Analysis of powertrain sound radiation behaviour by means of wave based technique

The powertrain and in particular the exhaust system are the dominant sources
during the so-called vehicle pass-by noise scenarios. In order to meet the
legal regulations regarding the limit values for the vehicle noise emissions
the computer aided engineering (CAE) tools came to the fore in the vehicle
design process over the last three decades. This new emerging technology
enabled that the acoustic performance of a product may be assessed in a cost-
efficient way by analysing the virtual prototypes. The boundary element method
(BEM) has become a well established tool for the analysis of acoustic problems
involving unbounded domains. Since the dynamic boundary variables are expressed
in terms of locally defined polynomial shape functions, a large number of
elements is, however, required in order to get a reasonable prediction
accuracy. As wavelengths shorten with increasing frequency, the computational
mesh has to be refined which yields increased computational efforts. As a
result, the practical applicability of the BEM is limited to low frequency
problems.
Recently, the wave based prediction technique (WBT) has been developed as an
alternative method for solving steady-state acoustic problems in the mid-
frequency range. The WBT has proven to be a robust and efficient prediction
tool for interior acoustics. This contribution outlines the recent developments
of the novel wave based approach and its application for three-dimensional
free-field sound radiation problems. Application to industry-sized problem
demonstrates the enhanced computational efficiency, which allows the practical
computational limitation to be shifted towards higher frequencies.