EN ISO 7779:2010

SLOVENSKI STANDARD
01-december-2010
1DGRPHãþD
SIST EN ISO 7779:2002
SIST EN ISO 7779:2002/A1:2004
SIST EN ISO 7779:2002/oprA2:2006
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WHOHNRPXQLNDFLMVNHRSUHPH,62
Acoustics - Measurement of airborne noise emitted by information technology and
telecommunications equipment (ISO 7779:2010)
Akustik - Geräuschemissionsmessung an Geräten der Informations- und
Telekommunikationstechnik (ISO 7779:2010)
Acoustique - Mesurage du bruit aérien émis par les équipements liés aux technologies
de l'information et aux télécommunications (ISO 7779:2010)
Ta slovenski standard je istoveten z: EN ISO 7779:2010
ICS:
17.140.20 Emisija hrupa naprav in Noise emitted by machines
opreme and equipment
35.020 Informacijska tehnika in Information technology (IT) in
tehnologija na splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 7779
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2010
ICS 17.140.20; 35.020 Supersedes EN ISO 7779:2001
English Version
Acoustics - Measurement of airborne noise emitted by
information technology and telecommunications equipment (ISO
7779:2010)
Acoustique - Mesurage du bruit aérien émis par les Akustik - Geräuschemissionsmessung an Geräten der
équipements liés aux technologies de l'information et aux Informations- und Telekommunikationstechnik (ISO
télécommunications (ISO 7779:2010) 7779:2010)
This European Standard was approved by CEN on 26 July 2010.

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 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 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, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2010 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 7779:2010: E
worldwide for CEN national Members.

Contents Page
Foreword .3

Foreword
This document (EN ISO 7779:2010) has been prepared by Technical Committee ISO/TC 43 "Acoustics" in
collaboration with Technical Committee CEN/TC 211 “Acoustics” the secretariat of which is held by DS.
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 February 2010, and conflicting national standards shall be withdrawn
at the latest by February 2010.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 7779:2001.
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, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 7779:2010 has been approved by CEN as a EN ISO 7779:2010 without any modification.

INTERNATIONAL ISO
STANDARD 7779
Third edition
2010-08-15
Acoustics — Measurement of airborne
noise emitted by information technology
and telecommunications equipment
Acoustique — Mesurage du bruit aérien émis par les équipements liés
aux technologies de l'information et aux télécommunications

Reference number
ISO 7779:2010(E)
©
ISO 2010
ISO 7779:2010(E)
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ii © ISO 2010 – All rights reserved

ISO 7779:2010(E)
Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.2
3 Terms and definitions .2
4 Conformity requirements.6
5 Installation and operating conditions .6
6 Method for determination of sound power levels of equipment in reverberation test rooms .9
7 Method for determination of sound power levels of equipment under essentially free-field
conditions over a reflecting plane .15
8 Method for determination of emission sound pressure levels at defined operator and
bystander positions .20
9 Information to be recorded and reported.27
Annex A (normative) Test accessories.32
Annex B (normative) Measurement surfaces.35
Annex C (normative) Installation and operating conditions for specific equipment categories.40
Annex D (informative) Identification and evaluation of prominent discrete tones .41
Annex E (informative) Detection of impulsive noise .59
Bibliography.61

ISO 7779:2010(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 7779 was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 1, Noise.
This third edition cancels and replaces the second edition (ISO 7779:1999), which has been technically
revised. It also incorporates the amendment, ISO 7779:1999/Amd.1:2003.

iv © ISO 2010 – All rights reserved

ISO 7779:2010(E)
Introduction
This International Standard specifies methods for the measurement of airborne noise emitted by information
technology and telecommunications (ITT) equipment. Hitherto, a wide variety of methods have been applied
by individual manufacturers and users to satisfy particular equipment or application needs. These diverse
practices have, in many cases, made comparison of noise emission difficult. This International Standard
simplifies such comparisons and is the basis for the declaration of the noise emission levels of ITT equipment.
In order to ensure accuracy, validity and acceptability, this International Standard is based on the basic
International Standards for determination of the sound power level and for determination of the emission
sound pressure level at the operator position(s) and bystander position(s). Furthermore, implementation is
simplified by conformity with these International Standards.
In many cases, free-field conditions over a reflecting plane are realised by hemi-anechoic rooms. These
rooms may be particularly useful during product design to locate and to improve individual contributing noise
sources. Reverberation rooms may be more economical for production control and for obtaining sound power
levels for noise emission declaration purposes.
The method for measuring the emission sound pressure level at the operator or bystander positions (based on
ISO 11201) is specified in a separate clause, as this level is not considered to be primary noise emission
declaration information. The measurements can, however, be carried out in conjunction with those for sound
power determination in a free field over a reflecting plane.
For comparison of similar equipment, it is essential that the installation conditions and mode of operation be
the same. In Annex C these parameters are standardized for many categories of equipment.
This International Standard is based on ECMA-74.

INTERNATIONAL STANDARD ISO 7779:2010(E)

Acoustics — Measurement of airborne noise emitted by
information technology and telecommunications equipment
1 Scope
This International Standard specifies procedures for measuring and reporting the noise emission of
information technology and telecommunications equipment.
NOTE 1 This International Standard is considered part of a noise test code (see 3.1.2) for this type of equipment, and
is based on basic noise emission standards (see 3.1.1) ISO 3741, ISO 3744, ISO 3745 and ISO 11201.
The basic emission quantity is the A-weighted sound power level which may be used for comparing
equipment of the same type but from different manufacturers, or for comparing different equipment.
Three basic noise emission standards for determination of the sound power levels are specified in this
International Standard in order to avoid undue restriction on existing facilities and experience. ISO 3741
specifies comparison measurements in a reverberation test room; ISO 3744 and ISO 3745 specify
measurements in an essentially free field over a reflecting plane. Any one of these three basic noise emission
standards can be selected and used exclusively in accordance with this International Standard when
determining sound power levels of a machine.
The A-weighted sound power level is supplemented by the A-weighted emission sound pressure level
determined at the operator position(s) or the bystander positions, based on basic noise emission standard
ISO 11201. This sound pressure level is not a worker's immission rating level, but it can assist in identifying
any potential problems that could cause annoyance, activity interference, or hearing damage to operators and
bystanders.
Methods for determination of whether the noise emission includes prominent discrete tones or is impulsive in
character are specified in Annexes D and E, respectively.
This International Standard is suitable for type tests and provides methods for manufacturers and testing
laboratories to obtain comparable results.
The methods specified in this International Standard allow the determination of noise emission levels for a
functional unit (see 3.1.4) tested individually.
The procedures apply to equipment which emits broad-band noise, narrow-band noise and noise which
contains discrete-frequency components, or impulsive noise.
The sound power and emission sound pressure levels obtained can serve noise emission declaration and
comparison purposes (see ISO 9296).
NOTE 2 The sound power and emission sound pressure levels obtained are not to be considered as installation noise
[4]
immission levels; however, they can be used for installation planning (see ECMA TR/27 ).
If sound power levels obtained are determined for a number of functional units of the same production series,
they can be used to determine a statistical value for that production series (see ISO 9296).
ISO 7779:2010(E)
2 Normative references
The following referenced documents are indispensable for the application 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 266, Acoustics — Preferred frequencies
ISO 3741, Acoustics — Determination of sound power levels and sound energy levels of noise sources using
sound pressure — Precision methods for reverberation test rooms
ISO 3744, Acoustics — Determination of sound power levels and sound energy levels of noise sources using
sound pressure — Engineering methods for an essentially free field over a reflecting plane
ISO 3745, Acoustics — Determination of sound power levels and sound energy levels of noise sources using
sound pressure — Precision methods for anechoic test rooms and hemi-anechoic test rooms
ISO 6926, Acoustics — Requirements for the performance and calibration of reference sound sources used
for the determination of sound power levels
ISO 9295, Acoustics — Measurement of high-frequency noise emitted by computer and business equipment
ISO 9296, Acoustics — Declared noise emission values of computer and business equipment
ISO 11201, Acoustics — Noise emitted by machinery and equipment — Determination of emission sound
pressure levels at a work station and at other specified positions in an essentially free field over a reflecting
plane with negligible environmental corrections
ISO 11203, Acoustics — Noise emitted by machinery and equipment — Determination of emission sound
pressure levels at a work station and at other specified positions from the sound power level
IEC 60942, Electroacoustics — Sound calibrators
IEC 61260, Electroacoustics — Octave-band and fractional-octave-band filters
IEC 61672-1, Electroacoustics — Sound level meters — Part 1: Specifications
ECMA-74, Measurement of airborne noise emitted by information technology and telecommunications
1)
equipment
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 3744, ISO 11201, and the following
apply.
3.1 General definitions
3.1.1
basic noise emission standard
B-type standard
standard which specifies the procedure for determining the noise emission of machinery and equipment in
such a way as to obtain reliable, reproducible results with a specified degree of accuracy
[2]
[ISO 12001:1996 , 3.1]
1) Available [viewed 2010-07-13] at: http://www.ecma-international.org/publications/files/ECMA-ST/ECMA-74.pdf
2 © ISO 2010 – All rights reserved

ISO 7779:2010(E)
3.1.2
noise test code
C-type standard
standard that is applicable to a particular class, family or type of machinery or equipment, which specifies all
the information necessary to carry out efficiently the determination, declaration and verification of the noise
emission characteristics under standardized conditions
[2]
[ISO 12001:1996 , 3.2]
NOTE This International Standard, together with ISO 9295 and ISO 9296, comprise the noise test code for ITT
equipment.
3.1.3
information technology and telecommunications equipment
ITT equipment
equipment for information processing, and components thereof, used in homes, offices, server installations,
telecommunications installations or similar environments
3.1.4
functional unit
unit of information technology and telecommunications equipment, either with or without its own end-use
enclosure, that is tested or intended to be tested in accordance with the procedures of this International
Standard
NOTE 1 A functional unit can comprise more than one unit of ITT equipment when such units are to be tested together
in accordance with the methods of this International Standard. A functional unit can also comprise one or more units of ITT
equipment coupled to one or more units of non-ITT equipment, such as power modules, water pumps, or refrigeration
units, when such equipment is necessary for the normal operation of the ITT equipment.
NOTE 2 Functional units of ITT equipment can take on a wide range of forms, including commercially available
products, prototype units under development or sub-assemblies and components thereof.
3.1.5
work station
operator position
position in the vicinity of the equipment under test which is intended for the operator
NOTE 1 Adapted from ISO 11201:2010, 3.11.
NOTE 2 This term does not refer to a computer “workstation”, which denotes a high-performance, single-user computer.
3.1.6
operating mode
condition in which the equipment under test is performing its intended function(s)
3.1.7
idle mode
one or more steady-state conditions in which the equipment being tested is energized but is not operating
3.1.8
floor-standing equipment
functional unit which is intended to be installed on the floor
3.1.9
table-top equipment
functional unit which has a complete enclosure and which is intended to be installed or used on a table, desk
or separate stand
3.1.10
wall-mounted equipment
functional unit which is normally mounted against or in a wall and which does not have a stand of its own
ISO 7779:2010(E)
3.1.11
sub-assembly
functional unit, generally without its own end-use enclosure, intended to be installed in another unit of ITT
equipment or assembled together with other sub-assemblies or units of ITT equipment into a single end-use
enclosure
3.1.12
rack-mountable unit
functional unit that is designed to be installed in an end-use enclosure, in the form of a rack, frame, or cabinet,
which can be fully enclosed, partially enclosed, or open frame
3.1.13
rack-enclosed system
functional unit in the form of a rack, frame, or cabinet containing one or more rack-mountable units
NOTE Rack-enclosed systems represent a wide variety of ITT equipment, depending on the particular configuration of
the rack-mountable units in the rack or enclosure. These may be server systems, storage systems, I/O systems,
networking systems or “integrated” systems of these or other types of rack-mountable units.
3.1.14
hand-held equipment
functional unit, generally small and lightweight, intended to be supported by the hand(s) during normal use
3.1.15
standard test table
rigid table having a top surface of at least 0,5 m and length of the top plane not less than 700 mm
NOTE The design for the standard test table is shown in Annex A.
3.2 Acoustical definitions
3.2.1
emission
noise emission
airborne sound radiated by a well-defined noise source (e.g. the equipment under test)
NOTE Noise emission descriptors can be incorporated into a product declaration and/or product specification. The
basic noise emission descriptors are the sound power level of the source itself and the emission sound pressure levels at
an operator position or at bystander positions (if no operator position is defined) in the vicinity of the source.
3.2.2
sound pressure
p
difference between instantaneous total pressure and static pressure
NOTE 1 Sound pressure is expressed in pascals.
NOTE 2 The symbol p is often used without modification to represent a root mean square (r.m.s.) sound pressure.
[3]
[ISO 80000-8:2007 , 9.2]
4 © ISO 2010 – All rights reserved

ISO 7779:2010(E)
3.2.3
sound pressure level
L
p
ten times the logarithm to the base 10 of the ratio of the square of the sound pressure, p, to the square of a
reference value, p0, expressed in decibels
p
L = 10lg dB
p
p
where the reference value, p , is 20 µPa
[3]
NOTE This definition is technically in accordance with ISO 80000-8:2007 , 8.22.
[22]
[ISO/TR 25417:2007 , 2.2]
3.2.4
time-averaged sound pressure level
L
pT
sound pressure level of a continuous steady sound that, within a measurement time interval, T, has the same
mean-square sound pressure as a sound under consideration which varies with time
3.2.5
emission sound pressure level
L
p
sound pressure level measured 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, but excluding the effects of
background noise
NOTE 1 The emission sound pressure level is expressed in decibels.
NOTE 2 Clause 8 specifies the method for determination of emission sound pressure level.
3.2.6
time-averaged emission sound pressure level
L
peqT
emission sound pressure level of a continuous steady sound that, within a measurement time interval, T, has
the same mean-square sound pressure as a sound under consideration which varies with time
T
⎡⎤1
pt dt
()
⎢⎥
∫
T 0
L = 10 lg dB
⎢⎥
pTeq
⎢⎥p
⎢⎥
⎣⎦
NOTE 1 The time-averaged emission sound pressure level is expressed in decibels.
NOTE 2 The emission sound pressure level is determined at the specified position(s) required by the noise test code
(i.e. this International Standard, for specific families of ITT equipment).
NOTE 3 In general, the subscripts “eq” and “T ” are omitted since time-averaged emission sound pressure levels are
necessarily determined over a certain measurement time interval.
3.2.7
A-weighted impulse sound pressure level
L
pAI
A-weighted sound pressure level determined with a sound level meter set for the I time-weighting
characteristic (impulse)
NOTE The A-weighted impulse sound pressure level is expressed in decibels.
ISO 7779:2010(E)
3.2.8
C-weighted peak sound pressure level
L
pCpeak
highest instantaneous value of the C-weighted sound pressure level determined over an operational cycle
NOTE The C-weighted peak sound pressure level is expressed in decibels.
3.2.9
sound power
P
rate per time at which airborne sound energy is radiated by a source
NOTE 1 Sound power is expressed in watts.
NOTE 2 In this International Standard, it is the time-averaged value of the sound power during the measurement
duration.
3.2.10
reference sound source
device which is intended for use as a stable source of sound, which has a known broad-band sound power
spectrum calibrated in accordance with ISO 6926 over the frequency range of interest
3.2.11
frequency range of interest
one-third-octave bands with centre frequencies specified in ISO 266 from 100 Hz to 10 000 Hz inclusive
NOTE For equipment which emits discrete tone(s) in the 16 kHz octave band, the procedures specified in ISO 9295
are used; see Table 4.
4 Conformity requirements
Measurements are in conformity with this International Standard if they meet the following requirements:
a) the measurement procedures, the installation and the operating conditions specified in this International
Standard are fully taken into account;
b) for the determination of sound power levels, one (and only one) of the methods specified in Clause 6 or 7
is used;
c) for determination of emission sound pressure level at the operator or bystander positions, the method
specified in Clause 8 is used.
5 Installation and operating conditions
5.1 Equipment installation
5.1.1 General
The equipment shall be installed according to its intended use. Installation conditions for many different
categories of ITT equipment are specified in Annex C; these shall be followed when noise emission
declaration information is to be obtained. If the normal installation is unknown or if several possibilities exist, a
representative condition shall be chosen and reported.
Care shall be taken to ensure that any electrical conduits, piping, air ducts or other auxiliary equipment
connected to the equipment being tested do not radiate significant amounts of sound energy into the test room.
If practicable, all auxiliary equipment necessary for the operation of the equipment shall be located outside the
test room and the test room shall be free from all objects which may interfere with the measurements.
6 © ISO 2010 – All rights reserved

ISO 7779:2010(E)
NOTE If the equipment is mounted near one or more reflecting planes, the sound power radiated by the equipment
can depend upon its position and orientation. It is possible that the determination of the radiated sound power is of interest
either for one particular equipment position and orientation or from the average value for several positions and orientations.
5.1.2 Floor-standing equipment
5.1.2.1 Requirements for reverberation test rooms
Floor-standing equipment shall be located at least 1,5 m from any wall of the room and no major surfaces
shall be parallel to a wall of the reverberation test room.
5.1.2.2 Requirements for hemi-anechoic rooms
Floor-standing equipment shall be installed on the reflecting (hard) floor at a sufficient distance (more than
2 m, if possible) from the walls, unless otherwise specified in Annex C.
The equipment shall be installed in a way which allows access to all sides except the reflecting plane(s). The
dimensions of the reflecting plane(s) shall extend beyond the test object by at least the measurement distance.
The requirements for reflection are specified in the Note to 7.3.1. The plane(s) shall not contribute to the
sound radiation due to their own vibrations.
5.1.2.3 Common requirements
If the equipment being tested consists of several frames bolted together in an installation or is too large for
testing purposes, the frames may be measured separately. In such circumstances, additional covers may be
required for the frames during the acoustical evaluation. These additional covers shall be acoustically
comparable with the other covers on the equipment. If a unit is mechanically or acoustically coupled to
another unit so that the noise emission levels of one are significantly influenced by the other, the equipment
being tested shall, where practicable, include all units coupled together in this way.
Floor-standing equipment which is to be installed only in front of a wall shall be placed on a hard floor in front
of a hard wall (see the Note to 7.3.1). The distance from the wall shall be in accordance with the
manufacturer's instructions or as specified in Annex C. If such information is not available, the distance shall
be 0,1 m.
5.1.3 Table-top equipment
5.1.3.1 Requirements for reverberation test rooms
Table-top equipment (see 3.1.9) shall be placed on the floor at least 1,5 m from any wall of the room unless a
table or stand is required for operation in accordance with Annex C (e.g. printers which take paper from or
stack paper on the floor). Such equipment shall be placed in the centre of the top plane of the standard test
table (see Annex A).
5.1.3.2 Requirements for hemi-anechoic rooms
Table-top equipment (see 3.1.9) shall be placed on the floor, unless a table or stand is required for operation
in accordance with Annex C (e.g. printers which take paper from or stack paper on the floor). Such equipment
shall be placed in the centre of the top plane of the standard test table (see Annex A). In any case, the
measurement surface defined in 7.6 terminates on the floor.
5.1.4 Wall-mounted equipment
Wall-mounted equipment (see 3.1.10) shall be affixed to a wall of the reverberation test room at least 1,5 m
from any other reflecting surface, unless otherwise specified. Alternatively, if operation permits, the equipment
may be laid with its mounting surface on the floor at least 1,5 m (more than 2 m, if possible, in hemi-anechoic
rooms) from any wall of the room.
If the equipment is usually installed by being recessed into a wall or other structure, a representative structure
shall be used for mounting during the measurements and described in the test report.
ISO 7779:2010(E)
5.1.5 Rack-mounted equipment
Rack-mounted equipment includes both individual rack-mountable units (see 3.1.12) and rack-enclosed
systems (see 3.1.13). Rack-mountable units shall either be tested outside of the rack or installed in a rack
enclosure in accordance with the requirements of ECMA-74. Rack-enclosed systems shall be tested either as
floor-standing equipment (see 5.1.2) or as table-top equipment (see 5.1.3) according to the type and size of
system. The specific installation and operation requirements of ECMA-74 shall be followed.
For rack-enclosed systems that are available in more than one configuration of rack-mountable units, the
particular configuration to be measured is usually governed by the purposes of the test and is thus not
specified in this International Standard (see ECMA-74 for more information).
5.1.6 Hand-held equipment
Hand-held equipment (see 3.1.14) shall be supported 0,25 m ± 0,03 m above the reflecting plane by a
vibration-isolating stand or fixture, or by appropriate vibration-isolating elements. If a hemispherical
measurement surface is used with any radius less than 1 m (see B.1), the hand-held equipment support
height shall be reduced to 0,125 m ± 0,015 m. The method of supporting the hand-held equipment shall not
interfere with the propagation of airborne sound from the equipment or generate any additional sound
radiation.
5.1.7 Sub-assemblies
A sub-assembly (see 3.1.11) shall be supported 0,25 m ± 0,03 m above the reflecting plane by a vibration-

isolating stand or fixture, or by appropriate vibration-isolating elements. If a hemispherical measurement
surface is used with a radius less than 1 m (see B.1), the sub-assembly support height shall be reduced to
0,125 m ± 0,015 m. The method of supporting the sub-assembly shall not interfere with the propagation of
airborne sound from the sub-assembly or generate any additional sound radiation.
If the above-specified support height is not adequate to allow the manufacturer's recommended air flow at the
sub-assembly's intake port, the height may be adjusted accordingly, but shall not exceed 0,5 m. The new
height shall be documented in the test report.
5.2 Input voltage and frequency
The equipment shall be operated at its nominal rated voltage and the rated power line frequency.
Phase-to-phase voltage variations shall not exceed 5 %.
5.3 Equipment operation
During the acoustical measurements, the equipment shall be operated in a manner typical of normal use.
Annex C specifies such conditions for many categories of equipment and shall be followed. However, if the
specified conditions are clearly contrary to the objective of providing uniform conditions closely corresponding
to the intended use of the product, then an additional mode or modes closely related to the intended use shall
be defined, tested and documented. Any subsequent declaration shall either:
⎯ declare both values, indicating that one is based on Annex C, and indicating that the other is declared by
the manufacturer to be typical use for the intended application; or
⎯ declare only the latter, indicating that it is not based on Annex C, but is declared by the manufacturer to
be typical use for the intended application.
When there are multiple operating modes specified in Annex C, at a minimum, the most typical operating
mode shall be tested and reported.
8 © ISO 2010 – All rights reserved

ISO 7779:2010(E)
The equipment shall be operated for a sufficient period of time before proceeding with the acoustical test to
allow temperature and other pertinent conditions to stabilize.
The noise shall be measured with the equipment in both the idle and operating modes. If the equipment is
designed to perform different functions, such as manual typing and automatic printing of stored information or
for printing in different print qualities, unless otherwise specified in Annex C, the noise of each individual mode
shall be determined and recorded. For equipment which, in normal functional operation, performs several
operating modes, such as document insertion, reading, encoding, printing and document eject, and for which
a typical operation cycle has not been defined in Annex C, such a typical cycle shall be defined for the
measurements and described in the test report.
For rack-mounted equipment in which the operation of several functional units is possible, the units intended
to operate together shall do so during the test; all other units shall be in idle mode. In the absence of
operational specifications provided by Annex C or by the manufacturer, an operating mode that represents the
most typical usage shall be tested. This mode shall be clearly described in the test report.
Some equipment does not operate continuously because of its mechanical design or its mode of operation
under program control. Long periods may occur during which the equipment is idle. The operating mode
measurements shall not include these idle periods. If it is not possible to operate the equipment continuously
during the acoustical evaluation, the time interval during which measurements have to be made shall be
described in the test plan, equipment specifications or other documentation.
Some equipment has operational cycles that are too short to allow reliable determination of the noise
emissions. In such cases, a typical cycle shall be repeated several times.
If the equipment being tested produces attention signals, such as tones or bells, such intermittent sound shall
not be included in an operating mode. During the acoustical evaluation in the operating mode(s), such
attention signals shall be inoperative or, if this is not possible, they shall be set to a minimum.
NOTE For certain applications, such signals as well as the maximum response of feedback signals of keyboards can
be of interest. Such measurements can be made, but they are not part of the methods specified in this International
Standard.
6 Method for determination of sound power levels of equipment in reverberation
test rooms
6.1 General
The method specified in this clause provides a comparison procedure for determination of the sound power
levels produced by ITT equipment in a reverberation test room, in accordance with the comparison method
specified in ISO 3741. It applies to equipment which radiates broad-band noise, narrow-band noise, noise
which contains discrete-frequency components or impulsive noise.
It is strongly recommended that the room be qualified for discrete-frequency components in accordance with
the relevant procedure specified in ISO 3741. This avoids the need to determine the number of microphone
positions and equipment locations each time equipment is measured.
6.2 Measurement uncertainty
Measurements carried out in accordance with this method yield standard deviations of reproducibility for the
frequency range of interest of this International Standard which are equal to, or less than, those given in
Table 1.
ISO 7779:2010(E)
Table 1 — Uncertainty in determining sound power levels in a reverberation test room
in accordance with Clause 6
Octave band One-third-octave-band Standard
centre frequencies centre frequencies deviation
Hz Hz dB
125 100 to 160 3,0
250 200 to 315 2,0
500 to 4 000 400 to 5 000 1,5
8 000 6 300 to 10 000 3,0
NOTE 1 For most ITT equipment, the A-weighted sound power level is determined by the sound power levels in the
250 Hz to 4 000 Hz octave bands. The A-weighted sound power level is determined with a standard deviation of
approximately 1,5 dB. A larger standard deviation can result when the sound power levels in other bands determine the
A-weighted sound power level.
NOTE 2 The standard deviations given in Table 1 reflect the cumulative effects of all causes of measurement
uncertainty, including variations from laboratory to laboratory, but excluding variations in the sound power level from
equipment to equipment or from test to test which can be caused, for example, by changes in the installation or operating
conditions of the equipment. The reproducibility and repeatability of the test results for the same piece of equipment and
the same measurement conditions can be considerably better (i.e. smaller standard deviations) than the uncertainties
given in Table 1 indicate.
NOTE 3 If the method specified in this clause is used to compare the sound power levels of similar equipment that are
omnidirectional and radiate broad-band noise, the uncertainty in this comparison yields a standard deviation which is less
than that given in Table 1, provided that the measurements are carried out in the same environment.
6.3 Test environment
6.3.1 General
Guidelines specified in ISO 3741 for the design of the reverberation test room, as applicable, shall be used.
Criteria for room absorption and the procedure for room qualifications, specified in ISO 3741, shall be used.
ISO 3741 shall be followed with regard to the following:
a) test room volume;
b) level of background noise.
6.3.2 Meteorological conditions
The requirements of ISO 3741 shall be followed.
The following conditions are recommended:
a) ambient pressure: 86 kPa to 106 kPa;
b) temperature: within the range defined by the manufacturer for the equipment, if a range is defined; if no
range is defined by the manufacturer, the recommended range is 15 °C to 30 °C;
c) relative humidity: within the range defined by the manufacturer for the equipment, if a range is defined; for
processing of paper and card media only, if no range is defined by the manufacturer, the recommended
range is 40 % to 70 %.
10 © ISO 2010 – All rights reserved

ISO 7779:2010(E)
For equipment whose noise emissions vary with ambient temperature in a prescribed manner (e.g. by varying
the speeds of air-moving devices), the room temperature during the measurement shall be 23 °C ± 2 °C.
For equipment whose noise emissions vary with altitude in a prescribed manner (e.g. by varying the speeds of
air-moving devices), the altitude of the test room shall either be less than or equal to 500 m or the equipment
shall be tested under conditions simulating its operation at an altitude less than or equal to 500 m.
NOTE This variation of speed of air-moving devices does not refer to the changing speed that is already accounted
for in the correction for ambient pressure described in the Note to 6.10.1.
6.4 Instrumentation
6.4.1 General
The requirements of this subclause (6.4), as well as the instrumentation requirements of ISO 3741, shall be
followed.
Digital integration is the preferred method of averaging.
6.4.2 The microphone and its associated cable
The instrumentation system, including the microphone and its associated cable, shall meet the requirements
of ISO 3741. If the microphone is moved, care shall be exercised to avoid introducing acoustical or electrical
noise (e.g. from gears, flexing cables, or sliding contacts) that could interfere with the measurements.
6.4.3 Frequency response of the instrumentation system
The requirements of ISO 3741 shall be followed.
6.4.4 Reference sound source
The reference sound source shall meet the requirements specified in ISO 6926 over the frequency range of
interest.
6.4.5 Filter characteristics
The requirements for an instrument specified in accordance with IEC 61260, class 1 shall be followed.
6.4.6 Calibration
During each series of measurements, a sound calibrator as specified in IEC 60942, class 1, shall be applied to
the microphone to verify the calibration of the entire measuring system at one or more frequencies over the
frequency range of interest. The compliance of the calibrator with the requirements of IEC 60942 shall be
verified once a y
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