Environmental testing - Part 2-65: Tests - Test Fg: Vibration - Acoustically induced method

IEC 60068-2-65:2013 provides standard procedures and guidance for conducting acoustic tests in order to determine the ability of a specimen to withstand vibration caused by a specified sound-pressure level environment to which it is, or is liable to be, subjected. This second edition cancels and replaces the second edition, published in 1993, and constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
- minor technical and editorial changes were made throughout the document as originally requested by the DE National Committee;
- following comments at the CD stage, particularly from the UK National Committee, significant technical and editorial additions were made to the standard for acoustic testing employing the progressive wave tube technique.

Essais d'environnement - Partie 2-65: Essais - Essai Fg: Vibrations - Méthode induite acoustiquement

La CEI 60068-2-65:2013 fournit des méthodes normalisées et un guide pour la conduite d'essais acoustiques afin de déterminer l'aptitude d'un spécimen à résister à des vibrations provoquées par un environnement de niveau de pression acoustique spécifié auquel il est, ou est susceptible d'être, exposé. Cette deuxième édition annule et remplace la deuxième édition, publiée en 1993, dont elle constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
- des modifications techniques et rédactionnelles mineures ont été faites dans toute la norme, tel qu'il a été demandé à l'origine par le Comité national allemand;
- conformément aux commentaires émis au stade CD, en particulier ceux du Comité national britannique, des ajouts techniques et éditoriaux significatifs ont été réalisés dans la norme pour l'essai acoustique employant le technique du tube à ondes progressives.

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Status
Published
Publication Date
05-Feb-2013
Current Stage
PPUB - Publication issued
Start Date
06-Feb-2013
Completion Date
06-Feb-2013
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IEC 60068-2-65
Edition 2.0 2013-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Environmental testing –
Part 2-65: Tests – Test Fg: Vibration – Acoustically induced method
Essais d’environnement –
Partie 2-65: Essais – Essai Fg: Vibrations – Méthode induite acoustiquement
IEC 60068-2-65:2013
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 60068-2-65
Edition 2.0 2013-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Environmental testing –
Part 2-65: Tests – Test Fg: Vibration – Acoustically induced method
Essais d’environnement –
Partie 2-65: Essais – Essai Fg: Vibrations – Méthode induite acoustiquement
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX V
ICS 19.040; 29.020 ISBN 978-2-83220-641-6

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – 60068-2-65 © IEC:2013
CONTENTS

FOREWORD ........................................................................................................................... 4

INTRODUCTION ..................................................................................................................... 6

1 Scope ............................................................................................................................... 7

2 Normative references ........................................................................................................ 7

3 Terms, definitions, symbols and abbreviations................................................................... 7

3.1 Terms and definitions .............................................................................................. 7

3.2 Symbols and abbreviations .................................................................................... 11

4 Acoustic environments and requirements for testing ........................................................ 11

4.1 Acoustic environment for testing ............................................................................ 11

4.1.1 General ..................................................................................................... 11

4.1.2 Reverberant field ....................................................................................... 13

4.1.3 Progressive wave field ............................................................................... 14

4.1.4 Cavity resonance ....................................................................................... 14

4.1.5 Standing wave ........................................................................................... 14

4.2 Sound sources ....................................................................................................... 14

4.3 Measuring apparatus ............................................................................................. 14

4.3.1 General ..................................................................................................... 14

4.3.2 Acoustic measurements ............................................................................. 14

4.3.3 Vibration response measurements ............................................................. 15

4.3.4 Analysis of results ...................................................................................... 15

4.4 Requirements for testing ........................................................................................ 15

4.4.1 Type of facility ........................................................................................... 15

4.4.2 Mounting .................................................................................................... 15

4.4.3 Specimen instrumentation .......................................................................... 16

4.4.4 Preparation of test control .......................................................................... 17

5 Recommended severities ................................................................................................ 18

6 Preconditioning ............................................................................................................... 18

7 Initial measurements ....................................................................................................... 19

8 Testing ........................................................................................................................... 19

8.1 Normal testing ....................................................................................................... 19

8.2 Accelerated testing ................................................................................................ 19

9 Intermediate measurements ............................................................................................ 19

10 Recovery ........................................................................................................................ 19

11 Final measurements ....................................................................................................... 19

12 Information to be given in the relevant specification ......................................................... 20

13 Information to be given in the test report ......................................................................... 20

Annex A (informative) Guidance for the test requirements..................................................... 22

Bibliography .......................................................................................................................... 30

Figure 1 – Third-octave band spectrum for aeronautical applications ..................................... 12

Figure 2 – Octave band spectra for fans derived from [4] ....................................................... 13

Figure 3 – Octave band spectrum for noisy industrial machinery derived from [4] ................... 13

Figure 4 – Typical locations of microphone checkpoints (1 – 6) on a fictitious surface

around a specimen ................................................................................................................ 17

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60068-2-65 © IEC:2013 – 3 –

Figure A.1 – Typical microphone arrangement around a specimen in a reverberation

chamber................................................................................................................................ 22

Figure A.2 – Typical microphone checkpoint arrangement around a long cylindrical

specimen .............................................................................................................................. 25

Table 1 – Tolerances for acoustic measurement .................................................................... 14

Table 2 – Overall sound pressure level and duration of exposure ........................................... 18

Table A.1 – Octave band/room volume relationship ............................................................... 23

Table A.2 – Reverberation room, ratios of dimensions ........................................................... 23

Table A.3 – Examples of sound sources with waveforms and typical power outputs................ 28

Table A.4 – Typical OASPL and exposure durations .............................................................. 28

---------------------- Page: 5 ----------------------
– 4 – 60068-2-65 © IEC:2013
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ENVIRONMENTAL TESTING –
Part 2-65: Tests –
Test Fg: Vibration –
Acoustically induced method
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,

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governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely

with the International Organization for Standardization (ISO) in accordance with conditions determined by

agreement between the two organizations.

2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

consensus of opinion on the relevant subjects since each technical committee has representation from all

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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

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Publications.

8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

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

International Standard IEC 60068-2-65 has been prepared by IEC technical committee 104:

Environmental conditions, classification and methods of test.

This second edition cancels and replaces the second edition, published in 1993, and

constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:

– minor technical and editorial changes were made throughout the document as originally

requested by the DE National Committee;

– following comments at the CD stage, particularly from the UK National Committee,

significant technical and editorial additions were made to the standard for acoustic testing

employing the progressive wave tube technique.
---------------------- Page: 6 ----------------------
60068-2-65 © IEC:2013 – 5 –
The text of this standard is based on the following documents:
FDIS Report on voting
104/591/FDIS 104/597/RVD

Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all the parts in the IEC 60068 series, published under the general title Environmental

testing, can be found on the IEC website.

The committee has decided that the contents of this publication will remain unchanged until the

stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data related to

the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
---------------------- Page: 7 ----------------------
– 6 – 60068-2-65 © IEC:2013
INTRODUCTION

Acoustic noise may produce significant vibration in components and equipment. In the acoustic

noise field, sound pressure fluctuations impinge directly on the specimen and the response

may be different to that produced by mechanical excitation.

Items particularly sensitive to acoustic noise include relatively lightweight items whose

dimensions are comparable to an acoustic wavelength in the frequency range of interest and

whose mass per unit area is low, such as dish antennas and solar panels, electronic devices,

printed circuit boards, optical elements, etc.

Acoustic testing is applicable to components, equipment, functional units and other products,

hereinafter referred to as “specimens”, which are liable to be exposed to and/or are required to

function in conditions of high sound pressure levels. It should be noted that, under service

conditions, the specimen may be subjected to simultaneous mechanical and acoustical

excitation.

High sound pressure levels may be generated by jet engines and other aircraft propulsion

systems, rocket motors, high-powered gas circulators, turbulent gas flow around aircraft or

launchers, etc. This part of IEC 60068 deals with acoustic testing in compressible gases and

can also be used to simulate the excitation response caused by turbulence resulting from high-

velocity separated gas flows.

The intent of the test procedure contained in this standard is to produce a high intensity

acoustic noise field by either reverberant methods (known as reverberant chamber testing) or

by progressive wave methods (known as progressive wave tube testing).

Testing for the effects of vibration caused by acoustic noise demands a certain degree of

engineering judgement and this should be recognized both by the manufacturer/supplier and

the purchaser of the specimen. Based on the guidance provided in this standard, the writer of

the relevant specification is expected to select the most appropriate method of test and values

of severity, taking account of the nature of the specimen and its intended use.

Since the acoustic levels occurring during testing are high enough to be damaging to human

hearing, appropriate protective measures need to be taken to reduce the noise exposure of

operators performing the test to a level regarded as permissible from the standpoint of hearing

conservation.
---------------------- Page: 8 ----------------------
60068-2-65 © IEC:2013 – 7 –
ENVIRONMENTAL TESTING –
Part 2-65: Tests –
Test Fg: Vibration –
Acoustically induced method
1 Scope

This part of IEC 60068 provides standard procedures and guidance for conducting acoustic

tests in order to determine the ability of a specimen to withstand vibration caused by a

specified sound-pressure level environment to which it is, or is liable to be, subjected.

For sound pressure level environments of less than 120 dB acoustic tests are not normally

required.

This standard determines the mechanical weakness and/or degradation in the performance of

specimens and to use this information, in conjunction with the relevant specification, to decide

on their acceptability for use. The methods of test may also be used as a means of establishing

the mechanical robustness or fatigue resistance of specimens.

Two procedures are described for conducting tests and for measurement of the sound

pressure levels within the acoustic noise field and considers the need for measurement of the

vibration responses at specified points on the specimen. It also gives guidance for the

selection of the acoustic noise environment, spectrum, sound pressure level and duration of

exposure.

The progressive wave tube method is relevant to material where aerodynamic turbulence will

excite part, or all, of the total external surface. Such applications include aircraft panel

assemblies where the excitation exists on one side only. The reverberant chamber method is

relevant where it is preferable to induce vibration onto the entire external surface of equipment

by distributed excitation rather than fixed points by means of electro-dynamic shakers.

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.
IEC 61672-1, Electroacoustics – Sound level meters – Part 1: Specifications

ISO/IEC 17025:2005, General requirements for the competence of testing and calibration

laboratories
3 Terms, definitions, symbols and abbreviations
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
---------------------- Page: 9 ----------------------
– 8 – 60068-2-65 © IEC:2013
3.1.1
acoustic horn

tube with increasing cross-section of generally exponential envelope, used to couple an

acoustic source to the test volume, for example the inside of a reverberation room, thus

achieving the maximum transfer of sound energy

Note 1 to entry: Each acoustic horn has individual transfer characteristics which affect the sound spectrum.

3.1.2
analysis integration time
time duration over which a signal is averaged
Note 1 to entry: See Clause A.8.
3.1.3
bandwidth
difference between the nominal upper and lower cut-off frequencies
Note 1 to entry: It may be expressed
a) in hertz,
b) as a percentage of the pass-band centre frequency, or

c) as the interval between the upper and lower nominal cut-off frequencies in octaves.

3.1.4
overall sound pressure level
OASPL
value computed from the third-octave or octave band sound pressure levels L
L /10
L = 10 log 10
G 10
i=1
where
L is the overall sound pressure level in dB;
L is the sound pressure level in the ith third-octave or octave band;
m is the number of third-octave or octave bands.
3.1.5
centre frequency
geometric mean of the nominal cut-off frequencies of a pass-band

Note 1 to entry: The nominal upper and lower cut-off frequencies of a filter pass-band are defined as those

frequencies above and below the frequency of maximum response of a filter at which the response to a sinusoidal

signal is 3 dB below the maximum response.

Note 2 to entry: The geometric mean is equal to (f × f ) , where f and f are the cut-off frequencies.

1 2 1 2
3.1.6
constant-bandwidth filter

filter which has a bandwidth of constant value when expressed in hertz; it is independent of the

centre frequency of the filter
3.1.7
cut-off frequency (of acoustic horn)
frequency below which an acoustic horn becomes increasingly ineffective

Note 1 to entry: This cut-off frequency is a main characteristic of an acoustic horn.

---------------------- Page: 10 ----------------------
60068-2-65 © IEC:2013 – 9 –
3.1.8
diffuse sound field

sound field which, in a given region, has statistically uniform energy density, for which the

directions of propagation at any point are randomly distributed

Note 1 to entry: In a diffuse sound field, the sound pressure level measured with a directional microphone would

give the same results whatever its orientation.

[SOURCE: IEC 60050-801:1994 [1] , definition 801-23-31, modified – Addition of the Note 1 to

entry]
3.1.9
electro-pneumatic transducer
hydraulic-pneumatic transducer

most generally employed laboratory source of acoustic noise to simulate sound pressure levels

encountered in a high operational ambient acoustic noise environment

Note 1 to entry: This transducer consists of a pneumatic transducer supplied with pressurized gas modulated by

an electromagnetic or hydraulic valve.

Note 2 to entry: This type of transducer provides a continuous spectrum of energy over a wide frequency band

with random amplitude distribution and is capable of providing a shaped sound spectrum to meet the specifications

in acoustic testing (see Clause A.5).
3.1.10
grazing incidence

angle between the direction of the acoustic wave and either the surface of the specimen and/or

the sensing surface of the acoustic transducer, 0 ° being parallel and 90 ° normal to the

surface
3.1.11
frequency interval
ratio of two frequencies
[SOURCE: IEC 60050-801:1994, definition 801-30-07]
3.1.11.1
octave
interval between two frequencies which have a ratio of 2
3.1.11.2
one-third octave
1/3
1/3
interval between two frequencies which have a ratio equal to 2

Note 1 to entry: Octave and third-octave frequency bands are defined by their geometric centre frequencies in

ISO 266 [2].
3.1.11.3
one-twelfth octave
1/12
1/12
interval between two frequencies which have a ratio equal to 2
3.1.12
measuring points

specific points in the sound field at which sound pressure is measured for the conduct of the

test
______________
Figures in square brackets refer to the bibliography.
---------------------- Page: 11 ----------------------
– 10 – 60068-2-65 © IEC:2013

Note 1 to entry: Measurements may be made at points within the specimen in order to assess its behaviour but

these are not considered as measuring points in the sense of this standard.
3.1.12.1
checkpoints

points located on a fictitious surface surrounding the specimen and at a fixed distance from it

3.1.12.2
reference points

points chosen from the checkpoints, whose signals are used to control the test so that the

requirements of this standard are satisfied
3.1.13
multipoint control
control achieved by using the average of the signals at the reference points

Note 1 to entry: When using multipoint control, each microphone signal relates to the sound pressure level at one

position. The average sound pressure level L can be computed as given in IEC 60050-801:1994, definition 801-

31-36, when
L /10
L = 10 log 10
AV 10
where
n is the number of reference points;
L is the sound pressure level in the ith third-octave or octave band.
3.1.14
narrowband frequency filter
band-pass filter for which the pass-band is generally smaller than third-octave
3.1.15
broadband frequency
wide band filter

band-pass filter for which the pass-band is relatively wide or broad, in general larger than an

octave
3.1.16
progressive wave tube

tube along which sound waves propagate from the acoustic source, which is coupled to a

suitable test section by an acoustic horn

Note 1 to entry: The tube is terminated by an acoustically absorptive termination placed at the end of the test

section to minimize reflection of the progressive acoustic waves in the frequency range of interest (see Clause A.2).

3.1.17
proportional-bandwidth filter
filter which has a bandwidth that is proportional to the frequency

Note 1 to entry: Octave bandwidth, third-octave bandwidth, etc. are typical bandwidths for proportional-bandwidth

filters.
3.1.18
reverberation chamber (or room)

chamber or room which has hard, highly reflective surfaces such that the sound field therein

becomes diffuse

Note 1 to entry: The geometry of the chamber or room may influence the test. Information on reverberant

chambers is given in Clause A.1.
---------------------- Page: 12 ----------------------
60068-2-65 © IEC:2013 – 11 –
3.1.19
sound absorption coefficient

fraction of incident sound power not reflected from the surface of a material at a given

frequency and under specified conditions

Note 1 to entry: Sound absorption is the property possessed by materials and objects for converting sound energy

to heat.

[SOURCE: IEC 60050-801:1994, definition 801-31-02, modified – word order of definition

reversed, Note 1 to entry replaces previous NOTE and bears no relation]
3.1.20
sound pressure

root mean-square of instantaneous sound pressures over a given time interval, unless

specified otherwise

Note 1 to entry: Sound pressure characterizes the variation of pressure about the static pressure, produced by

acoustic waves, which are variations of pressure caused by disturbances in a gaseous medium.

[SOURCE: IEC 60050-801:1994, definition 801-21-20, modified – addition of Note 1 to entry]

3.1.21
sound pressure level L
L = 20 log dB
p 10
3.2 Symbols and abbreviations
NOTE Where appropriate, a cross-reference to the definition is given.
OASPL overall sound pressure level in dB (derived from 801-22-07), see 3.1.4;
L overall sound pressure level in dB (see 3.1.4);
L sound pressure level in third-octave or octave band in dB (see 3.1.4);
L sound pressure level in dB (see 3.1.21);
L average soun
...

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