Acoustic Metamaterial With Air-Backed Diaphragm for Broadband Absorption: A Preliminary Study

2020 ◽  
Author(s):  
Qian Dong ◽  
Xiaolei Song ◽  
Subhrodeep Ray ◽  
Haijun Liu
Keyword(s):  
Impedance Match ◽  
Center Frequency ◽  
Acoustic Metamaterials ◽  
Perforated Plates ◽  
Broadband Absorption ◽  
Unit Cells ◽  
Equivalent Mass ◽  
3D Printed ◽  
Mass Spring ◽  
Sub Wavelength

Abstract Membrane-based acoustic metamaterials have been reported to achieve 100% absorption, the acoustic analogue of photonic black-hole. However, the bandwidth is usually very narrow around some local resonance frequency, which limits its practical use. To address this limitation and achieve a broadband absorption, this paper first establishes a theoretical framework for unit cells of air-backed diaphragms, modeled as an equivalent mass-spring-dashpot system. Based on the impedance match principle, three different approaches are numerically investigated by tuning the cavity length, the static pressure in the cavity, and the effective damping of perforated plates. A prototype with polyimide diaphragm and 3D printed substrate is then fabricated and characterized using an acoustic impedance tube. Preliminary experiments show the feasibility to achieve an absorption bandwidth of ∼200 Hz at center frequency of 1.45 kHz. This work pays the way for developing a sub-wavelength light weight broadband acoustic absorber for a variety of applications in noise control.

Sound Manipulation With Acoustic Metamaterials

2012 ◽  
Author(s):  
Lucian Zigoneanu ◽  
Bogdan-Ioan Popa ◽  
Steven A. Cummer
Keyword(s):  
Effective Density ◽  
Gradient Index ◽  
Acoustic Metamaterials ◽  
Acoustic Wave Propagation ◽  
Material Parameters ◽  
Unit Cells ◽  
Novel Applications ◽  
Practical Feasibility ◽  
Transformation Acoustics ◽  
Sub Wavelength

Acoustic metamaterials are engineered materials with properties hard or impossible to find in natural materials (e.g. negative effective density and/or negative bulk modulus). Therefore, a myriad of novel applications could be imagined and some of them have already been theoretically and/or experimentally demonstrated. Gradient index acoustic lenses, acoustic cloaks or acoustic absorbing panels are some common examples. Here, we review the coordinate transformation approach (transformation acoustics) which provides the material parameters needed to precisely control the acoustic wave propagation. Then, we use this technique to design an acoustic black hole and a 3D acoustic ground cloak. We use numerical simulations to explore the practical feasibility of the material parameters required by these applications and design non-resonant, highly sub-wavelength unit cells that will implement them in practice.

scholarly journals Moth wings are acoustic metamaterials

2020 ◽  
Vol 117 (49) ◽  
pp. 31134-31141 ◽  
Author(s):  
Thomas R. Neil ◽  
Zhiyuan Shen ◽  
Daniel Robert ◽  
Bruce W. Drinkwater ◽  
Marc W. Holderied
Keyword(s):  
High Performance ◽  
Sound Intensity ◽  
Acoustic Metamaterials ◽  
Noise Mitigation ◽  
Wing Membrane ◽  
Acoustic Metamaterial ◽  
Optical Metamaterials ◽  
Broadband Absorption ◽  
Unit Cells ◽  
Individual Contributions

Metamaterials assemble multiple subwavelength elements to create structures with extraordinary physical properties (1–4). Optical metamaterials are rare in nature and no natural acoustic metamaterials are known. Here, we reveal that the intricate scale layer on moth wings forms a metamaterial ultrasound absorber (peak absorption = 72% of sound intensity at 78 kHz) that is 111 times thinner than the longest absorbed wavelength. Individual scales act as resonant (5) unit cells that are linked via a shared wing membrane to form this metamaterial, and collectively they generate hard-to-attain broadband deep-subwavelength absorption. Their collective absorption exceeds the sum of their individual contributions. This sound absorber provides moth wings with acoustic camouflage (6) against echolocating bats. It combines broadband absorption of all frequencies used by bats with light and ultrathin structures that meet aerodynamic constraints on wing weight and thickness. The morphological implementation seen in this evolved acoustic metamaterial reveals enticing ways to design high-performance noise mitigation devices.

Dynamic analysis and control of an active engine mount system

2002 ◽  
Vol 216 (11) ◽  
pp. 921-931 ◽  
Author(s):  
Y-W Lee ◽  
C-W Lee
Keyword(s):  
Transfer Function ◽  
Dynamic Characteristics ◽  
Performance Test ◽  
Adaptive Controller ◽  
Lms Algorithm ◽  
Equivalent Mass ◽  
Engine Mount ◽  
Active Engine ◽  
The Stability ◽  
Mass Spring

Dynamic characteristics of a prototype active engine mount (AEM), designed on the basis of a hydraulic engine mount, have been investigated and an adaptive controller for the AEM has been designed. An equivalent mass-spring-damper AEM model is proposed, and the transfer function that describes the dynamic characteristics of the AEM is deduced from mathematical analysis of the model. The damping coefficient of the model is derived by considering the non-linear flow effect in the inertia track. Experiments confirmed that the model precisely describes the dynamic characteristics of the AEM. An adaptive controller using the filtered-X LMS algorithm is designed to cancel the force transmitted through the AEM. The stability of the LMS algorithm is guaranteed by using the secondary path transfer function derived on the basis of the dynamic model of the AEM. The performance test in the laboratory shows that the AEM system is capable of significantly reducing the force transmitted through the AEM.

A thin and optically transparent infrared-radar compatible stealth structure with low emissivity and broadband absorption

2021 ◽  
Author(s):  
Xiaoxue Tan ◽  
Juan Chen ◽  
Jianxing Li
Keyword(s):  
Dual Band ◽  
Center Frequency ◽  
Infrared Emissivity ◽  
Infrared Band ◽  
Functional Layer ◽  
Resistive Film ◽  
Broadband Absorption ◽  
Low Profile ◽  
Optically Transparent ◽  
Transparent Composite

Abstract In this paper, an optically transparent structure that combines broadband absorption and low infrared emissivity for dual-band stealth is proposed. The whole structure includes two functional layers. The periodic resistive film of the upper functional layer acts on infrared stealth. Its emissivity in the infrared band of 8-14μm is lower than 0.3. Another functional layer achieves greater than 90% wide absorption from 6 to 18.5 GHz. The whole optically transparent composite structure has a low profile of 0.141λ0, where λ0 is the wavelength of free space at the center frequency. It has an absorptivity that greater than 90% in the region of 5.7-16.5 GHz and has wide angular stability. Measured result is consistent with the simulation which verify the performance of the proposal. The infrared-radar compatible stealth structure proposed in this paper has potential application in the field of multi-spectrum compatible stealth.

scholarly journals Controlling Refraction Using Sub-Wavelength Resonators

2018 ◽  
Vol 8 (10) ◽  
pp. 1942
Author(s):  
Yue Chen ◽  
Robert Lipton
Keyword(s):  
Frequency Dependence ◽  
Free Space ◽  
Near Infrared ◽  
Center Frequency ◽  
Negative Index ◽  
Index Properties ◽  
Frequency Bands ◽  
Transmitted Signal ◽  
Sub Wavelength

We construct metamaterials from sub-wavelength nonmagnetic resonators and consider the refraction of incoming signals traveling from free space into the metamaterial. We show that the direction of the transmitted signal is a function of its center frequency and bandwidth. The directionality of the transmitted signal and its frequency dependence is shown to be explicitly controlled by sub-wavelength resonances that can be calculated from the geometry of the sub-wavelength scatters. We outline how to construct a medium with both positive and negative index properties across different frequency bands in the near infrared and optical regime.

scholarly journals MEMS mirrors using sub-wavelength High- Contrast-Gratings with asymmetric unit cells

2016 ◽  
Vol 19 (2) ◽  
pp. 52
Author(s):  
Milan Maksimović
Keyword(s):  
Spectral Response ◽  
Practical Interest ◽  
Optimization Procedure ◽  
Material Design ◽  
Unit Cell ◽  
High Contrast ◽  
Asymmetric Unit ◽  
Unit Cells ◽  
Thin Elements ◽  
Sub Wavelength

High-contrast gratings (HCG) are ultra-thin elements operating in sub-wavelength regime with the period of the grating smaller than the wavelength and with the high-index grating material fully surrounded by low-index material. Design of MEMS mirrors made from HCG with specific reflectivity response is of great practical interest in integrated optoelectronics. We theoretically investigate design of the spectral response for HCGs with the complex unit cells. We show that the spectral response can be tailored via the unit cell perturbations and with the asymmetric unit cell perturbations may introduce completely new spectral response. Our results can serve as guidance for the design of the complex HCGs and help with the choice of the efficient initial grating topology prior to global optimization procedure.

3D printed cross-shaped terahertz metamaterials with single-band, multi-band and broadband absorption

2021 ◽  
Vol 122 ◽  
pp. 111739
Author(s):  
Shengnan Li ◽  
Zhonglei Shen ◽  
Wei Yin ◽  
Liuyang Zhang ◽  
Xuefeng Chen
Keyword(s):  
Single Band ◽  
Broadband Absorption ◽  
3D Printed ◽  
Terahertz Metamaterials ◽  
Multi Band

Perfect, broadband, and sub-wavelength absorption with asymmetric absorbers: Realization for duct acoustics with 3D printed porous resonators

2021 ◽  
pp. 116687
Author(s):  
Jean Boulvert ◽  
Thomas Humbert ◽  
Vicente Romero-García ◽  
Gwénaël Gabard ◽  
Edith Roland Fotsing ◽  
...  
Keyword(s):  
Duct Acoustics ◽  
Wavelength Absorption ◽  
3D Printed ◽  
Sub Wavelength

scholarly journals 3D Printing of BaTiO3 Piezoelectric Ceramics for a Focused Ultrasonic Array

Sensors ◽  
2019 ◽  
Vol 19 (19) ◽  
pp. 4078 ◽  
Author(s):  
Jian Cheng ◽  
Yan Chen ◽  
Jun-Wei Wu ◽  
Xuan-Rong Ji ◽  
Shang-Hua Wu
Keyword(s):  
Grain Size ◽  
Electric Properties ◽  
Ultrasonic Transducers ◽  
Center Frequency ◽  
X Ray ◽  
Weight Percentage ◽  
Ultrasonic Array ◽  
Good Potential ◽  
3D Printed ◽  
Ray Patterns

BaTiO3 (BTO) ceramics were fabricated based on stereolithography technology. The microstructures and electric properties of the BTO ceramics were studied. X-ray patterns of sintered BTO ceramics indicated that the tetragonal phase had formed, and the grain size increased clearly as BTO weight percentage increased. Moreover, the BTO ceramics exhibited good electric properties, with a piezoelectric constant d33 of 166 pC/N at 80% BTO weight percentage. To evaluate the properties of 3D printed BTO ceramics, a 1.4 MHz focused ultrasonic array was fabricated and characterized. The −6dB bandwidth of the array was 40%, and the insertion loss at the center frequency was 50 dB. The results show that the printed BTO ceramics array have good potential to be used in ultrasonic transducers for various applications.

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