Archives of Acoustics, 36, 4, pp. 795–822, 2011

Optimization Design of Hybrid Mufflers on Broadband Frequencies Using the Genetic Algorithm

Min-Chie CHIU
Chung Chou University of Science and Technology Department of Mechanical and Automation Engineering

Recently, there has been research on high frequency dissipative mufflers. How-
ever, research on shape optimization of hybrid mufflers that reduce broadband noise
within a constrained space is sparse. In this paper, a hybrid muffler composed of
a dissipative muffler and a reactive muffler within a constrained space is assessed.
Using the eigenvalues and eigenfunctions, a coupling wave equation for the perfo-
rated dissipative chamber is simplified into a four-pole matrix form. To efficiently
find the optimal shape within a constrained space, a four-pole matrix system used
to evaluate the acoustical performance of the sound transmission loss (STL) is eval-
uated using a genetic algorithm (GA).
A numerical case for eliminating a broadband venting noise is also introduced. To
verify the reliability of a GA optimization, optimal noise abatements for two pure
tones (500 Hz and 800 Hz) are exemplified. Before the GA operation can be carried
out, the accuracy of the mathematical models has been checked using experimental
data. Results indicate that the maximal STL is precisely located at the desired target
tone. The optimal result of case studies for eliminating broadband noise also reveals
that the overall sound power level (SWL) of the hybrid muffler can be reduced
from 138.9 dB(A) to 84.5 dB(A), which is superior to other mufflers (a one-chamber
dissipative and a one-chamber reactive muffler). Consequently, a successful approach
used for the optimal design of the hybrid mufflers within a constrained space has
been demonstrated.
Keywords: dissipative; reactive; hybrid muffler; genetic algorithm; space constraints
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