ISO 10302-1:2011

Acoustics - Measurement of airborne noise emitted and structure-borne vibration induced by small air-moving devices - Part 1: Airborne noise measurement

ISO 10302-1:2011 specifies methods for measuring the airborne noise emitted by small air-moving devices (AMDs), such as those used for cooling electronic, electrical, and mechanical equipment where the sound power level of the AMD is of interest. Examples of these AMDs include propeller fans, tube-axial fans, vane-axial fans, centrifugal fans, motorized impellers, and their variations. ISO 10302-1:2011 describes the test apparatus and methods for determining the airborne noise emitted by small AMDs as a function of the volume flow rate and the fan static pressure developed by the AMD on the test apparatus. It is intended for use by AMD manufacturers, by manufacturers who use AMDs for cooling electronic equipment and similar applications, and by testing laboratories. It provides a method for AMD manufacturers, equipment manufacturers and testing laboratories to obtain comparable results. Results of measurements made in accordance with ISO 10302-1:2011 are expected to be used for engineering information and performance verification, and the methods can be cited in purchase specifications and contracts between buyers and sellers. The ultimate purpose of the measurements is to provide data to assist the designers of electronic, electrical or mechanical equipment which contains one or more AMDs. Based on experimental data, a method is given for calculating the maximum volume flow rate of the scaled plenum up to which ISO 10302-1:2011 is applicable.

Acoustique — Mesurage du bruit aérien émis et des vibrations de structure induites par les petits équipements de ventilation — Partie 1: Mesurage du bruit aérien

General Information

• Status: Withdrawn
• Publication Date: 05-Jan-2011
• ICS: 17.140.20 - Noise emitted by machines and equipment
• ICS: 23.120 - Ventilators. Fans. Air-conditioners
• Technical Committee: ISO/TC 43/SC 1 - Noise
• Drafting Committee: ISO/TC 43/SC 1/WG 23 - Measurement of noise from information technology, business and telecommunications equipment
• Current Stage: 9599 - Withdrawal of International Standard
• Start Date: 02-Feb-2024
• Completion Date: 13-Dec-2025

Relations

• Revised: ISO 10302-1:2024 - Acoustics - Measurement of airborne noise emitted and structure-borne vibration induced by small air-moving devices - Part 1: Airborne noise measurement
• Effective Date: 06-Jun-2022
• Revises: ISO 10302:1996 - Acoustics - Method for the measurement of airborne noise emitted by small air-moving devices
• Effective Date: 17-Mar-2009

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 10302-1
First edition
2011-01-15
Acoustics — Measurement of airborne
noise emitted and structure-borne
vibration induced by small air-moving
devices —
Part 1:
Airborne noise measurement
Acoustique — Mesurage du bruit aérien émis et des vibrations de
structure induites par les petits équipements de ventilation —
Partie 1: Mesurage du bruit aérien

Reference number
©
ISO 2011
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ii © ISO 2011 – All rights reserved

Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.1
3 Terms and definitions .2
3.1 General definitions.2
3.2 Acoustical definitions .3
3.3 Aerodynamic definitions.3
4 Limitations of measurement .5
5 Design and performance requirements for test plenum .5
5.1 General .5
5.2 Test plenum: Main assembly .6
5.3 Mounting panel assembly .6
5.4 Adjustable exit port assembly .7
5.5 Insertion loss of test plenum .7
5.6 Instrumentation for static pressure measurement .7
6 Installation.8
6.1 Installation of test plenum in test room .8
6.2 Direction of airflow .8
6.3 Mounting of air-moving device .8
7 Operation of air-moving device .8
7.1 Input power .8
7.2 Points of operation (AC and DC air-moving devices).9
8 Measurement procedures.10
8.1 General .10
8.2 Microphone positions for measurements in an essentially free field over a reflecting
plane .10
8.3 Preparations for measurements .11
8.4 Operational test of air-moving device.11
9 Measurement uncertainty.12
10 Information to be recorded.12
11 Information to be reported.13
Annex A (normative) Micro-fan p-q curve measurement method .23
Annex B (informative) Effects of air density .25
Annex C (informative) Data formats for presentation .26
Annex D (informative) Air-moving device acoustical noise specification .30
Annex E (informative) Guidance on the development of information on measurement uncertainty.31
Bibliography.37

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 10302-1 was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 1, Noise.
This first edition of ISO 10302-1 cancels and replaces ISO 10302:1996.
ISO 10302 consists of the following parts, under the general title Acoustics — Measurement of airborne noise
emitted and structure-borne vibration induced by small air-moving devices:
⎯ Part 1: Airborne noise measurement
⎯ Part 2: Structure-borne vibration measurements
iv © ISO 2011 – All rights reserved

Introduction
This part of ISO 10302 specifies in detail methods for determining and reporting the airborne noise emissions
of small air-moving devices (AMDs) used primarily for cooling electronic equipment, such as that for
information technology and telecommunications.
To provide compatibility with measurements of acoustical noise emitted by such equipment, this part of
ISO 10302 uses the noise emission descriptors and sound power measurement methods of ISO 7779. The
descriptor of overall airborne noise emission of the AMD under test is the A-weighted sound power level. The
one-third-octave-band sound power level is the detailed descriptor of the noise emission. Octave-band sound
power levels may be provided in addition to the one-third-octave-band sound power levels.

INTERNATIONAL STANDARD ISO 10302-1:2011(E)

Acoustics — Measurement of airborne noise emitted and
structure-borne vibration induced by small air-moving
devices —
Part 1:
Airborne noise measurement
1 Scope
This part of ISO 10302 specifies methods for measuring the airborne noise emitted by small air-moving
devices (AMDs), such as those used for cooling electronic, electrical, and mechanical equipment where the
sound power level of the AMD is of interest.
Examples of these AMDs include propeller fans, tube-axial fans, vane-axial fans, centrifugal fans, motorized
impellers, and their variations.
This part of ISO 10302 describes the test apparatus and methods for determining the airborne noise emitted
by small AMDs as a function of the volume flow rate and the fan static pressure developed by the AMD on the
test apparatus. It is intended for use by AMD manufacturers, by manufacturers who use AMDs for cooling
electronic equipment and similar applications, and by testing laboratories. It provides a method for AMD
manufacturers, equipment manufacturers and testing laboratories to obtain comparable results. Results of
measurements made in accordance with this part of ISO 10302 are expected to be used for engineering
information and performance verification, and the methods can be cited in purchase specifications and
contracts between buyers and sellers. The ultimate purpose of the measurements is to provide data to assist
the designers of electronic, electrical or mechanical equipment which contains one or more AMDs.
Based on experimental data, a method is given for calculating the maximum volume flow rate of the scaled
plenum up to which this part of ISO 10302 is applicable.
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 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
1)
sound pressure — Precision methods for anechoic test rooms and hemi-anechoic test rooms

1) To be published. (Revision of ISO 3745:2003.)
ISO 5801:2007, Industrial fans — Performance testing using standardized airways
ISO 7779:2010, Acoustics — Measurement of airborne noise emitted by information technology and
telecommunications equipment
ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
measurement (GUM:1995)
ANSI/ASA S2.32, Methods for the experimental determination of mechanical mobility —
Part 2: Measurements using single-point translational excitation
JBMS 72:2003, Acoustics — Method for the measurement of airborne noise emitted by micro-fans
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 7779 and the following apply.
3.1 General definitions
3.1.1
air-moving device
AMD
fan
device for moving air which utilizes a rotating impeller driven by an electric motor with electronic or mechanical
command
NOTE 1 An air-moving device has at least one inlet opening and at least one outlet opening. The openings can have
elements for connection to ductwork or to other parts of the airflow path.
NOTE 2 Tests can be run with a particular frame, motor, and rotor, but with different accessories (e.g. finger guards).
For the purposes of this part of ISO 10302, each such configuration is referred to as an air-moving device.
NOTE 3 Within some industries, including information technology, the unmodified term “fan” means “axial flow air-
moving device”, and the unmodified term “blower” means “centrifugal air-moving device”. In this part of ISO 10302, the
term “fan” is used to mean “air-moving device” and does not necessarily imply axial flow. Modifiers (such as axial,
centrifugal or mixed flow) are added as necessary to distinguish between types.
3.1.2
micro-fan
air-moving device which has a maximum volume flow rate less than or equal to 0,015 m /s
NOTE 1 Micro-fans are a subset of fans under test according to this part of ISO 10302.
NOTE 2 ISO 5801:2007, 22.4.2, Table 4 limits the range of applicability to Reynolds numbers of 12 000 or higher. This
Reynolds number corresponds to the lower limit of volume flow rate of approximately 0,01 m /s. Since lower volume fans
are of interest for many cooling applications, the methodology of JBMS-72:2003, Annex A is used to measure the p-q
curve of a micro-fan.
2 © ISO 2011 – All rights reserved

3.2 Acoustical definitions
3.2.1
sound power level
L
W
ten times the logarithm to the base 10 of the ratio of the sound power, P, to a reference value, P , expressed
in decibels
P
L = 10 lg dB (1)
W
P
where the reference value, P , is 1 pW
[6]
NOTE If a specific frequency weighting as specified in IEC 61672-1 and/or specific frequency bands are applied,
this should be indicated by appropriate subscripts; e.g. L denotes the A-weighted sound power level.
WA
3.2.2
frequency range of interest
range extending from the 100 Hz one-third-octave band to the 10 kHz one-third-octave band
[1]
NOTE 1 The centre frequencies of these one-third-octave bands are defined in ISO 266 .
NOTE 2 For small, low-noise fans to be measured (i.e. micro-fans), depending on the size of applicable plenum, the
radius of the test hemisphere may be reduced to less than 1 m, but not less than 0,5 m (see 8.2.1). However, a radius less
than 1 m could itself impose limits on the frequency range over which tests are performed. For details, reference is made
to ISO 7779:2010, B.1.
3.2.3
insertion loss of test plenum
ΔL
sound power level difference due to the presence of test plenum, defined as follows:
ΔL = L − L (2)
W,out W,in
where
L is the sound power level of a sound source determined when installed outside the test plenum;
W,out
L is the sound power level of a sound source determined when installed inside the test plenum
W,in
NOTE The insertion loss of the test plenum is expressed in decibels.
3.3 Aerodynamic definitions
3.3.1
test plenum
structure on to which the air-moving device under test is mounted for acoustical noise emission
measurements
NOTE The plenum provides a flow resistance to the air-moving device, but permits sound from the air-moving device
to radiate freely into the test room with only minimal attenuation. Thus, the sound power radiated by the air-moving device
can be determined from acoustical measurements made outside the test plenum.
3.3.2
air-moving device aerodynamic performance curve
“p-q curve”
presentation of fan static pressure as a function of volume flow rate under standard air conditions and
constant operating voltage and frequency
NOTE 1 For the purpose of this part of ISO 10302, a qualifier, “aerodynamic”, before “performance curve” is inserted to
distinguish from acoustical noise emission characteristics against volume flow rate.
NOTE 2 The presentation is derived in accordance with ISO 5801 or Annex A, which complement each other. The
method for small air-moving devices of volume flow rate up to 0,015 m /s is specified in Annex A.
NOTE 3 For convenience, in this part of ISO 10302, the term “p-q curve” is used.
3.3.3
point of operation
point on the air-moving device aerodynamic performance curve corresponding to a particular volume flow rate
NOTE The point of operation is controlled during a test by adjusting the “slider” on the test plenum exit port assembly.
3.3.4
overall static efficiency of air-moving device
η
o,s
volume flow rate multiplied by the fan static pressure and divided by the input electrical power
NOTE 1 The overall static efficiency, η , expressed as a percentage, is given by
o,s
pq
s,f V
η=× 100 (3)
o,s
P
input
where
p is the fan static pressure, in pascals;
s,f
q is the volume flow rate, in cubic metres per second;
V
P is the motor input power, in watts (true power, not including reactive component), supplied at the terminals of
input
the electric drive motor.
NOTE 2 The air-moving device is defined to include the motor, impeller and frame; therefore, the overall static
efficiency includes both the electromechanical efficiency of the motor and the aerodynamic efficiency of the impeller and
frame.
3.3.5
standard air density
density under standard air conditions
NOTE The value is 1,20 kg/m .
3.3.6
standard air conditions (for aerodynamic performance measurement)
specified meteorological conditions
NOTE For the purposes of this part of ISO 10302, the conditions are: 20 °C temperature; 50 % relative humidity; and
1,013 × 10 Pa ambient pressure.
4 © ISO 2011 – All rights reserved

4 Limitations of measurement
Experimental data show that this method is useful up to the maximum volume flow rate, q , as a function
V,max
of nominal air volume, V, of the plenum used and up to a fan static pressure of 750 Pa.
q
V,0
qV= (4)
V,max
V
where
q is the maximum volume flow rate of the scaled plenum, in cubic metres per second;
V,max
q is the maximum volume flow rate of the full-size plenum, in cubic metres per second,
V,0
q = 1 m /s;
V,0
V is the nominal air volume of the full-size plenum defined in Clause 6, in cubic metres, V = 1,3 m ;
0 0
V is the nominal air volume of the scaled plenum, in cubic metres.
NOTE 1 The value of the interior air volume of a full-size plenum of 1,3 m is rounded up from
1,296 m = 1,2 m (width) × 1,2 m (depth) × 0,9 m (height).
NOTE 2 It is noted that the “nominal air volume” means approximate air volume calculated from the outer dimensions
of the plenum. For instance, in case of 1/4 sized plenum, the nominal air volume of the plenum, excluding the leg height,
becomes V = blh = 0,3 m × 0,3 m × 0,225 m = 0,020 25 m , where b is width, l is depth, and h is height.
For the purposes of this part of ISO 10302, it is recommended that the smallest plenum possible be applied,
provided that the maximum volume flow rate of the fan is within the limit of Equation (4).
The method defined in this part of ISO 10302, by reference to ISO 7779, provides for determination of sound
power levels in a qualified environment, using either a comparison method in a reverberation test room based
on ISO 3741, or a direct method in essentially free-field conditions over a reflecting plane based on ISO 3744
or ISO 3745. The method specified in this part of ISO 10302 may be applied to air-moving devices (AMDs)
which radiate: a) broad-band noise; b) narrow-band noise; or c) noise that contains discrete frequency
components.
The method specified in this part of ISO 10302 permits the determination of acoustical noise emission levels
for an individual unit under test. If these levels are determined for several units of the same production series,
the results may be used to determine a statistical value for the production series.
CAUTION — Vibration, flow disturbances, insertion loss and other phenomena may alter radiated
sound power in the actual application; therefore, the results of measurements made in accordance
with this part of ISO 10302 may differ from the results obtained when AMDs are installed in equipment.
NOTE 3 This part of ISO 10302 does not describe measurement of the structure-borne noise generated by AMDs.
5 Design and performance requirements for test plenum
5.1 General
The design specified is intended to meet the limits stated for maximum volume flow rate and maximum fan
static pressure. The design provides an acoustically transparent, adjustable flow resistance to the AMD.
NOTE 1 See 5.5 for requirements for confirming acoustical transparency in accordance with this part of ISO 10302.
The reference design of the plenum is specified in 5.2 to 5.6 and shown in Figures 1 to 8. Also addressed in
these subclauses and elsewhere in this part of ISO 10302 are permitted variations from this design, primarily
the option of reducing the linear dimensions of the frame and some dimensions of other parts, while
maintaining geometric proportions, in the range from full to quarter scale. Such a reduction reduces the
maximum permitted volume flow rate of AMDs to be tested in direct proportion to the reduction in volume of
the plenum [see Equation (4)], i.e. by the linear scale raised to the third power.
NOTE 2 These variations can better accommodate the use of smaller or quieter fans as well as test chambers with
doors too narrow for the reference design plenum.
Permitted variations have been shown to yield standard deviations of reproducibility within the range of
Table 1. The degree to which other deviations from the reference design affect the uncertainty of the
determination of sound power levels of AMDs is not known.
5.2 Test plenum: main assembly
5.2.1 General: The test plenum shall consist of an airtight chamber constructed with a frame covered with
an airtight acoustically transparent polyester film, a mounting panel, and an adjustable exit port assembly as
shown in Figure 1.
The plenum shall conform to the requirements specified in 5.2.2 to 5.2.7.
5.2.2 Plenum size: Figure 1 shows the dimensions of the full-size plenum.
5.2.3 Covering: Isotropic polyester film of nominal thickness 25 µm to 50 µm. Batten strips may be used to
protect the covering (see Figures 1 and 2).
5.2.4 Frame: Suitable material with nominal size of 50 mm × 50 mm that provides structural integrity for the
plenum. Corner gussets are recommended for wood framing and may be needed for other materials (see
Figure 3). Frame linear dimensions including the thickness of the framing members shall be in scale with the
plenum size.
5.2.5 Frame material: Experience has shown that either a hardwood, such as birch, or aluminium tubing
provides sufficient strength, stiffness and durability and complies with the acoustical performance
requirements outlined in 5.5.
5.2.6 Vibration isolation: The test plenum feet or support should provide vibration isolation of the plenum
from the floor, for any size of plenum. The intent is to break the vibration-transmission path between the
plenum and the floor. Whichever method is chosen, the 0,1 m overall leg height should be maintained for the
full-size plenum (see Figures 1 and 3). The 0,1 m leg height shall be in scale with the plenum size.
5.2.7 Taps for fan static pressure: The pressure ring shall be mounted immediately behind the mounting
panel. The ring should be sized to match the perimeter of the mounting panel (see Figure 4). The perimeter
dimensions of the pressure ring shall be in scale with the plenum size. The tubing diameter and taps do not
scale, but remain constant.
5.3 Mounting panel assembly
The mounting panel assembly shall comprise some kind of adapter plate sealed and attached to a reinforced
rubber sheet which, in turn, is sealed and attached to the test plenum frame through the use of aluminium
retaining strips (see Figures 1, 4, and 5). The adapter plate is used to mount the fan securely to the rubber
panel. It may take the form of that shown in Figure 5, which is well suited to axial-flow fans, or some other
form more suitable to the particular air-moving device under test. The adapter plate should not cause any
disturbance to the air flow and should not cause any additional sound radiation other than that from the
air-moving device itself.
The mounting panel assembly (comprising adapter plate and flexible panel) may be replaced by a single
damped plate with comparable cut-outs (but no adapter plate) of specified material without significantly
affecting the airborne sound measurements.
6 © ISO 2011 – All rights reserved

The specification on the plate stock is mobility level (reference: 1 m/N s) of −45 dB from 25 Hz to 5 000 Hz
when measured in the middle of a plate of dimension 1,0 m with no fan-mounting hole and with the plate
freely suspended by two corners. The mobility level measurement shall be made in accordance with
ANSI/ASA S2.32.
The tolerance on mobility levels is ±8 dB from 25 Hz to 100 Hz, ±4 dB from 100 Hz to 200 Hz and ±2 dB from
200 Hz to 5 000 Hz. These tolerance limits ensure that the plate has sufficient damping to prevent excitation
of the frame. Such replacement panels are sometimes used in connection with fan vibration measurements
(which are addressed in ISO 10302-2). Using the same mounting panel for sound and vibration
measurements may improve the efficiency of combined tests. If the reference design mounting panel is
replaced, on the basis of impedance testing of the plate material, this shall be stated in the test report.
The opening of the adapter plate shall conform to the recommendations of the AMD manufacturer. The
openings in the clamp frame and rubber panel shall be larger than the opening in the adapter plate to
minimize disturbance of the airflow. The length, width, and thickness of the aluminium retainer strip as well as
the length and width of the reinforced rubber mounting panel shall be in scale with the plenum size. The other
dimensions, including the panel thickness, do not scale.
5.4 Adjustable exit port assembly
The adjustable exit port assembly shall comprise a fixed aperture plate and a slider (movable sliding plate) to
2 2
provide a continuously variable exit port of area from 0,0 m to 0,2 m for the full-size plenum (see Figures 6
to 8). The exit port maximum area shall be in scale with the square of the linear scale of the plenum.
NOTE The point of operation of the AMD is controlled during a test by adjusting the position of the slider on the exit
port assembly.
5.5 Insertion loss of test plenum
For the purpose of this part of ISO 10302, adequacy of the test plenum is evaluated by means of insertion loss
of the test plenum (3.2.3).
+3
The one-third-octave-band insertion loss of the test plenum shall be not greater than ( 0 ) dB and is
−2
recommended to be not greater than (0 ± 1,5) dB, when determined in accordance with the procedure
specified in steps a) to c).
a) The sound power levels of a sound source (e.g. a loudspeaker) shall be determined twice: once with the
source inside the test plenum and once with the source outside the plenum, but at the same location in
the test room. If insertion loss measurements are made in a free field over a reflecting plane, the
hemispherical microphone array should be centred on the sound power source.
b) Measurement uncertainties can arise if the loudspeaker sound power source is moved relative to
reflective surfaces (floor and mounting panel) between the two sound power determinations. Accordingly,
install the sound power source on the floor. Remove the mounting panel and rotate the plenum by 90° so
that the face normally covered by the mounting panel is parallel to the floor and the exit port is on the top
surface. The plenum can then be lowered or raised vertically to cover or expose the sound power source
without causing movement of the source.
c) The source shall be mounted to ensure that solid body radiation from the sound power source which is
transmitted into the test plenum frame or covering is minimized.
The exit port slider shall be closed during the insertion loss test.
5.6 Instrumentation for static pressure measurement
The fan static pressure developed inside the test plenum by the AMD shall be measured using a pressure ring
(shown in Figure 4). This pressure ring has four taps spaced 90° apart as shown, facing towards the centre of
the discharge of the AMD (in the plane of the ring). The pressure ring should be mounted on the frame that
supports the mounting panel. A pressure line can be brought out of the box by drilling a small, smooth, burr-
free hole through the frame. The fan static pressure should be read on a calibrated pressure meter.
The manometer or other pressure measuring device used shall have a resolution of 1 % or finer (e.g. 0,5 %)
of maximum fan static pressure.
Manometers shall have an uncertainty under conditions of steady pressure, not exceeding ±1 % of the point of
best efficiency on aerodynamic performance curve of AMD of interest, or 1,5 Pa, whichever is greater. For
more details, see ISO 5801:2007, 6.2.
6 Installation
6.1 Installation of test plenum in test room
The test plenum shall be installed on the floor of a test room which has been qualified for sound power level
determinations in accordance with ISO 7779:2010, Clause 6 or Clause 7, respectively.
6.2 Direction of airflow
The AMD should preferably be tested when discharging into the test plenum. Exceptions to this airflow
direction may be made to avoid undesirable flow conditions. For example, centrifugal fans or motorized
impellers without scrolls may be tested with the plenum on the inlet.
6.3 Mounting of air-moving device
The AMD shall be mounted on and sealed to the mounting panel assembly specified in 5.3 (either the rubber
sheet with adapter plate and clamp frame or the single damped panel). Additional vibration-isolated supports
which shall not interfere with the propagation of airborne sound shall be provided as necessary to maintain the
mounting plane parallel with the face of the test plenum; in particular, such supports may be required when
testing centrifugal fans, especially at low static pressures. In all cases, the mounting panel assembly shall
remain plane with the face of the plenum. For large AMDs, auxiliary support may be required to prevent the
weight of the device from bending or twisting the mounting panel. Such auxiliary support shall not interfere
with the propagation of airborne sound and shall be vibration-isolated from the air-moving device.
The AMD should be tested for each of its configurations (see Note 2 to 3.1.1).
In some cases, AMDs operating under conditions which keep the plenum exit port completely open can cause
the polyester film panels to flutter or vibrate, creating unwanted noise. In such cases, steps should be taken to
minimize noise due to fluttering or vibration. For example, the mounting panel assembly with the AMD can be
detached from the rest of the plenum and the latter moved out of the way. The mounting panel assembly should
be maintained planar and suspended above the floor of the test room at the same location as specified in 6.1.
7 Operation of air-moving device
7.1 Input power
7.1.1 Alternating current (AC) air-moving devices
The AMD shall be operated at each rated power line frequency, and within ±1,0 % of either:
a) the rated voltage (if any is stated); or
b) the mean voltage of a stated voltage range (e.g. 220 V for a stated range of 210 V to 230 V).
For power having more than two phases, phase-to-phase voltage variations shall not exceed 1 % of the rated
voltage.
NOTE Though the test procedure of Clause 7 is similar to those of ISO 7779, the tolerance of voltage given here is
much tighter than that in ISO 7779 (i.e. 5 % of the rated voltage).
8 © ISO 2011 – All rights reserved

7.1.2 Direct current (DC) air-moving devices
The AMD shall be operated within ±1 % of the rated nominal voltage.
Additional tests may be run at other voltages (e.g. rated maximum, rated minimum).
7.2 Points of operation (AC and DC air-moving devices)
7.2.1 Required points of operation
The AMD shall be tested at three points of operation for each of the required line frequencies and voltages
given in 7.1. These points of operation correspond to:
a) the adjustable exit port (slider) completely open;
b) 80 % of maximum volume flow rate on the p-q curve;
c) 20 % of maximum volume flow rate on the p-q curve.
The actual static pressure reading at each point of operation shall be recorded.
NOTE 1 In this part of ISO 10302, p-q curve measurement is a prerequisite for acoustical noise measurement. So the
“maximum volume flow rate” means the point on the p-q curve, which corresponds to the condition of static pressure equal
to 0. For instance, when the maximum volume flow rate of a fan under test is read as 0,01 m /s from the p-q curve, 80 %
3 3
of maximum volume flow rate means 0,01 m /s × 0,8 = 0,008 m /s.
NOTE 2 Within the framework of this part of ISO 10302, a clear distinction is made between “slider completely open”
and “maximum flow rate”. In ISO 10302:1996 and other conventional standards this was not the case. Condition a), “slider
completely open”, was referred to as the “maximum flow rate” or “free delivery” condition. However, air-flow resistance by
the plenum influences the actual point of operation. For example, the three smooth lines near the abscissa in Figure 9
indicate the system impedance curves of the quarter-scale, half-scale and full-scale plenum respectively, with slider
completely open.
7.2.2 Additional points of operation
Additional tests may be run at other points of operation, including the point of maximum overall static
efficiency, to establish the sound power level versus volume flow rate curve. Some AMDs (e.g. small tube-
axial fans) may be unstable when operated near the maximum overall static efficiency point. Tests should not
be conducted at unstable points of operation.
7.2.3 Procedure
Points of operation shall be established as in steps a) to c).
a) The fan static pressure at the designated percentage volume flow rates (see 7.2.1) shall be read from the
AMD aerodynamic performance curve (p-q curve) determined (prior to acoustical noise measurement) in
accordance with ISO 5801 or Annex A, as applicable, with the same direction of airflow.
b) If the ambient atmospheric density during the noise test differs by more than 1 % from that recorded in
accordance with ISO 5801 or Annex A, as applicable, the fan static pressure shall be corrected as
follows:
p
⎛⎞273 + t
amb,2
pp= (5)
⎜⎟
s,2 s,1
273 +tp
2amb,1
⎝⎠
where
p is the fan static pressure to be set on the test plenum, in pascals;
s,2
t is the air-flow temperature during acoustical noise measurement, in degrees Celsius;
p is the atmospheric pressure during acoustical noise measurement, in kilopascals;
amb,2
p is the fan static pressure during volume flow rate measurement, in pascals;
s,1
t is the air-flow temperature during volume flow rate measurement, in degree Celsius;
p is the atmospheric pressure during volume flow rate measurement, in kilopascals.
amb,1
c) The slider shall be adjusted to obtain a reading of the fan static pressure, p , within ±1 % of the
s,2
maximum fan static pressure, determined with a pressure-measuring instrument satisfying the
requirements of 5.6.
The fan and the fan static pressure shall be allowed to stabilize at each point of operation.
If measurements are made at the maximum overall static efficiency point, care should be taken when
adjusting the plenum for this point of operation. Some AMDs have three or more values of volume flow rate
corresponding to the same fan static pressure in the region of maximum overall static efficiency. Only the
point with the highest volume flow rate is the maximum overall static efficiency point. To obtain this point of
operation, start from free delivery and increase the static pressure until the point of operation is reached.
If an AMD is unstable (e.g. unsteady speed or pressure) at one of the recommended points of operation,
decrease the fan static pressure until stability is achieved and use the new point of operation thus reached.
The instability shall be reported and the alternative point of operation shall be described.
NOTE The AMD aerodynamic performance curve obtained according to ISO 5801 or Annex A can differ from the
performance on the test plenum. This difference is assumed to be equivalent to that typical of normal AMD applications,
and no corrections for test plenum differences are necessary.
8 Measurement procedures
8.1 General
Sound power levels shall be determined in accordance with ISO 7779. ISO 7779:2010, Clause 6 permits the
use of a comparison method in a reverberation test room, based on ISO 3741. ISO 7779:2010, Clause 7
permits sound power determination in an essentially free field over a reflecting plane based on ISO 3744 and
ISO 3745. If a method specified in ISO 7779:2010, Clause 7 is used, one of the sets of microphone positions
described in 8.2 is required.
NOTE When using the method of ISO 7779:2010, Clause 7, sound power levels can be influenced by air density.
This part of ISO 10302 follows ISO 7779:2010 for the corrections. For some cases requiring consideration of the influence
of air density, Annex B gives supplementary information.
8.2 Microphone positions for measurements in an essentially free field over a reflecting
plane
8.2.1 General
For the purposes of this part of ISO 10302, the measurement surfaces for determining sound power level are
hemispherical, selected from those specified in ISO 3744 and ISO 3745. The radius shall not be smaller than
0,5 m (see Note 2 to 3.2.2).
NOTE 1 In ISO 7779, measurement surfaces in forms other than hemispherical are specified for an essentially free
field over a reflecting plane. However, for the purpose of sound power level determination using the test plenum mounted
in such an acoustical environment, this part of ISO 10302 permits only hemispherical measurement surfaces.
One of the sets of microphone positions in either 8.2.2 or 8.2.3 should be used, but the radius shall not be
smaller than 0,5 m (see Note 2 to 3.2.2). In any case, the origin of the co-ordinates is located at the vertical
projection of the centre of the mounting opening on the reflecting plane. If a test plenum geometrically smaller
than that in Figure 1 is used, a radius of between 2 m and the geometrically scaled radius shall be used.
NOTE 2 These sets of microphone positions reduce interference effects caused by reflections from the plane and can
avoid intake or exhaust air streams.
10 © ISO 2011 – All rights reserved

8.2.2 Fixed points on a hemisphere
The locations of 10 positions associated with equal areas on the surface of the hemisphere are numbered
from 1 to 10 in Figure 10. The co-ordinates (x, y, z) are given in Table 2 and Figure 10.
NOTE For convenience, Table 2 and Figure 10 show co-ordinates of fixed positions on the hemispherical
measurement surface.
8.2.3 Coaxial circular paths in five or more parallel planes
Instead of fixed positions, circular paths consisting of coaxial circular paths according to ISO 3744 may be
used. See Figure 11.
8.3 Preparations for measurements
Steps a) to g) shall be taken in preparation for noise emission measurements on each AMD.
a) Record the name, model number, serial number, dimensions, nameplate data and complete description
of the AMD under test.
b) Obtain the AMD aerodynamic performance curve in accordance with ISO 5801 or Annex A, as applicable.
c) Check the calibration of the microphone(s) in conformity with ISO 7779:2010.
d) Measure the background noise levels in the test room in conformity with ISO 7779:2010.
e) Measure the ambient temperature, relative humidity, and ambient pressure.
f) If a method requiring the use of a reference sound source (RSS) is to be used, measure the sound
pressure levels produced by the RSS.
g) Zero the manometer or other pressure-measuring device used for measuring the fan static pressure in
the test plenum.
8.4 Operational test of air-moving device
Steps a) to h) shall be taken in carrying out the noise emission measurements on each AMD configuration.
a) Allow the AMD under test to warm up for a sufficient period of time before proceeding with the acoustical
test to allow the temperature to stabilize. If this time is unknown, the equipment shall be operated for at
least 30 min before the acoustical test.
b) Mount the AMD on the test plenum in accordance with 6.3.
c) Adjust the voltage (and frequency when AC powered) in accordance with 7.1.
d) Adjust the slider to obtain the desired point of operation in accordance with 7.2.
e) Determine the sound power level in conformity with ISO 7779:2010, Clause 6 or Clause 7, as applicable.
A-weighted sound power levels and one-third-octave-band sound power levels are required; octave-band
sound power levels are optional.
f) Record the data in conformity with Clause 10.
g) Repeat steps d) to f) for each point of operation.
h) Repeat steps c) to g) for each voltage as required.
In some tests of small centrifugal fans on a full-scale plenum, discrete tones not normally present in the
spectrum of the fan appeared; these apparently coincided with plenum resonance frequencies. This
phenomenon has not been widely noted, but if unexpected tones appear during testing, the possible cause
should be explored.
9 Measurement uncertainty
The uncertainty of results obtained from measurements in accordance with this part of ISO 10302 shall be
evaluated, preferably in compliance with ISO/IEC Guide 98-3. If reported, the expanded uncertainty together
with the corresponding coverage prob
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