An index of heterogeneity of sound absorbing porous materials
Keywords:Absorption, Acoustic impedance, Acoustic waves, Standards, Average relative standard deviation (ARSD), Heterogeneity, Inverted configurations
AbstractAn Index of heterogeneity, through-thickness homogeneity (TTH), of sound absorbing porous materials is calculated. The calculation of this TTH index only requires impedance tube measurements of the acoustical surface impedance on both faces of the tested material. A two-layer rigid frame porous system representing a single porous layer with a sudden change in its physical properties is studied to verify the validity of this TTH index. The sound absorption coefficient, complex wave number, and characteristic impedance of this equivalent single layer are computed in the normal and inverted positions. The heterogeneity of a material can be quantified by the average relative standard deviation (ARSD) of a bulk property measured respectively in both normal and inverted configurations. The ARSD of the three latter bulk properties are computed to identify the most sensitive bulk property to TTH.
How to Cite
Copyright on articles is held by the author(s). The corresponding author has the right to grant on behalf of all authors and does grant on behalf of all authors, a worldwide exclusive licence (or non-exclusive license for government employees) to the Publishers and its licensees in perpetuity, in all forms, formats and media (whether known now or created in the future)
i) to publish, reproduce, distribute, display and store the Contribution;
ii) to translate the Contribution into other languages, create adaptations, reprints, include within collections and create summaries, extracts and/or, abstracts of the Contribution;
iii) to exploit all subsidiary rights in the Contribution,
iv) to provide the inclusion of electronic links from the Contribution to third party material where-ever it may be located;
v) to licence any third party to do any or all of the above.