ISO 27327-2:2014
(Main)Fans — Air curtain units — Part 2: Laboratory methods of testing for sound power
Fans — Air curtain units — Part 2: Laboratory methods of testing for sound power
ISO 27327-2:2014 deals with the determination of the acoustic performance of air curtain units. In addition, it can be used to determine the acoustic performance of air curtain units combined with an ancillary device.
Ventilateurs — Rideaux d'air — Partie 2: Méthodes d'essai en laboratoire des niveaux de puissance acoustique
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Standards Content (Sample)
DRAFT INTERNATIONAL STANDARD ISO/DIS 27327-2
ISO/TC 117 Secretariat: BSI
Voting begins on Voting terminates on
2012-10-01 2013-01-01
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION МЕЖДУНАРОДНАЯ ОРГАНИЗАЦИЯ ПО СТАНДАРТИЗАЦИИ ORGANISATION INTERNATIONALE DE NORMALISATION
Fans — Air curtain units —
Part 2:
Laboratory methods of testing for sound power
Ventilateurs — Rideaux d'air —
Partie 2: Méthodes d'essai en laboratoire des niveaux de puissance acoustique
[Revision of first edition (ISO 13347-1:2004, ISO 13347-1:2004/Cor.1:2006, ISO 13347-2:2004 and
ISO 13347-2:2004/Cor.1:2006)]
ICS 17.140.20; 23.120
To expedite distribution, this document is circulated as received from the committee
secretariat. ISO Central Secretariat work of editing and text composition will be undertaken at
publication stage.
Pour accélérer la distribution, le présent document est distribué tel qu'il est parvenu du
secrétariat du comité. Le travail de rédaction et de composition de texte sera effectué au
Secrétariat central de l'ISO au stade de publication.
THIS DOCUMENT IS A DRAFT CIRCULATED FOR COMMENT AND APPROVAL. IT IS THEREFORE SUBJECT TO CHANGE AND MAY NOT BE
REFERRED TO AS AN INTERNATIONAL STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS BEING ACCEPTABLE FOR INDUSTRIAL, TECHNOLOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON OCCASION HAVE TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL TO BECOME
STANDARDS TO WHICH REFERENCE MAY BE MADE IN NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT, WITH THEIR COMMENTS, NOTIFICATION OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPORTING DOCUMENTATION.
© International Organization for Standardization, 2012
ISO/DIS 27327-2
Copyright notice
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ii © ISO 2012 – All rights reserved
ISO/CD 27327-2
Contents Page
1 Scope . 1
2 Normative References . 1
3 Terms, definitions, symbols and units . 2
3.1 Terms and definitions . 2
3.2 Air curtain unit sound power levels . 3
3.3 Other Symbols . 4
4 Limitations on use . 5
4.1 General . 5
4.2 Noise source . 5
4.3 Character of noise . 5
4.4 Uncertainty . 5
4.5 Quantities to be measured . 5
5 Measurement uncertainty . 5
6 Instrumentation . 7
6.1 General . 7
6.1.1 Microphone . 7
6.1.2 Microphone cable . 7
6.1.3 Sound level meter or other microphone amplifier . 7
6.2 Frequency analyser . 7
6.3 Turbulence screens and windshields . 8
6.3.1 Windshields . 8
6.3.2 Wind-generated false noise . 8
6.4 Reference sound source (RSS) . 8
7 Test procedure . 8
7.1 Comparison method . 8
7.2 Direct method . 8
8 Acoustic environment . 8
8.1 Test environment . 8
8.2 Reverberant room . 9
9 Air curtain unit installation conditions . 9
10 Air curtain unit operating conditions . 9
10.1 General . 9
10.2 Measurement of ambient conditions . 9
10.3 Air curtain unit rotational speed . 9
10.4 Determination of air curtain unit aerodynamic operating point . 9
10.5 Control of air curtain unit operating condition . 9
11 Test set-up . 10
11.1 Set-up categories . 10
11.2 Sound pressure levels . 15
11.2.1 Sound pressure levels, background (L ) . 15
pb
11.2.2 Sound pressure levels, RSS (L ) . 15
pqm
11.2.3 Sound pressure levels, air curtain unit (L ). 15
p
11.3 Aerodynamic performance . 15
11.4 Test conditions . 15
11.5 Mounting methods . 16
11.6 Microphone travel or positions . 17
ISO/CD 27327-2
12 Information to be recorded .19
12.1 General .19
12.2 Air curtain unit under test .19
12.2.1 Description of the air curtain unit under test .19
12.2.2 Operating conditions .19
12.2.3 Mounting conditions .19
12.3 Acoustic environment .19
12.3.1 Description of the test environment and method .19
12.3.2 Acoustical qualification of the test environment .20
12.3.3 Test data .20
12.3.4 Laboratory and instrumentation .20
12.3.5 Location of the air curtain unit in the test environment .20
12.3.6 Additional noise sources .20
12.4 Acoustical data appropriate to the method of test .20
13 Calculations and evaluations .21
13.1 Calculation of one-third octave band levels .21
13.2 Calculation of overall sound power levels .21
13.3 Calculation of A-weighted sound power level .22
13.4 Background corrections .22
13.5 Sound power level, L .23
W
13.6 Evaluation .23
14 Test report .23
14.1 General .23
14.2 Description of test site, arrangement of fan, location of measuring points .24
14.3 Instrumentation used .24
14.4 Subjective assessment of the noise character .24
14.5 Measured values of the noise character .24
Annex A (normative) Effect of rotational speed changes .25
Annex B (normative) Uncertainty analysis.26
B.1 General .26
B.2 Definitions .26
B.3 Uncertainties .26
B.4 Room response .26
B.4.1 Broad-band measurement in a reverberant room .27
B.4.2 Pure tone measurement in a reverberant room .27
B.4.3 Test for discrete-frequency components .27
B.5 Air curtain unit operating points .28
B.6 Instrument error .28
B.7 Reference sound source (RSS) .29
B.8 Octave band VS one-third octave band .29
Annex C (normative) Calibration of reference sound source .30
C.1 General .30
C.2 Equipment and facilities .30
C.3 Qualification .30
C.4 Procedure .30
C.5 RSS sound power levels .31
Annex D (informative) Filter weighted measurements .32
Annex E (normative) Room qualification for sound sources with broad-band sound .33
E.1 General .33
E.2 Instrumentation and equipment .33
E.3 Test procedures .33
E.4 Computation procedures .33
E.5 Qualification .34
Annex F (informative) Room qualification for sound sources with pure tones/narrow-band sound .35
F.1 General .35
F.2 Instrumentation and equipment .35
iv © ISO 2011 – All rights reserved
ISO/CD 27327-2
F.3 Test procedure . 35
F.3.1 Loudspeaker test . 35
F.3.2 Room test . 36
F.4 Computation . 36
F.5 Qualification . 36
ISO/CD 27327-2
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 27327-2 was prepared by Technical Committee ISO/TC 117, Fans, Subcommittee SC , .
ISO 27327 consists of the following parts, under the general title Fans — Air Curtain Units:
Part 1: Laboratory methods of testing for aerodynamic performance rating
Part 2: Determination of air curtain unit sound power levels under standardized laboratory conditions -
reverberant room method
vi © ISO 2011 – All rights reserved
ISO/CD 27327-2
Introduction
The need for this new International Standard, ISO 27327-2, has been evident for some time. Whilst a number
of national standards exist for the measurement of fan noise, none addressed the particular considerations
required for the noise testing of air curtain units.
Forming part of the ISO/TC 117 series of fan standards, this part of ISO 27327 deals with the determination of
the air curtain unit sound power level appropriate to a particular application. In describing the test and rating
procedures, numerous references are made to ISO 5801 and ISO 13347 as well as to other ISO standards.
The test procedures described in this part of ISO 27327 relate to laboratory conditions. The measurement of
performance under site conditions is not included. Acoustic system effects can be considerable where the
airflow into and out of the air curtain unit is not free from swirl, nor fully developed.
This part of ISO 27327 describes methods for determining sound power levels of air curtain units in one-third-
octave bandwidths and one-octave bandwidths.
Data obtained in accordance with this part of ISO 27327 may be used for the following purposes amongst
others:
a) comparison of air curtain units which are similar in size and type;
b) comparison of air curtain units which are different in size, type, design, speed, etc.;
c) determining whether an air curtain unit is suitable for a specified upper limit of sound emission;
d) scaling air curtain unit noise from one size and speed to another size and speed of the same type of air
curtain unit
e) prediction of sound pressure level in application of the air curtain unit;
f) engineering work to assist in developing machinery and equipment with lower sound emissions.
COMMITTEE DRAFT ISO/CD 27327-2
Fans — Air Curtain Units - Determination of air curtain unit
sound power levels under standardized laboratory conditions -
reverberant room method
1 Scope
This part of ISO 27327 deals with the determination of the acoustic performance of air curtain units. In addition,
it may be used to determine the acoustic performance of air curtain units combined with an ancillary device.
2 Normative References
The following referenced documents are indispensible 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 266:1997, Acoustics – Preferred frequencies
ISO 3740:2000, Acoustics – Determination of sound power levels of noise sources – Guidelines for the use of
basic standards
ISO 3741:2010, Acoustics – Determination of sound power levels and sound energy levels of noise sources
using sound pressure – Precision methods for reverberation test rooms
ISO 3743-1:2010, Acoustics – Determination of sound power levels and sound energy levels of noise sources
using sound pressure – Engineering methods for small movable sources in reverberant fields – Part 1:
Comparison method for hard-walled test room
ISO 3743-2:1994, Acoustics – Determination of sound power levels of noise sources using sound pressure –
Engineering methods for small, movable sources in reverberant fields – Part 2: Methods for special
reverberation test rooms
ISO 5801:2007, Industrial fans – Performance testing using standardized airways
ISO 6926:1999, Acoustics – Requirements for the performance and calibration of reference sound sources
used for the determination of sound power levels
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 13347-1:2004, Industrial Fans – Determination of fan sound power levels under standardized laboratory
conditions – Part 1: General overview
ISO 13347-2:2004, Industrial Fans – Determination of fan sound power levels under standardized laboratory
conditions – Part 2: Reverberant room method
ISO 13349:2010, Fans – Vocabulary and definitions of categories
ISO 27327-1:2009, Fans – Air curtain units – Part 1: Laboratory methods of testing for aerodynamic
performance rating
ISO/CD 27327-2
ISO 80000-1:2009, Quantities and units – Part 1: General
3 Terms, definitions, symbols and units
3.1 Terms and definitions
For the purposes of this document, the non-acoustical terms and units defined in ISO 5801, ISO 13349, ISO
27327-1, and ISO 1000 apply. The following definitions also apply, and are taken from ISO 3740 to 3747, ISO
13347-1, and ISO 13347-2 wherever possible. Some definitions have been expanded to fit the specific needs
of this document.
3.1.1
inlet sound power level
sound power level of an air curtain unit determined at the air curtain unit inlet in test installation type A.
3.1.2
outlet sound power level
sound power level of an air curtain unit determined at the air curtain outlet in test installation type A.
3.1.3
total sound power level
sound power level of an air curtain unit in test installation type E.
3.1.4
casing sound power level
sound power level radiated from an air curtain unit casing.
NOTE If the air curtain unit drive is external to the air curtain unit casing, the casing sound power shall include the
sound power generated by and radiated from the air curtain unit drive
3.1.5
frequency range of interest
frequency range including octave bands with centre frequencies between 63 Hz and 8 000 Hz and one-third
octave bands with centre frequencies between 50 Hz and 10 000 Hz.
NOTE For special purposes, the frequency range may be extended at either end, provided that the test environment
and instrument accuracy are satisfactory for use over the extended frequency range. For air curtain units which radiate
sound at predominantly high (or low) frequency, the frequency range of interest may be limited in order to optimise the test
facility and procedures.
3.1.6
blade passage frequency (BPF)
frequency of air curtain unit impeller blades passing a single fixed object.
NOTE The blade passage frequency is calculated by the following formula:
xn×
BPF = Hz
where
x is the number of blades;
n is the fan speed, expressed in revolutions per minute.
2 © ISO 2011 – All rights reserved
ISO/CD 27327-2
3.1.7
chamber
enclosure used to regulate flow and absorb sound; it may also conform to air test chamber conditions outlined
in ISO 5801.
3.1.8
air curtain unit inlet area
Α
summation of open areas (slots, holes, louvres, openings, etc.) through which air will flow into the air curtain unit; normally
a grille and/or air inlet opening
3.1.9
air curtain unit outlet area
Α
summation of open areas through which air will discharge out of the air curtain; normally a grille and/or air
outlet opening.
3.1.10
reverberant room
enclosure meeting the requirements of Annex A and/or Annex B of ISO 13347-2:2004
3.1.11
standard air
air with a density of 1,2 kg/m
NOTE 1 Standard air has a ratio of specific heats of 1,4 and a viscosity of 1,815 E-03 kg/m • s
NOTE 2 Air at 16 °C dry bulb temperature, 50 % relative humidity, and 100 kPa barometric pressure has these
properties, but this is not part of the definition.
NOTE 3 Air at 20 °C dry bulb temperature, 50 % relative humidity, and 101.325 kPa barometric pressure has these
properties, but this is not part of the definition.
3.2 Air curtain unit sound power levels
Considering all possible combinations for installation conditions specified in Clause 4, five different sound
power level (L ) descriptions are defined in Table 1; e.g., L (A,in).
W W
Table 1 — Sound power levels
Number Suffix Description
1 (A,in) free-inlet sound power level, type A installation.
2 (A,out) free-outlet sound power level; type A installation.
total sound power level; type E installation (includes the contributions from the
3 (E,tot)
inlet, outlet, casing, and drive).
4 (A,in+cas) free-inlet sound power level plus casing-radiated noise; type A installation
5 (A,out+cas) free-outlet sound power level plus casing-radiated noise; type A installation
NOTE 1 All of these symbols may be used to indicate levels in one-third octave or octave frequency bands as well as
overall sound power levels and A-weighted sound power levels, provided that the sound power to which the symbols
relate is clearly defined.
Where noise from the drive may contribute to the noise radiated from a casing, then this should be clearly stated by the
ISO/CD 27327-2
addition of +dr e.g., L (E,cas + dr).
W
NOTE 2 Not all of the above levels need to be measured for a particular air curtain unit.
NOTE 3 Where some portion of inlet noise is included in the measurement of outlet noise, this shall be clearly stated
by the addition of "+ in" or other similar notation; e.g., L (A,out+in).
W
3.3 Other Symbols
For consistency and mutual understanding, it is recommended that the symbols and units shown in Table 2 be
used in reporting and calculation. Unless otherwise noted, the subscript number refers to the mid-frequency of
the octave band or one-third octave band number.
Table 2 — Symbols, units
Symbol Term SI unit
A
air curtain unit inlet area
m
A
air curtain unit outlet area
m
c speed of sound m/s
minimum distance between equipment under test and reverberant room
D
m
min
measurement surface
f frequency Hz
-5
L
dB
sound pressure level, re 20 μpa (2 × 10 Pa)
p
L
corrected sound pressure level of the air curtain unit dB
pc
recorded sound pressure level of room background as measured over the normal
L
dB
pb
microphone path
L
background sound pressure level dB
pb
recorded sound pressure level of fan and room background as measured over the
L
dB
pm
normal microphone path
L
corrected sound pressure level of the RSS dB
pq
recorded sound pressure level of the RSS and room background as measured
L
dB
pqm
over the normal microphone path
L
recorded sound pressure level of pure tone noise source dB
ps
-12
L
sound power level, re 1 pW (1 × 10 W) dB
W
L
sound power level of RSS dB
Wr
λ wavelength m
M Mach number dimensionless
p sound pressure Pa
-5
p reference sound pressure, 20 μpa (2 × 10 Pa) -
ref
s standard deviation dB
θ air temperature K
W sound power W
-12
W reference sound power, re 1 pW (1 × 10 W) dB
ref
4 © ISO 2011 – All rights reserved
ISO/CD 27327-2
4 Limitations on use
4.1 General
For reverberant room tests, the size of the air curtain unit is limited to less than 2 % of the room volume.
The test procedures specified in this part of ISO 27327 are intended principally for tests conducted using
standardized test configurations and under specified environments and conditions and may not be appropriate
to site test conditions.
The air curtain unit installation conditions conform to the following two categories of installation types:
⎯ type A: free inlet, free outlet;
Used when measuring inlet noise only or outlet noise only; i.e., (i) ducted ACU’s or (ii) recessed ACU’s
where the air inlet and air discharge of the ACU communicate with separate spaces (air inlet – ceiling
void; air discharge – space to be served)
⎯ type E: free inlet, free outlet.
Used when measuring total noise; i.e., (i) surface mounted ACU’s or (ii) recessed ACU’s where the air
inlet and air discharge of the ACU communicate with the same space
4.2 Noise source
The noise source is an air curtain unit. The noise measured may contain contributions from the fan drive and
transmission.
4.3 Character of noise
Steady broadband with discrete frequency tones
4.4 Uncertainty
Engineering grade, as defined in ISO 3740
4.5 Quantities to be measured
Sound pressure levels in one-third octave frequency bands at discrete microphone positions or on a
prescribed path.
Air curtain unit aerodynamic performance indicators, where applicable; e.g., rotational speed, static pressure,
and flow rate.
5 Measurement uncertainty
Measurements made in conformance with this part of ISO 27327 tend to result in standard deviations which
are equal to or less than those given in Table 3. These standard deviations take into account the cumulative
effects of all causes of measurement uncertainty; such as source location, instrument calibration, and
sampling. They do not reflect variations in the sound power radiated by the air curtain unit itself due to, for
example, changes in installation type or manufacturing tolerances. For further information, refer to Annex E.
ISO/CD 27327-2
Table 3 — Uncertainty in determination of the frequency-band sound power levels
One-third octave
Standard deviation
band frequencies
dB
Hz
63 6,0*
125 3,0
250 3,0
500 3,0
1000 3,0
2000 3,0
4000 3,0
8000 3,0
The uncertainties in Table 3 do not allow for the variations in sound power levels due to manufacturing tolerances. These
are consequent differences between one air curtain unit and another of the same nominal design, rotational speed, etc. In
any specifications which are part of a contract, it is necessary to apply tolerances to sound values. These may be
calculated for a normal distribution of data by multiplying the quoted standard deviations by 2 to obtain 95 % confidence
limits. A further deviation should also be added to account for manufacturing tolerances, as described in ISO 13348.
Note 1 When octave-band data are calculated, the uncertainty of each octave band level will not be greater than the
largest uncertainty of the three constituent one-third octave bands.
Note 2 Only octave bands are shown for the reverberant room method in accordance with ISO 3743.
Note 3 Figures marked with "*" in Table 3 have only been added to ISO 3740:2000. For general purposes; therefore,
many existing rigs are designed to operate at a cut-off frequency of 100 Hz, thus giving the octave bands of interest as
those between 125 Hz and 8 000 Hz.
6 © ISO 2011 – All rights reserved
ISO/CD 27327-2
Some air curtain units have significant quantities of noise in the 63 Hz octave band, and, for special purposes, it is
permissible to extend the measurements to this band, provided the test environment and instrument accuracy are
satisfactory over this extended range.
The uncertainty given for these low frequencies can only be achieved by exercising extreme care, and wherever possible,
results should be restricted to octave bands of 125 Hz and above.
Note 4 Where the reverberant room is in full conformity with ISO 3743-1 (hard-walled test room), then the uncertainty
may be reduced.
Note 5 Sound power levels obtained by using the methods described herein are for a fully developed flow into the air
curtain unit, without pre-swirl, and straight-line flow out of the air curtain unit without swirl. Any disturbance in the airflow
will increase the levels in a real installation.
Note 6 The figures given in column 2 are taken from ISO 13347-2.
The standard deviations in Table 3 are equivalent to those obtained from the engineering methods described in ISO 3743
and ISO 3744, as appropriate. They are those which would result from a set of measurements which were undertaken on
a single air curtain unit in a large number of different laboratories and include the cumulative effects of all causes of
measurement uncertainty.
The repeatability of measurements in any one laboratory may be considerably better than the values in Table 3 would
indicate.
6 Instrumentation
6.1 General
Depending on the test method, the instrumentation shall be as specified in this part of ISO 27327, together
with ISO 3741, ISO 3743, ISO 3744, ISO 13347-1, and ISO 13347-2. ISO 13347-1 also details the
requirements for the reference sound source which shall be used to qualify the test room and shall be the
basis of the substitution method.
Instrumentation shall be so designed as to determine the mean-square value of the sound pressure in octave
and/or one-third octave bands averaged over time and space.
6.1.1 Microphone
A microphone of a standardized sound level meter shall be used.
6.1.2 Microphone cable
The microphone/cable system shall be such that the sensitivity does not change with temperature in the range
encountered in the test. Cable flexing due to either microphone traversing or airflow across the cable should
not introduce cable noise which interferes with the measurements.
6.1.3 Sound level meter or other microphone amplifier
The sound level meter or other amplifier used to amplify the microphone signal shall comply with the electrical
requirements for sound level meters. The flat response shall be used.
6.2 Frequency analyser
The frequency analyser shall have the capacity of frequency analysing into one-third octave bandwidths in
accordance with ISO 266.
ISO/CD 27327-2
6.3 Turbulence screens and windshields
6.3.1 Windshields
A microphone exposed to excessive air velocity will give a falsely high reading. This may be rectified by fitting
the microphone with a nose cone or a foam ball.
If the air velocity over the microphone is greater than 1 m/s, a nose cone or foam ball shall be used. If a foam
ball is used, the air velocity over the foam ball shall not exceed 15 m/s.
6.3.2 Wind-generated false noise
The flow of an airstream over a microphone fitted with a nose cone or foam ball will still generate an apparent
change in sound pressure level at the microphone, even though it is reduced when compared to an
unshielded microphone. This change is not attributable to the air curtain unit, but is a function of microphone
design.
6.4 Reference sound source (RSS)
A calibrated RSS shall conform to the requirements of Annex D.
7 Test procedure
7.1 Comparison method
The test method is based on a reference sound source (RSS) substitution for the determination of sound
power. The reference documents for this method are ISO 3743-1 and ISO 3743-2.
Application of the test method requires that the air curtain unit to be tested be set in position in a test room,
which is qualified according to the requirements of Annex F.
Once the test room has been qualified, sound pressure levels are recorded with the RSS operating. The air
curtain unit is then operated without the RSS in operation at the given test speed, and the air curtain unit
sound pressure levels are recorded. Since the sound power levels of the RSS are known, the substitution
method is used to determine the sound power levels of the air curtain unit for each operating point.
7.2 Direct method
The test method is based on measuring the reverberation times of the reverberation test room and using this
and the measured test room volume to calculate sound power levels from the sound pressure levels produced
by the air curtain unit under test.
The resulting sound pressure levels are sampled, filtered into one-third octave band widths, integrated and
averaged by means of a real time analyser using a spaced array of microphones. The value obtained at any
particular frequency is then corrected into sound power levels using a mathematical expression. Octave band
sound power levels are obtained by the logarithmic summation of the three equivalent one-third octave bands.
The reference document for this method is ISO 3741.
8 Acoustic environment
8.1 Test environment
The test environment shall be a reverberant environment.
8 © ISO 2011 – All rights reserved
ISO/CD 27327-2
8.2 Reverberant room
An enclosure meeting the requirements of Annex F is mandatory for the purposes of this part of ISO 27327.
An enclosure meeting the requirements of Annex G is recommended for broad-band sound testing and is
mandatory for the purpose of investigating pure tones and narrow bands.
9 Air curtain unit installation conditions
The measurement procedures specified in this part of ISO 27327 cover the following air curtain unit
installations (see Clause 4):
⎯ free inlet/free outlet (type A);
⎯ free inlet/free outlet (type E).
10 Air curtain unit operating conditions
10.1 General
The noise generated by an air curtain unit is related to its operating conditions; i.e., its rotational speed, air
curtain unit static pressure, and airflow rate. It is important that the aerodynamic duty is known when acoustic
measurements are being made. Care is required to ensure that methods of determining or controlling the
aerodynamic performance do not affect the noise generated by the fan or interfere with the acoustical
measurements.
10.2 Measurement of ambient conditions
The ambient air conditions of temperature, pressure, and humidity shall be within the limits specified in the
appropriate standards ISO 3743, ISO 3744, and ISO 3745.
10.3 Air curtain unit rotational speed
The air curtain unit rotational speed shall be measured and held steady (within 1 % change) during the sound
test. The fan rotational speed during the test shall be within 5 % of the specified rotational speed to minimise
the change in fan sound power when applying the conversion rules.
When it is not possible to test an air curtain unit within these limits, an indirect test at a different speed is
permitted, provided that the test is reported at the test speed and then scaled to the specified or nominal
speed (see Annex A).
10.4 Determination of air curtain unit aerodynamic operating point
The identification of the operating point shall preferably be by measurement of air curtain unit static pressure
using one of the methods specified in ISO 27327-1. The flow rate at the operating point may be inferred,
indirectly, by a determination of air curtain unit static pressure.
10.5 Control of air curtain unit operating condition
A throttling device shall be used to control the operating point. The sound level in the test environment
generated by the throttling device shall be at least 10 dB below the measured sound level from the air curtain
unit under test. The throttle arrangement shall be arranged integrally with the test chamber.
ISO/CD 27327-2
11 Test set-up
11.1 Set-up categories
A number of specific air curtain unit test set-ups are allowed. They are determined by the airflow direction and
the particular mounting arrangement of the test device. The air curtain unit sound pressure levels are
measured in a reverberant room, which may be connected to a chamber or any other system to provide
control and measurement of the air curtain unit air volume flow rate.
10 © ISO 2011 – All rights reserved
ISO/CD 27327-2
2 3
Sound/Vibration Isolation
Key
1 Air curtain unit
2 Reverberant room
3 Testing chamber
4 Air curtain unit inlet
5 Air curtain unit outlet
6 Optional secondary air curtain unit inlet isolated from reverberant room
Figure 1 — Installation Type A Outlet test set-up for air curtain unit outlet sound measurement
ISO/CD 27327-2
Sound/Vibration Isolation
Key
1 Air curtain unit
2 Reverberant room
3 Testing chamber
4 Air curtain unit inlet
5 Air curtain unit outlet
6 Opt
...
INTERNATIONAL ISO
STANDARD 27327-2
First edition
2014-02-15
Corrected version
2014-03-01
Fans — Air curtain units —
Part 2:
Laboratory methods of testing for
sound power
Ventilateurs — Rideaux d’air —
Partie 2: Méthodes d’essai en laboratoire des niveaux de puissance
acoustique
Reference number
©
ISO 2014
© ISO 2014
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
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Published in Switzerland
ii © ISO 2014 – All rights reserved
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols and units . 2
3.1 Terms and definitions . 2
3.2 Air curtain unit sound power levels . 3
3.3 Other symbols . 3
4 Limitations on use . 4
4.1 General . 4
4.2 Noise source . 5
4.3 Character of noise . 5
4.4 Uncertainty . 5
4.5 Quantities to be measured . 5
5 Measurement uncertainty . 5
6 Instrumentation . 7
6.1 General . 7
6.2 Frequency analyser . 7
6.3 Turbulence screens and windshields . 7
6.4 Reference sound source (RSS) . 8
7 Test procedure . 8
7.1 Comparison method . 8
7.2 Direct method . 8
8 Acoustic environment . 8
8.1 Test environment . 8
8.2 Reverberant room . 8
9 Air curtain unit installation conditions . 9
10 Air curtain unit operating conditions . 9
10.1 General . 9
10.2 Measurement of ambient conditions . 9
10.3 Air curtain unit rotational speed . 9
10.4 Determination of air curtain unit aerodynamic operating point . 9
10.5 Control of air curtain unit operating condition . 9
11 Test setup . 9
11.1 Setup categories . 9
11.2 Sound pressure levels .14
11.3 Aerodynamic performance .15
11.4 Test conditions .15
11.5 Mounting methods .15
11.6 Microphone travel or positions .15
12 Information to be recorded .16
12.1 General .16
12.2 Air curtain unit under test .17
12.3 Acoustic environment .17
12.4 Acoustical data appropriate to the method of test.18
13 Calculations and evaluations .19
13.1 Calculation of one-third octave band levels .19
13.2 Calculation of overall sound power levels .19
13.3 Calculation of A-weighted sound power level .19
13.4 Background corrections .20
13.5 Sound power level, L .20
W
13.6 Evaluation .21
14 Test report .21
14.1 General .21
14.2 Description of test site, arrangement of fan, location of measuring points.21
14.3 Instrumentation used .22
14.4 Subjective assessment of the noise character .22
14.5 Measured values of the noise character .22
Annex A (normative) Effect of rotational speed changes .23
Annex B (normative) Uncertainty analysis .24
Annex C (normative) Calibration of reference sound source.28
Annex D (informative) Filter weighted measurements .30
Annex E (normative) Room qualification for sound sources with broadband sound .31
Annex F (informative) Room qualification for sound sources with pure tones/narrow-
band sound .33
Bibliography .37
iv © ISO 2014 – All rights reserved
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers
to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 117, Fans.
ISO 27327 consists of the following parts, under the general title Fans — Air curtain units:
— Part 1: Laboratory methods of testing for aerodynamic performance rating
— Part 2: Laboratory methods of testing for sound power
The following parts are under preparation:
— Part 3: Test method to determine energy effectiveness [Technical Report]
This corrected version of ISO 27327-2:2014 incorporates the following correction:
— the sentence “This first edition of ISO 27327-2:2014 cancels and replaces ISO 13347-1:2004 and
ISO 13347-2:2004” has been removed from the Foreword.
Introduction
The need for this part of ISO 27327 has been evident for some time. While a number of national standards
exist for the measurement of fan noise, none addressed the particular considerations required for the
noise testing of air curtain units.
Forming part of the ISO/TC 117 series of fan standards, this part of ISO 27327 deals with the determination
of the air curtain unit sound power level appropriate to a particular application. In describing the test
and rating procedures, numerous references are made to ISO 5801 and ISO 13347, as well as to other ISO
standards.
The test procedures described in this part of ISO 27327 relate to laboratory conditions. The measurement
of performance under site conditions is not included. Acoustic system effects can be considerable where
the airflow into and out of the air curtain unit is not free from swirl nor fully developed.
This part of ISO 27327 describes methods for determining sound power levels of air curtain units in one-
third-octave bandwidths and one-octave bandwidths.
Data obtained in accordance with this part of ISO 27327 can be used for the following purposes, amongst
others:
a) comparison of air curtain units which are similar in size and type;
b) comparison of air curtain units which are different in size, type, design, speed, etc.;
c) determining whether an air curtain unit is suitable for a specified upper limit of sound emission;
d) scaling air curtain unit noise from one size and speed to another size and speed of the same type of
air curtain unit;
e) prediction of sound pressure level in application of the air curtain unit;
f) engineering work to assist in developing machinery and equipment with lower sound emissions.
vi © ISO 2014 – All rights reserved
INTERNATIONAL STANDARD ISO 27327-2:2014(E)
Fans — Air curtain units —
Part 2:
Laboratory methods of testing for sound power
1 Scope
This part of ISO 27327 deals with the determination of the acoustic performance of air curtain units.
In addition, it can be used to determine the acoustic performance of air curtain units combined with an
ancillary device.
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.
ISO 266:1997, Acoustics — Preferred frequencies
ISO 3740:2000, Acoustics — Determination of sound power levels of noise sources — Guidelines for the use
of basic standards
ISO 3741:2010, Acoustics — Determination of sound power levels and sound energy levels of noise sources
using sound pressure — Precision methods for reverberation test rooms
ISO 3743-1, Acoustics — Determination of sound power levels and sound energy levels of noise sources
using sound pressure — Engineering methods for small movable sources in reverberant fields — Part 1:
Comparison method for a hard-walled test room
ISO 3743-2, Acoustics — Determination of sound power levels of noise sources using sound pressure —
Engineering methods for small, movable sources in reverberant fields — Part 2: Methods for special
reverberation test rooms
ISO 3747, Acoustics — Determination of sound power levels and sound energy levels of noise sources using
sound pressure — Engineering/survey methods for use in situ in a reverberant environment
ISO 5801:2007, Industrial fans — Performance testing using standardized airways
ISO 6926:1999, Acoustics — Requirements for the performance and calibration of reference sound sources
used for the determination of sound power levels
ISO 13347-1:2004, Industrial fans — Determination of fan sound power levels under standardized laboratory
conditions — Part 1: General overview
ISO 13347-2:2004, Industrial fans — Determination of fan sound power levels under standardized laboratory
conditions — Part 2: Reverberant room method
ISO 13349:2010, Fans — Vocabulary and definitions of categories
ISO 27327-1:2009, Fans — Air curtain units — Part 1: Laboratory methods of testing for aerodynamic
performance rating
3 Terms, definitions, symbols and units
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 3740, ISO 3747, ISO 5801,
ISO 13347-1, ISO 13347-2, ISO 13349, ISO 27327-1 and the following apply.
3.1.1
inlet sound power level
sound power level of an air curtain unit determined at the air curtain unit inlet in test installation type A
3.1.2
outlet sound power level
sound power level of an air curtain unit determined at the air curtain outlet in test installation type A
3.1.3
total sound power level
sound power level of an air curtain unit in test installation type E
3.1.4
casing sound power level
sound power level radiated from an air curtain unit casing
Note 1 to entry: If the air curtain unit drive is external to the air curtain unit casing, the casing sound power shall
include the sound power generated by and radiated from the air curtain unit drive.
3.1.5
frequency range of interest
frequency range including octave bands with centre frequencies between 63 Hz and 8 000 Hz and one-
third octave bands with centre frequencies between 50 Hz and 10 000 Hz
Note 1 to entry: For special purposes, the frequency range can be extended at either end, provided that the test
environment and instrument accuracy are satisfactory for use over the extended frequency range. For air curtain
units which radiate sound at predominantly high (or low) frequency, the frequency range of interest can be limited
in order to optimize the test facility and procedures.
3.1.6
blade passage frequency (BPF)
frequency of air curtain unit impeller blades passing a single fixed object
Note 1 to entry: The blade passage frequency is calculated by the following formula:
xn
BPF= Hz
where
x is the number of blades;
n is the fan speed, expressed in revolutions per minute.
3.1.7
chamber
enclosure used to regulate flow and absorb sound; it can also conform to air test chamber conditions
outlined in ISO 5801
2 © ISO 2014 – All rights reserved
3.1.8
air curtain unit inlet area
Α
summation of open areas (slots, holes, louvres, openings, etc.) through which air will flow into the air
curtain unit; normally a grille and/or air inlet opening
3.1.9
air curtain unit outlet area
Α
summation of open areas through which air will discharge out of the air curtain; normally a grille and/or
air outlet opening
3.1.10
reverberant room
enclosure meeting the requirements of Annex A and/or Annex B of ISO 13347-2:2004
3.1.11
standard air
air with a density of 1,2 kg/m
-3
Note 1 to entry: Standard air has a ratio of specific heats of 1,4 and a viscosity of 1,815 × 10 kg/m·s.
Note 2 to entry: Air at 16 °C dry bulb temperature, 50 % relative humidity, and 100 kPa barometric pressure has
these properties, but this is not part of the definition.
Note 3 to entry: Air at 20 °C dry bulb temperature, 50 % relative humidity, and 101,325 kPa barometric pressure
has these properties, but this is not part of the definition.
3.2 Air curtain unit sound power levels
Considering all possible combinations for installation conditions specified in Clause 4, five different
sound power level (L ) descriptions are defined in Table 1, e.g. L (A,in).
W W
Table 1 — Sound power levels
Number Suffix Description
1 (A,in) free-inlet sound power level, type A installation
2 (A,out) free-outlet sound power level; type A installation
total sound power level; type E installation (includes the contributions from the
3 (E,tot)
inlet, outlet, casing, and drive)
4 (A,in+cas) free-inlet sound power level plus casing-radiated noise; type A installation
5 (A,out+cas) free-outlet sound power level plus casing-radiated noise; type A installation
NOTE 1 All of these symbols can be used to indicate levels in one-third octave or octave frequency bands, as well as overall
sound power levels and A-weighted sound power levels, provided that the sound power to which the symbols relate is clearly
defined.
Where noise from the drive can contribute to the noise radiated from a casing, then this should be clearly stated by the
addition of “+dr”, e.g. L (A,in+cas+dr).
W
NOTE 2 Not all of the above levels need to be measured for a particular air curtain unit.
NOTE 3 Where some portion of inlet noise is included in the measurement of outlet noise, this shall be clearly stated by the
addition of “+in” or other similar notation, e.g. L (A,out+in).
W
3.3 Other symbols
For consistency and mutual understanding, it is recommended that the symbols and units shown in
Table 2 be used in reporting and calculation. Unless otherwise noted, the subscript number refers to the
mid-frequency of the octave band or one-third octave band number.
Table 2 — Symbols, units
Symbol Term SI unit
A air curtain unit inlet area m
A air curtain unit outlet area m
c speed of sound m/s
minimum distance between equipment under test and reverberant room measure-
D m
min
ment surface
f frequency Hz
−5
L sound pressure level, re 20 μPa (2 × 10 Pa) dB
p
L corrected sound pressure level of the air curtain unit dB
pc
recorded sound pressure level of room background as measured over the normal
L dB
pb
microphone path
L
background sound pressure level dB
pb
recorded sound pressure level of air curtain unit and room background as meas-
L dB
pm
ured over the normal microphone path
L corrected sound pressure level of the RSS dB
pq
recorded sound pressure level of the RSS and room background as measured over
L dB
pqm
the normal microphone path
L recorded sound pressure level of pure tone noise source dB
ps
−12
L sound power level, re 1 pW (1 × 10 W) dB
W
L sound power level of RSS dB
Wr
λ wavelength m
M Mach number dimensionless
p sound pressure Pa
−5
p reference sound pressure, 20 μPa (2 × 10 Pa) -
ref
s standard deviation dB
θ air temperature K
W sound power W
−12
W reference sound power, re 1 pW (1 × 10 W) dB
ref
4 Limitations on use
4.1 General
For reverberant room tests, the size of the air curtain unit is limited to less than 2 % of the room volume.
The test procedures specified in this part of ISO 27327 are intended principally for tests conducted
using standardized test configurations and under specified environments and conditions and cannot be
appropriate to site test conditions.
The air curtain unit installation conditions conform to the following two categories of installation types:
— type A: free inlet, free outlet;
Used when measuring inlet noise only or outlet noise only, i.e. (i) ducted ACUs or (ii) recessed ACUs
where the air inlet and air discharge of the ACU communicate with separate spaces (air inlet – ceiling
void; air discharge – space to be served)
— type E: free inlet, free outlet.
4 © ISO 2014 – All rights reserved
Used when measuring total noise; i.e. (i) surface-mounted ACUs or (ii) recessed ACUs where the air
inlet and air discharge of the ACU communicate with the same space
4.2 Noise source
The noise source is an air curtain unit. The noise measured can contain contributions from the fan drive
and transmission.
4.3 Character of noise
Steady broadband with discrete frequency tones.
4.4 Uncertainty
Engineering grade, as defined in ISO 3740.
4.5 Quantities to be measured
Sound pressure levels in one-third octave frequency bands at discrete microphone positions or on a
prescribed path.
Air curtain unit aerodynamic performance indicators, where applicable, e.g. rotational speed, static
pressure, and flow rate.
5 Measurement uncertainty
Measurements made in conformance with this part of ISO 27327 tend to result in standard deviations
which are equal to or less than those given in Table 3. These standard deviations take into account
the cumulative effects of all causes of measurement uncertainty such as source location, instrument
calibration, and sampling. They do not reflect variations in the sound power radiated by the air curtain
unit itself due to, for example, changes in installation type or manufacturing tolerances. For further
information, refer to Annex B.
Table 3 — Uncertainty in determination of the frequency-band sound power levels
One-third octave band Standard deviation
frequencies
Hz dB
63 6,0*
125 3,0
250 3,0
500 3,0
1000 3,0
2000 3,0
4000 3,0
8000 3,0
The uncertainties in Table 3 do not allow for the variations in sound power levels due to manufacturing
tolerances. These are consequent differences between one air curtain unit and another of the same
nominal design, rotational speed, etc. In any specifications which are part of a contract, it is necessary to
apply tolerances to sound values. These can be calculated for a normal distribution of data by multiplying
the quoted standard deviations by 2 to obtain 95 % confidence limits. A further deviation should also be
added to account for manufacturing tolerances, as described in ISO 13348.
NOTE 1 When octave-band data are calculated, the uncertainty of each octave band level will not be greater
than the largest uncertainty of the three constituent one-third octave bands.
NOTE 2 Only octave bands are shown for the reverberant room method in accordance with ISO 3743 (both
parts).
NOTE 3 Figures marked with * in Table 3 have only been added to ISO 3740:2000. For general purposes,
therefore, many existing rigs are designed to operate at a cut-off frequency of 100 Hz, thus giving the octave
bands of interest as those between 125 Hz and 8 000 Hz.
Some air curtain units have significant quantities of noise in the 63 Hz octave band, and, for special
purposes, it is permissible to extend the measurements to this band, provided the test environment and
instrument accuracy are satisfactory over this extended range.
6 © ISO 2014 – All rights reserved
The uncertainty given for these low frequencies can only be achieved by exercising extreme care, and
wherever possible, results should be restricted to octave bands of 125 Hz and above.
NOTE 4 Where the reverberant room is in full conformity with ISO 3743-1 (hard-walled test room), then the
uncertainty can be reduced.
NOTE 5 Sound power levels obtained by using the methods described herein are for a fully developed flow
into the air curtain unit without pre-swirl and straight-line flow out of the air curtain unit without swirl. Any
disturbance in the airflow will increase the levels in a real installation.
NOTE 6 The figures given in column 2 are taken from ISO 13347-2.
The standard deviations in Table 3 are equivalent to those obtained from the engineering methods
described in ISO 3743 (both parts) and ISO 3744, as appropriate. They are those which would result
from a set of measurements which were undertaken on a single air curtain unit in a large number of
different laboratories and include the cumulative effects of all causes of measurement uncertainty.
The repeatability of measurements in any one laboratory can be considerably better than the values in
Table 3 would indicate.
6 Instrumentation
6.1 General
Depending on the test method, the instrumentation shall be as specified in this part of ISO 27327,
together with ISO 3741, ISO 3743 (both parts), ISO 3744, ISO 13347-1, and ISO 13347-2. ISO 13347-1 also
details the requirements for the reference sound source which shall be used to qualify the test room and
shall be the basis of the substitution method.
Instrumentation shall be so designed as to determine the mean-square value of the sound pressure in
octave and/or one-third octave bands averaged over time and space.
6.1.1 Microphone
A microphone of a standardized sound level meter shall be used.
6.1.2 Microphone cable
The microphone/cable system shall be such that the sensitivity does not change with temperature in the
range encountered in the test. Cable flexing due to either microphone traversing or airflow across the
cable should not introduce cable noise which interferes with the measurements.
6.1.3 Sound level meter or other microphone amplifier
The sound level meter or other amplifier used to amplify the microphone signal shall comply with the
electrical requirements for sound level meters. The flat response shall be used.
6.2 Frequency analyser
The frequency analyser shall have the capacity of frequency analysing into one-third octave bandwidths
in accordance with ISO 266.
6.3 Turbulence screens and windshields
6.3.1 Windshields
A microphone exposed to excessive air velocity will give a falsely high reading. This can be rectified by
fitting the microphone with a nose cone or a foam ball.
If the air velocity over the microphone is greater than 1 m/s, a nose cone or foam ball shall be used. If a
foam ball is used, the air velocity over the foam ball shall not exceed 15 m/s.
6.3.2 Wind-generated false noise
The flow of an airstream over a microphone fitted with a nose cone or foam ball will still generate an
apparent change in sound pressure level at the microphone, even though it is reduced when compared
to an unshielded microphone. This change is not attributable to the air curtain unit but is a function of
microphone design.
6.4 Reference sound source (RSS)
A calibrated RSS shall conform to the requirements of Annex C.
7 Test procedure
7.1 Comparison method
The test method is based on a reference sound source (RSS) substitution for the determination of sound
power. The reference documents for this method are ISO 3743-1 and ISO 3743-2.
Application of the test method requires that the air curtain unit to be tested be set in position in a test
room, which is qualified according to the requirements of Annex E.
Once the test room has been qualified, sound pressure levels are recorded with the RSS operating.
The air curtain unit is then operated without the RSS in operation at the given test speed and the air
curtain unit sound pressure levels are recorded. Since the sound power levels of the RSS are known,
the substitution method is used to determine the sound power levels of the air curtain unit for each
operating point.
7.2 Direct method
The test method is based on measuring the reverberation times of the reverberation test room and using
this and the measured test room volume to calculate sound power levels from the sound pressure levels
produced by the air curtain unit under test.
The resulting sound pressure levels are sampled, filtered into one-third octave band widths, integrated,
and averaged by means of a real time analyser using a spaced array of microphones. The value obtained
at any particular frequency is then corrected into sound power levels using a mathematical expression.
Octave band sound power levels are obtained by the logarithmic summation of the three equivalent one-
third octave bands.
The reference document for this method is ISO 3741.
8 Acoustic environment
8.1 Test environment
The test environment shall be a reverberant environment.
8.2 Reverberant room
An enclosure meeting the requirements of Annex E is mandatory for the purposes of this part of
ISO 27327. An enclosure meeting the requirements of Annex F is recommended for broadband sound
testing and is mandatory for the purpose of investigating pure tones and narrow bands.
8 © ISO 2014 – All rights reserved
9 Air curtain unit installation conditions
The measurement procedures specified in this part of ISO 27327 cover the following air curtain unit
installations (see Clause 4):
— free inlet/free outlet (type A);
— free inlet/free outlet (type E).
10 Air curtain unit operating conditions
10.1 General
The noise generated by an air curtain unit is related to its operating conditions, i.e. its rotational speed,
air curtain unit static pressure, and airflow rate. It is important that the aerodynamic duty is known
when acoustic measurements are being made. Care is required to ensure that methods of determining
or controlling the aerodynamic performance do not affect the noise generated by the fan or interfere
with the acoustical measurements.
10.2 Measurement of ambient conditions
The ambient air conditions of temperature, pressure, and humidity shall be within the limits specified
in the appropriate standards ISO 3743 (both parts), ISO 3744, and ISO 3745.
10.3 Air curtain unit rotational speed
The air curtain unit rotational speed shall be measured and held steady (within 1 % change) during the
sound test. The fan rotational speed during the test shall be within 5 % of the specified rotational speed
to minimize the change in fan sound power when applying the conversion rules.
When it is not possible to test an air curtain unit within these limits, an indirect test at a different speed
is permitted, provided that the test is reported at the test speed and then scaled to the specified or
nominal speed (see Annex A).
10.4 Determination of air curtain unit aerodynamic operating point
The identification of the operating point shall preferably be by measurement of air curtain unit static
pressure using one of the methods specified in ISO 27327-1. The flow rate at the operating point can be
inferred, indirectly, by a determination of air curtain unit static pressure.
10.5 Control of air curtain unit operating condition
A throttling device shall be used to control the operating point. The sound level in the test environment
generated by the throttling device shall be at least 10 dB below the measured sound level from the air
curtain unit under test. The throttle arrangement shall be arranged integrally with the test chamber.
11 Test setup
11.1 Setup categories
A number of specific air curtain unit test setups are allowed and are shown in Figures 1, 2, 3, 4, and
5. They are determined by the airflow direction and the particular mounting arrangement of the test
device. The air curtain unit sound pressure levels are measured in a reverberant room, which can be
connected to a chamber or any other system to provide control and measurement of the air curtain unit
air volume flow rate.
2 3
Sound/Vibration Isolation
Key
1 air curtain unit
2 reverberant room
3 testing chamber
4 air curtain unit inlet
5 air curtain unit outlet
6 optional secondary air curtain unit inlet
Figure 1 — Installation Type A Outlet test setup for air curtain unit outlet sound measurement
10 © ISO 2014 – All rights reserved
Sound/Vibration Isolation
Key
1 air curtain unit
2 reverberant room
3 testing chamber
4 air curtain unit inlet
5 air curtain unit outlet
6 optional secondary air curtain unit inlet
Figure 2 — Installation Type A Inlet test setup for air curtain unit inlet sound measurement
~10°
1 4
Key
1 air curtain unit
2 microphone path
3 reverberant room
4 air curtain unit inlet
5 air curtain unit outlet (generally pointed toward the centre of the room)
Figure 3 — Installation Type E test setup for air curtain unit total sound measurement
12 © ISO 2014 – All rights reserved
Dimensions in metres
1 1
≥3,0
D
MIN
d
D
D
MIN
MIN
N
a
d
a) Side elevation b) Front elevation
Key
1 reverberant room walls
2 ACU
3 ACU inlet
4 ACU discharge nozzle
5 sound/vibration isolating pads
a
Airflow.
Figure 4 — Installation Type E test setup for vertical air curtain unit total sound measurement
ed
D = 4 (1)
min
π
For air curtain units without a rectangular inlet, substitute the actual value of the inlet area for ed in
Formula (1).
For air curtain units with multiple inlets, substitute the sum of all inlet areas for ed in Formula (1).
The reverberant room and placement of the air curtain unit shall meet all requirements of ISO 13347-2.
e
N
w
D
MIN
min
min
min min
a) Side elevation b) Front elevation
Key
1 reverberant room walls
2 ACU inlet (inlet area = e×d)
3 support frame
4 ACU
5 ACU air discharge nozzle
a
Airflow.
Figure 5 — Installation Type E test setup for horizontal air curtain unit total sound
measurement
11.2 Sound pressure levels
11.2.1 Sound pressure levels, background (L )
pb
This includes sound pressure levels measured in the test room with the air curtain unit off. The
background noise includes all noise sources not directly associated with air curtain unit sound. Examples
of background sources are noise due to the motion of the microphone and any noise due to external
sources. Efforts should be made to keep the background noise level at a minimum.
11.2.2 Sound pressure levels, RSS (L )
pqm
These are the sound pressure levels in the test room with only the RSS operating. The levels include the
background noise.
11.2.3 Sound pressure levels, air curtain unit (L )
pm
For a set of tests at various air curtain unit points of operation, L and L above need to be observed
pb pqm
once, while L shall be determined for each operating point.
pm
NOTE 1 The observations above are valid only when taken in a room that has passed the room qualification
procedures outlined in Annex E or Annex F.
NOTE 2 For further information on symbols, refer to ISO 13347-1.
14 © ISO 2014 – All rights reserved
11.3 Aerodynamic performance
The control and measurement of the air curtain unit operating point on the fan characteristic shall be
performed using one of the methods specified in ISO 27327-1.
11.4 Test conditions
The test conditions shall be as nearly as possible the same for all sound pressure level readings. Operation
of the microphone traverse and any rotating boom shall be the same for all readings. Observers and
operators should not be in the test room during measurements, but if absolutely necessary, they shall
be away from the sound source and remain in the same position for all tests. Readings shall be a time-
weighted average over an integral number of microphone swings. The time span used shall be sufficient
to provide a constant value and shall be a minimum of 30 s for frequency bands of 160 Hz and below and
a minimum of 15 s for frequency bands of 200 Hz and above.
11.5 Mounting methods
The method of mounting air curtain units of connecting them to non-integral drivers and of connecting
them to airflow test facilities is not specified. Any conventional method can be used, including vibration
isolation devices and short flexible connectors. Other than these, sound and vibration absorptive
material cannot be incorporated in the test air curtain unit unless it is a standard part of the unit.
Driving motor and drive, when not an integral part of the air curtain unit, can be damped or enclosed in
any manner that does not expose sound absorption material to the test room. When the driving motor
and drive are an integral part of the test unit, they cannot be treated in any manner, and normal belt
tensions and bearings shall be used.
If the air curtain unit is intended to be mounted horizontally in use, the test unit shall be tested in
this orientation. It shall be installed using the fixing points and method of suspension/anchorage as
recommend
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