Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 104 for “"Acoustic field"”.
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Design and characterization of variable acoustic field amplitude and focusing ultrasonic transducers
… be used to generate various circularly symmetric acoustic field profiles. These transducers can also electronically simulate a circular phased array and generate a focused ultrasonic beam. A model which predicts the acoustic transducer output for a given scaled voltage input has been developed. …
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Improvement of three dimensional acoustic field estimation using tomographic reconstructions of the ocean
… of the ocean sound speed structure in improving acoustic field predictions for source localization, a 150 km by 350 km volume of ocean 3000 meters deep was synthetically modeled to be similar to the Gulf Stream system, including an eddy and a front. The features were Gaussian, with the eddy's …
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An investigation of the structurally induced acoustic field in a car passenger compartment
… range of interest to below 200 Hz. Firstly, the acoustic modes of a Rover Metro passenger compartment are predicted using the finite element method. A new method for the experimental acoustic modal analysis of cavities is introduced and verified for a rectangular rigid walled room. The method is …
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Investigation of acoustic field non-linearities by suspension of particles in a cylindrical resonating cavity.
Thesis: B.S., Massachusetts Institute of Technology, Department of Physics, 1973
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A study of stone fragmentation in shock wave lithotripsy by customizing the acoustic field and waveform shape
… pulsers, each capable of generating 1.2 kV. The acoustic field was characterized using a fiber optic probe hydrophone with a bandwidth of 30 MHz and a spatial resolution of 100 μm. When all elements were driven simultaneously, the focal waveform was a shock wave with peak pressures p+ =65±3MPa …
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Experimental Design, Data Analysis, and Modeling for Characterizing the Three-Dimensional Acoustic Field of a Seismic Airgun Array
In June 2003, the Littoral Acoustic Demonstration Center conducted an acoustic characterization experiment for a standard seismic exploration array. Two moorings with Environmental Acoustic Recording Systems (EARS) were deployed in the northern part of the Gulf of Mexico to measure ambient noise …
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Mean, variance, and temporal coherence of the 3D acoustic field forward propagated through random inhomogeneities in continental-shelf and deep ocean waveguides
When an acoustic field propagates through a multimodal waveguide, the effect of variations in medium properties induced by 3D random inhomogeneities accumulates by multiple forward scattering over range. This causes significant random fluctuations in the received field and greatly affects …
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Application of the Herschel-Quincke Tube Concept to Higher-Order Acoustic Modes in Two-Dimensional Ducts
… device for one-dimensional plane-wave sound fields has been studied in great detail in previous years. In this thesis, an analytical technique is developed to investigate the potential of the HQ tube concept to control higher-order duct modes. This analytical method involves modeling the …
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Effects of the geometric modifications on the shear layer excitation source in co-axial side branches
… between shear layer oscillations and the acoustic field within co-axial cavities, spotlighting the efficacy of the sound source model as a reliable semi-empirical modeling methodology. The focus is on how the downstream acoustic boundary conditions, when varied, markedly alter the acoustic …
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An integrated modal approach to surface and volume scattering in ocean acoustic waveguides
Acoustic propagation in the ocean can be strongly affected by small random variations in ocean properties, including rough surfaces and volume fluctuations in the ocean or seabed. Such inhomogeneities scatter part of the incident acoustic field, stripping energy from the coherent part of the field. …
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Applications of a fast helmholtz solver in exploration seismology
… thesis, I combine a fast Helmholtz solver, the field expansion method, with a reduced velocity model parameterization to address the impact of an uncertain or inaccurate velocity model. I modify the field expansion framework to accurately simulate the acoustic field for velocity models that …
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Active control of acoustic radiation due to discontinuities on thin beams
… were conducted to study the active control of acoustic radiation due to discontinuities on thin beams. One experiment investigated the radiation from a clamped end condition and the other investigated the radiation from a blocking mass. The beams were excited by subsonic flexural traveling …
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2D Aeroacoustic Analysis of Flow in the Flame Trench
… commercial software ANSYSFLUENT to predict the acoustic field associated with Space-Launch System (SLS). We consider a two-dimensional model of flame deflector, and flame trench. The ANSYS code is then used to simulate the internal flow. Both the steady state case is considered along with other …
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Investigation of the Herschel-Quincke tube concept in a rectangular lined duct
… finite piston sources. These sources couple the acoustic field inside the duct with the acoustic field within the HQ tubes. The accuracy of the analytical model was validated with experimental data. Three different types of experimental configurations were tested: liner only, HQ tube with a hard …
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A low frequency underwater sound propagation model
… sound propagation models attempt to derive the acoustic field originating from a sound source in a specific environment by either solving the wave equation directly or by solving an approximation there-of. This dissertation describes a normal mode direct solution with emphasis on the application …
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Acoustical characterization of glacierized fjords
… massive glaciers meet the ocean. This underwater acoustic environment is significantly louder than other ice-covered environments. The abundant acoustic information, coupled with the difficulty performing measurements on or near glacier termini, encourage the use of passive acoustic monitoring to …
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Underwater communication via particle velocity channels : principles, channel models, and system design
… measuring important non-scalar components of the acoustic field such as the particle velocity, which cannot be obtained by a single scalar pressure sensor. In the past few decades, extensive research has been conducted on the theory and design of vector sensors. On the other hand, underwater …
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Investigation of the Herschel-Quincke Tube Concept as a Noise Control Device for Turbofan Engines
… as finite piston sources that couple the acoustic field inside the inlet with the acoustic field within the HQ tubes. An optimization technique based on genetic algorithms was also developed to be able to design and optimize the system parameters. The accuracy of the model was validated …
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TIME-CONSERVATIVE FINITE-VOLUME METHOD WITH LARGE-EDDY SIMULATION FOR COMPUTATIONAL AEROACOUSTICS
… Its applicability to technically relevant aeroacoustic applications is demonstrated. The time-conservative finite-volume method has unique features and advantages in comparison to traditional methods. The main objectives of this study are to develop an advanced, high-resolution, low dissipation …
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