Reciprocating internal combustion engines — Measurement method for air cleaners — Sound power level of combustion air inlet noise and insertion loss using sound pressure

ISO/TS 19425:2015 specifies the measurement method and requirements for combustion air inlet noise of air cleaners which are installed on reciprocating internal combustion engines, including laboratory measurement (engineering method and survey method) and site measurement (survey method). ISO/TS 19425:2015 applies to all air cleaners installed on reciprocating internal combustion engines (reciprocating internal combustion engine is referred to as engine except particular explanation in the following text) falling within the field of application of ISO 3046‑1 and/or other air induction installation.

Moteurs alternatifs à combustion interne — Méthode de mesure du bruit des purificateurs d'air — Niveau de puissance sonore du bruit d'entrée d'air de combustion et de perte d'insertion utilisant une pression sonore

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Publication Date
08-Dec-2015
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9092 - International Standard to be revised
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31-Oct-2022
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ISO/TS 19425:2015 - Reciprocating internal combustion engines -- Measurement method for air cleaners -- Sound power level of combustion air inlet noise and insertion loss using sound pressure
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TECHNICAL ISO/TS
SPECIFICATION 19425
First edition
2015-12-15
Reciprocating internal combustion
engines — Measurement method for
air cleaners — Sound power level
of combustion air inlet noise and
insertion loss using sound pressure
Moteurs alternatifs à combustion interne — Méthode de mesure du
bruit des purificateurs d’air — Niveau de puissance sonore du bruit
d’entrée d’air de combustion et de perte d’insertion utilisant une
pression sonore
Reference number
ISO/TS 19425:2015(E)
©
ISO 2015

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ISO/TS 19425:2015(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2015, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2015 – All rights reserved

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ISO/TS 19425:2015(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Test environment . 5
4.1 General . 5
4.2 Criterion for background noise. 5
4.3 Criterion for acoustic adequacy of test environment . 6
5 Instrumentation . 6
5.1 General . 6
5.2 Calibration . 6
5.3 Application . 6
6 Installation and operation conditions . 7
6.1 General . 7
6.2 Installation condition . 7
6.3 Operation condition . 8
7 Measurement . 8
7.1 General . 8
7.2 Measurement uncertainty . 9
7.3 Characteristic source dimension .10
7.4 Measurement radius .10
7.5 Measurement surface and area .10
7.6 Microphone arrays .10
8 Calculation .12
8.1 General .12
8.2 Calculation of sound power level .12
8.2.1 Mean time-averaged sound pressure levels .12
8.2.2 Corrections for background noise .13
8.2.3 Corrections for environmental .13
8.2.4 Surface time-averaged sound pressure levels .14
8.2.5 Sound power levels .14
8.3 Calculation of insertion loss .14
9 Information to be recorded .15
10 Test report .16
Annex A (normative) Qualification procedures for the acoustic environment .17
Annex B (normative) Calculation of A-weighted sound power levels from frequency band levels 20
Annex C (normative) Sound power level under reference meteorological conditions.22
Bibliography .24
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ISO/TS 19425:2015(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 70, Internal combustion engines.
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ISO/TS 19425:2015(E)

Introduction
This Technical Specification specifies methods for measuring the sound power level of combustion air
inlet noise and the insertion loss of air cleaners installed on reciprocating internal combustion engines.
Sound power level of combustion air inlet noise, insertion loss, and transmission loss are parameters to
characterize the acoustic performance of air cleaners. Sound power levels of combustion air inlet noise
and insertion loss are important parameters to characterize the acoustic matching performance of air
cleaners and reciprocating internal combustion engines. Transmission loss is the difference in sound
power level of combustion air inlet noise between the noise before and after transmitting through the
air cleaner, which is the parameter to characterize the acoustic performance of the air cleaner itself and
is irrelevant with the reciprocating internal combustion engine. The matching parameters of the sound
power level of combustion air inlet noise and the insertion loss are used in this Technical Specification
as the measurement parameters.
The enveloping surface method of this Technical Specification is applicable for engineering method
(accuracy grade 2) and survey method (accuracy grade 3). Engineering method allows the determination
of the A-weighted and frequency-band sound power level, survey method allows the determination
of the A-weighted sound power level. The measurement result of sound power level is rounded to the
nearest 0,1 dB.
In the combustion air inlet noise control of air cleaner, the relevant members (including manufacturer,
installation, and the user) should make effective communication of acoustic information which
is obtained by measurement. The measurement result is valid only in the specified measurement
conditions by using the instrumentation as specified in this Technical Specification to obtain a clear
acoustic value. Engineering method or survey method may be selected according to the purpose of
noise measurement and measurement conditions.
The measurement surface defined based on the characteristics of noise source under test in this
Technical Specification is spherical. To meet the requirements of the measurement uncertainty, this
Technical Specification gives specification of the distance from the installation location of the noise
source to the reflecting plane (ground).
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TECHNICAL SPECIFICATION ISO/TS 19425:2015(E)
Reciprocating internal combustion engines —
Measurement method for air cleaners — Sound power
level of combustion air inlet noise and insertion loss using
sound pressure
1 Scope
This Technical Specification specifies the measurement method and requirements for combustion
air inlet noise of air cleaners which are installed on reciprocating internal combustion engines,
including laboratory measurement (engineering method and survey method) and site measurement
(survey method).
This Technical Specification applies to all air cleaners installed on reciprocating internal combustion
engines (reciprocating internal combustion engine is referred to as engine except particular explanation
in the following text) falling within the field of application of ISO 3046-1 and/or other air induction
installation.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 3046-1, Reciprocating internal combustion engines — Performance — Part 1: Declarations of power, fuel
and lubricating oil consumptions, and test methods — Additional requirements for engines for general use
ISO 3046-3, Reciprocating internal combustion engines — Performance — Part 3: Test measurements
ISO 6926, Acoustics — Requirements for the performance and calibration of reference sound sources used
for the determination of sound power levels
IEC 60942, Electroacoustics — Sound calibrators
IEC 61260, Electroacoustics — Octave-band and fractional-octave-band filters
IEC 61672-1, Electroacoustics — Sound level meters—Part 1: Specifications
3 Terms and definitions
For the purposes of this document, the terms and definitions defined in ISO 3046-1, ISO 3046-3,
ISO 6926, IEC 60942, IEC 61260 and IEC 61672-1 and the following apply.
3.1
sound pressure
p
difference between instantaneous pressure and static pressure
Note 1 to entry: It is expressed in pascals.
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ISO/TS 19425:2015(E)

3.2
sound pressure level
L
p
ten times the logarithm to the base 10 of the ratio of the square of the sound pressure (3.1), p, to the
square of a reference value, p
0
2
p
L =10lg
p
2
p
0
where the reference value, p , is 20 μPa
0
Note 1 to entry: If specific frequency and time weightings, as specified in IEC 61672-1, and/or specific frequency
bands are applied, this is indicated by appropriate subscripts, e.g. L denotes the A-weighted sound pressure level.
pA
Note 2 to entry: It is expressed in decibels.
3.3
time-averaged sound pressure level
L
p,T
ten times the logarithm to the base 10 of the ratio of the time average of the square of the sound pressure
(3.1), p, during a stated time interval of duration, T (starting at t and ending at t ), to the square of a
1 2
reference value, p
0
 t 
1 2
2
 
pt dt
()
 ∫ 
T t
1
 
L = 10lg
pT,  
2
 p 
0
 
 
 
where the reference value, p , is 20 μPa
0
Note 1 to entry: In general, the subscript “T” is omitted since time-averaged sound pressure levels are necessarily
determined over a certain measurement time interval (3.5).
Note 2 to entry: Time-averaged sound pressure levels are often A-weighted, in which case they are denoted by
L , which is usually abbreviated to L .
pA,T pA
Note 3 to entry: It is expressed in decibels.
3.4
surface time-averaged sound pressure level
L
P
mean(energy average) of the time-averaged sound pressure levels (3.3) over all the microphone positions,
or traverses, on the measurement surface (3.11), with the background noise correction (3.13), K , and the
1
environmental correction (3.14), K , applied
2
Note 1 to entry: It is expressed in decibels.
3.5
measurement time interval
T
portion or a multiple of an operational period or operational cycle of the noise source under test for
which the time-averaged sound pressure level (3.3) is determined
Note 1 to entry: It is expressed in seconds.
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ISO/TS 19425:2015(E)

3.6
acoustic free field
sound field in a homogeneous, isotropic medium free of boundaries
Note 1 to entry: In practice, an acoustic free field is a field in which the influence of reflections at the boundaries
or other disturbing objects are negligible over the frequency range of interest.
3.7
reflecting plane
sound-reflecting planar surface on which the noise source under test is located
3.8
acoustic free field over a reflecting plane
acoustic free field (3.6) in the half-space above an infinite reflecting plane (3.7) in the absence of any
other obstacles
3.9
frequency range of interest
the frequency range of octave bands with nominal mid-band frequencies from 63 Hz to 8 000 Hz
(including one-third octave bands with mid-band frequencies from 50 Hz to 10 000 Hz)
3.10
measurement radius
r
radius of a spherical measurement surface (3.11)
Note 1 to entry: It is expressed in metres.
3.11
measurement surface
hypothetical spherical surface of area, S, on which the microphone positions are located at which the
sound pressure levels (3.2) are measured, enveloping the noise source under test
3.12
background noise
noise from all sources other than the noise source under test
Note 1 to entry: Background noise includes contributions from airborne sound, noise from structure-borne
vibration, and electrical noise in the instrumentation.
3.13
background noise correction
K
1
correction applied to the mean (energy average) of the time-averaged sound pressure levels (3.3)
over all the microphone positions on the measurement surface (3.11), to account for the influence of
background noise (3.12)
Note 1 to entry: The background noise correction is frequency dependent; the correction in the case of a frequency
band is denoted by K , where f denotes the relevant mid-band frequency and that in the case of A-weighting is
1f
denoted by K .
1A
Note 2 to entry: It is expressed in decibels.
3.14
environmental correction
K
2
correction applied to the mean (energy average) of the time-averaged sound pressure levels (3.3) over all the
microphone positions on the measurement surface (3.11), to account for the influence of reflected sound
Note 1 to entry: The environmental correction is frequency dependent; the correction in the case of a frequency
band is denoted by K , where f denotes the relevant mid-band frequency, and that in the case of A-weighting is
2f
denoted by K .
2A
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ISO/TS 19425:2015(E)

Note 2 to entry: It is expressed in decibels.
3.15
sound power
W
through a surface, product of the sound pressure (3.1), p, and the component of the particle velocity, u ,
n
at a point on the surface in the direction normal to the surface, integrated over that surface
Note 1 to entry: The quantity relates to the rate per time at which airborne sound energy is radiated by a source.
Note 2 to entry: It is expressed in watts.
3.16
sound power level
L
W
ten times the logarithm to the base 10 of the ratio of the sound power (3.15) of a source, W, to a reference
value, W , expressed in decibels
0
W
L = 10lg
W
W
0
where the reference value, W , is 1 pW
0
Note 1 to entry: If a specific frequency weighting, as specified in IEC 61672-1, and/or specific frequency bands
are applied, this is indicated by appropriate subscripts, e.g. L denotes the A-weighted sound power level.
WA
Note 2 to entry: It is expressed in decibels.
3.17
air cleaner
air filter
device which removes particles suspended in the fresh charge as it is drawn into the engine
Note 1 to entry: The air cleaner generally comprises the entire part from its air inlet but does not include the air
induction manifold and pipe.
3.18
substitution pipe
rigid, non-absorbing circular pipe having the same length and the same cross section area of outlet as
the tested air cleaner (3.17)
3.19
bent transition pipe
bent pipe used to change the airflow direction and to connect two pipes of the same cross section area
3.20
characteristic source dimension
d
0
characteristic dimension of source to determine the measurement radius (3.10)
3.21
insertion loss
D
I
the difference between the sound power level (3.16) of combustion air inlet noise when the substitution
pipe (3.18)is installed on the engine and when the air cleaner (3.17) is installed on the engine
DL=−L
I(WWSP)(AC)
where
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ISO/TS 19425:2015(E)

L is the sound power level of combustion air inlet noise when the substitution pipe is in-
W(SP)
stalled on the engine, in decibels;
L is the sound power level of combustion air inlet noise when the air cleaner is installed on
W(AC)
the engine, in decibels
Note 1 to entry: It is expressed in decibels.
4 Test environment
4.1 General
For engineering method, the test environments that are applicable for measurements in accordance
with this Technical Specification are the following:
a) a room or a flat outdoor area which is adequately isolated from background noise and which
provides an acoustic free field over a reflecting plane;
b) a room or a flat outdoor area which is adequately isolated from background noise and in which an
environmental correction can be applied to allow for a limited contribution from the reverberant
field to the sound pressures on the measurement surface.
For survey method, the test environment that is applicable for measurements in accordance with this
Technical Specification is a room or a flat outdoor area which is adequately isolated from background
noise and which meets the qualification requirements given in 4.3.
Environmental conditions having an adverse effect on the microphones used for the measurements (e.g.
wind, impingement of air discharge, high or low temperatures) shall be avoided. The instructions of the
manufacturer of the measuring instrumentation regarding adverse environmental conditions shall be
followed. Particular care should be exercised to ensure that the plane does not radiate any appreciable
sound due to vibrations.
4.2 Criterion for background noise
For engineering method, the time-averaged sound pressure level of the background noise measured
and averaged over the microphone positions shall be at least 6 dB, and preferably more than 15 dB,
below the corresponding uncorrected time-averaged sound pressure level of the noise source under
test when measured in the presence of this background noise.
For frequency band measurements, the criteria for background noise may not be achievable in all
frequency bands, even when the background noise levels in the test room are extremely low and
well controlled.
For measurements in frequency bands, the following steps shall be followed to determine whether
meeting the requirements of the background noise criteria.
a) The A-weighted sound power level is computed using the data from every frequency band within
the frequency range of interest.
b) The computation of A-weighted sound power level is repeated but excluding those bands within
the frequency range of interest in which the A-weighted sound power level of the noise source
under test is at least 15 dB below the highest A-weighted band sound power level and for which
ΔL < 6 dB (see 8.2.2).
p
c) If the difference between these two levels is less than 0,5 dB, the A-weighted sound power level
determined from the data for all bands may be considered as conforming to the background noise
criteria of this Technical Specification, or the measurement is not valid.
For survey method, the time-averaged sound pressure level of the background noise measured and
averaged over the microphone positions, shall be at least 3 dB, and preferably more than 10 dB, below
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ISO/TS 19425:2015(E)

the corresponding uncorrected time-averaged sound pressure level of the noise source under test when
measured in the presence of this background noise.
4.3 Criterion for acoustic adequacy of test environment
Annex A specifies procedures for determining the magnitude of the environmental correction, K .
2
For engineering method, as long as it is practicable, the test environment shall be free from reflecting
objects other than the reflecting plane(s). The reflecting plane(s) shall extend at least 0,5 m beyond
the projection of the measurement surface on the plane(s). The sound absorption coefficient of the
reflecting plane(s) shall be less than 0,1 over the frequency range of interest.
NOTE 1 Smooth concrete or smooth sealed asphalt surface(s) are generally satisfactory.
Measurements in accordance with engineering method of this Technical Specification are only valid
where K ≤ 4 dB.
2A
NOTE 2 The environmental correction, K , is assumed to be zero for measurements made in hemi-anechoic
2
rooms which meet the requirements of ISO 3745.
The environmental correction, K , shall first be determined without reference to frequency band data,
2A
using one of the procedures of Annex A. Where it is decided to make measurements in frequency bands,
the relevant environmental correction K shall be determined in each band over the frequency range of
2
interest in accordance with A.4. L of a noise source shall be calculated in accordance with Annex B.
WA
Measurements in accordance with survey method of this Technical Specification are only valid
where K ≤ 7 dB.
2A
5 Instrumentation
5.1 General
The instrumentation system, including the microphones, cables and windscreen, if used, shall meet the
requirements of IEC 61672-1, class 1 for results of accuracy grade 2 and class 2 for results of accuracy
grade 3, and the filters shall meet the requirements of IEC 61260.
5.2 Calibration
Before and after each series of measurements, a sound calibrator meeting the requirements of
IEC 60942, class 1 shall be applied to each microphone to verify the calibration of the entire measuring
system at one or more frequencies within the frequency range of interest. Without any adjustment, the
difference between the readings made before and after each series of measurements shall be less than
or equal to 0,5 dB. If this value is exceeded, the results of the series of measurements shall be discarded.
The calibration of the sound calibrator, the compliance of the instrumentation system with the
requirements of IEC 61672-1, the compliance of the filter set with the requirements of IEC 61260, and
the compliance of the reference sound source with the requirements of ISO 6926 shall be verified at
intervals in a laboratory making calibrations traceable to appropriate standards.
Unless national regulations dictate otherwise, the sound calibrator should be calibrated at intervals
not exceeding 1 y, the reference sound source should be calibrated at intervals not exceeding 2 y, the
compliance of the instrumentation system with the requirements of IEC 61672-1 should be verified at
intervals not exceeding 2 y, and the compliance of the filter set with the requirements of IEC 61260
should be verified at intervals not exceeding 2 y.
5.3 Application
To minimize the influence of observers on the noise measurements, the microphones shall preferably
be mounted on a rigid frame or stand which is not connected to the vibrating surface; the microphone
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ISO/TS 19425:2015(E)

shall always be oriented in such a way that the angle of incidence of the sound waves is that for which
the microphone is calibrated and always be oriented to the centre of the air inlet.
The time-averaged sound pressure level shall be measured using an integrating sound level meter.
If the sound level meter is used to measure time-weighting sound pressure level, the time-weighting
characteristic “S” shall be used for the noise source under test operated in steady condition, and the
time-weighting characteristic “F” shall be used for the noise source under test operated in non-steady
condition (e.g. engine operated in the accelerated or decelerated condition). The measured average
value can be expressed as the time-averaged sound press
...

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