Acoustics - Determination of sound power radiated into a duct by fans and other air-moving devices - In-duct method (ISO 5136:2003)

This International Standard specifies a method for testing ducted fans and other air-moving devices to determine the sound power radiated into an anechoically terminated duct on the inlet and/or outlet side of the equipment. The method is applicable to fans which emit steady, broad-band, narrow-band and discrete-frequency sound and to air temperatures between - 50 °C and + 70 °C. The test duct diameter range is from 0,15 m to 2 m. Test methods for small (d 2 m) test ducts are described in the informative Annexes H and I, respectively. The maximum mean flow velocity at the microphone head for which the method is suitable depends on the type of microphone shield used, and is as follows: - foam ball 15 m/s; - nose cone 20 m/s; - sampling tube 40 m/s. Above these values the suppression of turbulent pressure fluctuations by the microphone shield (see 3.9) may be insufficient. It is expected that sound power tests will be conducted in conjunction with airflow performance tests in accordance with ISO 5801. The ducting arrangement will therefore normally incorporate a "star" type flow straightener on the outlet side of the fan which will minimize swirl (see 7.3). Where it is permissible to delete the straightener as, for example, with large fans to installation category C according to ISO 5801:1997, the method is limited to a swirl angle of 15°. (An example of a method for determining the angle of swirl is given in Annex J.).

Akustik - Bestimmung der von Ventilatoren und anderen Strömungsmaschinen in Kanäle abgestrahlten Schallleistung - Kanalverfahren (ISO 5136:2003)

1.1 Allgemeines
Diese Internationale Norm legt ein Verfahren zur Bestimmung der Schallleistung fest, die von kanalgebundenen
Ventilatoren und anderen Strömungsmaschinen in einen reflexionsarm endenden Kanal ansaugund/
oder ausblasseitig abgestrahlt werden.
ANMERKUNG 1 Der Einfachheit halber steht der Begriff „Ventilator“ im nachfolgenden Text für „Ventilator oder andere
Strömungsmaschine“.
Das Verfahren ist auf Ventilatoren anwendbar, die breitbandigen, schmalbandigen oder tonalen Dauerschall
aussenden. Sie gilt für Lufttemperaturen von −50 °bis +70 C. Der Bereich der Messkanaldurchmesser
erstreckt sich von 0,15 m bis 2 m. Messverfahren für kleinere (d < 0,15 m) und größere (d > 2 m) Messkanäle
sind in den informativen Anhängen H bzw. I beschrieben.
Die höchstzulässige mittlere Strömungsgeschwindigkeit am Mikrofonkopf, bei der das Verfahren anwendbar
ist, hängt folgendermaßen von der Art des Mikrofonwindschirms ab:
- Schaumstoff-Windball: 15 m/s
- Nasenkonus: 20 m/s
- Schlitzrohrsonde: 40 m/s
Oberhalb dieser Werte kann die Unterdrückung durch Turbulenz am Mikrofon verursachter Druckschwankungen
durch den Mikrofonwindschirm (siehe 3.9) unzureichend sein.
Es wird erwartet, dass Schallleistungsmessungen im Zusammenhang mit Luftstromleistungsmessungen nach
ISO 5801 durchgeführt werden. Die Kanalanordnung wird daher normalerweise einen sternförmigen
Strömungsgleichrichter auf der Ausblasseite des Ventilators aufweisen, der drallmindernd wirkt (siehe 7.3).
Wo es zulässig ist, auf den Gleichrichter zu verzichten, z. B. bei großen Ventilatoren der Einbaukategorie C
nach ISO 5801:1997, beträgt der höchstzulässige Drallwinkel 15°. (Ein Beispiel für ein Verfahren zur Bestimmung
des Drallwinkels ist Anhang J zu entnehmen.)
ANMERKUNG 2 Die in ISO 5801 definierten Einbaukategorien besagen, dass der Ventilator entweder nur ausblasseitig
(Kategorie B), nur ansaugseitig (Kategorie C) oder ausblas- und ansaugseitig (Kategorie D) mit einem Kanal verbunden
ist.

Acoustique - Détermination de la puissance acoustique rayonnée dans un conduit par des ventilateurs et d'autres systèmes de ventilation - Méthode en conduit (ISO 5136:2003)

L'ISO 5136 prescrit une méthode d'essais des ventilateurs et autres systèmes de ventilation en conduit, en vue de déterminer la puissance acoustique rayonnée dans un conduit ayant une terminaison anéchoïque à l'aspiration et/ou au refoulement.
La méthode est applicable aux ventilateurs qui émettent des bruits stables à large bande, à bande étroite et à fréquence discrète. Elle s'applique pour des températures d'air comprises entre - 50 °C et + 70 °C. Le diamètre du conduit de mesurage est compris entre 0,15 m et 2 m. Les méthodes de mesurage qui s'appliquent aux conduits de mesurage de petite (d < 0,15 m) et de grande (d > 2 m) taille sont fournies respectivement dans les annexes H et I.
La vitesse maximale de l'écoulement moyen au droit du microphone pour l'application de la méthode dépend du type de protection utilisé. Cette protection peut être l'un des trois dispositifs suivants :
boule antivent 15 m/s ;
ogive antivent 20 m/s ;
sonde microphonique 40 m/s.
Au-delà de ces valeurs, l'atténuation des fluctuations de pression turbulente par la protection microphonique peut s'avérer insuffisante.
La source de bruit à laquelle s'applique la méthode décrite dans l'ISO 5136 est un ventilateur dont au moins une ouïe est raccordée à un conduit. Elle peut également s'appliquer à d'autres dispositifs combinant un ventilateur et un atténuateur, ou à des équipements intégrant des ventilateurs pouvant être assimilés à des « boîtes noires ».
Exemples de ventilateurs et d'équipements concernés par l'ISO 5136 :
ventilateurs centrifuges à enveloppe,
ventilateurs hélicoïdes à enveloppe,
ventilateurs mixtes à enveloppe,
centrales de traitement d'air raccordées,
dépoussiéreurs raccordés,
unités de conditionnement d'air raccordées, et
fours raccordés.
L'ISO 5136 est également applicable à d'autres sources aérodynamiques telles que plénums, registres et dispositifs de réglage de débit, sous réserve que passe un courant d'air discret induit par un ventilateur auxiliaire, et à condition que le rapport signal/bruit des pressions acoustiques sur les fluctuations de pression turbulente dans le conduit de mesurage soit d'au moins 6 dB.
Elle ne s'applique pas aux ventilateurs ou équipements qui ne sont pas raccordés à un conduit.

Akustika - Določanje zvočne moči, ki jo v kanal sevajo ventilator in drugi stroji za transport zraka - Metoda za merjenje v kanalu (ISO 5136:2003)

General Information

Status
Published
Public Enquiry End Date
14-Jun-2009
Publication Date
12-Oct-2009
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
28-Aug-2009
Due Date
02-Nov-2009
Completion Date
13-Oct-2009

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SLOVENSKI STANDARD
SIST EN ISO 5136:2009
01-november-2009
1DGRPHãþD
SIST EN ISO 5136:2004

$NXVWLND'RORþDQMH]YRþQHPRþLNLMRYNDQDOVHYDMRYHQWLODWRULQGUXJLVWURML]D

WUDQVSRUW]UDND0HWRGD]DPHUMHQMHYNDQDOX ,62

Acoustics - Determination of sound power radiated into a duct by fans and other air-

moving devices - In-duct method (ISO 5136:2003)

Akustik - Bestimmung der von Ventilatoren und anderen Strömungsmaschinen in Kanäle

abgestrahlten Schallleistung - Kanalverfahren (ISO 5136:2003)

Acoustique - Détermination de la puissance acoustique rayonnée dans un conduit par

des ventilateurs et d'autres systèmes de ventilation - Méthode en conduit (ISO
5136:2003)
Ta slovenski standard je istoveten z: EN ISO 5136:2009
ICS:
17.140.20 Emisija hrupa naprav in Noise emitted by machines
opreme and equipment
23.120 =UDþQLNL9HWUQLNL.OLPDWVNH Ventilators. Fans. Air-
QDSUDYH conditioners
SIST EN ISO 5136:2009 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN ISO 5136:2009
---------------------- Page: 2 ----------------------
SIST EN ISO 5136:2009
EUROPEAN STANDARD
EN ISO 5136
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2009
ICS 17.140.20; 23.120 Supersedes EN ISO 5136:2003
English Version
Acoustics - Determination of sound power radiated into a duct by
fans and other air-moving devices - In-duct method (ISO
5136:2003)

Acoustique - Détermination de la puissance acoustique Akustik - Bestimmung der von Ventilatoren und anderen

rayonnée dans un conduit par des ventilateurs et d'autres Strömungsmaschinen in Kanäle abgestrahlten

systèmes de ventilation - Méthode en conduit (ISO Schallleistung - Kanalverfahren (ISO 5136:2003)

5136:2003)
This European Standard was approved by CEN on 20 July 2009.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European

Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national

standards may be obtained on application to the CEN Management Centre or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation

under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the

official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,

France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,

Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2009 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 5136:2009: E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN ISO 5136:2009
EN ISO 5136:2009 (E)
Contents Page

Foreword ..............................................................................................................................................................3

Annex ZA (informative) Relationship between this European Standard and the Essential

Requirements of EU Directive 98/37/EC ..............................................................................................4

Annex ZB (informative) Relationship between this European Standard and the Essential

Requirements of EU Directive 2006/42/EC ..........................................................................................5

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SIST EN ISO 5136:2009
EN ISO 5136:2009 (E)
Foreword

The text of ISO 5136:2003 has been prepared by Technical Committee ISO/TC 43 “Acoustics” of the

International Organization for Standardization (ISO) and has been taken over as EN ISO 5136:2009 by

Technical Committee CEN/TC 211 “Acoustics” the secretariat of which is held by DS.

This European Standard shall be given the status of a national standard, either by publication of an identical

text or by endorsement, at the latest by February 2010, and conflicting national standards shall be withdrawn

at the latest by February 2010.

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

rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.

This document supersedes EN ISO 5136:2003.

This document has been prepared under a mandate given to CEN by the European Commission and the

European Free Trade Association, and supports essential requirements of EC Directives.

For relationship with EC Directives, see informative Annexes ZA and ZB, which are integral parts of this

document.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following

countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech

Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,

Sweden, Switzerland and the United Kingdom.
Endorsement notice

The text of ISO 5136:2003 has been approved by CEN as a EN ISO 5136:2009 without any modification.

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SIST EN ISO 5136:2009
EN ISO 5136:2009 (E)
Annex ZA
(informative)
Relationship between this European Standard and the Essential
Requirements of EU Directive 98/37/EC

This European Standard has been prepared under a mandate given to CEN by the European Commission

and the European Free Trade Association to provide a means of conforming to Essential Requirements of the

New Approach Directive 98/37/EC, amended by 98/79/EC on machinery.

Once this standard is cited in the Official Journal of the European Communities under that Directive and has

been implemented as a national standard in at least one Member State, compliance with the normative

clauses of this standard confers, within the limits of the scope of this standard, a presumption of conformity

with the relevant Essential Requirements of that Directive and associated EFTA regulations.

WARNING - Other requirements and other EU Directives may be applicable to the product(s) falling within the

scope of this standard.
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SIST EN ISO 5136:2009
EN ISO 5136:2009 (E)
Annex ZB
(informative)
Relationship between this European Standard and the Essential
Requirements of EU Directive 2006/42/EC

This European Standard has been prepared under a mandate given to CEN by the European Commission

and the European Free Trade Association to provide a means of conforming to Essential Requirements of the

New Approach Directive 2006/42/EC on machinery.

Once this standard is cited in the Official Journal of the European Communities under that Directive and has

been implemented as a national standard in at least one Member State, compliance with the normative

clauses of this standard confers, within the limits of the scope of this standard, a presumption of conformity

with the relevant Essential Requirements of that Directive and associated EFTA regulations.

WARNING — Other requirements and other EU Directives may be applicable to the product(s) falling within

the scope of this standard.
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SIST EN ISO 5136:2009
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SIST EN ISO 5136:2009
INTERNATIONAL ISO
STANDARD 5136
Second edition
2003-04-01
Acoustics — Determination of sound
power radiated into a duct by fans and
other air-moving devices — In-duct
method
Acoustique — Détermination de la puissance acoustique rayonnée
dans un conduit par des ventilateurs et d'autres systèmes de
ventilation — Méthode en conduit
Reference number
ISO 5136:2003(E)
ISO 2003
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SIST EN ISO 5136:2009
ISO 5136:2003(E)
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ii © ISO 2003 — All rights reserved
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SIST EN ISO 5136:2009
ISO 5136:2003(E)
Contents Page

Foreword............................................................................................................................................................ iv

Introduction ........................................................................................................................................................ v

1 Scope...................................................................................................................................................... 1

1.1 General................................................................................................................................................... 1

1.2 Types of sound source......................................................................................................................... 1

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

3 Terms, definitions and symbols .......................................................................................................... 2

4 Uncertainty of the measurement method...........................................................................................7

5 Test facilities and instrumentation...................................................................................................... 8

5.1 General requirements ........................................................................................................................... 8

5.2 Duct specifications ............................................................................................................................... 9

5.3 Instrumentation ................................................................................................................................... 16

5.4 System calibration .............................................................................................................................. 19

6 Test arrangement ................................................................................................................................ 20

6.1 Sampling tube mounting.................................................................................................................... 20

6.2 Microphone position........................................................................................................................... 20

6.3 Operating condition control equipment ...........................................................................................21

7 Test procedure .................................................................................................................................... 21

7.1 Operating conditions .......................................................................................................................... 21

7.2 Sound pressure level readings.......................................................................................................... 21

7.3 Measurements with and without flow straightener on the outlet side .......................................... 22

7.4 Inlet side measurements — Large fans: installation category D (according to

ISO 5801:1997)..................................................................................................................................... 22

8 Calculations......................................................................................................................................... 23

8.1 Average sound pressure level........................................................................................................... 23

8.2 Sound power level .............................................................................................................................. 23

9 Information to be recorded ................................................................................................................ 24

10 Information to be reported ................................................................................................................. 24

Annex A (normative) Determination of the combined mean flow velocity and modal correction

C ........................................................................................................................................................ 25

3,4

Annex B (normative) Determination of the signal-to-noise ratio of sound vs. turbulent pressure

fluctuation in the test duct ................................................................................................................. 31

Annex C (normative) Computational procedures for calculating the A-weighted sound power level

from one-third-octave-band sound power levels............................................................................. 34

Annex D (informative) Example of calculation of C for a given duct diameter and mean flow

3,4

velocity................................................................................................................................................. 35

Annex E (informative) Guidelines for the design and construction of an anechoic termination............. 38

Annex F (informative) Evaluation of performance of anechoic terminations ............................................ 47

Annex G (informative) Sampling tube information........................................................................................ 50

Annex H (informative) Test method for small ducted fans........................................................................... 54

Annex I (informative) Test method for large ducted fans............................................................................. 58

Annex J (informative) Measurement of the swirl component ...................................................................... 65

Bibliography ..................................................................................................................................................... 66

© ISO 2003 — All rights reserved iii
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SIST EN ISO 5136:2009
ISO 5136:2003(E)
Foreword

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

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

technical committees. Each member body interested in a subject for which a technical committee has been

established has the right to be represented on that committee. International organizations, governmental and

non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the

International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standards

adopted by the technical committees are circulated to the member bodies for voting. Publication as an

International Standard requires approval by at least 75 % of the member bodies casting a vote.

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

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

ISO 5136 was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 1, Noise.

This second edition cancels and replaces the first edition (ISO 5136:1990), which has been technically revised.

iv © ISO 2003 — All rights reserved
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SIST EN ISO 5136:2009
ISO 5136:2003(E)
Introduction

This International Standard describes a procedure for the measurement of sound pressure levels in the inlet

or outlet ducts of a fan and a method to use these sound pressure levels to calculate the sound power levels

radiated by the fan to the duct system.

Annex A lists values of coefficients for the determination of the combined mean flow velocity and modal

correction. Annex B specifies two procedures for the determination of the signal-to-noise ratio of sound versus

turbulence. A computational procedure for the calculation of the A-weighted sound power level from one-third-

octave band levels is given in Annex C. Annex D shows an example of the calculation of the combined mean

flow velocity and modal correction.

The sound power radiated into a duct by a fan or other air-moving device depends to some extent on the type

of duct, characterized by its acoustical impedance. For a measurement method, the test duct has, therefore,

to be clearly specified. In this International Standard, the test duct is of circular cross-section and terminated

anechoically. Details of typical anechoic terminations are given in Annex E. The sound power obtained under

these special conditions is a representative value for actual applications, as the anechoic termination forms an

impedance about midway between the higher and lower impedances found in practice. The sound power

radiated in actual applications can, in theory, be estimated from data on air-moving devices and duct

impedances. Since this information is at present incomplete, these effects are not usually considered in

acoustical calculations.

In order to suppress the turbulent pressure fluctuations at the microphone, the use of a long cylindrical

windscreen (“sampling tube”) is preferred. The microphone, with the sampling tube, is mounted at a radial

position such that the sound pressure is well related to the sound power by the plane wave formula to an

acceptable extent, even in the frequency range in which higher-order acoustic modes are possible.

The uncertainty of measurement (see Clause 4) is given in terms of the standard deviation to be expected if

the measurements were repeated in many different laboratories.

The procedures for measuring the operating conditions (performance measurements) are not specified in

detail in this International Standard. The operating conditions are specified in ISO 5801.

This International Standard is one of a series specifying different methods for determining the sound power

levels of fans and other air-moving devices.

In general, the sound powers radiated from a fan inlet or outlet into free space and into a duct are different

because of the reflection of sound energy at the fan inlet or outlet plane when there is no connected duct. The

in-duct method according to this International Standard is suitable for determining the sound power radiated

into a duct by a fan inlet or outlet. The sound power radiated into free space by a fan inlet or outlet should be

determined using the a reverberation room method (ISO 3741, ISO 3743), a free-field method (ISO 3744,

ISO 3745, ISO 3746) or a sound intensity method (ISO 9614).
© ISO 2003 — All rights reserved v
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SIST EN ISO 5136:2009
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SIST EN ISO 5136:2009
INTERNATIONAL STANDARD ISO 5136:2003(E)
Acoustics — Determination of sound power radiated into a duct
by fans and other air-moving devices — In-duct method
1 Scope
1.1 General

This International Standard specifies a method for testing ducted fans and other air-moving devices to

determine the sound power radiated into an anechoically terminated duct on the inlet and/or outlet side of the

equipment.

NOTE 1 For the sake of brevity, wherever the term “fan” occurs in the text, it means “fan or other air-moving device”.

The method is applicable to fans which emit steady, broad-band, narrow-band and discrete-frequency sound

and to air temperatures between − 50 °C and + 70 °C. The test duct diameter range is from 0,15 m to 2 m.

Test methods for small (d < 0,15 m) and large (d > 2 m) test ducts are described in the informative Annexes H

and I, respectively.

The maximum mean flow velocity at the microphone head for which the method is suitable depends on the

type of microphone shield used, and is as follows:
 foam ball 15 m/s;
 nose cone 20 m/s;
 sampling tube 40 m/s.

Above these values the suppression of turbulent pressure fluctuations by the microphone shield (see 3.9) may

be insufficient.

It is expected that sound power tests will be conducted in conjunction with airflow performance tests in

accordance with ISO 5801. The ducting arrangement will therefore normally incorporate a “star” type flow

straightener on the outlet side of the fan which will minimize swirl (see 7.3). Where it is permissible to delete

the straightener as, for example, with large fans to installation category C according to ISO 5801:1997, the

method is limited to a swirl angle of 15°. (An example of a method for determining the angle of swirl is given in

Annex J.)

NOTE 2 The installation categories defined in ISO 5801 imply that the fan is either ducted on the outlet side only

(category B), on the inlet side only (category C) or on both sides (category D).
1.2 Types of sound source

The method described in this International Standard is applicable to a sound source in which a fan is

connected to ducts on at least one side. It is also applicable to other fan/attenuator combinations or equipment

incorporating fans which can be considered as “black boxes”.
Examples of fans and other equipment covered by this International Standard are
 ducted centrifugal fans,
 ducted axial flow fans,
© ISO 2003 — All rights reserved 1
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SIST EN ISO 5136:2009
ISO 5136:2003(E)
 ducted mixed-flow fans,
 ducted air-handling units,
 ducted dust-collection units,
 ducted air-conditioning units, and
 ducted furnaces.

This International Standard is also applicable to other aerodynamic sources such as boxes, dampers and

throttle devices provided that a quiet air flow delivered by an auxiliary fan is available, and the signal-to-noise

ratio of sound pressures to turbulent pressure fluctuations in the test duct is at least 6 dB (see 7.2.1).

An alternative method to determine the sound power level of the flow-generated noise of such aerodynamic

sound sources, which does not require the measurement of sound pressure in a flow environment, is

described in ISO 7235. The method was originally devised for the determination of the flow noise level of

ducted silencers. The sound power is determined in a reverberation room connected to the test duct via a

transition element.

In the case of ducted fans with closely coupled attenuators, the signal-to-noise ratio of sound pressures to

turbulent pressures may be insufficient when using the in-duct method. Therefore the method described in

ISO 7235 is recommended for such fan/attenuator combinations.
This International Standard is not applicable to non-ducted fans or equipment.
2 Normative references

The following referenced documents are indispensable for the application of this document. For dated

references, only the edition cited applies. For undated references, the latest edition of the referenced

document (including any amendments) applies.
ISO 266, Acoustics — Preferred frequencies
ISO 5801:1997, Industrial fans — Performance testing using standardized airways
IEC 60651:2001, Sound level meters
IEC 60942:1997, Electroacoustics — Sound calibrators
IEC 61260, Electroacoustics — Octave-band and fractional-octave-band filters
3 Terms, definitions and symbols

For the purpose of this document, the following terms and definitions apply. The symbols are given in Table 1.

3.1
fan inlet area
surface plane bounded by the upstream extremity of the fan

NOTE 1 The inlet area is, by convention, taken as the gross area in the inlet plane inside the casing. No deduction is

made for motors, fairings or other obstructions.
2 © ISO 2003 — All rights reserved
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SIST EN ISO 5136:2009
ISO 5136:2003(E)

NOTE 2 Where motors, fairings or other obstructions extend beyond an inlet or outlet flange at which the performance

for ducted installation is to be determined, the casing should be extended by a duct of the same size and shape as the

inlet or outlet and of sufficient length to cover the obstruction. The test airway dimensions should be measured from the

plane through the outermost extension of the obstruction as if this were the plane of the inlet or outlet flange.

NOTE 3 The fan inlet area is expressed in square metres (m ).
NOTE 4 Adapted from ISO 5801:1997.
3.2
fan outlet area
surface plane bounded by the downstream extremity of the fan

NOTE 1 The outlet area is, by convention, taken as the gross area in the outlet plane inside the casing. No deduction is

made for motors, fairings or other obstructions.

NOTE 2 Some free-outlet fans without casings have no well-defined outlet area. For the purpose of determining the

fan's dynamic pressure, a nominal area may then be defined and stated, e.g. the area within the ring of a propeller wall fan

or the circumferential outlet area of an open-running centrifugal impeller. The corresponding fan dynamic pressure and fan

pressure will also be nominal and should be so described.
NOTE 3 The fan outlet area is expressed in square metres (m ).
NOTE 4 Adapted from ISO 5801:1997.
3.3
ducts
any of the airways defined in 3.3.1, 3.3.2 and 3.3.3
3.3.1
test duct
duct in which the fan sound power is measured
NOTE The test duct has an anechoic termination.
3.3.2
terminating duct
duct opposite to the test duct, if both sides of the fan are ducted
NOTE The terminating duct has an anechoic termination.
3.3.3
intermediate duct

duct fitted on the intake side and on the discharge side of the fan to ensure desired flow conditions

NOTE The intermediate duct connects to the test duct or the terminating duct, if necessary by a transition section

(see Figure 7).
3.4
measurement plane
radial plane in the test duct in which the microphone diaphragm is located
3.5
sound pressure level
L = 10 lg dB (1)
© ISO 2003 — All rights reserved 3
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SIST EN ISO 5136:2009
ISO 5136:2003(E)

where p is the root mean square value of the sound pressure and the reference sound pressure p is equal

to 20 µPa

NOTE 1 The width of a restricted frequency band should be indicated, for example, octave-band sound pressure level,

one-third-octave-band sound pressure level.

NOTE 2 L , L and L are the sound pressure levels at each of the three measurement positions in the test duct.

p1 p2 p3

L is the spatially averaged sound pressure level obtained from averaging over the measurement positions in the test

duct. It may also be obtained from a continuous circumferential traverse (see 7.2.4).

L is the spatially averaged sound pressure level at the measurement plane, corrected for the combined free-field

response C (see Table 1 and 8.1).
NOTE 3 The sound pressure level is expressed in decibels (dB).
3.6
sound power level
L = 10 lg dB (2)
where P is the sound power and the reference sound power P is equal to 1 pW

NOTE 1 The width of a restricted frequency band should be indicated, for example, octave-band sound power level,

one-third-octave-band sound power level.
NOTE 2 The sound power level is expressed in decibels (dB).
3.7
fan sound power
sound power radiated into the test duct by the fan
3.8
frequency band range of interest
one-third-octave bands with centre frequencies between 50 Hz and 10 000 Hz

NOTE For information only, the frequency range of interest may be extended up to 20 000 Hz. For fans which radiate

predominantly high- or low-frequency sound, the frequency range of interes
...

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