Dynamic Mass Density and Acoustic Metamaterials

This paper studies a novel kind of low-frequency broadband acoustic metamaterials with small size based on the mechanisms of negative mass density and multi-cavity coupling. The structure consists of a closed resonant cavity and an open resonant cavity, which can be equivalent to a homogeneous medium with effective negative mass density in a certain frequency range by using the parameter inversion method. The negative mass density makes the anti-resonance area increased, which results in broadened band gaps greatly. Owing to the multi-cavity coupling mechanism, the local resonances of the lower frequency mainly occur in the closed cavity, while the local resonances of the higher frequency mainly in the open cavity. Upon the interaction between the negative mass density and the multi-cavity coupling, there exists two broad band gaps in the range of 0–1800 Hz, i.e. the first-order band gap from 195 Hz to 660 Hz with the bandwidth of 465 Hz and the second-order band gap from 1157 Hz to 1663 Hz with the bandwidth of 506 Hz. The acoustic metamaterials with small size presented in this paper could provide a new approach to reduce the low-frequency broadband noises.

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Anisotropic dynamic mass density for fluid–solid composites

Physica B Condensed Matter ◽

10.1016/j.physb.2012.02.025 ◽

2012 ◽

Vol 407 (20) ◽

pp. 4093-4096 ◽

Cited By ~ 6

Author(s):

Ying Wu ◽

Jun Mei ◽

Ping Sheng

Keyword(s):

Mass Density ◽

Dynamic Mass ◽

Solid Composites

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Analytical Model for Low-Frequency Transmission Loss Calculation of Zero-Prestressed Plates With Arbitrary Mass Loading

Journal of Vibration and Acoustics ◽

10.1115/1.4042927 ◽

2019 ◽

Vol 141 (4) ◽

Cited By ~ 1

Author(s):

William T. Edwards ◽

Chia-Ming Chang ◽

Geoffrey McKnight ◽

Steven R. Nutt

Keyword(s):

Boundary Conditions ◽

Analytical Model ◽

Transmission Loss ◽

Mass Density ◽

Low Frequency ◽

Sound Attenuation ◽

Mode Shapes ◽

Natural Mode ◽

Rectangular Plates ◽

Acoustic Metamaterials

As the importance of sound attenuation through weight-critical structures has grown and mass law based strategies have proven impractical, engineers have pursued alternative approaches for sound attenuation. Membrane-type acoustic metamaterials have demonstrated sound attenuation significantly higher than mass law predictions for narrow, tunable bandwidths. Similar phenomena can be achieved with plate-like structures. This paper presents an analytical model for the prediction of transmission loss through rectangular plates arbitrarily loaded with rigid masses, accommodating any combination of clamped and simply supported boundary conditions. Equations of motion are solved using a modal expansion approach, incorporating admissible eigenfunctions given by the natural mode shapes of single-span beams. The effective surface mass density is calculated and used to predict the transmission loss of low-frequency sound through the plate–mass structure. To validate the model, finite element results are compared against analytical predictions of modal behavior and shown to achieve agreement. The model is then used to explore the influence of various combinations of boundary conditions on the transmission loss properties of the structure, revealing that the symmetry of plate mounting conditions strongly affects transmission loss behavior and is a critical design parameter.

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Investigation on the Band Gap and Negative Properties of Concentric Ring Acoustic Metamaterial

Shock and Vibration ◽

10.1155/2018/1369858 ◽

2018 ◽

Vol 2018 ◽

pp. 1-12 ◽

Cited By ~ 2

Author(s):

Meng Chen ◽

Dan Meng ◽

Heng Jiang ◽

Yuren Wang

Keyword(s):

Band Gap ◽

Effective Mass ◽

Coupling Effect ◽

Mass Density ◽

Band Gaps ◽

Acoustic Metamaterials ◽

Concentric Ring ◽

Resonance Modes ◽

Negative Effective Mass ◽

Single Oscillator

The acoustic characteristics of 2D single-oscillator, dual-oscillator, and triple-oscillator acoustic metamaterials were investigated based on concentric ring structures using the finite element method. For the single-oscillator, dual-oscillator, and triple-oscillator models investigated here, the dipolar resonances of the scatterer always induce negative effective mass density, preventing waves from propagating in the structure, thus forming the band gap. As the number of oscillators increases, relative movements between the oscillators generate coupling effect; this increases the number of dipolar resonance modes, causes negative effective mass density in more frequency ranges, and increases the number of band gaps. It can be seen that the number of oscillators in the cell is closely related to the number of band gaps due to the coupling effect, when the filling rate is of a certain value.

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