Acoustics - Characterization of sources of structure-borne sound and vibration - Indirect measurement of blocked forces (ISO 20270:2019)

This document specifies a method where a vibrating component (a source of structure-borne sound or vibration) is attached to a passive structure (or receiver) and is the cause of vibration in, or structure-borne sound radiation from, the assembly. Examples are pumps installed in ships, servo motors in vehicles or machines and plant in buildings. Almost any vibrating component can be considered as a source in this context.
Due to the need to measure vibration at all contact degrees of freedom (DOFs) (connections between the source and receiver), this document can only be applied to assemblies for which such measurement is possible.
This document is applicable only to assemblies whose frequency response functions (FRFs) are linear and time invariant.
The source can be installed into a real assembly or attached to a specially designed test stand (as described in 5.2).
The standard method has been validated for stationary signals such that the results can be presented in the frequency domain. However, the method is not restricted to stationary signals: with appropriate data processing, it is also applicable to time-varying signals such as transients and shocks (provided linearity and time invariance of the FRFs are preserved).
This document provides a method for measurement and presentation of blocked forces, together with guidelines for minimizing uncertainty. It provides a method evaluating the quality of the results through an on-board validation procedure but does not comment on the acceptability or otherwise of the results.

Akustik - Charakterisierung von Körperschall- und Schwingungsquellen - Indirekte Messung von blockierten Kräften (ISO 20270:2019)

Acoustique - Caractérisation des sources de bruit solidien et de vibrations - Mesurage indirect des forces bloquées (ISO 20270:2019)

Le présent document spécifie une méthode dans laquelle un composant vibrant (une source de bruit solidien ou de vibrations) est fixé à une structure (ou récepteur) passive et provoque des vibrations dans l'assemblage ou un rayonnement sonore solidien de l'assemblage. Des pompes installées dans des navires, des servomoteurs dans des véhicules ou des machines et une installation dans des bâtiments en sont des exemples. Presque tous les composants vibrants peuvent être considérés comme une source dans ce contexte.
En raison de la nécessité de mesurer les vibrations à tous les degrés de liberté (DDL) de contact (connexions entre la source et le récepteur), le présent document ne peut s'appliquer qu'aux assemblages pour lesquels un tel mesurage est possible.
Le présent document n'est applicable qu'aux assemblages dont les fonctions de réponse en fréquence (FRF) sont linéaires et invariables dans le temps.
La source peut être installée dans un assemblage réel ou fixé sur un banc d'essai spécialement conçu (tel que décrit en 5.2).
La méthode normalisée a été validée pour des signaux stationnaires de sorte que les résultats puissent être présentés dans le domaine de fréquences. Toutefois, la méthode ne se limite pas aux signaux stationnaires: moyennant un traitement approprié des données, elle est également applicable à des signaux variant dans le temps tels que des transitoires et des chocs (à condition que la linéarité et l'invariance dans le temps des FRF soient conservées).
Le présent document fournit une méthode de mesure et de présentation des forces bloquées, ainsi que des lignes directrices visant à réduire le plus possible l'incertitude. Il fournit une méthode d'évaluation de la qualité des résultats au moyen d'une procédure d'auto-validation, sans toutefois commenter l'acceptabilité ou non des résultats.

Akustika - Opredelitev virov zvoka in vibracij, ki jih prenaša konstrukcija - Posredno merjenje blokiranih sil (ISO 20270:2019)

General Information

Status
Published
Public Enquiry End Date
15-Sep-2022
Publication Date
16-Jan-2023
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
01-Dec-2022
Due Date
05-Feb-2023
Completion Date
17-Jan-2023

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SLOVENSKI STANDARD
SIST EN ISO 20270:2023
01-februar-2023
Akustika - Opredelitev virov zvoka in vibracij, ki jih prenaša konstrukcija -
Posredno merjenje blokiranih sil (ISO 20270:2019)

Acoustics - Characterization of sources of structure-borne sound and vibration - Indirect

measurement of blocked forces (ISO 20270:2019)
Akustik - Charakterisierung von Körperschall- und Schwingungsquellen - Indirekte
Messung von blockierten Kräften (ISO 20270:2019)

Acoustique - Caractérisation des sources de bruit solidien et de vibrations - Mesurage

indirect des forces bloquées (ISO 20270:2019)
Ta slovenski standard je istoveten z: EN ISO 20270:2022
ICS:
17.140.20 Emisija hrupa naprav in Noise emitted by machines
opreme and equipment
SIST EN ISO 20270:2023 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN ISO 20270:2023
---------------------- Page: 2 ----------------------
SIST EN ISO 20270:2023
EN ISO 20270
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2022
EUROPÄISCHE NORM
ICS 17.140.20
English Version
Acoustics - Characterization of sources of structure-borne
sound and vibration - Indirect measurement of blocked
forces (ISO 20270:2019)

Acoustique - Caractérisation des sources de bruit Akustik - Charakterisierung von Körperschall- und

solidien et de vibrations - Mesurage indirect des forces Schwingungsquellen - Indirekte Messung von

bloquées (ISO 20270:2019) blockierten Kräften (ISO 20270:2019)
This European Standard was approved by CEN on 23 October 2022.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this

European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by

translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 20270:2022 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN ISO 20270:2023
EN ISO 20270:2022 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

Endorsement notice ..................................................................................................................................................... 3

---------------------- Page: 4 ----------------------
SIST EN ISO 20270:2023
EN ISO 20270:2022 (E)
European foreword

The text of ISO 20270:2019 has been prepared by Technical Committee ISO/TC 43 "Acoustics” of the

International Organization for Standardization (ISO) and has been taken over as EN ISO 20270:2022 by

Technical Committee CEN/TC 211 “Acoustics” the secretariat of which is held by DIN.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by April 2023, and conflicting national standards shall be

withdrawn at the latest by April 2023.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN shall not be held responsible for identifying any or all such patent rights.

Any feedback and questions on this document should be directed to the users’ national standards body.

A complete listing of these bodies can be found on the CEN website.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,

Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of

North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the

United Kingdom.
Endorsement notice

The text of ISO 20270:2019 has been approved by CEN as EN ISO 20270:2022 without any modification.

---------------------- Page: 5 ----------------------
SIST EN ISO 20270:2023
---------------------- Page: 6 ----------------------
SIST EN ISO 20270:2023
INTERNATIONAL ISO
STANDARD 20270
First edition
2019-11
Acoustics — Characterization of
sources of structure-borne sound and
vibration — Indirect measurement of
blocked forces
Acoustique — Caractérisation des sources de bruit solidien et de
vibrations — Mesurage indirect des forces bloquées
Reference number
ISO 20270:2019(E)
ISO 2019
---------------------- Page: 7 ----------------------
SIST EN ISO 20270:2023
ISO 20270:2019(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2019

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
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved
---------------------- Page: 8 ----------------------
SIST EN ISO 20270:2023
ISO 20270:2019(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

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

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

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

4 Selection of degrees of freedom (DOFs) ....................................................................................................................................... 6

4.1 General ........................................................................................................................................................................................................... 6

4.2 Source receiver interface ................................................................................................................................................................ 7

4.3 Contact DOFs............................................................................................................................................................................................. 7

4.4 Indicator DOFs ....................................................................................................................................................................................... 8

4.4.1 General...................................................................................................................................................................................... 8

4.4.2 All indicator DOFs at contact area .................................................................................................................... 8

4.4.3 No indicator DOF at contact area ....................................................................................................................... 8

4.4.4 Some indicator DOFs at contact area ............................................................................................................. 8

4.5 Validation DOFs ...................................................................................................................................................................................... 8

5 Test arrangement ................................................................................................................................................................................................. 8

5.1 General ........................................................................................................................................................................................................... 8

5.2 Representativeness of the receiver ....................................................................................................................................... 8

5.3 Design of test receiver ...................................................................................................................................................................... 9

5.4 Avoidance of secondary noise sources ............................................................................................................................... 9

6 Measuring equipment ..................................................................................................................................................................................10

6.1 General ........................................................................................................................................................................................................10

6.2 Multi-channel analyser .................................................................................................................................................................10

6.3 Vibration sensors ...............................................................................................................................................................................10

6.4 Means of excitation ...........................................................................................................................................................................10

7 Test procedure .....................................................................................................................................................................................................10

7.1 General ........................................................................................................................................................................................................10

7.2 Operational test ...................................................................................................................................................................................12

7.3 Frequency response function (FRF) test .......................................................................................................................12

7.3.1 General...................................................................................................................................................................................12

7.3.2 Direct FRF measurement .......................................................................................................................................12

7.3.3 Reciprocal FRF measurement............................................................................................................................12

7.4 Preliminary test with artificial excitation .....................................................................................................................13

8 Analysis procedure ..........................................................................................................................................................................................13

9 Uncertainties and validation ................................................................................................................................................................14

9.1 General ........................................................................................................................................................................................................14

9.2 On-board validation .........................................................................................................................................................................15

9.3 Preliminary validation using artificial excitation ...................................................................................................15

10 Test report ................................................................................................................................................................................................................15

Annex A (informative) Example of a test report: Electric rear axle drive in a passenger car;

transfer path analysis (TPA) and estimation of blocked forces in situ according to

ISO 20270:2019 ..................................................................................................................................................................................................17

Annex B (informative) Tests for validity of measurement data ............................................................................................24

Annex C (informative) Case studies ....................................................................................................................................................................26

Annex D (informative) Criteria for selection of indicator and validation DOFs ...................................................31

Annex E (informative) Prediction of sound and vibration ..........................................................................................................35

Bibliography .............................................................................................................................................................................................................................37

© ISO 2019 – All rights reserved iii
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SIST EN ISO 20270:2023
ISO 20270:2019(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 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 43, Acoustics, Subcommittee SC 1, Noise.

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 © ISO 2019 – All rights reserved
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SIST EN ISO 20270:2023
ISO 20270:2019(E)
Introduction

This document has been developed in response to demand from mechanical industries for an agreed

method of specifying the "source strength" of sources of structure-borne sound and vibration. Quantities

[2]

which independently characterize a source are the free velocity and blocked force: ISO 9611 specifies

a measurement procedure for the former in which the machine, a vibration source, is mounted on soft

mounts to approximate free suspension. The blocked forces are the forces the operating machine would

exert when constrained by a perfectly rigid foundation. They can potentially be measured directly by

inserting force transducers in between the operating machine and a rigid foundation. However, this

document describes an indirect method for measurement of blocked forces using an inverse method.

Whereas the measurement of free velocity requires the source to be resiliently mounted and direct

measurement of blocked forces requires the machine mounts to be blocked, the indirect measurement,

as defined in this document, can theoretically be carried out with the source attached to any receiver

structure. Essentially the same measurement techniques are used in the diagnosis of structure-borne

sound using "transfer path analysis" (TPA), also called "source path contribution" analysis (SPC).

A method of characterizing sources of structure-borne sound and vibration by the indirect measurement

of blocked forces at the points of connection to supporting, or receiver, structures is described in this

document. The measurement method is applied in situ, which means that the source is connected to a

receiver structure while the measurements are performed. In theory, the use of any receiver structure

is valid provided the vibration source mechanisms of the specimen remain representative of those in a

real installation. Therefore, the receiver structure can be part of a real installation, such as a machine

foundation or a building, but can also be a specially designed test stand if it provides representative

dynamic loading for the source.

The method specifies a two-stage measurement procedure comprising, first, a passive test in which

frequency response functions (FRF) of the assembled source-receiver structure are measured, and

secondly, measurement of vibration in an operational test. The blocked forces are obtained by solving

the inverse problem. It is well known that inverse solutions of this type can result in very large errors,

particularly if there is inconsistency in the input data. Such errors vary significantly depending on the

case and the skill of the operator. Therefore, a means of estimating the uncertainties in the blocked

force, through a process called on-board validation, forms an essential part of this measurement

procedure.

The blocked forces are obtained in narrow frequency bands that can subsequently be converted to

approximate octave or third octave frequency bands.
[3]

The in situ blocked force method is intended to complement the reception plate method of EN 15657 .

The reception plate method offers a simplified approach in which forces and velocities are effectively

averaged over the feet of an operating machine by mounting on a standard plate. The approximations

allow measurements to be simplified but information about distribution and phase of the forces and

velocities is lost. This document aims to provide an alternative for structure borne sound sources not

compatible with the reception plate approach or where more detail is needed about the distribution of

the forces.

The blocked forces obtained from this document can be used for the following purposes:

a) obtaining data for preparing technical specifications for vibrationally active components (sources);

b) obtaining input data for prediction of vibration in, or sound radiated sound from, structures

connected to the source;

c) obtaining diagnostic information about the contribution of particular blocked forces to a target

vibration or sound pressure (in situ transfer path analysis).

Prediction of sound and vibration in a new assembly [as in b) above] does not form a normative part of

this document, although guidelines for prediction are provided in Annex E. For prediction purposes,

extra data are needed in addition to the measured blocked forces. Specifically, the frequency response

functions (FRFs) of the new assembly (which consists of the source connected to the new receiver

© ISO 2019 – All rights reserved v
---------------------- Page: 11 ----------------------
SIST EN ISO 20270:2023
ISO 20270:2019(E)

structure) need to be known. These FRFs can in principle be measured (if the assembly is available

for measurement), calculated (for example using numerical methods) or calculated by combining the

FRFs of the separate source and the receiver structures (dynamic substructuring) whether measured

or calculated.
vi © ISO 2019 – All rights reserved
---------------------- Page: 12 ----------------------
SIST EN ISO 20270:2023
INTERNATIONAL STANDARD ISO 20270:2019(E)
Acoustics — Characterization of sources of structure-
borne sound and vibration — Indirect measurement of
blocked forces

IMPORTANT — The electronic file of this document contains colours which are considered to be

useful for the correct understanding of the document. Users should therefore consider printing

this document using a colour printer.
1 Scope

This document specifies a method where a vibrating component (a source of structure-borne sound or

vibration) is attached to a passive structure (or receiver) and is the cause of vibration in, or structure-

borne sound radiation from, the assembly. Examples are pumps installed in ships, servo motors in

vehicles or machines and plant in buildings. Almost any vibrating component can be considered as a

source in this context.

Due to the need to measure vibration at all contact degrees of freedom (DOFs) (connections between

the source and receiver), this document can only be applied to assemblies for which such measurement

is possible.

This document is applicable only to assemblies whose frequency response functions (FRFs) are linear

and time invariant.

The source can be installed into a real assembly or attached to a specially designed test stand (as

described in 5.2).

The standard method has been validated for stationary signals such that the results can be presented

in the frequency domain. However, the method is not restricted to stationary signals: with appropriate

data processing, it is also applicable to time-varying signals such as transients and shocks (provided

linearity and time invariance of the FRFs are preserved).

This document provides a method for measurement and presentation of blocked forces, together

with guidelines for minimizing uncertainty. It provides a method evaluating the quality of the results

through an on-board validation procedure but does not comment on the acceptability or otherwise of

the results.
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 7626-1, Mechanical vibration and shock — Experimental determination of mechanical mobility —

Part 1: Basic terms and definitions, and transducer specifications

ISO7626-2, Mechanical vibration and shock — Experimental determination of mechanical mobility —

Part 2: Measurements using single-point translation excitation with an attached vibration exciter

3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
© ISO 2019 – All rights reserved 1
---------------------- Page: 13 ----------------------
SIST EN ISO 20270:2023
ISO 20270:2019(E)

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
blocked force

dynamic force applied by an operational source (3.4) to a perfectly rigid receiver (3.5) structure

3.2
frequency response function
FRF

frequency-dependent ratio of the motion-response Fourier transform to the Fourier transform of the

excitation force of a linear system

Note 1 to entry: Excitation can be harmonic, random or transient functions of time. The test results obtained with

one type of excitation can thus be used for predicting the response of the system to any other type of excitation.

Note 2 to entry: Motion may be expressed in terms of velocity, acceleration or displacement; the corresponding

frequency-response function designations are mobility, accelerance and dynamic compliance or impedance,

effective (i.e. apparent) mass and dynamic stiffness, respectively.
[SOURCE: ISO 2041:2018, 3.1.53]
3.3
in situ blocked force vector
f ()f

complex blocked force (3.1) at the contact degrees of freedom (DOFs) (3.8), arranged into an n × 1 vector

at each frequency according to:
 ff 
c,1
 
 
ff()
 
c,2
f ()f =
 
 
 
ff()
 
cn,
 

where ff() is the complex Fourier spectrum component of the blocked force at frequency f and at

ci,
contact degree of freedom (DOF) i

Note 1 to entry: Forces can be considered as generalized forces, that is, including rotational components like

moments.
3.4
source

active substructure which contains the mechanisms of structure-borne sound or vibration generation

and comprises all parts of the assembly (3.6) on the active side of the source-receiver interface (3.7)

Note 1 to entry: Typically, the source is a separable component although this is not a requirement for the method.

Note 2 to entry: See Figure 1.
3.5
receiver

passive substructure comprising all parts of the assembly (3.6) on the passive side of the source-receiver

interface (3.7)

Note 1 to entry: The receiver may comprise the remaining parts of an assembled machine other than the source,

a test bench or a foundation structure such as a building.
2 © ISO 2019 – All rights reserved
---------------------- Page: 14 ----------------------
SIST EN ISO 20270:2023
ISO 20270:2019(E)

Note 2 to entry: By definition, there are no source mechanisms within the receiver so it is a purely passive

structure.
Note 3 to entry: See Figure 1.
3.6
assembly
installation comprising the source (3.4) and receiver (3.5) connected together
Note 1 to entry: See Figure 1.
Key
1 source (active structure)
2 receiver (passive structure)
3 assembly
s internal source excitation (not accessible)
in situ blocked force vector at the set of contact DOFs, c
v validation velocity (or acceleration) vector at the set of validation DOFs, v
v indicator velocity (or acceleration) vector at the set of validation DOFs, r
Y typical structural FRF between validation DOFs, v, and contact DOFs, c
Y typical structural FRF between indicator DOFs, r, and contact DOFs, c

H typical vibro-acoustic FRF between prediction DOFs, a, and contact DOFs, c (see NOTE 3)

p structure-borne sound predicted at DOFs, a, in the fluid around the receiver (see NOTE 3)

NOTE 1 Indicator DOFs can be located anywhere on the receiver, including the source-receiver interface.

NOTE 2 The obtained blocked force vector can be used to predict vibration in, and radiated sound from, the

receiver structure (see Annex E).

NOTE 3 A vibration source (1) connected to a passive receiver (2) causes vibration (v ) in, or structure-borne

sound (p ) radiated from, the assembly (3) at interfaces (r, v) and (a), respectively. The internal excitation, s, is

unknown, requiring the source to be characterized at the source-receiver interface by blocked forces f , inferred

from v and the assembly FRF matrix Y . Additional structural, Y , and
...

SLOVENSKI STANDARD
oSIST prEN ISO 20270:2022
01-september-2022
Akustika - Opredelitev virov zvoka in vibracij, ki jih prenaša konstrukcija -
Posredno merjenje blokiranih sil (ISO 20270:2019)

Acoustics - Characterization of sources of structure-borne sound and vibration - Indirect

measurement of blocked forces (ISO 20270:2019)
Akustik - Charakterisierung von Körperschall- und Schwingungsquellen - Indirekte
Messung von blockierten Kräften (ISO 20270:2019)

Acoustique - Caractérisation des sources de bruit solidien et de vibrations - Mesurage

indirect des forces bloquées (ISO 20270:2019)
Ta slovenski standard je istoveten z: prEN ISO 20270
ICS:
17.140.20 Emisija hrupa naprav in Noise emitted by machines
opreme and equipment
oSIST prEN ISO 20270:2022 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
oSIST prEN ISO 20270:2022
---------------------- Page: 2 ----------------------
oSIST prEN ISO 20270:2022
INTERNATIONAL ISO
STANDARD 20270
First edition
2019-11
Acoustics — Characterization of
sources of structure-borne sound and
vibration — Indirect measurement of
blocked forces
Acoustique — Caractérisation des sources de bruit solidien et de
vibrations — Mesurage indirect des forces bloquées
Reference number
ISO 20270:2019(E)
ISO 2019
---------------------- Page: 3 ----------------------
oSIST prEN ISO 20270:2022
ISO 20270:2019(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2019

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
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved
---------------------- Page: 4 ----------------------
oSIST prEN ISO 20270:2022
ISO 20270:2019(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

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

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

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

4 Selection of degrees of freedom (DOFs) ....................................................................................................................................... 6

4.1 General ........................................................................................................................................................................................................... 6

4.2 Source receiver interface ................................................................................................................................................................ 7

4.3 Contact DOFs............................................................................................................................................................................................. 7

4.4 Indicator DOFs ....................................................................................................................................................................................... 8

4.4.1 General...................................................................................................................................................................................... 8

4.4.2 All indicator DOFs at contact area .................................................................................................................... 8

4.4.3 No indicator DOF at contact area ....................................................................................................................... 8

4.4.4 Some indicator DOFs at contact area ............................................................................................................. 8

4.5 Validation DOFs ...................................................................................................................................................................................... 8

5 Test arrangement ................................................................................................................................................................................................. 8

5.1 General ........................................................................................................................................................................................................... 8

5.2 Representativeness of the receiver ....................................................................................................................................... 8

5.3 Design of test receiver ...................................................................................................................................................................... 9

5.4 Avoidance of secondary noise sources ............................................................................................................................... 9

6 Measuring equipment ..................................................................................................................................................................................10

6.1 General ........................................................................................................................................................................................................10

6.2 Multi-channel analyser .................................................................................................................................................................10

6.3 Vibration sensors ...............................................................................................................................................................................10

6.4 Means of excitation ...........................................................................................................................................................................10

7 Test procedure .....................................................................................................................................................................................................10

7.1 General ........................................................................................................................................................................................................10

7.2 Operational test ...................................................................................................................................................................................12

7.3 Frequency response function (FRF) test .......................................................................................................................12

7.3.1 General...................................................................................................................................................................................12

7.3.2 Direct FRF measurement .......................................................................................................................................12

7.3.3 Reciprocal FRF measurement............................................................................................................................12

7.4 Preliminary test with artificial excitation .....................................................................................................................13

8 Analysis procedure ..........................................................................................................................................................................................13

9 Uncertainties and validation ................................................................................................................................................................14

9.1 General ........................................................................................................................................................................................................14

9.2 On-board validation .........................................................................................................................................................................15

9.3 Preliminary validation using artificial excitation ...................................................................................................15

10 Test report ................................................................................................................................................................................................................15

Annex A (informative) Example of a test report: Electric rear axle drive in a passenger car;

transfer path analysis (TPA) and estimation of blocked forces in situ according to

ISO 20270:2019 ..................................................................................................................................................................................................17

Annex B (informative) Tests for validity of measurement data ............................................................................................24

Annex C (informative) Case studies ....................................................................................................................................................................26

Annex D (informative) Criteria for selection of indicator and validation DOFs ...................................................31

Annex E (informative) Prediction of sound and vibration ..........................................................................................................35

Bibliography .............................................................................................................................................................................................................................37

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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 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 43, Acoustics, Subcommittee SC 1, Noise.

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 © ISO 2019 – All rights reserved
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Introduction

This document has been developed in response to demand from mechanical industries for an agreed

method of specifying the "source strength" of sources of structure-borne sound and vibration. Quantities

[2]

which independently characterize a source are the free velocity and blocked force: ISO 9611 specifies

a measurement procedure for the former in which the machine, a vibration source, is mounted on soft

mounts to approximate free suspension. The blocked forces are the forces the operating machine would

exert when constrained by a perfectly rigid foundation. They can potentially be measured directly by

inserting force transducers in between the operating machine and a rigid foundation. However, this

document describes an indirect method for measurement of blocked forces using an inverse method.

Whereas the measurement of free velocity requires the source to be resiliently mounted and direct

measurement of blocked forces requires the machine mounts to be blocked, the indirect measurement,

as defined in this document, can theoretically be carried out with the source attached to any receiver

structure. Essentially the same measurement techniques are used in the diagnosis of structure-borne

sound using "transfer path analysis" (TPA), also called "source path contribution" analysis (SPC).

A method of characterizing sources of structure-borne sound and vibration by the indirect measurement

of blocked forces at the points of connection to supporting, or receiver, structures is described in this

document. The measurement method is applied in situ, which means that the source is connected to a

receiver structure while the measurements are performed. In theory, the use of any receiver structure

is valid provided the vibration source mechanisms of the specimen remain representative of those in a

real installation. Therefore, the receiver structure can be part of a real installation, such as a machine

foundation or a building, but can also be a specially designed test stand if it provides representative

dynamic loading for the source.

The method specifies a two-stage measurement procedure comprising, first, a passive test in which

frequency response functions (FRF) of the assembled source-receiver structure are measured, and

secondly, measurement of vibration in an operational test. The blocked forces are obtained by solving

the inverse problem. It is well known that inverse solutions of this type can result in very large errors,

particularly if there is inconsistency in the input data. Such errors vary significantly depending on the

case and the skill of the operator. Therefore, a means of estimating the uncertainties in the blocked

force, through a process called on-board validation, forms an essential part of this measurement

procedure.

The blocked forces are obtained in narrow frequency bands that can subsequently be converted to

approximate octave or third octave frequency bands.
[3]

The in situ blocked force method is intended to complement the reception plate method of EN 15657 .

The reception plate method offers a simplified approach in which forces and velocities are effectively

averaged over the feet of an operating machine by mounting on a standard plate. The approximations

allow measurements to be simplified but information about distribution and phase of the forces and

velocities is lost. This document aims to provide an alternative for structure borne sound sources not

compatible with the reception plate approach or where more detail is needed about the distribution of

the forces.

The blocked forces obtained from this document can be used for the following purposes:

a) obtaining data for preparing technical specifications for vibrationally active components (sources);

b) obtaining input data for prediction of vibration in, or sound radiated sound from, structures

connected to the source;

c) obtaining diagnostic information about the contribution of particular blocked forces to a target

vibration or sound pressure (in situ transfer path analysis).

Prediction of sound and vibration in a new assembly [as in b) above] does not form a normative part of

this document, although guidelines for prediction are provided in Annex E. For prediction purposes,

extra data are needed in addition to the measured blocked forces. Specifically, the frequency response

functions (FRFs) of the new assembly (which consists of the source connected to the new receiver

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structure) need to be known. These FRFs can in principle be measured (if the assembly is available

for measurement), calculated (for example using numerical methods) or calculated by combining the

FRFs of the separate source and the receiver structures (dynamic substructuring) whether measured

or calculated.
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oSIST prEN ISO 20270:2022
INTERNATIONAL STANDARD ISO 20270:2019(E)
Acoustics — Characterization of sources of structure-
borne sound and vibration — Indirect measurement of
blocked forces

IMPORTANT — The electronic file of this document contains colours which are considered to be

useful for the correct understanding of the document. Users should therefore consider printing

this document using a colour printer.
1 Scope

This document specifies a method where a vibrating component (a source of structure-borne sound or

vibration) is attached to a passive structure (or receiver) and is the cause of vibration in, or structure-

borne sound radiation from, the assembly. Examples are pumps installed in ships, servo motors in

vehicles or machines and plant in buildings. Almost any vibrating component can be considered as a

source in this context.

Due to the need to measure vibration at all contact degrees of freedom (DOFs) (connections between

the source and receiver), this document can only be applied to assemblies for which such measurement

is possible.

This document is applicable only to assemblies whose frequency response functions (FRFs) are linear

and time invariant.

The source can be installed into a real assembly or attached to a specially designed test stand (as

described in 5.2).

The standard method has been validated for stationary signals such that the results can be presented

in the frequency domain. However, the method is not restricted to stationary signals: with appropriate

data processing, it is also applicable to time-varying signals such as transients and shocks (provided

linearity and time invariance of the FRFs are preserved).

This document provides a method for measurement and presentation of blocked forces, together

with guidelines for minimizing uncertainty. It provides a method evaluating the quality of the results

through an on-board validation procedure but does not comment on the acceptability or otherwise of

the results.
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 7626-1, Mechanical vibration and shock — Experimental determination of mechanical mobility —

Part 1: Basic terms and definitions, and transducer specifications

ISO7626-2, Mechanical vibration and shock — Experimental determination of mechanical mobility —

Part 2: Measurements using single-point translation excitation with an attached vibration exciter

3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
blocked force

dynamic force applied by an operational source (3.4) to a perfectly rigid receiver (3.5) structure

3.2
frequency response function
FRF

frequency-dependent ratio of the motion-response Fourier transform to the Fourier transform of the

excitation force of a linear system

Note 1 to entry: Excitation can be harmonic, random or transient functions of time. The test results obtained with

one type of excitation can thus be used for predicting the response of the system to any other type of excitation.

Note 2 to entry: Motion may be expressed in terms of velocity, acceleration or displacement; the corresponding

frequency-response function designations are mobility, accelerance and dynamic compliance or impedance,

effective (i.e. apparent) mass and dynamic stiffness, respectively.
[SOURCE: ISO 2041:2018, 3.1.53]
3.3
in situ blocked force vector
f ()f

complex blocked force (3.1) at the contact degrees of freedom (DOFs) (3.8), arranged into an n × 1 vector

at each frequency according to:
 ff 
c,1
 
 
ff()
 
c,2
f ()f =
 
 
 
ff()
 
cn,
 

where ff() is the complex Fourier spectrum component of the blocked force at frequency f and at

ci,
contact degree of freedom (DOF) i

Note 1 to entry: Forces can be considered as generalized forces, that is, including rotational components like

moments.
3.4
source

active substructure which contains the mechanisms of structure-borne sound or vibration generation

and comprises all parts of the assembly (3.6) on the active side of the source-receiver interface (3.7)

Note 1 to entry: Typically, the source is a separable component although this is not a requirement for the method.

Note 2 to entry: See Figure 1.
3.5
receiver

passive substructure comprising all parts of the assembly (3.6) on the passive side of the source-receiver

interface (3.7)

Note 1 to entry: The receiver may comprise the remaining parts of an assembled machine other than the source,

a test bench or a foundation structure such as a building.
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Note 2 to entry: By definition, there are no source mechanisms within the receiver so it is a purely passive

structure.
Note 3 to entry: See Figure 1.
3.6
assembly
installation comprising the source (3.4) and receiver (3.5) connected together
Note 1 to entry: See Figure 1.
Key
1 source (active structure)
2 receiver (passive structure)
3 assembly
s internal source excitation (not accessible)
in situ blocked force vector at the set of contact DOFs, c
v validation velocity (or acceleration) vector at the set of validation DOFs, v
v indicator velocity (or acceleration) vector at the set of validation DOFs, r
Y typical structural FRF between validation DOFs, v, and contact DOFs, c
Y typical structural FRF between indicator DOFs, r, and contact DOFs, c

H typical vibro-acoustic FRF between prediction DOFs, a, and contact DOFs, c (see NOTE 3)

p structure-borne sound predicted at DOFs, a, in the fluid around the receiver (see NOTE 3)

NOTE 1 Indicator DOFs can be located anywhere on the receiver, including the source-receiver interface.

NOTE 2 The obtained blocked force vector can be used to predict vibration in, and radiated sound from, the

receiver structure (see Annex E).

NOTE 3 A vibration source (1) connected to a passive receiver (2) causes vibration (v ) in, or structure-borne

sound (p ) radiated from, the assembly (3) at interfaces (r, v) and (a), respectively. The internal excitation, s, is

unknown, requiring the source to be characterized at the source-receiver interface by blocked forces f , inferred

from v and the assembly FRF matrix Y . Additional structural, Y , and vibro-acoustic FRFs, H , can be used for

r rc vc ac
validation and prediction purposes.
Figure 1 — Test assembly
3.7
source-receiver interface

hypothetical surface which separates the source (3.4) structure from the receiver (3.5) structure

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3.8
contact degrees of freedom
contact DOFs

DOFs located on the source receiver interface through which structure-borne sound or vibration is

transmitted from the source (3.4) to the receiver (3.5) structure

Note 1 to entry: n is the number of DOFs and c is the subscript used for contact DOFs.

Note 2 to entry: See 4.3 for a full definition.
3.9
indicator degrees of freedom
indicator DOFs
DOFs on the receiver (3.5) at which vibration responses are measured

Note 1 to entry: m is the number of DOFs and r is the subscript used for indicator DOFs.

Note 2 to entry: See 4.4.
3.10
validation degrees of freedom
validation DOFs

DOFs on the receiver (3.5) structure (not at the contact area) at which "spare" vibration responses are

measured so as to provide a comparison for the on-board validation

Note 1 to entry: p is the number of DOFs and v is the subscript used for validation DOFs.

Note 2 to entry: See 4.5.
Note 3 to entry: The validation is described in Clause 9.
3.11
indicator velocity vector
v ( f )

complex velocity (or acceleration) at the indicator DOFs (3.9), arranged into an m × 1 vector at each

frequency according to:
vf()
 
r,1
 
vf()
 
 r,2 
v f =
 
 
 
 
 rm, 

where v ( f ) is the complex Fourier spectrum component of the velocity (or acceleration) at frequency f

r,j
and at indicator DOFs j

Note 1 to entry: Consistent quantities shall be used throughout: either velocity and mobility, or acceleration and

accelerance.
3.12
measured validation velocity vector
v ( f )
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complex velocity (or acceleration) at the validation DOFs (3.10), arranged into a p × 1 vector at each

frequency according to:
vf()
 
v,1
 
 ()
 v,2 
v ()f =
 
 
 
 vp, 
 

where v ( f ) is the complex Fourier spectrum component of the velocity (or acceleration) at frequency f

v,k
and at indicator degree of freedom k
3.13
predicted validation velocity vector
v ' f

complex velocity (or acceleration) vector which has the same form as the measured validation velocity

vector (3.12) but contains predicted rather than measured data
Note 1 to entry: It is calculated according to Clause 8.
3.14
operational test

test in which vibration responses are measured at the indicator (3.9) and validation DOFs (3.10) while

the source (3.4) is in operation under a given set of operational conditions (3.16)

3.15
operational test using artificial excitation

test in which vibration responses are measured at the indicator (3.9) and validation DOFs (3.10) in the

same way as for an operational test (3.16) except that the source (3.4) is switched off and excitation is

provided by an instrumented hammer or shaker
3.16
operational conditions

defined set of circumstances under which the source (3.4) operates for the operational test (3.14),

including speed, load and any other settings or conditions particular to the source which can affect

source operation
3.17
artificial excitation

set of circumstances similar to operational conditions (3.16) except that the source (3.4) is switched off and

the source structure is excited artificially by a controlled force from an instrumented hammer or shaker

3.18
background noise conditions

conditions similar to operational conditions (3.16) except that the source (3.4) is switched off while any

other auxiliary equipment required to operate or load the source, e.g. hydraulic pumps, generators or

actuators, and/or other secondary sources of noise, e.g. wind noise, are active
3.19
on-board validation
procedure used for determining the quality of the blocked force (3.1) data
Note 1 to entry: The on-board validation is described in Clause 9.
3.20
frequency response function test
FRF test
test in which the response to a unit point force (mechanical m
...

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