuring L , the number of vehicle pass-bys shall be counted during the measurement time interval.
eq
If the measurement result is converted to other traffic conditions, distinction shall be made between at least
the two categories of vehicles “heavy” and “light”. To determine if the traffic conditions are representative, the
average traffic speed shall be measured and the type of road surface noted.
NOTE A common definition of a heavy vehicle is one exceeding the mass 3 500 kg. Often heavy vehicles are divided
into several sub-categories depending on the number of wheel axles.
The number of vehicle pass-bys needed to average the variation in individual vehicle noise emission depends
on the required accuracy of the measured L . If no better information is available, the standard uncertainty
eq
denoted by X in Table 1 can be calculated by means of Equation (1):
10
X ≅ dB (1)
n
where n is the total number of vehicle pass-bys.
NOTE Equation (1) refers to mixed road traffic. If only one category of vehicles is involved, the standard uncertainty will
be smaller.
When L from individual vehicle pass-bys are registered and used together with traffic statistics to calculate
E
L over the reference time interval, the minimum number of vehicles per category shall be 30.
eq
6.2.2 L measurement
max
The maximum sound pressure levels as defined in ISO 1996-1 differ among vehicle categories. Within each
vehicle category, a certain spread of maximum sound pressure levels is encountered due to individual
differences among vehicles and variation in speed or driving patterns. 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.
4 © ISO 2007 – All rights reserved
---------------------- Page: 9 ----------------------
ISO 1996-2:2007(E)
6.3 Rail traffic
6.3.1 L measurement
eq
Measurements shall consist of the pass-by noise from at least 20 trains. Each category of train potentially
contributing significantly to the overall L shall be represented by at least five pass-bys. If necessary,
eq
measurements shall be continued on a subsequent day.
6.3.2 L measurement
max
To determine the maximum sound pressure level for a certain category of train, the maximum sound pressure
level during at least 20 pass-bys shall be recorded. If it is not possible to obtain this 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.
6.4 Air traffic
6.4.1 L measurement
eq
Measurements shall consist of the pass-by noise from five or more of each type of aircraft contributing
significantly to the sound pressure level to be determined. Ensure that traffic pattern (runway use, take-off and
landing procedures, airfleet mix, time-of-day distribution of the traffic) is relevant for the issue under
consideration.
6.4.2 L measurement
max
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 five 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. If it is not possible to obtain
this many recordings, it shall be stated in the report how many aircraft pass-bys are analysed and the
influence on the uncertainty shall be assessed.
NOTE Pass-by noise can be caused by aircraft in flight or on the ground, e.g. taxiing.
6.5 Industrial plants
6.5.1 L measurement
eq
The source operating conditions shall be divided into classes. For each class, the time variation of the sound
emission from the plant shall be reasonably stationary in a stochastical sense. The variation shall be less than
the variation in transmission-path attenuation due to varying weather conditions (see Clause 7). The time
variation of the sound emission from the plant shall be determined from 5 min to 10 min L values measured
eq
at a distance long enough to include noise contributions from all major sources and short enough to minimize
meteorological effects (see Clause 7) during a certain operating condition. If the source is cyclic, the
measurement time shall encompass a whole number of cycles. A new categorization of the operating
conditions shall be made if the criterion is exceeded. If the criterion is met, measure L during each class of
eq
operating condition and calculate the resulting L , taking into account the frequency and duration of each
eq
class of operating condition.
6.5.2 L measurement
max
If the purpose is to measure the maximum sound pressure level of noise from industrial plants, ensure that the
measurement period contains the plant operating condition with the highest noise emission occurring at the
nearest proximity to the receiver location. Maximum sound pressure levels shall be determined from at least
five events of the most noisy relevant operation condition.
NOTE The operating condition is defined by the activity as well as its location.
© ISO 2007 – All rights reserved 5
---------------------- Page: 10 ----------------------
ISO 1996-2:2007(E)
6.6 Low-frequency sound sources
Examples of low-frequency sound sources are helicopters, sound from bridge vibrations, subway trains,
stamping plants, pneumatic construction equipment, etc. ISO 1996-1:2003, Annex C, contains a further
discussion on low-frequency sound. Procedures to measure low-frequency noise are given in 8.3.2 and 8.4.9.
7 Weather conditions
7.1 General
The weather conditions shall be representative of the noise exposure situation under consideration.
The road or rail surface shall be dry and the ground surface shall not be covered with snow or ice and should
be neither frozen nor soaked by excessive amounts of water, unless such conditions are to be investigated.
Sound pressure levels vary with the weather conditions. For soft ground such variation is modest when
Equation (2) applies:
hh+
sr
W 0,1 (2)
r
where
h is the source height;
s
h is the receiver height;
r
r is the distance between the source and receiver.
If the ground is hard, larger distances are acceptable.
The meteorological conditions during measurement shall be described or, if necessary, monitored. When the
condition in Equation (2) is not fulfilled, the weather conditions can seriously affect the results of the
measurement. General guidance is given in 7.2 and 7.3, while more precise guidance is given in Annex A.
Upwind of the source, measurements have large uncertainties and such conditions are not usually suitable for
short-term environmental-noise measurements.
7.2 Conditions favourable to sound propagation
To facilitate the comparison of results, it is convenient to carry out measurements under selected
meteorological conditions, so that the results are reproducible. This is the case under rather stable sound
propagation conditions.
Such conditions exist when the sound paths are refracted downwards, for example during downwind, meaning
high sound pressure levels and moderate level variation. The sound path radius of curvature, R, is positive
and its value depends on the wind speed and temperature gradients near the ground, as expressed in
Equation (A.1).
With one dominant source, choose meteorological conditions with downward sound-ray curvature from the
source to the receiver and adopt measurement time intervals corresponding to the conditions given in
Annex A, for example R < 10 km.
As a guidance, the condition R < 10 km holds when
⎯ the wind is blowing from the dominant sound source to the receiver (daytime within an angle of ± 60°,
night-time within an angle of ± 90°),
6 © ISO 2007 – All rights reserved
---------------------- Page: 11 ----------------------
ISO 1996-2:2007(E)
⎯ the wind speed, measured at a height of 3 m to 11 m above the ground, is between 2 m/s and 5 m/s
during the daytime or more than 0,5 m/s at night-time,
⎯ no strong, negative temperature gradient occurs near the ground, e.g. when there is no bright sunshine
during the daytime.
7.3 Average sound pressure levels under a range of weather conditions
Estimating average environmental noise levels as they occur over a range of weather conditions requires long
measurement time intervals, often several months. Alternatively, well monitored, short-term measurements
representing different weather conditions can be combined with calculations taking weather statistics into
account to determine long-term averages.
The combination of source operating conditions and weather-dependent sound propagation shall be taken into
account, so that every important component of sound exposure is represented in the measurement results.
To determine a long-term average noise level as it can occur during a year, it is necessary to take into
account the variations in sou
...
SLOVENSKI STANDARD
oSIST ISO 1996-2:2007
01-julij-2007
$NXVWLND2SLVPHUMHQMHLQRFHQDKUXSDYRNROMXGHO 'RORþDQMHUDYQLKUXSDY
RNROMX
Acoustics - Description, measurement and assessment of environmental noise - Part 2:
Determination of environmental noise levels
Ta slovenski standard je istoveten z:
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
oSIST ISO 1996-2:2007 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
INTERNATIONAL ISO
STANDARD 1996-2
Second edition
2007-03-15
Acoustics — Description, measurement
and assessment 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
Reference number
ISO 1996-2:2007(E)
©
ISO 2007
---------------------- Page: 2 ----------------------
ISO 1996-2:2007(E)
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© ISO 2007
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
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Published in Switzerland
ii © ISO 2007 – All rights reserved
---------------------- Page: 3 ----------------------
ISO 1996-2:2007(E)
Contents Page
Foreword. v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 2
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 . 5
6.4 Air traffic . 5
6.5 Industrial plants . 5
6.6 Low-frequency sound sources. 6
7 Weather conditions. 6
7.1 General. 6
7.2 Conditions favourable to sound propagation. 6
7.3 Average sound pressure levels under a range of weather conditions . 7
8 Measurement procedure . 7
8.1 Principle. 7
8.2 Selection of measurement time interval. 7
8.3 Microphone location. 7
8.4 Measurements. 9
9 Evaluation of the measurement result. 10
9.1 General. 10
9.2 Time-integrated levels, L and L . 11
E eqT
9.3 Maximum level, L . 11
max
9.4 Exceedance levels, L . 12
N,T
9.5 Indoor measurements . 12
9.6 Residual sound . 13
10 Extrapolation to other conditions . 13
10.1 Location . 13
10.2 Other time and operating conditions. 13
11 Calculation. 14
11.1 General. 14
11.2 Calculation methods. 14
12 Information to be recorded and reported.15
Annex A (informative) Meteorological window and measurement uncertainty due to weather . 16
Annex B (informative) Microphone positions relative to reflecting surfaces . 23
Annex C (informative) Objective method for assessing the audibility of tones in noise —
Reference method. 27
© ISO 2007 – All rights reserved iii
---------------------- Page: 4 ----------------------
ISO 1996-2:2007(E)
Annex D (informative) Objective method for assessing the audibility of tones in noise —
Simplified method . 36
Annex E (informative) National source-specific calculation methods. 37
Bibliography . 40
iv © ISO 2007 – All rights reserved
---------------------- Page: 5 ----------------------
ISO 1996-2:2007(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.
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 second edition of ISO 1996-2, together with ISO 1996-1:2003, cancels and replaces the first edition
(ISO 1996-2:1987), ISO 1996-1:1982 and ISO 1996-3:1987. It also incorporates the Amendment
ISO 1996-2:1987/Amd.1:1998.
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 environmental noise levels
© ISO 2007 – All rights reserved v
---------------------- Page: 6 ----------------------
INTERNATIONAL STANDARD ISO 1996-2:2007(E)
Acoustics — Description, measurement and assessment 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. This part of ISO 1996
can be used to measure with any frequency weighting or in any frequency band. Guidance is given to
evaluate the uncertainty of the result of a noise assessment.
NOTE 1 As this part of ISO 1996 deals with measurements under actual operating conditions, there is no relationship
between this part of ISO 1996 and other ISO standards specifying emission measurements under specified operating
conditions.
NOTE 2 For the sake of generality, the frequency and time weighting subscripts have been omitted throughout this part
of ISO 1996.
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 1996-1:2003, Acoustics — Description, measurement and assessment of environmental noise —
Part 1: Basic quantities and assessment procedures
ISO 7196, Acoustics — Frequency-weighting characteristic for infrasound measurements
IEC 60942:2003, Electroacoustics — Sound calibrators
IEC 61260:1995, Electroacoustics — Octave-band and fractional-octave band filters
IEC 61672-1:2002, Electroacoustics — Sound level meters — Part 1: Specifications
Guide to the expression of uncertainty in measurement (GUM), BIPM/IEC/IFCC/ISO/IUPAC/IUPAP/OIML,
1993 (corrected and reprinted, 1995)
© ISO 2007 – All rights reserved 1
---------------------- Page: 7 ----------------------
ISO 1996-2:2007(E)
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
3.2
calculation method
set of algorithms to calculate the sound pressure level at arbitrary locations from measured or predicted sound
emission and sound attenuation data
3.3
prediction method
subset of a calculation method, intended for the calculation of future noise levels
3.4
measurement time interval
time interval during which a single measurement is conducted
3.5
observation time interval
time interval during which a series of measurements is conducted
3.6
meteorological window
set of weather conditions during which measurements can be performed with limited and known variation in
measurement results due to weather variation
3.7
soundpath radius of curvature
R
radius approximating the curvature of the sound paths due to atmospheric refraction
NOTE R is expressed in kilometres.
3.8
low-frequency sound
sound containing frequencies of interest within the range covering the one-third octave bands from 16 Hz to
200 Hz
4 Measurement uncertainty
The uncertainty of sound pressure levels determined as described in this part of ISO 1996 depends on the
sound source and the measurement time interval, the weather conditions, the distance from the source and
the measurement method and instrumentation. The measurement uncertainty shall be determined in
accordance with the 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 2, providing a coverage probability of approximately
95 %. Table 1 refers to A-weighted equivalent continuous sound pressure levels only. Higher uncertainties
can be expected on maximum levels, frequency band levels and levels of tonal components in noise.
NOTE 1 Table 1 is not complete. When preparing this part of ISO 1996, insufficient information was available. In many
cases, it is appropriate to add more uncertainty contributions, e.g. the one associated with the selection of microphone
location.
NOTE 2 Cognizant authorities can set other levels of confidence. A coverage factor of 1,3, for example, provides a
level of confidence of 80 % and a coverage factor of 1,65, a level of confidence of 90 %.
2 © ISO 2007 – All rights reserved
---------------------- Page: 8 ----------------------
ISO 1996-2:2007(E)
In test reports, the coverage probability shall always be stated together with the expanded uncertainty.
Table 1 — Overview of the measurement uncertainty for L
Aeq
Standard uncertainty Combined standard Expanded
uncertainty measurement
Due to Due to Due to weather Due to residual
uncertainty
a d
σ
instrumentation operating and ground sound
t
b c
± 2,0 σ
conditions conditions
22 2 2 t
1, 0++X YZ+
1,0 Z
dB dB
X Y
dB dB
dB dB
a
For IEC 61672-1:2002 class 1 instrumentation. If other instrumentation (IEC 61672-1:2002 class 2 or IEC 60651:2001/
IEC 60804:2000 type 1 sound level meters) or directional microphones are used, the value will be larger.
b
To be determined from at least three, and preferably five, 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 are required to determine the repeatability
standard deviation. For road-traffic noise, some guidance on the value of X is given in 6.2.
c
The value varies depending upon the measurement distance and the prevailing meteorological conditions. A method using a
simplified meteorological window is provided in Annex A (in this case Y = σ ). For long-term measurements, it is necessary to deal with
m
different weather categories separately and then combined together. For short-term measurement, variations in ground conditions are
small. However, for long-term measurements, these variations can add considerably to the measurement uncertainty.
d
The value varies depending on the difference between measured total values and the residual sound.
5 Instrumentation
5.1 Instrumentation system
The instrumentation system, including the microphone, wind shield, cable and recorders, if any, shall conform
to the requirements of one of the following:
⎯ a class 1 instrument as specified in IEC 61672-1:2002,
⎯ a class 2 instrument as specified in IEC 61672-1:2002.
A wind shield shall always be used during outdoor measurements.
Cognizant authorities may require instruments conforming with IEC 61672-1:2002 class 1.
NOTE 1 IEC 61672-1:2002 class 1 instruments are specified over the range of air temperatures from − 10 °C to
+ 50 °C and IEC 61672-1:2002 class 2 instruments from 0 °C to + 40 °C.
NOTE 2 Most sound level meters that meet the requirements in IEC 60651 and IEC 60804 also meet the acoustic
requirements of IEC 61672-1.
For measurements in octave or one-third-octave bands, the class 1 and class 2 instrumentation systems shall
meet the requirements of a class 1 or class 2 filter, respectively, specified in IEC 61260:1995.
5.2 Calibration
Immediately before and after each series of measurements, a class 1, or, in the case of class 2 instruments, a
class 1 or a class 2 sound calibrator in accordance with IEC 60942:2003 shall be applied to the microphone to
check the calibration of the entire measuring system at one or more frequencies.
If measurements take place over longer periods of time, e.g. over a day or more, then the measurement
system should be checked either acoustically or electrically at regular intervals, e.g. once or twice a day.
© ISO 2007 – All rights reserved 3
---------------------- Page: 9 ----------------------
ISO 1996-2:2007(E)
It is recommended to verify the compliance of the calibrator with the requirements of IEC 60942 at least once
a year and the compliance of the instrumentation system with the requirements of the relevant IEC standards
at least every two years in a laboratory with traceability to national standards.
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.
NOTE The operating conditions of this part of ISO 1996 are always the actual ones. Accordingly, they normally differ
from the operating conditions stated in International Standards for noise emission measurements.
The equivalent continuous sound pressure level, L of noise from rail and air traffic can often be determined
eqT,
most efficiently by measuring a number of single event sound exposure levels, L , and calculating the
E
equivalent continuous sound pressure level based on these. Direct measurement of the equivalent continuous
sound pressure level, L , is possible when the noise is stationary or time varying, such as is the case with
eqT
noise from road traffic and industrial plants. Single-event sound exposure levels, L , from road vehicles can
E
be measured only at roads with a small traffic volume.
6.2 Road traffic
6.2.1 L measurement
eq
When measuring L , the number of vehicle pass-bys shall be counted during the measurement time interval.
eq
If the measurement result is converted to other traffic conditions, distinction shall be made between at least
the two categories of vehicles “heavy” and “light”. To determine if the traffic conditions are representative, the
average traffic speed shall be measured and the type of road surface noted.
NOTE A common definition of a heavy vehicle is one exceeding the mass 3 500 kg. Often heavy vehicles are divided
into several sub-categories depending on the number of wheel axles.
The number of vehicle pass-bys needed to average the variation in individual vehicle noise emission depends
on the required accuracy of the measured L . If no better information is available, the standard uncertainty
eq
denoted by X in Table 1 can be calculated by means of Equation (1):
10
X ≅ dB (1)
n
where n is the total number of vehicle pass-bys.
NOTE Equation (1) refers to mixed road traffic. If only one category of vehicles is involved, the standard uncertainty will
be smaller.
When L from individual vehicle pass-bys are registered and used together with traffic statistics to calculate
E
L over the reference time interval, the minimum number of vehicles per category shall be 30.
eq
6.2.2 L measurement
max
The maximum sound pressure levels as defined in ISO 1996-1 differ among vehicle categories. Within each
vehicle category, a certain spread of maximum sound pressure levels is encountered due to individual
differences among vehicles and variation in speed or driving patterns. 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.
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ISO 1996-2:2007(E)
6.3 Rail traffic
6.3.1 L measurement
eq
Measurements shall consist of the pass-by noise from at least 20 trains. Each category of train potentially
contributing significantly to the overall L shall be represented by at least five pass-bys. If necessary,
eq
measurements shall be continued on a subsequent day.
6.3.2 L measurement
max
To determine the maximum sound pressure level for a certain category of train, the maximum sound pressure
level during at least 20 pass-bys shall be recorded. If it is not possible to obtain this 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.
6.4 Air traffic
6.4.1 L measurement
eq
Measurements shall consist of the pass-by noise from five or more of each type of aircraft contributing
significantly to the sound pressure level to be determined. Ensure that traffic pattern (runway use, take-off and
landing procedures, airfleet mix, time-of-day distribution of the traffic) is relevant for the issue under
consideration.
6.4.2 L measurement
max
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 five 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. If it is not possible to obtain
this many recordings, it shall be stated in the report how many aircraft pass-bys are analysed and the
influence on the uncertainty shall be assessed.
NOTE Pass-by noise can be caused by aircraft in flight or on the ground, e.g. taxiing.
6.5 Industrial plants
6.5.1 L measurement
eq
The source operating conditions shall be divided into classes. For each class, the time variation of the sound
emission from the plant shall be reasonably stationary in a stochastical sense. The variation shall be less than
the variation in transmission-path attenuation due to varying weather conditions (see Clause 7). The time
variation of the sound emission from the plant shall be determined from 5 min to 10 min L values measured
eq
at a distance long enough to include noise contributions from all major sources and short enough to minimize
meteorological effects (see Clause 7) during a certain operating condition. If the source is cyclic, the
measurement time shall encompass a whole number of cycles. A new categorization of the operating
conditions shall be made if the criterion is exceeded. If the criterion is met, measure L during each class of
eq
operating condition and calculate the resulting L , taking into account the frequency and duration of each
eq
class of operating condition.
6.5.2 L measurement
max
If the purpose is to measure the maximum sound pressure level of noise from industrial plants, ensure that the
measurement period contains the plant operating condition with the highest noise emission occurring at the
nearest proximity to the receiver location. Maximum sound pressure levels shall be determined from at least
five events of the most noisy relevant operation condition.
NOTE The operating condition is defined by the activity as well as its location.
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ISO 1996-2:2007(E)
6.6 Low-frequency sound sources
Examples of low-frequency sound sources are helicopters, sound from bridge vibrations, subway trains,
stamping plants, pneumatic construction equipment, etc. ISO 1996-1:2003, Annex C, contains a further
discussion on low-frequency sound. Procedures to measure low-frequency noise are given in 8.3.2 and 8.4.9.
7 Weather conditions
7.1 General
The weather conditions shall be representative of the noise exposure situation under consideration.
The road or rail surface shall be dry and the ground surface shall not be covered with snow or ice and should
be neither frozen nor soaked by excessive amounts of water, unless such conditions are to be investigated.
Sound pressure levels vary with the weather conditions. For soft ground such variation is modest when
Equation (2) applies:
hh+
sr
W 0,1 (2)
r
where
h is the source height;
s
h is the receiver height;
r
r is the distance between the source and receiver.
If the ground is hard, larger distances are acceptable.
The meteorological conditions during measurement shall be described or, if necessary, monitored. When the
condition in Equation (2) is not fulfilled, the weather conditions can seriously affect the results of the
measurement. General guidance is given in 7.2 and 7.3, while more precise guidance is given in Annex A.
Upwind of the source, measurements have large uncertainties and such conditions are not usually suitable for
short-term environmental-noise measurements.
7.2 Conditions favourable to sound propagation
To facilitate the comparison of results, it is convenient to carry out measurements under selected
meteorological conditions, so that the results are reproducible. This is the case under rather stable sound
propagation conditions.
Such conditions exist when the sound paths are refracted downwards, for example during downwind, meaning
high sound pressure levels and moderate level variation. The sound path radius of curvature, R, is positive
and its value depends on the wind speed and temperature gradients near the ground, as expressed in
Equation (A.1).
With one dominant source, choose meteorological conditions with downward sound-ray curvature from the
source to the receiver and adopt measurement time intervals corresponding to the conditions given in
Annex A, for example R < 10 km.
As a guidance, the condition R < 10 km holds when
⎯ the wind is blowing from the dominant sound source to the receiver (daytime within an angle of ± 60°,
night-time within an angle of ± 90°),
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ISO 1996-2:2007(E)
⎯ the wind speed, measured at a height of 3 m to 11 m above the ground, is between 2 m/s and 5 m/s
during the daytime or more than 0,5 m/s at night-time,
⎯ no strong, negative temperature gradient occurs near the ground, e.g. when there is no bright sunshine
during the daytime.
7.3 Average sound pressure levels under a range of weather conditions
Est
...
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