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You searched for subject:(acoustic cloaks). Showing records 1 – 2 of 2 total matches.

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NSYSU

1. Lin, Jau-Cho. Design and Experimental Research of Acoustic Cloak in the Air.

Degree: PhD, Mechanical and Electro-Mechanical Engineering, 2017, NSYSU

The issue of random controlling wave propagation is very popular in the research literature. The techniques for controlling wave propagation can avoid unwanted wave disturbance, help control a specific wave to randomly propagate, and hide the object free from detection. The sound insulation performances of a traditional sound proof industrial element are based on the mass density of the object. Therefore, high sound insulation elements always come at the high cost, great volume, and heavy weight. The theories of acoustic cloak and metamaterials driven by new discoveries in recent decades have supplied the potential for developing novel strategies and new technologies in the control of acoustic noise. This study investigated the cloak of air borne acoustic wave based on the recently proposed theories of coordinate transformation and researches the design, fabrication and experimental analysis of acoustic cloak shell for meta-composite material in air applications. The material properties of three-dimensional (3D) cloak shell were developed according to the spatial transformation in three directions of a geometry coordinate system. Depending on the derived material properties, the anisotropic material properties of a cloak shell could be obtained. To realize the acoustic cloak, the designed tube-cavity meta-composite structure formulized the layered structure for the cloak shell. Cloak shell structures provide the anisotropic material properties of a cloak shell and control the acoustic wave propagation through its structural geometric design. Both elliptical and circle cloak shells were designed and numerically evaluated herein. The analysis of plane waves passing through the elliptical cloak shell explains the effectiveness of the meta-composite material in its acoustic cloaking performance over a frequency range of 800 to 1250 Hz in 1/3 octave band. The results demonstrated that anisotropic properties of the proposed cloak make it possible to alter the direction of acoustic waves propagating from the original path and direct them to travel along a pre-determined path. In addition, the circle cloak shell also provides acoustic invisibility in 1000 Hz. According to the dimension parameters of the cloak shell structure, the full 3D diagram of a meta-composite cloak circle shell was plotted and the real cloak shell specimen was manufactured by the 3D print technique for experimental evaluation. The experiment analyzed the acoustic cloak effect of a circle cloak shell in a semi-anechoic room under a free field environment. Experimental results demonstrate the effectiveness of the circle cloak shell in the air at a design frequency of 1000 Hz. The research results present a way to comply with anisotropic cloak shell for acoustic purposes. These research findings provide new strategies and coating structure design for the physical realization of an invisibility cloak in the air. Advisors/Committee Members: Bor-Tsuen Wang (chair), Jao-Hwa Kuang (chair), Shao-Yi Hsia (chair), Wei-Chih Lin (chair), Shiuh-Kuang Yang (committee member), Chi-Hui Chien (chair), Mei-Ling Wu (chair), Jyin-Wen Cheng (chair).

Subjects/Keywords: acoustic metamaterial; acoustic invisibility; metamaterial; acoustic cloaks; transformation acoustic

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Lin, J. (2017). Design and Experimental Research of Acoustic Cloak in the Air. (Doctoral Dissertation). NSYSU. Retrieved from http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0627117-211756

Chicago Manual of Style (16th Edition):

Lin, Jau-Cho. “Design and Experimental Research of Acoustic Cloak in the Air.” 2017. Doctoral Dissertation, NSYSU. Accessed October 28, 2020. http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0627117-211756.

MLA Handbook (7th Edition):

Lin, Jau-Cho. “Design and Experimental Research of Acoustic Cloak in the Air.” 2017. Web. 28 Oct 2020.

Vancouver:

Lin J. Design and Experimental Research of Acoustic Cloak in the Air. [Internet] [Doctoral dissertation]. NSYSU; 2017. [cited 2020 Oct 28]. Available from: http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0627117-211756.

Council of Science Editors:

Lin J. Design and Experimental Research of Acoustic Cloak in the Air. [Doctoral Dissertation]. NSYSU; 2017. Available from: http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0627117-211756

2. Smoker, Jason James. Design of a Programmable Active Acoustic Metamaterial.

Degree: Mechanical Engineering, 2012, University of Maryland

Metamaterials are artificial materials engineered to provide properties which may not be readily available in nature. The development of such class of materials constitutes a new area of research that has grown significantly over the past decade. Acoustic metamaterials, specifically, are even more novel than their electromagnetic counterparts arising only in the latter half of the decade. Acoustic metamaterials provide a new tool in controlling the propagation of pressure waves. However, physical design and frequency tuning, is still a large obstacle when creating a new acoustic metamaterial. This dissertation describes active and programmable design for acoustic metamaterials which allows the same basic physical design principles to be used for a variety of application. With cloaking technology being of a great interest to the US Navy, the proposed design approach would enable the development of a metamaterial with spatially changing effective parameters while retaining a uniform physical design features. The effective parameters would be controlled by tuning smart actuators embedded inside the metamaterial structure. Since this design is based on dynamic effective parameters that can be electrically controlled, material property ranges of several orders of magnitude could potentially be achieved without changing any physical parameters. With such unique capabilities, physically realizable acoustic cloaks can be achieved and objects treated with these active metamaterials can become acoustically invisible. Advisors/Committee Members: Baz, Amr (advisor).

Subjects/Keywords: Mechanical engineering; Acoustics; Materials Science; acoustic cloaks; active acoustic metamaterials; effective bulk modulus; effective density; metamaterials; programmable metamaterials

cloaks which set up the foundation for acoustic cloaks. The third subsection continues the… …and the gas. Many acoustic cloak researchers have turned to other aspects of the cloaks such… …Chapter 5 : Experimental Demonstration of an Active Acoustic Metamaterial with Tunable… …100 5.4: Calculation of the Acoustic Impedance using Two Microphone Measurements 103 5.5… …Acoustic Metamaterial Cell Construction… 

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Smoker, J. J. (2012). Design of a Programmable Active Acoustic Metamaterial. (Thesis). University of Maryland. Retrieved from http://hdl.handle.net/1903/13834

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Smoker, Jason James. “Design of a Programmable Active Acoustic Metamaterial.” 2012. Thesis, University of Maryland. Accessed October 28, 2020. http://hdl.handle.net/1903/13834.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Smoker, Jason James. “Design of a Programmable Active Acoustic Metamaterial.” 2012. Web. 28 Oct 2020.

Vancouver:

Smoker JJ. Design of a Programmable Active Acoustic Metamaterial. [Internet] [Thesis]. University of Maryland; 2012. [cited 2020 Oct 28]. Available from: http://hdl.handle.net/1903/13834.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Smoker JJ. Design of a Programmable Active Acoustic Metamaterial. [Thesis]. University of Maryland; 2012. Available from: http://hdl.handle.net/1903/13834

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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