Advanced search options

Advanced Search Options 🞨

Browse by author name (“Author name starts with…”).

Find ETDs with:

in
/  
in
/  
in
/  
in

Written in Published in Earliest date Latest date

Sorted by

Results per page:

Sorted by: relevance · author · university · dateNew search

You searched for subject:(acoustic invisibility). Showing records 1 – 3 of 3 total matches.

Search Limiters

Last 2 Years | English Only

No search limiters apply to these results.

▼ Search Limiters


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

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

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 29, 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. 29 Oct 2020.

Vancouver:

Lin J. Design and Experimental Research of Acoustic Cloak in the Air. [Internet] [Doctoral dissertation]. NSYSU; 2017. [cited 2020 Oct 29]. 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


NSYSU

2. Wu, Jia-liang. Design and Analysis of the Surface Impedance Type Acoustic Invisible Cloak.

Degree: Master, Mechanical and Electro-Mechanical Engineering, 2018, NSYSU

The issue of controlling wave propagation has become a very popular research in recent years. Its application can be noise controlling, wave communication and hiding the object free from detection. Noise controlling was based on sound-absorbing materials in the past. However, high performance sound-absorbing materials come at large volume and high cost. Therefore, it must develop new technologies to solve this problem. The theories of acoustic cloak and metamaterials were gradually published in recent. They can control the path of the wave and make the wave field invisible. However, the acoustic materials with these characteristics do not exist in nature. The purpose of the study was to design and fabricate invisible cloak in air. In this study, the author design the surface impedance type acoustic invisible cloak in the air. To realize this cloak, the thesis combines cavities and tubes with metamaterials. The acoustic cloak shell with complex parameters can be designed. The cloak shell was designed and verified by numerical analysis. For numerical analysis, the thesis uses ANSYS workbench simulation software to verify the effect of the surface impedance type acoustic invisible cloak. The response range at dimensionless frequencies are studied. The results demonstrated the effectiveness of the surface impedance type acoustic invisible cloak and they could work in broadband. These research findings provide new strategies and surface impedance design for the physical realization of an invisibility cloak in the air. Advisors/Committee Members: Hsia Shao-Yi (chair), Yang Shiuh-Kuang (committee member), Cheng Jyin-Wen (chair), Wang,Bor-Tsuen (chair), Lee Ping-Hung (chair).

Subjects/Keywords: Surface impedance type acoustic invisible cloak; Acoustic impedance cloak; Metamaterials; Wave invisibility

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

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

APA (6th Edition):

Wu, J. (2018). Design and Analysis of the Surface Impedance Type Acoustic Invisible Cloak. (Thesis). NSYSU. Retrieved from http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0617118-162842

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):

Wu, Jia-liang. “Design and Analysis of the Surface Impedance Type Acoustic Invisible Cloak.” 2018. Thesis, NSYSU. Accessed October 29, 2020. http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0617118-162842.

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

MLA Handbook (7th Edition):

Wu, Jia-liang. “Design and Analysis of the Surface Impedance Type Acoustic Invisible Cloak.” 2018. Web. 29 Oct 2020.

Vancouver:

Wu J. Design and Analysis of the Surface Impedance Type Acoustic Invisible Cloak. [Internet] [Thesis]. NSYSU; 2018. [cited 2020 Oct 29]. Available from: http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0617118-162842.

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

Council of Science Editors:

Wu J. Design and Analysis of the Surface Impedance Type Acoustic Invisible Cloak. [Thesis]. NSYSU; 2018. Available from: http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0617118-162842

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

3. García Chocano, Víctor Manuel. New devices for noise control and acoustic cloaking .

Degree: 2015, Universitat Politècnica de València

[EN] The aim of this work is to design new acoustic devices based on arrangements of scattering units. First, the use of sonic crystals as noise barriers for traffic noise control is comprehensively analyzed. Due to the limitations of the conventional structures based on rigid scatterers, the inclusion of absorbing elements is proposed. Two different types of absorbers are here considered: porous materials and microperforated plates. In the first case, the attenuation characteristics of barriers made with cylinders containing rubber crumb is analyzed. The second proposal is based on the construction of cylindrical microperforated shells. Analytical approaches modelling the behavior of the barriers have been developed in both cases. These models show a satisfactory agreement with the corresponding experimental realizations. Finally, it is performed an optimization process in order to obtain efficient sound barriers intended to attenuate traffic noise. Another application considered in this work is the construction of cloaks to render objects acoustically invisible. In particular, cloaks made with rigid inclusions are designed to operate with airborne sound. The first proposal consists of a cloak that utilizes the temperature of the background to control the properties of the effective medium. In addition, two and three-dimensional cloaks have been developed through the scattering cancellation technique. These devices have been designed by means of an optimization procedure and their performance has been experimentally demonstrated.; [ES] El objetivo de este trabajo es el diseño de nuevos dispositivos acústicos basados en disposiciones de centros de dispersión. En primer lugar, el uso de cristales sónicos como barreras acústicas para el control de ruido de tráfico es analizado en detalle. Debido a las limitaciones que presentan las estructuras convencionales basadas en centros de dispersión rígidos, se propone la inclusión de elementos absorbentes en los mismos. Se han considerado dos tipos distintos de absorbente: materiales porosos y placas microperforadas. En el primer caso se analizan las propiedades atenuadoras de barreras formadas por cilindros que contienen granza de caucho. La segunda solución se basa en la construcción de coronas microperforadas. En ambos casos se han desarrollado modelos analíticos que permiten determinar el comportamiento de las barreras. Dichos modelos muestran un acuerdo satisfactorio con las correspondientes realizaciones experimentales. Finalmente se ha realizado un proceso de optimización con objeto de obtener barreras eficientes para la atenuación de ruido de tráfico. Otra aplicación considerada en este trabajo es el desarrollo de dispositivos de invisibilidad acústica. Concretamente se pretenden diseñar mantos constituidos con elementos rígidos para ondas acústicas en aire. La primera propuesta consiste en un manto que utiliza la temperatura del medio externo para controlar sus propiedades efectivas. Además se han desarrollado mantos en dos y tres dimensiones a través de la… Advisors/Committee Members: Sánchez-Dehesa Moreno-Cid, José (advisor).

Subjects/Keywords: Acoustic cloaking; Invisibility; Scattering cancellation; Noise control; Sonic crystal; Noise barrier; Rubber crumb; Microperforated shell

…noise control and acoustic cloaking by D. V´ ıctor Manuel Garc´ ıa Chocano Doctor of Science… …Valencia, March 2015 The aim of this work is to design new acoustic devices based on arrangements… …pollution . . . . . . . . . 1.2 Rubber crumb as acoustic absorbent 1.3 Sonic crystals… …scattering theory 2.1 The acoustic wave equation . 2.2 Scattering by a single cylinder 2.2.1 Fluid… …3.1.2 Phenomenological models 3.1.3 Microstructural models . . 3.2 Acoustic model of rubber… 

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

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

APA (6th Edition):

García Chocano, V. M. (2015). New devices for noise control and acoustic cloaking . (Doctoral Dissertation). Universitat Politècnica de València. Retrieved from http://hdl.handle.net/10251/53026

Chicago Manual of Style (16th Edition):

García Chocano, Víctor Manuel. “New devices for noise control and acoustic cloaking .” 2015. Doctoral Dissertation, Universitat Politècnica de València. Accessed October 29, 2020. http://hdl.handle.net/10251/53026.

MLA Handbook (7th Edition):

García Chocano, Víctor Manuel. “New devices for noise control and acoustic cloaking .” 2015. Web. 29 Oct 2020.

Vancouver:

García Chocano VM. New devices for noise control and acoustic cloaking . [Internet] [Doctoral dissertation]. Universitat Politècnica de València; 2015. [cited 2020 Oct 29]. Available from: http://hdl.handle.net/10251/53026.

Council of Science Editors:

García Chocano VM. New devices for noise control and acoustic cloaking . [Doctoral Dissertation]. Universitat Politècnica de València; 2015. Available from: http://hdl.handle.net/10251/53026

.