scholarly journals Sound Attenuation of Membranes Loaded with Square Frame-Shaped Masses

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
J. S. Chen ◽  
D. W. Kao
Keyword(s):  
Effective Mass ◽  
Sound Wave ◽  
Present Model ◽  
Transmission Loss ◽  
Mass Density ◽  
Sound Attenuation ◽  
Loss Peak ◽  
In Series ◽  
Thin Membranes ◽  
Multiple Transmission

This study examines sound transmission of thin membranes with square frame-shaped masses. Numerical results indicate that multiple transmission loss peaks can be generated by adding more frame mass inclusions. The number and the location of the peaks are controlled by the number of frames, the frame distribution, and the frame width. Near the transmission loss peak frequencies, the dynamic effective mass density turns from positive to negative. The validity of the present model has been verified by comparing the analytical results with FE results. Two types of cell arrangements are also considered in this study, namely, cells in series and cells in array. It is seen that either the stacked or array configurations can produce better sound attenuation than single-celled structures. Moreover, the frequency band where sound wave is blocked can be broadened by stacking more layers with different mass magnitudes. Furthermore, additional frequency bands due to the periodicity of the structure are found in the stacked configurations.

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

2019 ◽  
Vol 141 (4) ◽  
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.

Transmission Loss of Membrane-Type Acoustic Metamaterial with Negative Effective Mass

2017 ◽  
Vol 898 ◽  
pp. 1749-1756 ◽  
Author(s):  
Guo Chang Lin ◽  
Song Qiao Chen ◽  
Yu Liang Li ◽  
Hui Feng Tan
Keyword(s):  
Effective Mass ◽  
Transmission Loss ◽  
Mass Density ◽  
Small Mass ◽  
Equivalent Model ◽  
Sound Insulation ◽  
Rubber Membrane ◽  
Acoustic Metamaterial ◽  
Spring Force ◽  
Membrane Type

The transmission loss (TL) of membrane-type acoustic metamaterials consisting of small mass and rubber membrane was studied. By establishing a mass-spring equivalent model of metamaterial structural unit, which regards rubber membrane as having the dual role of damping force and spring force, we demonstrated that effective mass density of this membrane-type acoustic metamaterial was negative in the band gap range by theoretical analysis. Based on the theory of plane wave propagation, we studied the sound insulation of this membrane-type acoustic metamaterial. The result showed that membrane-type metamaterial was based on the principle of dipole resonance, which made the membrane-type acoustic metamaterial appear high reflection and low transmission phenomenon so as to achieve the aim of reducing noise. By optimal design, the sound attenuation frequency range of this membrane-type acoustic metamaterial was reduced to 20Hz-100Hz, greatly enhancing the ability of this metamaterial in terms of low-frequency sound insulation. We obtained the distribution of sound intensity at the optimum transmission frequency and the best reflection frequency by coupled acoustic-structural analysis. The best sound insulation frequency was matched with the second order and the third order eigenfrequency of this membrane-type acoustic metamaterial unit, and the strain energy was concentrated at the joint of small mass and the membrane. The total sound insulation of acoustic metamaterial plate was better than the single metamaterial unit.

Effective mass density for periodic solid-fluid composties

2012 ◽  
Vol 131 (4) ◽  
pp. 3372-3372 ◽  
Author(s):  
Jun Mei ◽  
Ying Wu ◽  
Zhengyou Liu ◽  
Ping Sheng
Keyword(s):  
Effective Mass ◽  
Mass Density

Modeling the myocardial dilution curve of a pure intravascular indicator

1997 ◽  
Vol 273 (4) ◽  
pp. H2062-H2071 ◽  
Author(s):  
J. S. Lee ◽  
J. Karch ◽  
A. R. Jayaweera ◽  
J. R. Lindner ◽  
L. P. Lee ◽  
...  
Keyword(s):  
Contrast Medium ◽  
Present Model ◽  
Temporal Change ◽  
Mean Transit Time ◽  
Dilution Curve ◽  
Heterogeneous Flow ◽  
Myocardial Blood Volume ◽  
In Series ◽  
First Moment ◽  
Concentration Curves

The dispersion and dilution of contrast medium through the myocardial vasculature is examined first with a serial model comprised of arterial, capillary, and venous components in series to determine their time-concentration curves (TCC) and the myocardial dilution curve (MDC). Analysis of general characteristics shows that the first moment of the MDC, adjusted for that of the aortic TCC and mean transit time (MTT) from the aorta to the first intramyocardial artery, is one-half the MTT of the myocardial vasculature and that the ratio of the area of the MDC and aortic TCC is the fractional myocardial blood volume (MBV). The use of known coronary vascular morphometry and a set of transport functions indicates that the temporal change in MDC is primarily controlled by the MTT. An analysis of several models with heterogeneous flow distributions justifies the procedures to calculate MTT and MBV from the measured MDC. Compared with previously described models, the present model is more general and provides a physical basis for the effects of flow dispersion and heterogeneity on the characteristics of the MDC.

scholarly journals Tunable Two-Layer Dual-Band Metamaterial with Negative Modulus

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3229
Author(s):  
Limei Hao ◽  
Meiling Men ◽  
Yazhe Wang ◽  
Jiayu Ji ◽  
Xiaole Yan ◽  
...  
Keyword(s):  
Mass Density ◽  
Hollow Spheres ◽  
Volume Ratio ◽  
Blue Shift ◽  
Relative Volume ◽  
Hole Diameter ◽  
Dual Band ◽  
Resonant Frequencies ◽  
In Series ◽  
Simulation Results

A tunable dual-band acoustic metamaterial (AM) with nested two-layer split hollow spheres (TLSHSs) is presented here, which was achieved by adjusting the hole diameter and the ratio of the two layers’ volumes. This work comprises theoretical and numerical studies. Based on sound-force analogy (SFA), TLSHSs can be considered equivalent to a model of two spring oscillators in series. The equations of two resonant frequencies were derived, which precisely provided the relation between two resonant frequencies and the hole diameter as well as the ratio of the two layers’ volumes. The analytical formulas and simulation results by the finite element method (FEM) showed that there were two resonant frequencies for the TLSHSs, and their dynamic modulus became negative near the resonant frequencies. As the the diameter of two holes increased, both of the resonant frequencies underwent a blue shift. As the relative volume ratio increased, both of the resonant frequencies underwent a red shift. The calculation and simulation results were in good agreement. This kind of precisely controllable dual-band AM with negative modulus can easily be coupled to other structures with negative mass density, thereby achieving a double-negative AM in an expected frequency range.

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