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Inverse acoustic property characterization using impedance tube measurements
Wevita Vidanalage Dona, Dilanki Terrenska
Wevita Vidanalage Dona, Dilanki Terrenska
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2020-05
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Abstract
The ever-increasing demand for improved fuel-efficiency and weight reduction has
resulted in increased focus on porous materials. Cellular porous materials offer designers a route
towards improving structural properties while improving the structure functionality—such as
increase thermal dissipation, fluid transport, and acoustic absorption. The acoustic properties of
porous materials, the subject of this thesis, offer an ideal solution for reducing aircraft noise
emanated from commercial turbofan engines. However, including such materials within
engineering design requires an improved understanding of their acoustic properties and the
dependence of these properties on the various transport parameters associated with porous
materials.
While these properties may be directly measured using lab instrumentation, such
measurements are often time consuming and require significant investment. The recently
developed inverse characterization technique which allows the calculation of acoustic transport
properties from impedance tube measurements offers a cheaper and more efficient alternative to
such direct methods. To this end, the focus of this thesis is to clarify the suitability of this method
when applied to various porous materials. Here, we compare the direct measurement with
predictions obtained using the commercial inverse characterization software FOAMX, which uses
impedance tube absorption data to inversely calculate acoustic transport properties using either the
equivalent fluid model or the poroelastic model. The study compare the predictions obtained by
both models and demonstrate the suitability of each method for various porous material. The
results obtained show that the calculated material parameters can vary drastically depending on
the method used and material model selected by the user. Further, the effect of the measured
material properties on the predicted absorption behavior is compared with experimental results.
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Thesis (M.S.)-- Wichita State University, College of Engineering, Dept. of Aerospace Engineering
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Wichita State University
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Copyright 2020 by Wevita Vidanalage Dona Dilanki Terrenska
All Rights Reserved