Abstract
This paper deals with the problem of the effect of discretization level
and certain other parameters characterizing the measurement setup on
accuracy of the process of determination of the sound radiation efficiency
by means of the Discrete Calculation Method (DCM) described by Hashimoto
(2001).
The idea behind DCM consists in virtual division of an examined sound
radiating structure into rectangular elements each of which is further
assumed to contribute to the total radiation effect in the same way as a
rigid circular piston having the surface area equal to this of the
corresponding virtual element and vibrating in an infinite rigid baffle.
The advantage of the method over conventional sound radiation efficiency
measurement techniques consists in the fact that instead of acoustic
pressure values, source (plate) vibration velocity amplitude values are
measured in a selected number of regularly distributed points. In many
cases, this allows to determine the sound radiation efficiency with
sufficient accuracy, especially for the low frequency regime.
The key part of the paper is an analysis of the effect of discretization level
(i.e. the choice of the number of points at which vibration amplitude
measurements are to be taken with the use of accelerometers) on results
obtained with the use of the method and their accuracy. The problem of
determining an optimum level of discretization for given excitation
frequency range is a very important issue as the labor intensity
(time-consuming aspect) of the method is one of its main flaws. As far as
the technical aspect of the method is concerned, two different geometrical
configurations of the measurement setup were tested.
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