The matrix condensation technique in conjunction with the substructuri
ng principle has been previously used to model complex commercial auto
motive mufflers. Though complete 3-D finite element modelling is parti
ally eliminated, it still requires the nodal-coordinate data and conne
ctivity data of the elements forming the segment of each substructure.
It also demands the connectivity of the degrees of freedom left after
matrix condensation. Thus, the data preparation phase is tedious and
cannot be claimed to be simple. Moreover, the existing FEM code requir
es the user to have a knowledge of acoustic. theory and finite element
modelling. This paper describes a way to completely eliminate the dat
a preparation phase. Given the geometric dimensions of the muffler as
input, the muffler performance is obtained as the output. The results
obtained are compared with analytical and experimental results for sim
ple as well as extended-tube expansion chambers, with or without an of
fset.