Acoustics - Requirements for the performance and calibration of reference sound sources used for the determination of sound power levels (ISO 6926:2016)

ISO 6926:2016 specifies the acoustical performance requirements for reference sound sources:
-      temporal steadiness (stability) of the sound power output;
-      spectral characteristics;
-      directivity.
Temporal steadiness is defined in terms of the standard deviation of repeatability (see 5.2). The spectral characteristics can be verified in either a hemi-anechoic room or a reverberation test room from measurements of the frequency band sound power levels in accordance with this International Standard (see 5.4). The performance requirements on directivity index can only be verified in a hemi-anechoic room (see 5.5.)
ISO 6926:2016 also specifies procedures for providing level calibration data and uncertainty on a sound source intended for use as a reference sound source in terms of its sound power level under reference meteorological conditions as defined in Clause 4 in octave and in one-third-octave bands, and with frequency weighting A.
ISO 6926:2016 is titled as a calibration standard even though the method is conducted in a testing laboratory and the level calibration results are not directly traceable to national standards of measure in a strict metrological sense. Testing laboratories performing this method are not expected to meet all requirements normally associated with a calibration laboratory.
NOTE          ISO/IEC 17025[15] specifies different requirements for the competence of testing laboratories and calibration laboratories respectively. Laboratories testing reference sound sources in accordance with this International Standard would typically comply with the requirements for testing laboratories but not necessarily with those for calibration laboratories.
ISO 6926:2016 specifies methods to calibrate reference sound sources not only in a free field over a reflecting plane but also in reverberation test rooms at different distances from the boundary surfaces. For the position of the reference sound source on one reflecting plane, the two different test environments mentioned above are considered equivalent for frequency bands above or equal to 200 Hz. At 160 Hz and below, some systematic differences can occur (see 11.2). For frequencies below 100 Hz, an alternative calibration method using sound intensity is given.
The sound source can either be placed directly on the floor or mounted on a stand to be used at a certain elevation above the floor. According to this International Standard, stand-mounted sources are calibrated in reverberation test rooms. Floor-mounted sources are either calibrated in hemi-anechoic or in reverberation test rooms. For floor-mounted sources in hemi-anechoic rooms, this International Standard is valid only for sources whose maximum vertical dimension is less than 0,5 m and whose maximum horizontal dimension is less than 0,8 m. According to this International Standard, only floor-mounted reference sound sources can be used when carrying out measurements on a measurement surface. For reference sound sources to be used or calibrated under reverberant conditions, no such restrictions on maximum dimensions apply.

Akustik - Anforderungen an die Eigenschaften und die Kalibrierung von Vergleichsschallquellen für die Bestimmung von Schallleistungspegeln (ISO 6926:2016)

Diese Internationale Norm legt Anforderungen an die akustischen Eigenschaften von Vergleichsschallquellen fest:
   zeitliche Stabilität der abgestrahlten Schallleistung,
   Spektralverteilung,
   Richtcharakteristik.
Die zeitliche Stabilität ist als Wiederholstandardabweichung definiert (siehe 5.2). Die Spektral¬verteilung kann entweder in einem reflexionsarmen Halbraum oder in einem Hallraum auf der Grundlage von Messungen der Schallleistungspegel in Frequenzbändern nach dieser Internationalen Norm verifiziert werden (siehe 5.4). Die Anforderungen an das Richtwirkungsmaß können nur in einem reflexionsarmen Halbraum verifiziert werden (siehe 5.5).
In dieser Internationalen Norm sind außerdem Verfahren zur Bereitstellung von Daten zur Pegel¬kalibrierung und zur Bestimmung der Unsicherheit einer Schallquelle festgelegt, die hinsichtlich ihres Schallleistungs¬pegels unter den in Abschnitt 4 definierten meteorologischen Bezugsbedingungen in Oktav- und Terzbändern und mit der Frequenzbewertung A für den Einsatz als Vergleichsschallquelle vorgesehen ist.
Die vorliegende Internationale Norm wird als Kalibriernorm bezeichnet, obwohl das Verfahren in einem Prüflaboratorium (Prüfstand) durchgeführt wird und die Ergebnisse der Pegelkalibrierung nicht direkt im strengen messtechnischen Sinne auf nationale Messnormale rückführbar sind. Von den Prüf¬laboratorien, die dieses Verfahren durchführen, wird nicht erwartet, dass sie alle Anforderungen erfüllen, die üblicherweise an ein Kalibrierlaboratorium gestellt werden.
ANMERKUNG   ISO/IEC 17025 [15] legt verschiedene Anforderungen an die Kompetenz von Prüflaboratorien und Kalibrier¬laboratorien fest. Laboratorien, in denen Vergleichsschallquellen nach dieser Internationalen Norm geprüft werden, erfüllen typischerweise die Anforderungen an Prüflaboratorien, nicht jedoch notwendigerweise diejenigen an Kalibrierlaboratorien.
Diese Internationale Norm legt Verfahren für die Kalibrierung von Vergleichsschallquellen nicht nur im freien Feld über einer reflektierenden Ebene, sondern auch in Hallräumen bei verschiedenen Abständen zu den Begrenzungsflächen fest. Für die Position der Vergleichsschallquelle auf einer reflektierenden Ebene können die beiden vorstehend genannten Prüfumgebungen für Frequenzbänder ab mindestens 200 Hz als gleich¬wertig angesehen werden. Bei 160 Hz und darunter können gewisse systematische Unterschiede auftreten (siehe 11.2). Für Frequenzen unterhalb von 100 Hz ist ein alternatives Kalibrierverfahren unter Anwendung der Schallintensität angegeben.
Die Schallquelle kann entweder direkt auf dem Boden aufgestellt oder zur Verwendung in einer bestimmten Höhe über dem Boden an einem Ständer befestigt werden. Nach dieser Internationalen Norm werden an einem Ständer befestigte Schallquellen in Hallräumen kalibriert. Auf dem Boden aufgestellte Schallquellen werden entweder in reflexionsarmen Halbräumen oder in Hallräumen kalibriert. Bei auf dem Boden aufgestellten Schallquellen in reflexionsarmen Halbräumen gilt diese Internationale Norm nur für Schall¬quellen, deren größtes vertikales Maß weniger als 0,5 m und deren größtes horizontales Maß weniger als 0,8 m beträgt. Nach dieser Internationalen Norm können für Messungen auf einer Messfläche nur auf dem Boden aufgestellte Vergleichsschallquellen verwendet werden. Für Vergleichsschallquellen, die in Hallräumen verwendet oder kalibriert werden sollen, gelten die genannten Einschränkungen für die Höchstmaße nicht.

Acoustique - Prescriptions relatives aux performances et à l'étalonnage des sources sonores de référence pour la détermination des niveaux de puissance acoustique (ISO 6926:2016)

ISO 6926:2016 spécifie les exigences relatives aux performances acoustiques des sources sonores de référence:
-      stabilité dans le temps de la puissance acoustique émise;
-      caractéristiques spectrales;
-      directivité.
La stabilité dans le temps est définie en termes d'écart-type de répétabilité (voir 5.2). Les caractéristiques spectrales peuvent être vérifiées soit dans une salle semi-anéchoïque, soit dans une salle d'essai réverbérante, à partir du mesurage des niveaux de puissance acoustique par bande de fréquences conformément à la présente Norme internationale (voir 5.4). Les exigences de performance relatives à l'indice de directivité ne peuvent être vérifiées que dans une salle semi-anéchoïque (voir 5.5).
ISO 6926:2016 définit également des modes opératoires pour obtenir les données et l'incertitude de l'étalonnage des niveaux d'une source sonore destinée à être utilisée comme source sonore de référence, le résultat étant exprimé par un niveau de puissance acoustique par bandes d'octave et de tiers d'octave, et avec la pondération fréquentielle A, dans les conditions météorologiques de référence telles que définies à l'Article 4.
ISO 6926:2016 est appelée norme d'étalonnage bien que la méthode soit applicable dans un laboratoire d'essai et que les résultats de l'étalonnage des niveaux ne se rapportent pas directement à des normes nationales de mesure dans un sens métrologique strict. Il n'est pas attendu que les laboratoires d'essai appliquant cette méthode satisfassent à toutes les exigences normalement associées à un laboratoire d'étalonnage.
NOTE          L'ISO/IEC 17025[15] spécifie différentes exigences pour les compétences respectives des laboratoires d'essai et des laboratoires d'étalonnage. Les laboratoires qui soumettent à l'essai des sources sonores de référence conformément à la présente Norme internationale doivent normalement se conformer aux exigences des laboratoires d'essai, mais pas nécessairement à celles des laboratoires d'étalonnage.
ISO 6926:2016 spécifie des méthodes d'étalonnage pour les sources sonores de référence non seulement en champ libre au-dessus d'un plan réfléchissant, mais aussi dans des salles d'essais réverbérantes à diverses distances des surfaces délimitantes. Pour la position de la source sonore de référence au-dessus d'un plan réfléchissant unique, les deux environnements d'essai différents mentionnés ci-dessus sont considérés comme équivalents pour les bandes de fréquences supérieures ou égales à 200 Hz. À 160 Hz et au-dessous, des écarts systématiques peuvent exister (voir 11.2). Pour les fréquences inférieures à 100 Hz, une autre méthode d'étalonnage utilisant l'intensité acoustique est donnée.
La source sonore peut être conçue spécifiquement soit pour être posée directement sur le sol, soit pour être montée sur un support afin d'être utilisée à une certaine distance du sol. Conformément à la présente Norme internationale, les sources montées sur un support sont étalonnées dans des salles d'essai réverbérantes. Les sources au sol sont étalonnées dans des salles d'essai semi-anéchoïques ou réverbérantes. Pour des sources au sol en salles semi-anéchoïques, la présente Norme internationale s'applique uniquement aux sources dont la dimension verticale maximale est inférieure à 0,5 m et dont la dimension horizontale maximale est inférieure à 0,8 m. Conformément à la présente Norme internationale, seules les sources sonores de référence posées au sol peuvent être utilisées pour eff

Akustika - Zahteve za lastnosti in umerjanje referenčnih virov zvoka pri ugotavljanju ravni zvočnih moči (ISO 6926:2016)

Ta mednarodni standard določa zahteve glede akustičnih lastnosti za referenčne vire zvoka:
– časovna stalnost (stabilnost) izhoda zvočne moči;
– spektralne značilnosti;
– usmerjenost.
Časovna stalnost je določena v smislu standardnega odklona ponovljivosti (glej točko 5.2). Spektralne značilnosti je mogoče potrditi v polgluhem prostoru ali v prostoru za preizkus odmevov iz meritev ravni zvočne moči v frekvenčnem pasu skladno s tem mednarodnim standardom (glej točko 5.4). Zahteve glede lastnosti v zvezi z indeksom usmerjenosti je mogoče potrditi le v polgluhem prostoru (glej točko 5.5).
Ta mednarodni standard določa tudi postopke za zagotavljanje podatkov za umerjanje ravni in negotovosti pri zvočnem viru, namenjenem za uporabo kot referenčni zvočni vir v smislu njegove ravni zvočne moči pod referenčnimi meteorološkimi pogoji, kot je določeno v točki 4 za oktavne in terčne pasove ter s frekvenčnim vrednotenjem A.
Ta mednarodni standard je poimenovan kot standard umerjanja, čeprav je metoda izvedena v laboratoriju za preskušanje in iz rezultatov umerjanja ravni ni mogoče neposredno ugotoviti državnih standardov mere v strogem meroslovnem smislu. Od laboratorijev za preskušanje, ki uporabljajo to metodo, se ne pričakuje izpolnjevanje vseh zahtev, ki so običajno povezane z laboratoriji za umerjanje.
OPOMBA: Standard ISO/IEC 17025[15] določa različne zahteve za usposobljenost laboratorijev za preskušanje in umerjanje. Laboratoriji, kjer se preskušajo referenčni viri zvoka v skladu s tem mednarodnim standardom, so običajno skladni z zahtevami za laboratorije za preskušanje, ne pa nujno z zahtevami za laboratorije za umerjanje.
Ta mednarodni standard določa metode za umerjanje referenčnih virov zvoka ne le v prostem polju nad odsevno ravnino, temveč tudi v prostorih za preskus odmevov pri različnih razdaljah od mejnih površin. Za položaj referenčnega vira zvoka na eni odsevni ravnini se zgoraj omenjeni različni okolji preskusa štejeta kot enakovredni pri frekvenčnih pasovih 200 Hz ali višjih. Pri 160 Hz in nižjih vrednostih je mogoče, da pride do nekaterih sistemskih razlik (glej točko 11.2). Za frekvence pod 100 Hz je na voljo drugačna metoda umerjanja z intenzivnostjo zvoka.
Zvočni vir je mogoče postaviti neposredno na tla ali na stojalo, ki se uporablja na določeni višini. Po tem mednarodnem standardu se viri na stojalu umerjajo v prostorih za preskus odmevov. Viri na tleh se umerjajo v polgluhih prostorih ali prostorih za preskus odmevov. Pri talnih virih v polgluhih prostorih ta mednarodni standard velja le za vire, katerih največja navpična dolžina je manjša od 0,5 m, največja vodoravna dolžina pa manjša od 0,8 m. Po tem mednarodnem standardu je mogoče pri izvajanju meritev na površini za merjenje uporabljati le talne referenčne vire zvoka. Za referenčne vire zvoka, ki se bodo uporabljali ali umerjali v prostoru, kjer je prisoten odmev, takšne omejitve ali največje dolžine ne veljajo.

General Information

Status
Published
Publication Date
09-Feb-2016
Technical Committee
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
01-Sep-2015

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SLOVENSKI STANDARD
SIST EN ISO 6926:2016
01-april-2016
1DGRPHãþD
SIST EN ISO 6926:2002
$NXVWLND=DKWHYH]DODVWQRVWLLQXPHUMDQMHUHIHUHQþQLKYLURY]YRNDSUL
XJRWDYOMDQMXUDYQL]YRþQLKPRþL ,62
Acoustics - Requirements for the performance and calibration of reference sound
sources used for the determination of sound power levels (ISO 6926:2016)
Akustik - Anforderungen an die Eigenschaften und die Kalibrierung von

Vergleichsschallquellen für die Bestimmung von Schallleistungspegeln (ISO 6926:2016)

Acoustique - Prescriptions relatives aux performances et à l'étalonnage des sources

sonores de référence pour la détermination des niveaux de puissance acoustique (ISO

6926:2016)
Ta slovenski standard je istoveten z: EN ISO 6926:2016
ICS:
17.140.01 $NXVWLþQDPHUMHQMDLQ Acoustic measurements and
EODåHQMHKUXSDQDVSORãQR noise abatement in general
SIST EN ISO 6926:2016 en

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

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SIST EN ISO 6926:2016
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SIST EN ISO 6926:2016
EN ISO 6926
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2016
EUROPÄISCHE NORM
ICS 17.140.01 Supersedes EN ISO 6926:2001
English Version
Acoustics - Requirements for the performance and
calibration of reference sound sources used for the
determination of sound power levels (ISO 6926:2016)

Acoustique - Prescriptions relatives aux performances Akustik - Anforderungen an die Eigenschaften und die

et à l'étalonnage des sources sonores de référence pour Kalibrierung von Vergleichsschallquellen für die

la détermination des niveaux de puissance acoustique Bestimmung von Schallleistungspegeln (ISO

(ISO 6926:2016) 6926:2016)
This European Standard was approved by CEN on 26 December 2015.

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-CENELEC 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-CENELEC Management

Centre has the same status as the official versions.

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

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 6926:2016 E

worldwide for CEN national Members.
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SIST EN ISO 6926:2016
EN ISO 6926:2016 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 6926:2016
EN ISO 6926:2016 (E)
European foreword

This document (EN ISO 6926:2016) has been prepared by Technical Committee ISO/TC 43 “Acoustics”

in collaboration with Technical Committee CEN/TC 211 “Acoustics” the secretariat of which is held by

DIN.

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 August 2016, and conflicting national standards shall

be withdrawn at the latest by August 2016.

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 6926:2001.

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

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

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,

France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,

Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
Endorsement notice

The text of ISO 6926:2016 has been approved by CEN as EN ISO 6926:2016 without any modification.

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SIST EN ISO 6926:2016
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SIST EN ISO 6926:2016
INTERNATIONAL ISO
STANDARD 6926
Third edition
2016-01-15
Acoustics — Requirements for the
performance and calibration of
reference sound sources used for the
determination of sound power levels
Acoustique — Prescriptions relatives aux performances et à
l’étalonnage des sources sonores de référence pour la détermination
des niveaux de puissance acoustique
Reference number
ISO 6926:2016(E)
ISO 2016
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SIST EN ISO 6926:2016
ISO 6926:2016(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2016, Published in Switzerland

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
copyright@iso.org
www.iso.org
ii © ISO 2016 – All rights reserved
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SIST EN ISO 6926:2016
ISO 6926:2016(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

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

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

3 Terms and definitions ..................................................................................................................................................................................... 2

4 Reference meteorological conditions ............................................................................................................................................. 4

5 Performance requirements ....................................................................................................................................................................... 5

5.1 General ........................................................................................................................................................................................................... 5

5.2 Temporal steadiness (stability) of sound power output ......... ............................................................................ 5

5.3 Total broadband sound power level ..................................................................................................................................... 5

5.4 Spectral characteristics.................................................................................................................................................................... 5

5.5 Directivity .................................................................................................................................................................................................... 6

5.6 Recalibration ............................................................................................................................................................................................. 6

6 Instrumentation .................................................................................................................................................................................................... 7

6.1 General ........................................................................................................................................................................................................... 7

6.2 Microphone in a hemi-anechoic room ................................................................................................................................ 7

6.3 Microphone in a reverberation test room ....................................................................................................................... 7

6.4 Microphone frequency response correction ................................................................................................................. 7

6.5 Verification ................................................................................................................................................................................................. 8

6.6 Microphone calibration check ................................................................................................................................................... 8

7 Installation and operation of the reference sound source during calibration ....................................8

7.1 General ........................................................................................................................................................................................................... 8

7.2 Requirements in hemi-anechoic rooms ............................................................................................................................ 9

7.3 Requirements in reverberation rooms ............................................................................................................................... 9

8 Calibration procedure in hemi-anechoic rooms ................................................................................................................. 9

8.1 Test environment .................................................................................................................................................................................. 9

8.2 Microphone positions ....................................................................................................................................................................... 9

8.2.1 General...................................................................................................................................................................................... 9

8.2.2 Meridional paths .............................................................................................................................................................. 9

8.2.3 Spiral path.............................................................................................................................................................................. 9

8.2.4 Fixed point array .............................................................................................................................................................. 9

8.2.5 Coaxial circular paths .................................................................................................................................................. 9

8.3 Measurements ......................................................................................................................................................................................10

8.3.1 General...................................................................................................................................................................................10

8.3.2 Directivity index ............................................................................................................................................................10

8.3.3 Temporal steadiness ..................................................................................................................................................10

8.4 Calculations .............................................................................................................................................................................................11

9 Calibration procedure in reverberation test rooms .....................................................................................................12

9.1 Test environment ...............................................................................................................................................................................12

9.2 Microphone positions ....................................................................................................................................................................12

9.3 Measurements ......................................................................................................................................................................................12

9.3.1 General...................................................................................................................................................................................12

9.3.2 Temporal steadiness ..................................................................................................................................................13

9.4 Calculations .............................................................................................................................................................................................13

10 Alternative calibration procedure at low frequencies ...............................................................................................13

11 Measurement uncertainty .......................................................................................................................................................................13

11.1 General ........................................................................................................................................................................................................13

11.2 Typical values of the reproducibility standard deviation ...............................................................................14

12 Information to be recorded ....................................................................................................................................................................15

© ISO 2016 – All rights reserved iii
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SIST EN ISO 6926:2016
ISO 6926:2016(E)

13 Information to be reported ....................................................................................................................................................................15

Annex A (informative) Guidance on the determination of C ..................................................................................................16

Annex B (normative) Alternative calibration procedure at low frequencies ..........................................................18

Bibliography .............................................................................................................................................................................................................................19

iv © ISO 2016 – All rights reserved
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SIST EN ISO 6926:2016
ISO 6926:2016(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 43, Acoustics, Subcommittee SC 1, Noise.

This third edition cancels and replaces the second edition (ISO 6926:1999), which has been technically

revised with the following changes:

— the clause on measurement uncertainty has been updated with stricter reference to

ISO/IEC Guide 98-3 and moved backwards in the standard to be more in line with ISO 3745;

— the corrections for meteorological conditions have been brought in line with ISO 3745 and a new

Annex A on the acoustic radiation impedance correction has been introduced;

— an alternative method using sound intensity for low frequency calibration in hemi-anechoic rooms

not fully qualified for low frequencies has been introduced in a new Annex B.
© ISO 2016 – All rights reserved v
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SIST EN ISO 6926:2016
ISO 6926:2016(E)
Introduction

Reference sound sources are used extensively in “comparison methods” for determining the noise

emissions of physically stationary sound sources. A reference sound source, of known sound power

output, is used to establish the numerical relationship between the sound power level of a source, in a

given location in a given acoustic environment and the space- and time-averaged sound pressure level

at a set of microphone positions. Once that relationship is established, it is straightforward to measure

the average sound pressure level produced by an “unknown source” and to determine the sound power

level produced by that source.

This International Standard defines the important physical and performance characteristics of

reference sound sources and specifies procedures for their calibration, primarily to determine the

sound power level of other sound sources.

This International Standard supplements a group or family of International Standards, the ISO 3740

group, which describes various methods for determining the sound power levels of machines

and equipment. This group of International Standards specifies the acoustical requirements for

measurements that are appropriate for different test environments.

Five International Standards in the ISO 3740 group include procedures in which a reference sound

source is used: ISO 3741, ISO 3743-1, ISO 3744, ISO 3746 and ISO 3747. ISO 3740 gives guidelines for the

use of all the International Standards in the group.

Note that the sound power output of reference sound sources will vary, in particular at low frequencies,

with the distance from the source to nearby reflecting planes. Sound power data of reference sound

sources are thus valid only for the position used during the calibration.

In addition to being useful for determining sound power levels by the comparison method, reference

sound sources can be used for qualification tests on an acoustic environment and to estimate the

influence of an acoustic environment on the sound pressure levels produced by one or more sound

sources located in that environment. Examples of International Standards referring to reference sound

sources with these applications are ISO/TR 11690-3 and ISO 14257. Requirements other than those of

this International Standard can be applicable in these cases.
vi © ISO 2016 – All rights reserved
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SIST EN ISO 6926:2016
INTERNATIONAL STANDARD ISO 6926:2016(E)
Acoustics — Requirements for the performance and
calibration of reference sound sources used for the
determination of sound power levels
1 Scope

This International Standard specifies the acoustical performance requirements for reference sound

sources:
— temporal steadiness (stability) of the sound power output;
— spectral characteristics;
— directivity.

Temporal steadiness is defined in terms of the standard deviation of repeatability (see 5.2). The

spectral characteristics can be verified in either a hemi-anechoic room or a reverberation test room

from measurements of the frequency band sound power levels in accordance with this International

Standard (see 5.4). The performance requirements on directivity index can only be verified in a hemi-

anechoic room (see 5.5.)

This International Standard also specifies procedures for providing level calibration data and

uncertainty on a sound source intended for use as a reference sound source in terms of its sound power

level under reference meteorological conditions as defined in Clause 4 in octave and in one-third-octave

bands, and with frequency weighting A.

This International Standard is titled as a calibration standard even though the method is conducted in

a testing laboratory and the level calibration results are not directly traceable to national standards of

measure in a strict metrological sense. Testing laboratories performing this method are not expected

to meet all requirements normally associated with a calibration laboratory.
[15]

NOTE ISO/IEC 17025 specifies different requirements for the competence of testing laboratories and

calibration laboratories respectively. Laboratories testing reference sound sources in accordance with this

International Standard would typically comply with the requirements for testing laboratories but not necessarily

with those for calibration laboratories.

This International Standard specifies methods to calibrate reference sound sources not only in a

free field over a reflecting plane but also in reverberation test rooms at different distances from the

boundary surfaces. For the position of the reference sound source on one reflecting plane, the two

different test environments mentioned above are considered equivalent for frequency bands above or

equal to 200 Hz. At 160 Hz and below, some systematic differences can occur (see 11.2). For frequencies

below 100 Hz, an alternative calibration method using sound intensity is given.

The sound source can either be placed directly on the floor or mounted on a stand to be used at a

certain elevation above the floor. According to this International Standard, stand-mounted sources are

calibrated in reverberation test rooms. Floor-mounted sources are either calibrated in hemi-anechoic

or in reverberation test rooms. For floor-mounted sources in hemi-anechoic rooms, this International

Standard is valid only for sources whose maximum vertical dimension is less than 0,5 m and whose

maximum horizontal dimension is less than 0,8 m. According to this International Standard, only floor-

mounted reference sound sources can be used when carrying out measurements on a measurement

surface. For reference sound sources to be used or calibrated under reverberant conditions, no such

restrictions on maximum dimensions apply.
© ISO 2016 – All rights reserved 1
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ISO 6926:2016(E)
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 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 3744:2010, Acoustics — Determination of sound power levels and sound energy levels of noise sources

using sound pressure — Engineering methods for an essentially free field over a reflecting plane

ISO 3745:2012, Acoustics — Determination of sound power levels and sound energy levels of noise sources

using sound pressure — Precision methods for anechoic rooms and hemi-anechoic rooms

ISO 9613-1:1993, Acoustics — Attenuation of sound during propagation outdoors — Part 1: Calculation of

the absorption of sound by the atmosphere

ISO 9614-3, Acoustics — Determination of sound power levels of noise sources using sound intensity —

Part 3: Precision method for measurement by scanning
IEC 60942:2003, Electroacoustics — Sound calibrators

IEC 61094-1, Measurement microphones — Part 1: Specifications for laboratory standard microphones

IEC 61094-4, Measurement microphones — Part 4: Specifications for working standard microphones

IEC 61183, Electroacoustics — Random-incidence and diffuse-field calibration of sound level meters

IEC 61260-1, Electroacoustics — Octave-band and fractional-octave-band filters — Part 1: Specifications

IEC 61672-1, Electroacoustics — Sound level meters — Part 1: Specifications
IEC 61672-3:2013, Electroacoustics — Sound level meters — Part 3: Periodic tests

IEC 62585, Electroacoustics — Methods to determine corrections to obtain the free-field response of a

sound level meter

ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in

measurement (GUM:1995)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
reference sound source
RSS

portable, generally electroacoustical or aerodynamic sound source or other noise-generating device,

and associated control circuitry giving a broadband stable output complying with the requirements of

this International Standard
3.2
free sound field over a reflecting plane

sound field in a homogeneous, isotropic medium in the half-space above an infinite, reflecting plane in

the absence of other reflecting obstacles
3.3
hemi-anechoic room
test room in which a free sound field over a reflecting plane is obtained
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SIST EN ISO 6926:2016
ISO 6926:2016(E)
3.4
reverberation test room
test room meeting the requirements of ISO 3741
3.5
measurement surface

hypothetical surface of area, S, on which the microphone positions are located at which the sound

pressure levels are measured, enveloping the source under test and, in the case of a hemi-anechoic

room, terminating on the reflecting plane on which the source is located
Note 1 to entry: The measurement surface area is expressed in metres squared.
3.6
surface sound pressure level

energy-average of the time-averaged sound pressure levels at all the microphone positions, or traverses,

on the measurement surface, with the background noise corrections, K , applied at each microphone

position or traverse
Note 1 to entry: Surface sound pressure level is expressed in decibels.
Note 2 to entry: For definition and calculation of K , see ISO 3745.
3.7
sound power level

ten times the logarithm to the base 10 of the ratio of the sound power of a source, P, to a reference value,

P , expressed in decibels
L =10lg dB
where the reference value, P , is 1 pW

Note 1 to entry: If a specific frequency weighting as specified in IEC 61672–1, and/or specific frequency bands are

applied, this should be indicated by appropriate subscripts; e.g. L denotes the A-weighted sound power level.

[17]

Note 2 to entry: This definition is technically in accordance with ISO 80000-8:2007, 8-23.

[SOURCE: ISO/TR 25417:2007, 2.9]
3.8
measurement radius
radius of a hemi-spherical measurement surface
3.9
directivity index
measure of the extent to which a source radi
...

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