ISO/FDIS 20145
(Main)Pneumatic fluid power — Test methods for measuring acoustic emission pressure levels of exhaust silencers
Pneumatic fluid power — Test methods for measuring acoustic emission pressure levels of exhaust silencers
This document specifies two methods of measuring the level of acoustic pressure at the outlet of an exhaust silencer: — the first method, called "steady-state mode", is intended to evaluate the noise level under steady state flow, i.e. constant upstream pressure (steady-state test according to ISO 6358‑1); and — the second method, called "discharge", is intended to measure the noise level during the decrease of the pneumatic pressure (discharge test according to ISO 6358‑2). This document is applicable to pneumatic exhaust silencers and devices designed to reduce the sound produced by discharges of compressed air, entering in the scope of application of ISO 6358‑1 and ISO 6358‑2.
Transmissions pneumatiques — Méthode d'essai de mesure du niveau de pression d'émission acoustique des silencieux d'échappement
Le présent document spécifie deux méthodes de mesure du niveau de pression acoustique à la sortie d'un silencieux d'échappement: — la première méthode, appelée «mode de régime stationnaire», est destinée à évaluer le niveau acoustique à un débit en régime stationnaire, c'est-à-dire à une pression amont constante (essai en régime stationnaire conformément à l'ISO 6358-1); et — la seconde méthode, appelée «décharge», vise à mesurer le niveau acoustique au cours de la diminution de la pression pneumatique (essai de décharge conformément à l'ISO 6358-2). Le présent document est applicable aux dispositifs et silencieux d'échappement pneumatiques conçus pour réduire le bruit produit par les décharges d'air comprimé, qui entrent dans le domaine d'application des ISO 6358-1 et ISO 6358-2.
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Standards Content (Sample)
FINAL DRAFT
International
Standard
ISO/TC 131/SC 5
Pneumatic fluid power — Test
Secretariat: AFNOR
methods for measuring acoustic
Voting begins on:
emission pressure levels of exhaust
2025-11-12
silencers
Voting terminates on:
2026-01-07
Transmissions pneumatiques — Méthode d'essai de mesure
du niveau de pression d'émission acoustique des silencieux
d'échappement
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 SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
FINAL DRAFT
International
Standard
ISO/TC 131/SC 5
Pneumatic fluid power — Test
Secretariat: AFNOR
methods for measuring acoustic
Voting begins on:
emission pressure levels of exhaust
silencers
Voting terminates on:
Transmissions pneumatiques — Méthode d'essai de mesure
du niveau de pression d'émission acoustique des silencieux
d'échappement
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 SUPPOR TING DOCUMENTATION.
© ISO 2025
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland Reference number
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and units. 3
5 Test set-up . 3
5.1 Test bench .3
5.2 Pneumatic pressure measurement .3
5.3 Flow measurement .3
5.4 Sound pressure measurement .3
5.4.1 General .3
5.4.2 Measurement at one position .4
5.4.3 Measurement at three positions .4
5.5 Acoustic instrumentation .5
6 Test procedure . 6
6.1 Characterization and validation of the test facilities .6
6.2 Quantities to be measured .6
6.2.1 Basic quantities to be measured .6
6.2.2 Acquisition parameters of basic quantities — Steady-state mode . .6
6.2.3 Acquisition parameters of basic quantities — Discharge mode .6
6.3 Measurements .7
6.3.1 General .7
6.3.2 Specimens tested .7
6.3.3 Specific cases .7
6.3.4 Ambient conditions during measurement .7
6.4 The acoustic quantity to be determined .8
6.5 Calculation of background noise correction K .8
1A
6.5.1 General .8
6.5.2 Case of measurement in steady-state mode .8
6.5.3 Case of measurement in discharge mode .9
6.6 Uncertainty on measurement .10
7 Presentation of test results . 10
7.1 Information to be written in the test report.10
7.2 Information to be declared .10
8 Identification statement . 10
Annex A (informative) Calculation of environmental correction K .11
2A
Annex B (informative) Example of the acoustic correction of industrial facilities .13
Annex C (informative) Example of reports . 17
Annex D (informative) Uncertainties . 19
Annex E (informative) Sound attenuation effect of silencers .22
Bibliography .33
iii
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 131 Fluid power systems, Subcommittee SC 5,
Control products and components.
This second edition cancels and replaces the first edition (ISO 20145:2019), which has been technically
revised.
The main changes are as follows:
— addition of a new Annex E on sound attenuation effect of silencers.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
This acoustic test procedure is intended to provide a common framework to industrial companies to evaluate
the sound pressure levels of pneumatic exhaust silencers.
It defines two methods of measuring the level of acoustic pressure at the outlet of an exhaust silencer. These
methods should be capable of being applied by pneumatic equipment manufacturers in their facilities on test
benches in accordance with ISO 6358-1 and ISO 6358-2.
The first method, called "steady-state mode”, is intended to evaluate the noise level under steady state flow,
1)
i.e. constant upstream pressure. This measurement is performed at 630 kPa at least to permit comparison
between silencers at the most frequently used operating pressure (or at the maximum admissible pressure
if lower than 630 kPa).
The second method, called “discharge mode”, is intended to measure the noise level during the decrease
of the pneumatic pressure (discharge test according to ISO 6358-2). To ensure the compatibility with the
steady-state flow method, the pressure range includes 630 kPa (or the maximum admissible pressure if
lower than 630 kPa).
5 2
1) 1 bar = 0,1 MPa =10 Pa; 1 MPa = 1 N/mm .
...
ISO/FDIS 20145:2025(en)
ISO /TC 131/SC 5/WG 5
Secretariat: AFNOR
Date: 2025-10-11xx
Pneumatic fluid power — Test methods for measuring acoustic
emission pressure levels of exhaust silencers
Transmissions pneumatiques — Méthode d'essai de mesure du niveau de pression d'émission acoustique des
silencieux d'échappement
FDIS stage
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
EmailE-mail: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
Contents
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and units . 3
5 Test set-up . 3
5.1 Test bench . 3
5.2 Pneumatic pressure measurement . 3
5.3 Flow measurement . 3
5.4 Sound pressure measurement . 4
5.5 Acoustic instrumentation . 5
6 Test procedure . 6
6.1 Characterization and validation of the test facilities . 6
6.2 Quantities to be measured. 6
6.3 Measurements . 7
6.4 The acoustic quantity to be determined . 8
6.5 Calculation of background noise correction K . 8
1A
6.6 Uncertainty on measurement . 10
7 Presentation of test results . 11
7.1 Information to be written in the test report . 11
7.2 Information to be declared . 11
8 Identification statement . 11
Annex A (informative) Calculation of environmental correction K . 12
2A
Annex B (informative) Example of the acoustic correction of industrial facilities . 14
Annex C (informative) Example of reports . 18
Annex D (informative) Uncertainties . 21
Annex E (informative) Sound attenuation effect of silencers . 24
Bibliography . 34
iii
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 131 Fluid power systems, Subcommittee SC 5,
Control products and components.
This second edition cancels and replaces the first edition (ISO 20145:2019), which has been technically
revised.
The main changes are as follows:
— — addition of a new Annex EAnnex E on sound attenuation effect of silencers.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
This acoustic test procedure is intended to provide a common framework to industrial companies to evaluate
the sound pressure levels of pneumatic exhaust silencers.
It defines two methods of measuring the level of acoustic pressure at the outlet of an exhaust silencer. These
methods should be capable of being applied by pneumatic equipment manufacturers in their facilities on test
benches in accordance with ISO 6358-1 and ISO 6358-2.
The first method, called "steady-state mode”, is intended to evaluate the noise level under steady state flow,
1)
i.e. constant upstream pressure. This measurement is performed at 630 kPa at least to permit comparison
between silencers at the most frequently used operating pressure (or at the maximum admissible pressure if
lower than 630 kPa).
The second method, called “discharge mode”, is intended to measure the noise level during the decrease of the
pneumatic pressure (discharge test according to ISO 6358-2). To ensure the compatibility with the steady-
state flow method, the pressure range includes 630 kPa (or the maximum admissible pressure if lower than
630 kPa).
1) 5 2
1 bar = 0,1 MPa =10 Pa; 1 MPa = 1 N/mm .
v
Pneumatic fluid power — Test methods for measuring acoustic
emission pressure levels of exhaust silencers
1 Scope
This document specifies two methods of measuring the level of acoustic pressure at the outlet of an exhaust
silencer:
— — the first method, called "steady-state mode”, is intended to evaluate the noise level under steady state
flow, i.e. constant upstream pressure (steady-state test according to ISO 6358--1);
— — the second method, called “discharge”, is intended to measure the noise level during the decrease of
the pneumatic pressure (discharge test according to ISO 6358--2).
This document is applicable to pneumatic exhaust silencers and devices designed to reduce the sound
produced by discharges of compressed air, entering in the scope of application of ISO 6358--1 and ISO 6358--
2.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 4871, Acoustics — Declaration and verification of noise emission values of machinery and equipment
ISO 5167--2, Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section
conduits running full — Part 2: Orifice plates
ISO 6358--1, Pneumatic fluid power — Determination of flow-rate characteristics of components using
compressible fluids — Part 1: General rules and test methods for steady-state flow
ISO 6358--2, Pneumatic fluid power — Determination of flow-rate characteristics of components using
compressible fluids — Part 2: Alternative test methods
ISO 11202:2010, Acoustics — Noise emitted by machinery and equipment — Determination of emission sound
pressure levels at a work station and at other specified positions applying approximate environmental
corrections
ISO 11654, Acoustics — Sound absorbers for use in buildings — Rating of sound absorption
IEC 60942, Electroacoustics — Sound calibrators
IEC 61672--1, Electroacoustics — Sound level meters — Part 1: Specifications
IEC 61260, Electroacoustics — Octave-band and fractional-octave-band filters
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 11202 and ISO 6358--1 and the
following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— — ISO Online browsing platform: available at https://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/
3.1 3.1
emission sound pressure
p
sound pressure, at a specified position near a noise source, when the source is in operation under specified
operating and mounting conditions on a reflecting plane surface, excluding the effects of background noise (
3.5) as well as the effects of reflections other than those from the plane or planes permitted for the purpose of
the test.
Note 1 to entry: Emission sound pressure is expressed in pascals.
3.2 3.2
emission sound pressure level
L
p
ten times the logarithm to the base 10 of the ratio of the square of the emission sound pressure, p, (3.1) to the
square of a reference value, p
𝑝
𝐿 = 10lg( )
p
𝑝
where the reference value, p , is equal to 20 μPa
Note 1 to entry: Emission sound pressure level is expressed in decibels.
3.3 3.3
measured equivalent continuous sound pressure level (A-weighted)
L ,T
Aeq
ten times the logarithm to the base 10 of the ratio of the time average of the square of the emission sound
pressure, p, (3.1) 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
1 𝑡
∫ 𝑝 (𝑡)𝑑𝑡
𝑡
𝑇
𝐿 = 10lg
Aeq,𝑇
𝑝
where the reference value, p , is equal to 20 μPa and L is the measured value obtained using the "L "
0 Aeq,T Aeq
position of the sonometer.
Note 1 to entry: LAeq,T measured equivalent continuous sound pressure level is expressed in dB(A).
Note 2 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 emission sound pressure level.
A
Note 3 to entry: The formula in 3.3 is equivalent to that for the environmental noise descriptor “equivalent continuous
sound pressure level”. However, the emission quantity defined above is used to characterize the noise emitted by a source
under test and assumes that standardized measurement and operating conditions as well as a controlled acoustical
environment are used for the measurements.
3.4 3.4
frequency range of interest
sound levels determined for frequencies from 100 Hz to
...
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