Estimating the acoustic behavior of plastics
parts under the influence of structure-borne sound
E. Schmachtenberg, T. Krumpholz, and T. Arping*
Pontstraße 49, 52062
*
to whom correspondence should be addressed1
Introduction
Optimizing
parts from the acoustic angle is a complex task on account of the subjective
and non-linear correlations that exist between sound emission (level, spectrum,
variation over time, etc.) and sound perception (loudness, tonality, sharpness,
roughness, annoyance, etc.), and it is a task that is assuming increasing
importance today in view of its significance for the environment (noise burden
on organisms) and the quality of life (sound quality).
A
cohesive process for the acoustic design of engineering parts, based on a
computer simulation, is frequently impossible, since highly sophisticated
numerical and theoretical processes are required for the solution. This is
particularly so if subjective perception constitutes the selection criterion. A
predominantly experimental approach is thus still adopted to assessing the
acoustic quality of engineering objects today. This involves noise emissions
from different sample parts being recorded with the aid of a dummy-head
recording system, for example /1/, and the quality of these recordings then
being assessed by test persons who compare two recordings at a time. Providing
that the appropriate questions are posed and the assessment is performed in a
suitable manner (e.g. factor analysis), the quality can then be established in
this way. Processes of this type naturally take up a great deal of time and thus
are cost-intensive.
The
aim of a comprehensive, acoustic optimization procedure must therefore be to
speed up the development of what, in the present case, are plastic parts so as
to keep the costly manufacture of samples to a minimum, on the one hand, and to
reduce the time required to perform the psychometric tests, on the other. The
envisaged solution is an all-in computer simulation of the acoustic behavior, based on material investigations that are
conducted on test specimens. This can be achieved by having a simulation of the
component behavior integrated in the CAE process, for
example. Use can be made here of the familiar processes currently employed for
calculating the mechanical strength, such as finite element analysis (FEA).
Only very few processes of this type have been introduced for the field of
acoustic optimization, however, with results that are not yet up to the
standard required /2/.