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Research Papers

Active Acoustic Metamaterial With Simultaneously Programmable Density and Bulk Modulus

[+] Author and Article Information
W. Akl

Design and Production Engineering Department,
Ain Shams University,
Cairo, 11517, Egypt

A. Baz

Mechanical Engineering Department,
University of Maryland,
College Park, MD 20742
e-mail: baz@umd.edu

1Corresponding author.

Contributed by the Noise Control and Acoustics Division of ASME for publication in the JOURNAL OF VIBRATION AND ACOUSTICS. Manuscript received August 25, 2011; final manuscript received October 4, 2012; published online March 28, 2013. Assoc. Editor: Lonny Thompson.

J. Vib. Acoust 135(3), 031001 (Mar 28, 2013) (17 pages) Paper No: VIB-11-1186; doi: 10.1115/1.4023141 History: Received August 25, 2011; Revised October 04, 2012

Acoustic metamaterials are those structurally engineered materials that are composed of periodic cells designed in such a fashion to yield specific material properties (density and bulk modulus) that would affect the wave propagation pattern within in a specific way. All the currently exerted efforts are focused on studying passive metamaterials with fixed material properties. In this paper, the emphasis is placed on the development of a new class of composite one-dimensional active acoustic metamaterials (CAAMM) with effective densities and bulk moduli that are programmed to vary according to any prescribed patterns along its volume. A cylindrical water-filled cylinder coupled to two piezoelectric elements form a composite cell to act as a base unit for a periodic metamaterial structure. Two different configurations are considered. In the first configuration, a piezoelectric panel is flash-mounted to the face of the cylinder, while the other is side-mounted to the cylinder wall, introducing a variable stiffness along the wave propagation path. In the second configuration, the face-mounted piezoelectric panel remains unchanged, while the side-mounted panel is replaced with an active Helmholtz resonator with piezoelectric base panel. A detailed theoretical lumped-parameter model for the two configurations is present, from which the stiffness of both active elements is controlled via charge feedback control to yield arbitrary homogenized effective bulk modulus and density over a very wide frequency range. Numerical examples are presented to demonstrate the performance characteristics of the proposed. The CAAMM presents a viable approach to the development of effective domains with a controllable wave propagation pattern to suit many applications.

Copyright © 2013 by ASME
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Figures

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Fig. 5

Uncontrolled homogenized bulk modulus and density for a cavity with face- and side-mounted flexible panels

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Fig. 6

Electrical circuit analogous to the cavity with active panels

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Fig. 4

Electrical circuit analogous to the cavity with side- and face-mounted panel

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Fig. 3

Acoustic cavity coupled to two flexible panels. (a) Single main acoustic cavity. (b) Cavity divided in two equal sections. (c) Flexible panel equivalent spring-mass system.

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Fig. 2

Electric circuit analogy of an acoustic cavity coupled to a flexible panel

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Fig. 1

Acoustic cavity coupled with a flexible panel

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Fig. 7

Reduced electrical circuit analogous to the cavity with active panels

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Fig. 8

(a),(c)–(b),(d) Stiffness and control voltage of side- and face-mounted panels. (e),(f) Resultant homogenized bulk modulus and density (20 times those of water).

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Fig. 9

(a),(c)–(b),(d) Stiffness and control voltage of side- and face-mounted panels. (e),(f) Resultant homogenized bulk modulus and density (0.05 times those of water).

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Fig. 12

Uncontrolled homogenized bulk modulus and density for a cavity with Helmholtz resonator and a face-mounted panel

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Fig. 15

(a),(c)–(b),(d) Stiffness and control voltage of Helmholtz and face-mounted panels. (e),(f) Resultant homogenized bulk modulus and density (0.05 times those of water).

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Fig. 13

Electrical circuit analogous to the cavity with active Helmholtz resonator and face-mounted panel

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Fig. 14

(a),(c)–(b),(d) Stiffness and control voltage of Helmholtz and face-mounted panels. (e),(f) Resultant homogenized bulk modulus and density (20 times those of water).

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Fig. 10

Helmholtz resonator coupled to an acoustic cavity and a face-mounted panel. (a) Single main acoustic cavity. (b) Cavity divided in two equal sections.

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Fig. 11

Electrical circuit analogous to the cavity with Helmholtz resonator and a face-mounted panel

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