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16
“Uncertainty-noise” Le Mans
Acoustique
&
Techniques n° 40
Treatment of Measurement Uncertainties
in International and European Standards on
Acoustics
ational Metrology Institutes and calibration laboratories
have, for several decades, evaluated the uncertainty of their
measurement results and stated corresponding figures
in calibration certificates as an indicator of accuracy and
reliability. In the course of increasing cross-border co-operation,
especially during the realization of the inner European market,
best measurement capabilities of laboratories based on
uncertainty estimations received more and more attention
and became even an important marketing factor. It was then
obvious that a common understanding on how to determine
and to express measurement uncertainty was essential to
make data reliable and comparable. These considerations led
to an agreement on an internationally harmonized procedure
for the evaluation of uncertainty which was issued in 1993
by six well recognized international organizations and today
is known world-wide as the “Guide to the expression of
uncertainty in measurement” (GUM).
Basically, it has already been recognized at an early stage
that uncertainties of quantitative test results should be
evaluated as well and that the principles of the GUM were
equally applicable to all kind of measurements including those
used by testing laboratories. Nevertheless, only exceptionally
did those laboratories estimate and state their uncertainties
in test reports. This was mainly due to a considerable lack
of knowledge in this field. Moreover, a certain reluctance of
customers was observed indicating that they did not really
like to be confronted with the fact that test results are not
“exact” per se.
This attitude, however, changed over the years when customers
became aware that any kind of measurement results can only
be reliably compared when their corresponding uncertainties
are known and that, quite often, valid statements about the
compliance of a product with specified limits can only be made
if the uncertainty of test results is taken into account. This
became especially relevant when manufacturers developed a
vital interest to have test results for their products recognized
internationally thus avoiding duplications of tests. As in
calibration, a growing interest of customers can be predicted
to select among competing testing laboratories the one which
provides most reliable results at a reasonable price.
This imposed some pressure on testing laboratories which
considerably increased when ISO/IEC 17025, General
requirements for the competence of testing and calibration
laboratories, was first issued in 1999. Since then, this standard
forms the basis for laboratory accreditation around the world.
It requires that “testing laboratories shall have and shall apply
procedures for estimating the uncertainty of measurement”
and, moreover, that “when estimating the uncertainty of
Klaus Brinkmann
ISO/TC 43 Chairman
Sauerbruchstrasse, 31
D-38116 Braunschweig
GERMANY
Roger Higginson
CEN/TC 211 Chairman
Higginson Acoustics Ltd
9, Segbury Grove
Bracknell
BERKSHIRE RG12 9JL
UNITED KINGDOM
Leif Nielsen
ISO/TC 43 and CEN/TC 211 Secretariat
Danish Standards Associaton
Kollegievej, 6
DK-2920 Charlottenlund
DENMARK
This paper presents the adopted policy of the
International and European standards committees
ISO/TC 43 “Acoustics”, ISO/TC 43/SC 1 “Noise”
and CEN/TC 211 “Acoustics”. It further discusses
the recent experience with the implementation
of these requirements in standards of these
committees on acoustical noise measurement.
Cet article présente la politique adoptée par les
comités de normalisation européens et international
ISO/TC 43 «Acoustique», ISO/TC 43/SC 1 «Bruit»
et CEN/TC 211 «Acoustique». De plus, il présente
la récente expérience de mise en œuvre de ces
exigences dans les normes de ces comités sur la
mesure en acoustique.
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