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Tesi sul tema "Sound-waves"

Autore: Grafiati
Pubblicato: 4 giugno 2021
Ultima modifica: 1 agosto 2024

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1

Zinoviev, Alexei. "Application of the Multi-Modal Integral Method (MMIM) to sound wave scattering in an acoustic waveguide". Title page, contents and abstract only, 1999. http://hdl.handle.net/2440/37720.

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The current work is devoted to the problem of sound wave scattering by elastic cylindrical objects in a plain acoustic waveguide. The Multi- Modal Integral Method (MMIM) is proposed, which is based on nonstandard representation of the Green's function. It combines advantages of integral equation and eigenfunction methods and provides a quickly converging and highly accurate solution, taking into account all the waveguide modes up to infinite order. As illustrations of application of this method, acoustic diffraction is calculated from a system of several parallel homogeneous cylinders and from an air-filled cylindrical elastic shell. Numerical solutions are found for various versions of the system of elastic cylinders in a fluid layer with perfectly soft and rigid boundaries. Phase - frequency and amplitude - frequency characteristics are found for modal coefficients of the scattered field. Sharp increase of their amplitudes is found near resonance frequencies of the waveguide and the scattering cylinders. Pictures of the source density on the surface of the cylinders show that the nature of their distribution strongly depends on the frequency and the mutual location of the cylinders in the waveguide. Field structure near the cylinders reveals that higher-order waveguide modes play a significant role in the scattering process. Spatial distribution of the acoustic power flow near the scattering object is calculated for several frequencies and two sets of elastic properties of the cylinder. It is shown that at the critical frequencies of the waveguide as well as at the internal resonances of the cylinder the acoustic energy flows in closed paths in some regions of the waveguide. Near the internal resonances of the cylinder the closed paths are located in the near vicinity of the scattering object and partially go through its interior. It is suggested that re-radiation of the energy stored in the vortices may contribute to the echo phenomenon. The integral reflection coefficient is calculated for a system waveguide/shell for different values of wall thickness and distance between the shell and the waveguide bottom. Maxima and minima in the reflection coefficient associated with cut-on frequencies of the waveguide modes and structural resonances of the shell are identified. The calculations show that the conventional definition of target strength in a shallow waveguide is inappropriate. Different kinds of resonances are identified in frequency and angular dependencies of the velocity amplitude of the shell surface. These resonances belong to the following groups: a) critical frequencies of the waveguide modes, b) structural resonances of the elastic shell, c) resonance oscillations of the gas-filled interior of the shell, d) resonance oscillations of the coupled fluid-shell. Application of the Multi-Modal Integral Method (MMIM) to Sound Wave Scattering in an Acoustic Waveguide. Temporal sequences of pictures showing the spatial structure of the total and scattered fields in the near and far field zones are obtained. It is shown that the incident field produces waves of acoustic pressure propagating along the boundary of the scattering object, which, in turn, generate the scattered acoustic field. In the process of propagation, the waves may interact with each other via the fluid or the scattering object. This leads to significant changes of the structure of the acoustic field and of the amount of acoustic energy reflected from the scatterer. It is also shown that, in most cases, standing waves exist between the scatterer and the waveguide boundaries. Accuracy of the Multi-Modal Integral Method is discussed. It is shown that the implementation of the method requires few computer resources for good accuracy of the solution.
Thesis (Ph.D.)--School of Mechanical Engineering, 1999.
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2

Chambers, James P. "Scale model experiments on the diffraction and scattering of sound by geometrical step discontinuities and curved rough surfaces". Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/17858.

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3

Yargus, Michael W. "Experimental study of sound waves in sandy sediment /". Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/6075.

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4

Menchon, Enrich Ricard. "Spatial adiabatic passage: light, sound and matter waves". Doctoral thesis, Universitat Autònoma de Barcelona, 2013. http://hdl.handle.net/10803/129476.

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El naixement de la Mecànica Quàntica va proporcionar el marc teòric que permetia poder explicar fenòmens prèviament observats experimentalment, com ara la radiació del cos negre, l'efecte fotoelèctric o les línies espectrals de gasos atòmics, i també va permetre entendre millor aspectes fonamentals relacionats amb la dualitat ona-partícula i la interacció entre radiació i matèria. La Mecànica Quàntica ha estat també l'origen de disciplines més específiques com l'Òptica Quàntica o la Informació Quàntica, les quals s’ocupen parcialment del que es coneix com Enginyeria Quàntica. En aquest context, s'han proposat processos de passatge adiabàtic, que consisteixen en el seguiment adiabàtic d'un estat propi del sistema, i que permeten un control molt robust i eficient de la transferència de població entre dos estats assimptòtics. Com molts altres processos en Mecànica Quàntica, els processos de passatge adiabàtic són purament oscil•latoris i poden ser considerats en altres sistemes físics no quàntics que suportin quantitats oscil•lants. En aquesta tesi, s'analitzen processos de passatge adiabàtic en diferents sistemes físics per a controlar la propagació de llum, so i ones de matèria en sistemes de guies acoblades, i la transferència d'àtoms freds individuals en trampes de potencial harmòniques. Adicionalment, utilitzem la robustesa i l'alta eficiència del passatge adiabàtic per proposar nous dispositius i discutir noves implementacions en aquests diversos camps. Específicament, demostrem experimentalment el passatge espacial adiabàtic de llum en un sistema de tres guies TIR d'òxid de silici compatibles-CMOS acoblades mitjançant el camp evanescent, que consisteix en una transferència completa d'intensitat de llum entre les guies externes del sistema. L'avantatge d'usar el passatge espacial adiabàtic respecte els acobladors direccionals estàndard és que la transferència de llum és robusta enfront de fluctuacions tecnològiques i no depèn de valors precisos dels paràmetres. Aquest és el primer dispositiu de passatge espacial adiabàtic per llum fabricat amb tecnologia compatible-CMOS, el que permet una integració massiva i de baix cost. A més, també demostrem experimentalment que aquest sistema de guies es comporta simultàniament com a filtre passa alts i passa baixos, amb unes característiques que el fan una alternativa a altres tipus de filtres integrables com filtres basats en interferència o en absorció. Adicionalment, adrecem el passatge espacial adiabàtic d'ones sonores en sistemes de dos defectes lineals acoblats en cristalls sònics. Calculant els diagrames de bandes per analitzar els supermodes del sistema disponibles i modificant apropiadament la geometria dels defectes lineals al llarg de la propagació, dissenyem dispositius que funcionen com a divisors i acobladors adiabàtics mutifreqüència i com a analitzadors de diferència de fase. També, proposem un mètode per injectar, extreure i filtrar en velocitat àtoms neutres en trampes en forma d'anell mitjançant el passatge espacial adiabàtic utilitzant dues guies addicionals. La proposta es basa en el seguiment adiabàtic d’un estat propi transversal del sistema. Realitzem càlculs semianalítics que encaixen perfectament amb els resultats de simulacions numèriques de l'equació de Schrödinger. També mostrem que la nostra proposta podria ser implementada experimentalment utilitzant paràmetres realistes d'àtoms ultrafreds en potencials òptics dipolars. Finalment, estudiem el passatge adiabàtic d'un àtom fred individual en un triple pou de potencial bidimensional, anant més enllà dels sistemes coneguts, que són de manera efectiva unidimensionals i estudiant les possibilitats que sorgeixen dels graus de llibertat addicionals. D'una banda, un sistema de tres pous de potencial amb les trampes en una geometria triangular es proposa per a interferometria d'ones de matèria, aprofitant un creuament de nivells que apareix en l'espectre d'energia. D'altra banda, es genera moment angular satisfactòriament en una configuració similar on les trampes tenen freqüències d'atrapament diferents, seguint simultàniament dos estats propis del sistema.
The birth of Quantum Mechanics provided a theoretical framework that could explain some previously experimentally reported phenomena, such as the black body radiation, the photoelectric effect or the spectral lines of atomic gases, and also allowed for a better understanding of fundamental aspects related to the wave-particle duality and the interaction between radiation and matter. Quantum Mechanics has been also the origin of more specific disciplines such as Quantum Optics or Quantum Information science, which are partially devoted to a more applied research field that is known as Quantum Engineering. In this context, adiabatic passage processes consisting in the adiabatic following of an eigenstate of the system, which allows for a very robust and efficient control of the population transfer between two asymptotic states have been proposed. As many other processes in Quantum Mechanics, adiabatic passage processes are purely oscillatory and can be extended to other non-quantum physical systems, which also support oscillating quantities. In this thesis, spatial adiabatic passage processes are addressed in different oscillatory physical systems to control light, sound and matter waves propagation in systems of coupled waveguides, and the transfer of single cold atoms in harmonic potentials. Additionally, we make use of the robustness and high efficiency of the adiabatic passage to propose new devices and discuss new implementations in these various fields. To be specific, we experimentally demonstrate the spatial adiabatic passage of light in a system of three evanescent-coupled CMOS-compatible silicon oxide TIR waveguides, which consists in a complete transfer of light intensity between the outermost waveguides of the system. The advantage of using spatial adiabatic passage compared to standard directional couplers is that the light transfer is robust in front of technological fluctuations and does not depend on precise parameter values. Additionally, this is the first spatial adiabatic passage of light device fabricated in CMOS-compatible technology, which allows for massive and low cost integration. Furthermore, we also experimentally show that this system of coupled waveguides behaves as a simultaneously low- and high-pass spectral filter, with features that makes it an alternative to other integrated filters like interferenceñbased and absorbance-based filters. In addition, we address the spatial adiabatic passage of sound waves in systems of two coupled linear defects in sonic crystals. By calculating the band diagrams to analyze the available supermodes of the system and modifying the geometry of the linear defects along the propagation distance appropriately, we design devices working as a multifrequency adiabatic splitter, as a coupler and also as a phase difference analyser. Furthermore, we discuss a novel method to inject, extract and velocity filter neutral atoms in a ring trap via a spatial adiabatic passage process by using two extra waveguides. The proposal is based on the adiabatic following of a transversal eigenstate of the system. Semianalytical calculations are performed, which perfectly match with the results of the numerical integration of the Schrˆdinger equation. We also show that our proposal could be experimentally implemented for realistic state-of-the-art parameters of ultracold atoms in optical dipole potentials. Finally, we study the spatial adiabatic passage of a single cold atom in two-dimensional triple-well potentials, going beyond the well-understood effective one-dimensional systems and studying the possibilities arising from the additional degrees of freedom. On the one hand, a system of three coupled identical harmonic potentials with the traps lying in a triangular configuration is proposed for matter wave interferometry taking profit of a level crossing appearing in the energy spectrum. On the other hand, angular momentum is successfully generated in a similar configuration where the three harmonic traps have different trapping frequencies by simultaneously following two eigenstates of the system.
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5

Legendre, César. "On the interactions of sound waves and vortices". Doctoral thesis, Universite Libre de Bruxelles, 2015. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209147.

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Abstract (sommario):
The effects of vortices on the propagation of acoustic waves are numerous, from simple convection effects to instabilities in the acoustic phenomena, including absorption,

reflection and refraction effects. This work focusses on the effects of mean flow

vorticity on the acoustic propagation. First, a theoretical background is presented

in chapters 2-5. This part contains: (i) the fluid dynamics and thermodynamics

relations; (ii) theories of sound generation by turbulent flows; and (iii) operators taken

from scientific literature to take into account the vorticity effects on acoustics. Later,

a family of scalar operators based on total enthalpy terms are derived to handle mean

vorticity effects of arbitrary flows in acoustics (chapter 6). Furthermore, analytical

solutions of Pridmore-Brown’s equation are featured considering exponential boundary

layers whose profile depend on the acoustic parameters of the problem (chapter 7).

Finally, an extension of Pridmore-Brown’s equation is formulated for predicting the

acoustic propagation over a locally-reacting liner in presence of a boundary layer of

linear velocity profile superimposed to a constant cross flow (chapter 8).


Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished

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6

Zinoviev, Alexei lurjevich. "Application of the Multi-Modal Integral Method (MMIM) to sound wave scattering in an acoustic waveguide". Click here to access, 1999. http://thesis.library.adelaide.edu.au/public/adt-SUA20050905.140025.

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Thesis (Ph.D.)--University of Adelaide, Dept. of Mechanical Engineering, 2000.
Title from screen page (viewed September 13 2005). Includes bibliographical references. Also available in print version.
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7

Wang, Qiang. "Atmospheric refraction and propagation over curved surfaces". n.p, 1997. http://ethos.bl.uk/.

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8

Dostal, Jack Alan. "An investigation into student understanding of longitudinal standing waves". Thesis, Montana State University, 2008. http://etd.lib.montana.edu/etd/2008/dostal/DostalJ1208.pdf.

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This study investigates the difficulties that introductory university physics students have with the concept of longitudinal standing waves in the context of standing waves in pipes. My goal is to identify difficulties that persist even after standard instruction on longitudinal standing waves and attempt to improve upon that method of instruction. The study follows a four-step design. I first use exploratory surveys and interviews with students to elicit the difficulties present in students\' understanding of longitudinal standing waves in pipes. I then use the information gained to create and assessment instrument, the Standing Waves Diagnostic Test, and a curricular intervention, the Longitudinal Standing Waves Tutorial. I then undertake a three-step process of pre-testing students with the Standing Wave Diagnostic Test, intervention with the Longitudinal Standing Waves Tutorial, and post-testing again with the Standing Wave Diagnostic Test to determine the impact of the intervention. This is then compared to data from students in classes where the intervention is not used. Students using the intervention significantly outperform their non-intervention counterparts on the Standing Wave Diagnostic Test. The results of the students pre- and post-tests indicate that significant improvement in students\' understandings of longitudinal standing waves can be achieved by the use of the tutorial.
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9

Cornell, Jason E. "Verification of the single scattering analytical model for mode coupling effects caused by solitons". Thesis, Monterey, California : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/Sep/09Sep_Cornell.pdf.

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Thesis (M.S. in Applied Physics)--Naval Postgraduate School, September 2009.
Thesis Advisor(s): Colosi, John A. ; Smith, Kevin B. "September 2009." Description based on title screen as viewed on November 5, 2009. Author(s) subject terms: Shallow-water environment, 3-D simulations, vertical mode coupling, Internal Solitary Waves, solitons, acoustic variability. Includes bibliographical references (p. 55). Also available in print.
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10

Ailes-Sengers, Lynn H. "Pulse broadening, polarimetric and angular memory effects of wave scattering from very rough surfaces /". Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/5856.

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11

Wang, Shuai School of Electrical Engineering &amp Telecommunication UNSW. "Soundfield analysis and synthesis: recording, reproduction and compression". Awarded by:University of New South Wales. School of Electrical Engineering and Telecommunication, 2007. http://handle.unsw.edu.au/1959.4/31502.

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Globally, the ever increasing consumer interest in multichannel audio is a major factor driving the research intent in soundfield reconstruction and compression. The popularity of the well commercialized 5.1 surround sound system and its 6-Channel audio has been strongly supported by the advent of powerful storage medium, DVD, as well as the use of efficient telecommunication techniques. However, this popularity has also revealed potential problems in the development of soundfield systems. Firstly, currently available soundfield systems have rather poor compatibility with irregular speaker arrangements. Secondly, bandwidth requirement is dramatically increased for multichannel audio representation with good temporal and spatial fidelity. This master???s thesis addresses these two major issues in soundfield systems. It introduces a new approach to analyze and sysnthesize soundfield, and compares this approach with currently popular systems. To facilitate this comparison, the behavior of soundfield has been reviewed from both physical and psychoacoustic perspectives, along with an extensive study of past and present soundfield systems and multichannel audio compression algorithms. The 1th order High Spatial Resolution (HSR) soundfield recording and reproduction has been implemented in this project, and subjectively evaluated using a series of MUSHRA tests to finalize the comparison.
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12

Bell, Alexander J. "An acoustical investigation of the concert harp". Thesis, University of St Andrews, 1988. http://hdl.handle.net/10023/2768.

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This thesis is a report of acoustical research on the concert harp. The harp has an established place in the symphony orchestra and is reacquiring its role as a solo chamber instrument that it had before the development of the modern piano. As far as can be determined, this is the first doctoral thesis on the concert harp and serves as an introduction to the science of the instrument, The experimental methods employed- holographic interferonietry, input admittance measurements, Chiadni glitter pattern methods, sound pressure level measurements- have all been successfully used with work on other musical instruments. Theoretical calculations are used to underpin the experimental results for several of the subjects reported. The experimental results are also compared with the results of similar tests on different musical instruments. Analyses of the violin, guitar and piano are particularly used in discussions. This work is specifically on the "Orchestra" concert harp, manufactured and sold by the Salvi Harp organisation, though reference Is made in Chapter 3 to the "Electra" concert harp, which is also a Salvi harp. The "Orchestra" harp has a similar design to many other concert harps built by different luthiers around the world. This thesis is structured as follows. The first chapter is a review of historical and contemporary research an stringed musical instruments. The next chapter is a detailed description of the Salvi "Orchestra" harps the dimensions of all the inportant features are given, the tensions and materials of the strings are reported and there is also a short description on the playing of the instrument. The next five chapters form the kernal of the research report and deal with the vibrations of the constituent part of the "Orchestra" and finally the completed, strung harp itself. In Chapter 3, the vibrations of the free soundboard are reported in some detail. Analysis is made at a number of stages of the construction of the soundboard itself. The position of the neutral axis on the soundboard is also given. There is also reference to the soundboard of the Salvi "Electra" harp. Chapter 4 deals with the air resonances in the enclosed air volume of the "Orchestra" soundbox. Both a Helmholtzian air mode and higher order air modes are discussed. Theoretical models are used for both forms of air modes, Chapter 5 is a report of the vibrational modes of the "Orchestra" soundbox using both Chladni glitter patterns and holographic interferonietry. The results of Chapter 5 are confirmed and expanded by the work in Chapter 6, where input admittance measurements are made on the soundbox.Chapter 7 investigates the vibrational modes of the soundbox, both in the isolated state and as part of a completed, strung harp. This is followed by a chapter on the directivity of the "Orchestra" harp in which the principal areas of radiation from the harp are reported. The next chapter deals with attempts to relate objective measurements with subjective opinions of six concert harps. The last chapter summarises the principal results of the various analyses reported in this thesis. Suggestions for further research on the harp are made. There are also suggestions for the improvement of the Salvi "Orchestra" harp. There are three appendices at the end of this work. The first deals with the testing of spruce samples intended for the soundboards of the harps. The effect of the veneer is also discussed. The second appendix deals with the production and physical properties of gut harp strings. The third appendix describes the changes to the resonant modes of an isolated soundbox produced by changing the shape of the straining and cover bars of the soundboard.
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13

Terrill, Eric J. "Acoustic measurements of air entrainment by breaking waves /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1998. http://wwwlib.umi.com/cr/ucsd/fullcit?p9907829.

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14

Popple, Damian Francis. "The interaction of two-dimensional sound waves with several compliant strips". Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243562.

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15

Abbott, James Fuller. "The interaction of sound and shock waves with flexible porous materials". Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13858.

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16

Lu, Paul ChihPeng. "Passive cancellation of low frequency sound waves using optimized embedded mechanisms". Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1876285421&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.

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17

Soukup, Darin J. "A coupled local mode approach to laterally heterogeneous anisotropic media, volume scattering, and T-wave excitation /". Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/6847.

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18

Hacene-Djaballah, Nouri. "Floating floor attenuation of impact structure-borne sound in timber construction". Fairfax, VA : George Mason University, 2009. http://hdl.handle.net/1920/4598.

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Thesis (M.S.)--George Mason University, 2009.
Vita: p. 42. Thesis director: Girum Urgessa. Submitted in partial fulfillment of the requirements for the degree of Master of Science in Civil, Environmental, and Infrastructure Engineering. Title from PDF t.p. (viewed Oct. 12, 2009). Includes bibliographical references (p. 39-41). Also issued in print.
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19

Bowen, Stephen Gerard. "Forward scattering of a pulsed continuous wave signal through laminar and turbulent thermal plumes". Thesis, Springfield, Va. : Available from the National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA271210.

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Thesis (Degree of Ocean Engineer)-- Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution, Sept. 1993.
Thesis advisor(s): Catipovic, Josko. September 1993. Bibliography: p. 72-74. Also available online.
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20

Burger, Gert Cloete. "Optimisation of the pulse-echo method with an application to acoustic thermometry". Thesis, Cape Peninsula University of Technology, 2010. http://hdl.handle.net/20.500.11838/1105.

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Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2009
In acoustics, pulse echo methods are well known as a means of measuring time of Hight. Traditional techniques for generating acoustic waves in solid ferromagnetic waveguides include piezoelectric, capacitive and magnetostriction. Piezoelectric and capacitive techniques are preferred due to the inefficiency of magnetostriction caused by electro-mechanical coupling losses and the fact that most ferromagnetic materials show low levels of magnetostriction. The aim of this study was to optimise the magnetostrictive effects for sensing applications based on a ferromagnetic waveguide using the pulse echo method. The results obtained were implemented in the design of an acoustic thermometer. Two configurations for signal generation and recovery were examined, the use of a single wound copper coil acting as a transceiver coil, and the use of separate transmit and receive coils. Results obtained using the latter configuration indicated better signal to noise ratio's and provided the flexibility to manipulate the point of signal recovery. The pulse echo method was implemented and optimised. An acoustic thermometer based on an existing design was developed by inducing a partial reflection from a set position in the waveguide, defining a sensing probe. Awareness of the elastic properties of the waveguide material enabled the guaging of its temperature by measuring the acoustic pulse velocity in the probe. The accuracy of the instrument was increased through signal conditioning, examined together with cross correlation and an increased sampling frequency. Systematic errors were resolved through calibration, giving the instrument an overall accuracy of ±O.56"C for the range of temperatures between 2O"C and 400"C.
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21

Chase, Yun S. "Sound diffraction by an underwater ridge with finite impedance". Thesis, Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/17773.

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22

Kim, Jeong Hoon. "Stochastic turning point problem". Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/40038.

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A one-dimensional refractive, randomly-layered medium is considered in an acoustic context. A time harmonic plane wave emitted by a source is incident upon it and generates totally reflected fields which consist of "signal" and "noise". The statistical properties, i.e., mean and correlation functions, of these fields are to be obtained. The variations of the medium structure are assumed to have two spatial scales; microscopic random fluctuations are superposed upon slowly varying macroscopic variations. With an intermediate scale of the wavelength, the interplay of total internal reflection (geometrical acoustics) and random multiple scattering (localization phenomena) is analyzed for the turning point problem. The problem, in particular, above the turning point is formulated in terms of a transition scale. Two limit theorems for stochastic differential equations with multiple spatial scales, called Theorem 1 and Theorem 2, are derived. They are applied to the stochastic initial value problems for reflection coefficients in the regions above and below the turning point, respectively. Theorem 1 is an extension of a limit theorem on O( 1) scaled interval to infinite scale and provides uniformly-valid approximate statistics for random multiple scattering in the region above the turning point (transition as well as outer regions). Theorem 2 deals with stochastic problems with a rapidly varying deterministic component and approximates the reflection process in the region below the turning point which is characterized by the random noise. Finally, the evolution of the reflection coefficient statistics in the whole region is described by combining the two results as a product of a transformation at the turning point and two evolution operators corresponding to the two regions.
Ph. D.
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23

WEYKER, ROBERT RICHARD. "RESONANCE AND ASYMPTOTIC SERIES BASED IDENTIFICATION OF AN ACOUSTICALLY RIGID SPHERE (SINGULARITY EXPANSION METHOD)". Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/183850.

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Identification of the resonances and the local determination of the radius of curvature of an acoustically rigid sphere from simulated transient input-output data is presented. The scattering from the sphere is formulated using three techniques: the classic Mie-Lorenz series, the singularity expansion method (SEM), and the asymptotic series approximation. The Mie-Lorenz series is used to provide synthetic data. The SEM and the asymptotic series are used to develop two parametric inverse models. The scattered velocity potential is separated into three components: the reflection, the first creeping wave, and the second creeping wave. The effect of removing various components of the scattered potential on the resonance identification is shown, along with the effect of adding small amounts of noise. We find that the identification of a few resonances requires a relatively high order autoregressive, moving-average model. In addition, we show that removing the reflection from the synthetic output has only a small effect on the single or multiple output identified resonances. However, we find that changing the time origin, removing the second creeping wave, or adding small amounts of noise results in large errors in the identified resonances. We find that the radius of curvature can be accurately determined from synthetic data using the asymptotic series based identification. In addition, the identification is robust in the presence of noise, and requires only a low order asymptotic series model.
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24

Farell, Cesar E. "A theoretical investigation of the low-frequency sound generated by breaking waves". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0002/MQ40967.pdf.

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25

Zhang, Qin. "Acoustic pulse diffraction by curved and planar structures with edges". Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/32005.

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Efficient and accurate solutions of acoustic wave diffraction by a rigid step discontinuity and a curved half-plane are derived by the uniform geometrical theory of diffraction. These solutions can be used in seismic data processing to evaluate and, eventually, to improve the existing data processing procedures. They can also find applications in electromagnetics, microwave antenna design, acoustic design and sound engineering. The rigid step discontinuity solution given in this thesis is more accurate than the existing solutions which are based on Kirchhoff theory of diffraction. This solution removes the previous restriction on the source and the receiver arrangement. It also provides high efficiency by the use of ray theory. This solution is further generalized to two offset half-planes and an inclined wedge. Solutions for more complicated structures can be obtained by superposition of these solutions with added interactions. The complex source position method is used to extend the omnidirectional point source solution to a beam source solution. The effect of changes of the directivity and orientation of the beam source is studied. Time-domain single and double diffraction coefficients are determined through direct Fourier transforming and convolution. An infinite impulse response filter is applied to the time-domain direct computation of single diffraction. This combination achieves a total saving of 75% of computing time over the frequency-domain approach. Diffraction by a curved half-plane is analyzed with the inclusion of creeping wave diffraction and second order edge diffraction. An acoustic model of a curved half-plane is designed to verify the theory. The experimental results obtained by Mellema have verified the existence of the creeping wave diffraction and weak traces of the second order edge diffraction.
Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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26

Kearns, James A. "An investigation of the diffraction of an acoustic plane wave by a curved surface of finite impedance". Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/16749.

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27

McCall, George Samuel II. "An experimental apparatus for measuring underwater acoustic scattering from complex finite cylindrical shells". Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/17667.

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28

Xie, Jishi. "Acoustic reflection from temperature microstructure". Thesis, The University of Sydney, 1989. https://hdl.handle.net/2123/26377.

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This thesis develops a numerical technique to predict the acoustic reflection from an arbitrary sound speed microstructure in the ocean (or a temperature microstructure in the fresh water). This numerical technique is able to reproduce the theoretical formulas for calculating the reflection coefficients of two analytically defined transition layers. The 50 kHz acoustic reflection coefficients from the temperature The 50 kHz acoustic reflection coefficients from the temperature microstructure measured in a fresh-water reservoir was predicted to be less than -90 dB and was found to be much weaker than the observed volume scattering which was due to the biological activities.
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29

Treeby, Bradley E. "The effect of hair on human sound localisation cues". University of Western Australia. School of Mechanical Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0192.

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The acoustic scattering properties of the human head and torso match well with those of simple geometric shapes. Consequently, analytical scattering models can be utilised to account for the sound localisation cues introduced by these features. The traditional use of such models assumes that the head surface is completely rigid in nature. This thesis is concerned with modelling and understanding the effect of terminal scalp hair (i.e., a non-rigid head surface) on the auditory localisation cues. The head is modelled as a sphere, and the acoustical characteristics of hair are modelled using a locally-reactive equivalent impedance parameter. This allows the scattering boundary to be defined on the inner rigid surface of the head. The boundary assumptions are validated experimentally, through impedance measurement at oblique incidence and analysis of the near-field scattering pattern of a uniformly covered sphere. The impedance properties of human hair are also discussed, including trends with variations in sample thickness, bulk density, and fibre diameter. A general solution for the scattering of sound by a sphere with an arbitrarily distributed, locally reactive surface impedance is then presented. From this, an analytical solution is derived for a surface boundary that is evenly divided into two uniformly distributed hemispheres. For this boundary condition, cross-coupling is shown to exist between incoming and scattered wave modes of equi-order when the degrees are non-equal and opposite in parity. The overall effect of impedance on the resultant scattering characteristics is discussed in detail, both for uniform and for hemispherically divided surface boundaries. Finally, the analytical formulation and the impedance characteristics of hair are collectively utilised to investigate the effect of hair on human auditory localisation cues. The hair is shown to produce asymmetric perturbations to both the monaural and binaural cues. These asymmetries may help to resolve localisation confusions between sound stimuli positioned in the front and rear hemi-fields. The cue changes in the azimuth plane are characterised by two predominant features and remain consistent regardless of the decomposition baseline (i.e., the inclusion of a pinna offset, neck, etc). Experimental comparisons using a synthetic hair material show a good agreement with simulated results.
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30

Tai, Chih-Che, Karin Keith e Jamie Price. "Sound and Waves: An Integrated K–8 Approach Supporting the NGSS and CCSS". Digital Commons @ East Tennessee State University, 2015. https://dc.etsu.edu/etsu-works/1000.

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31

Podo, Smardie D. "Comparison of layering effects in the propagation of transient planar stress waves". Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/18378.

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32

Guigou, Catherine R. J. "Active control of sound radiation due to subsonic wave scattering from discontinuities on thin elastic beams". Diss., This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-06062008-171425/.

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33

Ille, Jean-Francois. "Interaction of spatial scales in acoustic radiation from hemi-capped cylinders". Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/16091.

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34

Puentes, Heras M. "The use of SAW methods in probing near-surface elastic properties". Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299101.

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35

Mellema, Garfield Richard. "Subcritical acoustic scattering across a rough fluid-solid interface /". Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/6098.

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36

Johnson, Jeffrey B. "Interpretation of infrasound generated by erupting volcanoes and seismo-acoustic energy partitioning during strombolian explosions /". Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/6830.

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37

Aktas, Murat K. Farouk Bakhtier. "Thermoacoustically induced and acoustically driven flows and heat transfer in enclosures /". Philadelphia, Pa. : Drexel University, 2004. http://dspace.library.drexel.edu/handle/1860/313.

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38

Fung, Kin-Hung. "Phononic band gap of locally resonant sonic materials with finite thickness /". View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202004%20FUNG.

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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004.
Includes bibliographical references (leaves 73-74). Also available in electronic version. Access restricted to campus users.
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39

Opfer, Holger. "Active cancellation of 3D Tollmien-Schlichting waves in the presence of sound and vibrations". Doctoral thesis, Köln : Dt. Zentrum für Luft- und Raumfahrt e.V., Bibliotheks- und Informationswesen, 2002. http://www.gbv.de/dms/goettingen/370770838.pdf.

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40

Pang, Wai Ming. "Scattering of sound waves by a plane membrane with fixed constraints over circular regions". Thesis, Imperial College London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268026.

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41

Peterson, Reed Monty. "The Sound of the Waves: Nature and Man in the Works of Kunikida Doppo". Thesis, The University of Arizona, 2004. http://hdl.handle.net/10150/560520.

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42

MEN'SHOV, Igor, e Yoshiaki NAKAMURA. "On Instability of Acoustic Waves Propagating in Stratified Vortical Flows". The Japan Society of Mechanical Engineers, 2002. http://hdl.handle.net/2237/9091.

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43

Roush, Douglas L. "Three-dimensional analysis of Azimuthal dependence of sound propagation through shallow-water internal solitary waves". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Jun%5FRoush.pdf.

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Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, June 2006.
Thesis Advisor(s): John A. Colosi. "June 2006." Includes bibliographical references (p.43). Also available in print.
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44

Prior, Mark Kevan. "Low frequency sound propagation in sea surface mixed layers in the presence of internal waves". Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243119.

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45

Kierkegaard, Axel. "Numerical investigations of generation and propagation of sound waves in low mach number internal flows /". Stockholm : Department of Aeronautical and Vehicle Engineering, Royal Institute of Technology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9388.

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46

Shrivastava, Shamit. "Non-linear solitary sound waves in lipid membranes and their possible role in biological signaling". Thesis, Boston University, 2014. https://hdl.handle.net/2144/11049.

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Thesis (Ph. D.)--Boston University
Biological macromolecules self-assemble under entropic forces to form a dynamic 20 interfacial medium where the elastic properties arise from the curvature of the entropic potential of the interface. Elastic interfaces should be capable of propagating localized perturbations analogous to sound waves. However, (1) the existence and (2) the possible role of such waves in affecting biological functions remain unexplored. Both these aspects of "sound' as a signaling mechanism in biology are explored experimentally on mixed monolayers of lipids-fluorophores-proteins at the air/water interface as a model biological interface. This study shows - for the first time - that the nonlinear susceptibility near a thermodynamic transition in a lipid monolayer results in nonlinear solitary sound waves that are of 'all or none ' nature. The state dependence of the nonlinear propagation is characterized by studying the velocity-amplitude relationship and results on distance dependence, effect of geometry and collision of solitary waves are presented. Given that the lipid bilayers and real biological membranes have such nonlinearities in their susceptibility diagrams, similar solitary phenomenon should be expected in biological membranes. In fact the observed characteristics of solitary sound waves such as, their all or none nature, a biphasic pulse shape with a long tail and optp-mechano-electro-thermal coupling etc. are strikingly similar to the phenomenon of nerve pulse propagation as observed in single nerve fibers. Finally given the strong correlation between the activity of membrane bound enzymes and the susceptibility and the fact that the later varies within a single solitary pulse, a new thermodynamic basis for biological signaling is proposed. The state of the interface controls both the nature of sound propagation and its impact on incorporated enzymes and proteins. The proof of concept is demonstrated for acetylcholine esterase embedded in a lipid monolayer, where the enzyme is spatiotemporally "knocked out" by a propagating sound wave.
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47

Maess, Matthias. "Material characterization using nonlinear wave propagation". Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/19311.

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48

Quijano, Jorge. "Radiative Transfer Theory Applied to Ocean Bottom Modeling". PDXScholar, 2010. https://pdxscholar.library.pdx.edu/open_access_etds/516.

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Research on the propagation of acoustic waves in ocean bottom sediment is of interest for active sonar applications such as target detection and remote sensing. Currently, all seabed scattering models available in the literature are based on the full solution of the wave equation, which sometimes leads to mathematically intractable problems. In the electromagnetics community, an alternative formulation that overcomes some of this complexity is radiative transfer theory, which has established itself as an important technique for remote sensing. In this work, radiative transfer (RT) theory is proposed for the first time as a tool for the study of seabed acoustic scattering. The focus of this work is the development of a complete model for the interaction of acoustic energy with water-saturated sediments. The general geometry considered in this study consists of multiple elastic layers containing random distributions of inhomogeneities. The accuracy of the proposed model is assessed by rigorous experimental work, with data collected from random media in which acoustic properties such as the concentration and size of scatterers, background material, and the presence of elastic boundaries are controlled parameters. First, the ultrasound RT model is implemented for layers of finite thickness. The range of applicability of the proposed model is then illustrated using scaled experiments conducted at the Northwest Electromagnetics and Acoustics Research Laboratory (NEAR-Lab). Next, the model is applied to field data collected in a region with gassy sediments and compared to the formulation originally used to explain these data. Finally, insight into the emerging area of study of the time-dependent RT formulation is presented, and its role in the representation of finite broadband pulses is discussed.
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49

Warren, Daniel. "The scattering of sound waves in two-dimensional ducts with discontinuities in height and material property". Thesis, Brunel University, 1999. http://bura.brunel.ac.uk/handle/2438/6618.

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Eigen-mode matching techniques offer a versatile approach for solving acoustic scattering problems in ducts. However, until recently, these techniques have been restricted to problems in which the boundary conditions contain at most one derivative, that is, Neumann, Dirichlet or Robin's conditions. Here a method is developed to solve scattering problems in ducts that are discontinuous in height and have at least one surface described by a high order boundary condition. Attention is focussed on the membrane condition, but the method can be extended to elastic plates and other higher order conditions. An original orthogonality condition is derived and used to solve two problems. Limiting cases of the results are compared with some special cases solveable by standard Fourier techniques and (for the case of no height discontinuity) the Wiener-Hopf technique.
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50

Engineer, Jeremy Cyrus. "A theoretical investigation into the interaction of sound waves with planar and cylindrical nonlinear elastic surfaces". Thesis, Keele University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334285.

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