Optimal Impedance for Acoustic Liners: From Cremer to Nonlocal Concepts
Emanuele De Bono, Alessandro Casaburo, Giuseppe Petrone, Manuel Collet, Sergio De Rosa
Abstract. The Cremer impedance is, so far, the only analytical result concerning optimal locally reacting impedances for acoustic liners. Nevertheless, the unfulfillment of the reality condition makes the Cremer impedance unachievable in a broadband sense. Moreover, the maximization of the attenuation of the principal duct mode in an infinite lined duct, as in Cremer, does not take into account the influence of backward reflection at the interface between rigid and lined portions of the duct. Therefore, the actual optimal impedance for locally reacting liners is usually obtained by numerical optimization of the insertion loss. Nevertheless, leveraging nonlocality, both in active and passive acoustic metamaterials, has allowed to achieve anomalous reflection, dispersion tailoring, higher isolation and nonreciprocity. These extraordinary control capabilities should be explored to conceive innovative concepts towards generalized impedance behaviours, where also nonlocality is contemplated and optimized. This paper first questions the optimality of Cremer-like impedances, and then it investigates an alternative boundary operator taking into account nonlocal interactions in the acoustic liner.
Keywords
Acoustic Liners, Cremer Impedance, Nonlocal, Noise Control, Advection Boundary Law
Published online 7/20/2026, 6 pages
Copyright © 2026 by the author(s)
Published under license by Materials Research Forum LLC., Millersville PA, USA
Citation: Emanuele De Bono, Alessandro Casaburo, Giuseppe Petrone, Manuel Collet, Sergio De Rosa, Optimal Impedance for Acoustic Liners: From Cremer to Nonlocal Concepts, Materials Research Proceedings, Vol. 69, pp 325-330, 2026
DOI: https://doi.org/10.21741/9781644904251-58
The article was published as article 58 of the book CEAS – AIDAA Conference 2025
Content from this work may be used under the terms of the Creative Commons Attribution 3.0 license. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
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