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

General Information

Status
Published
Publication Date
05-Feb-2014
Technical Committee
Current Stage
9093 - International Standard confirmed
Start Date
18-Sep-2019
Completion Date
18-Sep-2019
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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 27327-2:2014(E)
ISO 2014
---------------------- Page: 1 ----------------------
ISO 27327-2:2014(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2014

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form

or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior

written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of

the requester.
ISO copyright office
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Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
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Published in Switzerland
ii © ISO 2014 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 27327-2:2014(E)
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

© ISO 2014 – All rights reserved iii
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ISO 27327-2:2014(E)

13.4 Background corrections ...............................................................................................................................................................20

13.5 Sound power level, L .................................................................................................................................................................20

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
---------------------- Page: 4 ----------------------
ISO 27327-2:2014(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

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

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation 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.
© ISO 2014 – All rights reserved v
---------------------- Page: 5 ----------------------
ISO 27327-2:2014(E)
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
---------------------- Page: 6 ----------------------
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
© ISO 2014 – All rights reserved 1
---------------------- Page: 7 ----------------------
ISO 27327-2:2014(E)
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:

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
---------------------- Page: 8 ----------------------
ISO 27327-2:2014(E)
3.1.8
air curtain unit inlet area

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

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 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).

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).
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.
© ISO 2014 – All rights reserved 3
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ISO 27327-2:2014(E)
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
L sound pressure level, re 20 μPa (2 × 10 Pa) dB
L corrected sound pressure level of the air curtain unit dB
recorded sound pressure level of room background as measured over the normal
L dB
microphone path
background sound pressure level dB
recorded sound pressure level of air curtain unit and room background as meas-
L dB
ured over the normal microphone path
L corrected sound pressure level of the RSS dB
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
−12
L sound power level, re 1 pW (1 × 10 W) dB
L sound power level of RSS dB
λ wavelength m
M Mach number dimensionless
p sound pressure Pa
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
---------------------- Page: 10 ----------------------
ISO 27327-2:2014(E)

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.
© ISO 2014 – All rights reserved 5
---------------------- Page: 11 ----------------------
ISO 27327-2:2014(E)
Table 3 — Uncertainty in determination of the frequency-band sound power levels
One-third octave band Standard deviation
frequencies
Hz dB
63 6,0*
100
125 3,0
160
200
250 3,0
315
400
500 3,0
630
800
1000 3,0
1250
1600
2000 3,0
2500
3150
4000 3,0
5000
6300
8000 3,0
10000

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 n
...

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
---------------------- Page: 1 ----------------------
ISO/DIS 27327-2
Copyright notice

This ISO document is a Draft International Standard and is copyright-protected by ISO. Except as permitted

under the applicable laws of the user’s country, neither this ISO draft nor any extract from it may be

reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic,

photocopying, recording or otherwise, without prior written permission being secured.

Requests for permission to reproduce should be addressed to either ISO at the address below or ISO’s

member body in the country of the requester.
ISO copyright office
Case postale 56  CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Reproduction may be subject to royalty payments or a licensing agreement.
Violators may be prosecuted.
ii © ISO 2012 – All rights reserved
---------------------- Page: 2 ----------------------
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

11.2.2  Sound pressure levels, RSS (L ) .................................................................................................. 15

pqm

11.2.3  Sound pressure levels, air curtain unit (L )...................................................................................... 15

11.3  Aerodynamic performance ................................................................................................................. 15

11.4  Test conditions .................................................................................................................................... 15

11.5  Mounting methods .............................................................................................................................. 16

11.6  Microphone travel or positions .......................................................................................................... 17

© ISO 2011 – All rights reserved iii
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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

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

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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

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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
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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.

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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
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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.
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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

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

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

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ISO/CD 27327-2
addition of +dr e.g., L (E,cas + dr).

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 inclu
...

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