SIST EN ISO 3743-2:2009/oprA1:2013
(Amendment)Acoustics - Determination of sound power levels of noise sources using sound pressure - Engineering methods for small, movable sources in reverberant fields - Part 2: Methods for special reverberation test rooms - Amendment 1 (ISO 3743-2:1994/DAM 1:2013)
Acoustics - Determination of sound power levels of noise sources using sound pressure - Engineering methods for small, movable sources in reverberant fields - Part 2: Methods for special reverberation test rooms - Amendment 1 (ISO 3743-2:1994/DAM 1:2013)
2013-05-28 LVO: Draft for // ENQ received in ISO/CS (see notification of 2013-05-27 in dataservice).
Akustik - Bestimmung der Schallleistungspegel von Geräuschquellen aus Schalldruckmessungen - Verfahren der Genauigkeitsklasse 2 für kleine, transportable Quellen in Hallfeldern - Teil 2: Verfahren für Sonder-Hallräume - Änderung 1 (ISO 3743-2:1994/DAM 1:2013)
Acoustique - Détermination des niveaux de puissance acoustique émis par les sources de bruit à partir de la pression acoustique - Méthodes d'expertise en champ réverbéré applicables aux petites sources transportables - Partie 2: Méthodes en salle d'essai réverbérante spéciale - Amendement 1 (ISO 3743-2:1994/DAM 1:2013)
Akustika - Ugotavljanje ravni zvočnih moči virov hrupa z merjenjem zvočnega tlaka - Inženirske metode za majhne premične vire v odmevnih poljih - 2. del: Metode za posebne odmevnice - Dopolnilo 1 (ISO 3743-2:1994/DAM 1:2013)
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Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 3743-2:2009/prA1:2013
01-oktober-2013
$NXVWLND8JRWDYOMDQMHUDYQL]YRþQLKPRþLYLURYKUXSD]PHUMHQMHP]YRþQHJD
WODND,QåHQLUVNHPHWRGH]DPDMKQHSUHPLþQHYLUHYRGPHYQLKSROMLKGHO
0HWRGH]DSRVHEQHRGPHYQLFH'RSROQLOR ,62 '$0
Acoustics - Determination of sound power levels of noise sources using sound pressure -
Engineering methods for small, movable sources in reverberant fields - Part 2: Methods
for special reverberation test rooms - Amendment 1 (ISO 3743-2:1994/DAM 1:2013)
Akustik - Bestimmung der Schallleistungspegel von Geräuschquellen aus
Schalldruckmessungen - Verfahren der Genauigkeitsklasse 2 für kleine, transportable
Quellen in Hallfeldern - Teil 2: Verfahren für Sonder-Hallräume - Änderung 1 (ISO 3743-
2:1994/DAM 1:2013)
Acoustique - Détermination des niveaux de puissance acoustique émis par les sources
de bruit à partir de la pression acoustique - Méthodes d'expertise en champ réverbéré
applicables aux petites sources transportables - Partie 2: Méthodes en salle d'essai
réverbérante spéciale - Amendement 1 (ISO 3743-2:1994/DAM 1:2013)
Ta slovenski standard je istoveten z: EN ISO 3743-2:2009/prA1
ICS:
17.140.01 $NXVWLþQDPHUMHQMDLQ Acoustic measurements and
EODåHQMHKUXSDQDVSORãQR noise abatement in general
SIST EN ISO 3743-2:2009/prA1:2013 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 3743-2:2009/prA1:2013
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SIST EN ISO 3743-2:2009/prA1:2013
DRAFT AMENDMENT ISO 3743-2:1994/DAM 1
ISO/TC 43/SC 1 Secretariat: DS
Voting begins on Voting terminates on
2013-08-08 2014-01-08
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION • МЕЖДУНАРОДНАЯ ОРГАНИЗАЦИЯ ПО СТАНДАРТИЗАЦИИ • ORGANISATION INTERNATIONALE DE NORMALISATION
Acoustics — Determination of sound power levels of noise
sources using sound pressure — Engineering methods for
small, movable sources in reverberant fields —
Part 2:
Methods for special reverberation test rooms
AMENDMENT 1
Acoustique — Détermination des niveaux de puissance acoustique émis par les sources de bruit à partir de la
pression acoustique — Méthodes d'expertise en champ réverbéré applicables aux petites sources
transportables —
Partie 2: Méthodes en salle d'essai réverbérante spéciale
AMENDEMENT 1
ICS 17.140.01
ISO/CEN PARALLEL PROCESSING
This draft has been developed within the International Organization for Standardization (ISO), and
processed under the ISO-lead mode of collaboration as defined in the Vienna Agreement.
This draft is hereby submitted to the ISO member bodies and to the CEN member bodies for a parallel
five-month enquiry.
Should this draft be accepted, a final draft, established on the basis of comments received, will be
submitted to a parallel two-month approval vote in ISO and formal vote in CEN.
To expedite distribution, this document is circulated as received from the committee
secretariat. ISO Central Secretariat work of editing and text composition will be undertaken at
publication stage.
Pour accélérer la distribution, le présent document est distribué tel qu'il est parvenu du
secrétariat du comité. Le travail de rédaction et de composition de texte sera effectué au
Secrétariat central de l'ISO au stade de publication.
THIS DOCUMENT IS A DRAFT CIRCULATED FOR COMMENT AND APPROVAL. IT IS THEREFORE SUBJECT TO CHANGE AND MAY NOT BE
REFERRED TO AS AN INTERNATIONAL STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS BEING ACCEPTABLE FOR INDUSTRIAL, TECHNOLOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT, WITH THEIR COMMENTS, NOTIFICATION OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPORTING DOCUMENTATION.
© International Organization for Standardization, 2013
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SIST EN ISO 3743-2:2009/prA1:2013
ISO 3743-2:1994/DAM 1
COPYRIGHT PROTECTED DOCUMENT
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All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any
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ii © ISO 2013 – All rights reserved
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SIST EN ISO 3743-2:2009/prA1:2013
ISO 3743-2:1994/DAM 1
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.
Amendment 1 to ISO 3743-2:1994 was prepared by Technical Committee ISO/TC 43, Acoustics,
Subcommittee SC 1, Noise.
iii
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SIST EN ISO 3743-2:2009/prA1:2013
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SIST EN ISO 3743-2:2009/prA1:2013
DRAFT AMENDMENT ISO 3743-2:1994/DAM 1
Acoustics — Determination of sound power levels of noise
sources using sound pressure — Engineering methods for
small, movable sources in reverberant fields — Part 2: Methods
for special reverberation test rooms — AMENDMENT 1
Page iii: Introduction, 0.1, second sentence:
Delete the phrase “as shown in table 0.1”.
Page v:
Delete Table 0.1
Page 2: 1.4 Measurement uncertainty
Replace the existing text in 1.4 with the following:
1.4 Measurement uncertainty
1.4.1 Methodology
The uncertainties of sound power levels, u(L ), in decibels, determined according to this part of ISO 3743 are
W
estimated by the total standard deviation, σ , in decibels:
tot
u(L ) ≈ σ (1)
W tot
This total standard deviation is obtained using the modelling approach described in ISO/IEC Guide 98-3. This
requires a mathematical model which in case of lack of knowledge can be substituted with results from
measurements, including results from round robin tests.
In this context this standard deviation is expressed by the standard deviation of reproducibility of the method,
σ , in decibels, and the standard deviation, σ , in decibels, describing the uncertainty due to the
R0 omc
variations of the operating and mounting conditions of the source under test according to:
2 2
σ = σ + σ (2)
tot omc
R0
Equation (2) shows that variations of operating and mounting conditions expressed by σ should be taken
omc
into account before a measurement procedure with a certain grade of accuracy (characterized by σ ) is
R0
selected for a specific machine family (see 1.4.5 and Annex D.3).
NOTE If different measurement procedures offered by the ISO 3740 series are used, systematic numerical deviations
(biases) may additionally occur.
Derived from σ the expanded measurement uncertainty U, in decibels, shall be calculated from
,
tot
U = k σ (3)
tot
1
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SIST EN ISO 3743-2:2009/prA1:2013
ISO 3743-2:1994/DAM 1
The expanded uncertainty depends on the degree of confidence that is desired. For a normal distribution of
measured values, there is a 95% confidence that the true value lies within the range [L - U] to [L + U]. This
W W
corresponds to a coverage factor of k = 2.
If the purpose of determining the sound power level is to compare the result with a limit value, it might be more
appropriate to apply the coverage factor for a one-sided normal distribution. In that case, the coverage factor
k = 1,6 corresponds to a 95 % confidence.
1.4.2 Determination of σ
omc
The standard deviation σ [see Equation (D.1)] which describes the uncertainty associated with the
omc
variations of the operating and mounting conditions for the particular source under test shall be taken into
account when determining the measurement uncertainty. It can be determined separately from repeated
measurements carried out on the same source at the same location by the same persons, using the same
measuring instruments and the same measurement position(s). To determine σ repeated sound pressure
omc
levels are measured either at the microphone position associated with the highest sound pressure level, or
measured and averaged over the entire measurement surface. Measured levels are then corrected for
background noise. For each of these repeated measurements, the mounting of the machine and its operating
′
conditions are to be readjusted. For the individual sound source under test, σ is designated as σ . It is
omc omc
possible that a noise test code provides a value of σ which is representative for the machine family
omc
concerned. This value should take into account all possible variations of operating and mounting conditions
that are within the scope of the noise test code.
NOTE If the sound power has only a small variation with time and the measurement procedure is defined properly, a
value of 0,5 dB for σ may be applicable. In other cases, for example, a large influence of the material flow in and out
omc
of the machine or material flow that may vary in an unforeseeable manner, a value of 2 dB may be appropriate. However,
in extreme cases such as strongly varying noise generated by the processed material (stone breaking machines, metal
cutting machines and presses operating under load) a value of 4 dB may result.
1.4.3 Determination of σ
R0
1.4.3.1 General
The standard deviation σ includes uncertainty due to all conditions and situations allowed by this part of
R0
ISO 3743 (different radiation characteristics of the source under test, different instrumentation, different
realizations of the measurement procedure), except the influence due to variations of the sound power of the
source under test. The latter is considered separately by σ .
omc
The values of σ given in Table 1 reflect the current knowledge. They are typical upper bounds taking into
R0
consideration the great variety of machines and equipment covered by this part of ISO 3743. Machinery-
specific values may be derived from round robin tests (see 1.4.3.2) or by using the mathematical modelling
approach (see 1.4.3.3). They should be given in noise test codes specific to machinery families (see 1.4.2 and
Annex D).
1.4.3.2 Round Robin Test
The round robin test for determining σ has to be carried out according to ISO 5725, where the sound
R0
power level of the source under test is determined under reproducibility conditions i.e. different persons
carrying out measurements at different testing locations with different measuring instruments. Such a test
′
provides the total standard deviation σ relevant for the individual sound source which has been used for
tot
the round robin test. Participating laboratories in round robin tests should cover all possible practical
situations.
2
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SIST EN ISO 3743-2:2009/prA1:2013
ISO 3743-2:1994/DAM 1
′
This total standard deviation σ , in decibels, of all results obtained with a round robin test includes the
tot
′ ′
standard deviation σ and allows σ to be determined by using Equation (4):
omc R0
2 2
′ ′ ′ (4)
σ = σ − σ
R0 tot omc
′
If σ values obtained from many different pieces of machinery belonging to the same family deviate within a
R0
small range only, their mean value can be regarded as typical for the application of this part of ISO 3743 to
this particular family and used as σ . Whenever available, such value should be given in the noise test code
R0
specific to the machine family concerned (together with σ ) and used in particular for the purpose of
omc
declaring noise emission values.
If no round robin test has been carried out, the existing knowledge about the noise emission from a particular
family of machines may be used to estimate realistic values of σ .
R0
For certain applications the effort for the round robin test can be reduced by omitting measurements for
different locations, e.g. if machines under test usually are installed under conditions with a small background
noise correction K , or if the noise emission of a machine should be checked at the same location again.
1
Results of such delimited tests should be denoted by σ , and this designation should also be used for
R0, DL
tests on large machines being not movable in space.
Values for can be expected to be lower than those given in Table 1.
σ
R0, DL
The determination of σ using Equation (4) is imprecise if σ is only slightly higher than σ . In this
R0 tot omc
case Equation (4) provides a small value of σ but with a low accuracy. To limit this inaccuracy σ
R0 omc
should not exceed σ / 2 .
tot
1.4.3.3 Modelling approach for σ
R0
Generally σ , in decibels, is dependent upon several partial uncertainty components, c ⋅u , associated with
R0 i i
the different measurement parameters such as uncertainties of instruments, environmental corrections,
microphone positions, etc. If these contributions are assumed to be uncorrelated σ can be described by
R0
the modelling approach presented in ISO/IEC Guide 98-3, as follows:
2 2 2
( ) ( ) ( ) (5)
σ ≈ c u + c u + . + c u
R0 1 1 2 2 n n
In Equation (5) the uncertainty components due to the variations of the sound emission of the source are not
included. These components are covered by σ . Annex D discusses each component of the uncertainty
omc
σ according to existing knowledge.
R0
NOTE If the uncertainty components in the modelling approach are correlated Equation (5) does not apply.
Furthermore, the modelling approach requires detailed knowledge to determine the individual terms in Equation (5).
By contrast, the estimation of σ based on round robin tests does not require assumptions about possible
R0
correlations between the individual terms of Equation (5). Therefore estimation by round robin is presently
more realistic than a modelling approach when possible correlations between terms and their dependency
from all other influencing parameters are not well understood. However, round robin tests are not always
possible and are often replaced by experience from earlier measurements.
3
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SIST EN ISO 3743-2:2009/prA1:2013
ISO 3743-2:1994/DAM 1
1.4.4 Typical upper bound values of σ
R0
Table 1 shows typical upper bound values of the standard deviation σ for accuracy grade 2 that may cover
R0
most of the applications of this part of ISO 3743 (References [12][13]). In special cases or if certain
requirements of this part of ISO 3743 are not met for a machine family or if it is anticipated that actual values
of σ for a given family of machines are smaller than those given in Table 1, a round robin test is
R0
recommended to obtain machine-specific values of σ .
R0
Table 1 —Typical upper bound values of the standard deviation of reproducibility of the method, σ ,
R0
for octave band and A-weighted sound power levels determined in accordance with this part of
ISO 3743
Frequency Octave mid-band Standard deviation of
bandwidth frequency
reproducibility, σ
R0
Hz dB
125 5,0
250 3,0
Octave
500 – 4 000 2,0
8 000 3,0
a
A-weighted 2,0
a
Applicable to noise sources which emit sound with a relatively “flat” spectrum in the
frequency range from 100 Hz to 10 000 Hz.
1.4.5 Total standard deviation σ and expanded uncertainty U
tot
The total standard deviation and the expanded uncertainty shall be determined using Equation (2) and
Equation (3) respectively. For the purpose of this part of ISO 3743, a normal distribution is assumed. Thus a
coverage factor of k = 2 shall be used corresponding to a coverage probability of 95%. The coverage factor
and coverage probability have to be reported together with the expanded measurement uncertainty.
EXAMPLE Accuracy grade 2; σ = 2,0 dB; coverage factor k = 2; measured L = 82 dB. Machine-specific
A
W
omc
determinations of σ have not been undertaken thus the value is taken from Table 1 (σ = 2,0 dB). Using
R0 R0
Equations (3) and (2) it follows
2 2
U = 2 × 2 + 2 dB = 5,8 dB
Additional examples of calculated values for σ are given in D.3.
tot
NOTE The expanded uncertainty as described in this part of ISO 3743 does not include the standard deviation of
production which is used in ISO 4871 [8] for the purpose of making a noise declaration for batches of machines.
Page 3: Clause 2 Normative references
Add the following reference:
ISO 5725 (all parts), Accuracy (trueness and precision) of measurement methods and results
4
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SIST EN ISO 3743-2:2009/prA1:2013
ISO 3743-2:1994/DAM 1
Correct the title of ISO 3741:1988 as follows:
ISO 3741, Acoustics — Determination of sound power levels and sound energy levels of noise sources using
sound pressure — Precision methods for reverberation test rooms
Correct the title of ISO 3743-1 as follows:
ISO 3743-1, Acoustics — Determination of sound power levels and sound energy levels of noise sources
using sound pressure — Engineering methods for small movable sources in reverberant fields — Part 1:
Comparison method for a hard-walled test room
Correct the title of ISO 3745 as follows:
ISO 3745, Acoustics — Determination of sound power levels and sound energy levels of noise sources using
sound pressure — Precision methods for anechoic rooms and hemi-anechoic rooms
Correct the title of ISO 6926 as follows:
ISO 6926, Acoustics — Requirements for the performance and calibration of reference sound sources used
for the determination of sound power levels
Add the following reference:
ISO/IEC Guide 98-3, Uncertainty in measurement — Part 3: Guide to the expression of uncertainty in
measurement (GUM:1995)
Replace IEC 225:1966 by the following:
IEC 61260:1995, Electroacoustics — Octave-band and fractional-octave-band filters
Replace IEC 651:1979 and IEC 8041985 by the following:
IEC 61672-1:2002, Electroacoustics — Sound level meters — Part 1: Specifications
Replace IEC 942:1988 by the following:
IEC 60942:2003, Electroacoustics — Sound calibrators
Page 10: 8.2 Direct method for determining sound power levels
Add the following sentence at the end of 8.2:
Reduced atmospheric pressure creates a bias in the sound power level. At altitudes greater than 500 m,
sound power levels, L , corresponding to the reference barometric pressure of 101,325 kPa and
Wref,atm
reference atmospheric temperature 23,0 °C shall be calculated according to Annex E.
Page 11: 8.3 Comparison method for determining band power levels
Add the following sentence at the end of 8.3:
Reduced atmospheric pressure creates a bias in the sound power level. At altitudes greater than 500 m,
sound power levels, L , corresponding to the reference barometric pressure of 101,325 kPa and
Wref,atm
reference atmospheric temperature 23,0 °C shall be calculated according to Annex E.
5
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SIST EN ISO 3743-2:2009/prA1:2013
ISO 3743-2:1994/DAM 1
Page 11:
Add the following new clause:
8.4 A-weighted sound power levels determined by the comparison method
Calculation of the A-weighted sound power level of the noise source under test from the measurements made
in octave bands according to 8.3 shall be performed using the procedure given in Annex F.
Page 20: Annex D (informative) Bibliography
In the heading delete “Annex D (informative)”, and shift this annex to the end of the document.
Page 20: Bibliography
Delete all dates of issue.
Correct the title of ISO 1996-1 as follows:
ISO 1996-1, Acoustics — Description, measurement and assessment of environmental noise — Part 1: Basic
quantities and assessment procedures
Correct the title of ISO 3740 as follows:
ISO 3740, Acoustics — Determination of sound power levels of noise sources — Guidelines for the use of
basic standards
Delete ISO 3742.
Correct the title of ISO 3744 as follows:
ISO 3744, Acoustics — Determination of sound power levels and sound energy levels of noise sources using
sound pressure — Engineering methods for an essentially free field over a reflecting plane
Delete ISO 3745.
Correct the title of ISO 3746 as follows:
ISO 3746, Acoustics — Determination of sound power levels and sound energy levels of noise sources using
sound pressure — Survey method using an enveloping measurement surface over a reflecting plane
Correct the title of ISO 3747 as follows:
ISO 3747, Acoustics — Determination of sound power levels and sound energy levels of noise sources using
sound pressure — Engineering/survey methods for use in situ in a reverberant environment
Correct the title of ISO 4871 as follows:
ISO 4871, Acoustics — Declaration and verification of noise emission values of machinery and equipment
6
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SIST EN ISO 3743-2:2009/prA1:2013
ISO 3743-2:1994/DAM 1
Add the following references:
[10] ISO 9613-1, Acoustics — Attenuation of sound during propagation outdoors — Part 1: Calculation of the
absorption of sound by the atmosphere
[12] HELLWEG, R.D. International round robin test of ISO/DIS 7779. In: Proceedings Inter-Noise 1988,
Avignon, 1988, pp. 1105-1108
[13] VORLÄNDER, M., RAABE, G. Intercomparison on sound power measurements by use of reference sound
sources, BCR-project 3347/1/0/168/89/11 – BCR – D30, 1993
[14] DAVIES, R.S. Equation for the determination of the density of moist air. Metrologia 1992, 29, pp. 67-70
[15] HÜBNER, G. Accuracy consideration on the meteorological correction for a normalized sound power level.
In: Proceedings Inter-Noise 2000, Nice, 2000
7
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SIST EN ISO 3743-2:2009/prA1:2013
ISO 3743-2:1994/DAM 1
Add new Annex D
Annex D
(informative)
Guidance on the development of information on measurement
uncertainty
D.1 General
The accepted format for the expression of uncertainties generally associated with methods of measurement is
that given in the ISO/IEC Guide 98-3. This format incorporates a budget of uncertainty components, in which
all various sources of uncertainty are identified and from which the combined total measurement uncertainty
can be obtained.
To determine the noise emission of machines and equipment it is advisable to split up its total uncertainty into
two different groups of uncertainty components:
those that are intrinsic to the measurement procedure and
those that result from the variations of the sound emission of the machine.
Based on present knowledge this annex provides additional explanations and information by which
ISO/IEC Guide 98-3 could be applied in practice for this part of ISO 3743.
This annex complements Clause 1.4.
D.2 Considerations on the total standard deviation σ
tot
The measurement uncertainty used in this part of ISO 3743 is determined by the expanded measurement
uncertainty U, which is derived directly from the total standard deviation σ [see Equation (3)] with σ
tot tot
being the approximation of the relevant u(L ) as defined in the ISO/IEC Guide 98-3.
W
This total standard deviation σ results from the two components σ and σ (see 1.4.1, Equation (2)),
tot R0 omc
which are significantly different in nature.
Both quantities are assumed to be statistically independent and are determined separately.
The machinery specific standard deviation σ cannot be calculated and has to be determined by repeated
omc
measurements as described in D.3. Information on the standard deviation σ is given in D.4.
R0
NOTE The expanded uncertainty as described in this part of ISO 3743 does not include the standard deviation of
production which is used in ISO 4871 [6] for the purpose of making a noise declaration for batches of machines.
8
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SIST EN ISO 3743-2:2009/prA1:2013
ISO 3743-2:1994/DAM 1
D.3 Considerations on σ
omc
The standard deviation σ , described in 1.4.2, is calculated by
omc
N
1
2
σ = (L − L ) dB (D.1)
omc ∑ p, j pav
N −1
j =1
where
L is the sound pressure level measured at a prescribed position and corrected for background
p, j
noise for the jth repetition of the prescribed operating and mounting conditions, and
L is its arithmetic mean level calculated for all these repetitions.
pav
These measurements are carried out at the microphone position associated with the highest sound pressure
L
level on the measurement surface. When measurements are averaged over the measurement surface, ,
p, j
and L , are replaced in Equation (D.1), by L , and L , respectively.
pav
p, j pav
In general, the mounting and operating conditions to be used for noise emission measurements are
prescribed by machinery specific noise test codes. Otherwise, these conditions have to be defined precisely
and described in the test report.
Some recommendations for defining these conditions and consequences for the expected values of σ are
omc
given hereafter.
The test conditions have to represent normal usage and to conform to manufacturers and users
recommended practice. However, even in normal usage, slightly different modes of operation, variations in
material flow and other conditions varying between different phases of operation may occur. This uncertainty
covers both the uncertainty due to variation in long term operating conditions (e.g. from day to day) and
fluctuations of noise emission measurements repeated immediately after readjusting mounting and operating
conditions.
Machines that are exclusively standing on soft springs or on heavy concrete floors will not normally exhibit any
effect of mounting. However, there can be large discrepancies between measurements on heavy concrete
floors and those made “in situ". The uncertainty due to mounting can be highest for machinery that is
connected to auxiliary equipment. Hand-held machines may also cause problems. This parameter should be
investigated if movement of the machine or mounts causes changes in noise. If there is a range of possible
mounting conditions to be included in a single declaration, then σ is estimated from the standard
omc
deviation of the sound levels for these mounting conditions. If there is any known effect due to mounting,
recommended mounting conditions should be documented in the relevant noise test code or manufacturers’
recommended practice.
In respect to the main uncertainty quantity, σ , investigations on σ have a higher priority compared to
tot omc
those on the other uncertainty components leading to σ (see Equation (2)). This is because σ may be
R0 omc
significantly larger in practice than e.g. σ = 2 dB for accuracy grade 2 measurements as given in Table 1.
R0
If σ > σ , the application of measurement procedures with a high accuracy, i.e. a low value of σ
omc R0 R0
makes no sense economically because this is not going to result in a lower value of the total uncertainty.
9
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SIST EN ISO 3743-2:2009/prA1:2013
ISO 3743-2:1994/DAM 1
Table D.1 — Examples of calculated total A-weighted standard deviations σ for 3 different cases
tot
Operating and mounting conditions
Stable unstable very unstable
Standard deviation σ , dB
Standard
omc
deviation of
0,5 2,0 4,0
reproducibility
of the method,
Total standard deviation σ , dB
σ , dB tot
R0
0,5
0,7 2,1 4,0
(Accuracy grade 1)
2
2,1 2,8 4,5
(Accuracy grade 2)
3
3,0 3,6 5,0
(Accuracy grade 3)
These examples show that it might be superfluous to extend the measuring effort to ensure a measurement of
accuracy grade 1 if the uncertainty associated with the mounting and operating conditions is large.
Furthermore σ > σ may create substantial misunderstandings with respect to the true relevant total
omc R0
standard deviation σ , because the different grades of accuracy of this part of ISO 3743 are presently
tot
defined by the value of σ only.
R0
D.4 Considerations on σ
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D.4.1 General
Upper bound values of σ are given in Table 1. Additionally in 1.4.3 it is recommended to investigate values
R0
of σ that are relevant to individual machines or machine families in order to achieve more realistic values.
R0
These investigations are to be carried out either by measurements under reproducibility conditions as
...
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