Intercomparison on sound power measurements by use of reference sound sources (synthesis report)

Directorate-General For The Information Society And Media European Commission

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Industrial research and development

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• Publié par: DIRECTORATE-GENERAL-FOR-THE-INFORMATION-SOCIETY-AND-MEDIA-EUROPEAN-COMMISSION
• Nombre de lectures: 15
• Langue: English
• Poids de l'ouvrage: 4 Mo

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ISSN 1018-5593
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APPLIED METROLOGY
INTERCOMPARISON ON
SOUND POWER MEASUREMENTS BY USE
OF REFERENCE SOUND SOURCES
(synthesis report)
Report
EUR 15873 EN
Blow-up from microfiche original s
European Commission
bcr information
APPLIED METROLOGY
INTERCOMPARISON ON
SOUND POWER MEASUREMENTS BY USE
OF REFERENCE SOUND SOURCES
(synthesis report)
M. VORLÄNDER, G. RAABE, H. BIETZ
Physikalisch-Technische Bundesanstalt
Bundesallee 100, D-38116 Braunschweig
Contract nr. 3347/1/0/168/89/11-BCR-D(30)
i/ C
Directorate-General
PARL EUROP. Biblioth. Science, Research and Development
1994 N-<ÈUR15873EN Published by the
EUROPEAN COMMISSION
Directorate-General XIII
Telecommunications, Information Market and Exploitation of Research
L-2920 LUXEMBOURG
LEGAL NOTICE
Neither the European Commission nor any person acting on behalf of the Commission
is responsible for the use which might be made of the following information
Catalogue number: CD-NA-15873-EN-C
ECSC — EC — EAEC, Brussels • Luxembourg, 1994 ABSTRACT
In the first phase of the project, sound power levels of reference sound sources type
B&K 4204 were measured by PTB and B&K using several different methods and acoustic
environments. On the basis of the results, two methods were prescribed :
a) hemi-free field rooms, similar to the technique described in ISO 3745 : meridional
scan using moving microphone and correction for air attenuation;
b) reverberation rooms, similar to the technique described in ISO 3741 : distribution
of six discrete microphone and four source positions, and usage of reverberation
time Ty.
In the second phase of the project, sound power measurements on reference sound
sources B&K 4204 were performed in an intercomparison among eight laboratories in
seven hemi-free field rooms and in seven reverberation rooms. Personnel of the
laboratories and of PTB calibrated the sources using the two prescribed methods.
The main results from the intercomparison are summarized as follows :
* Reproducibility of sound power measurements can be improved markedly by using
the prescribed methods instead of the standardized methods used today.
* Measurements in hemi-free field rooms and in reverberation rooms give the same
results, except in the frequency ranges below 100 Hz and above 10 kHz.
* Disturbing influences of the hemi-free field rooms are surprisingly small.
* Individual influences of reverberation rooms are important, but can be kept small
with certain restrictions concerning volume and shape. 1-
PHASEI 2-
Contents
1. Introduction 1
2. Participating laboratories
3. Measurement environments and methods 2
3.1 Semi-free field measurements 3
3.1.1 Outdoors
3.1.2 Indoor measurements 4
3.2 Diffuse sound field
3.3 Integration time 5
4. Measurement program 6
5. Data processing of test results 8
5.1 Semi-free field measurements
5.1.1 Sound pressure measurements
5.1.2 Intensity measurements 9
5.2 Reverberation rooms 11
6. Overall comparison of the methods2
6.1 Differences between sources3
6.2sn methods in semi-free field 14
6.2.1 Spatial averaging 1
6.2.2 Intensity method6
6.2.3 Difference between indoor and outdoor
measurements7
6.2.4 Measurement uncertainty 16.3 Differences between methods in diffuse fields 18
6.3.1 Spatial averaging 1
6.3.2 Absorption correction9
6.3.3 Measurement uncertainty 20
6.4 Differences between heights3
7. Prescribed methods for intercomparison measurements 25
7.1 Remarks 27
8. Participating laboratories and time schedule for intercomparisons . 28