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An Effective Methodology For Suppressing Structure-Borne Sound Radiation, Lingguang Chen 2017 Wayne State University

An Effective Methodology For Suppressing Structure-Borne Sound Radiation, Lingguang Chen

Wayne State University Dissertations

ABSTRACT

AN EFFECTIVE METHODOLOGY FOR SUPPRESSING

STRUCTURE-BORNE SOUND RADIATION

by

LINGGUANG CHEN

December 2017

Advisor: Dr. Sean F. Wu

Major: Mechanical Engineering

Degree: Doctor of Philosophy

This dissertation is primarily concerned with the development of an effective methodology for reducing structure-borne sound radiation from an arbitrarily shaped vibrating structure. There are three major aspects that separate the present methodology from all the previous ones. Firstly, it is a non-contact and non-invasive approach, which is applicable to a class of vibrating structures encountered in engineering applications. Secondly, the input data consists of a combined normal surface velocity distribution on a portion ...


A Transfer Matrix Approach To Determine The Low Frequency Insertion Loss Of Enclosures Including Applications, Shujian He 2017 University of Kentucky

A Transfer Matrix Approach To Determine The Low Frequency Insertion Loss Of Enclosures Including Applications, Shujian He

Theses and Dissertations--Mechanical Engineering

Partial enclosures are commonly used to reduce machinery noise. However, it is well known in industry that enclosures sometimes amplify the sound at low frequencies due to strong acoustic resonances compromising the performance. These noise issues are preventable if predicted prior to prototyping and production. Though boundary and finite element approaches can be used to accurately predict partial enclosure insertion loss, modifications to the model require time for remeshing and solving. In this work, partial enclosure performance at low frequencies is simulated using a plane wave transfer matrix approach. Models can be constructed and the effect of design modifications can ...


An Investigation Into Wind Turbine Acoustic Noise Variability, Steven Redford Buck 2017 University of Colorado at Boulder

An Investigation Into Wind Turbine Acoustic Noise Variability, Steven Redford Buck

Aerospace Engineering Sciences Graduate Theses & Dissertations

Wind turbine acoustic noise has been the subject of significant research in recent decades due to rapid growth in the wind energy industry. Available space with a reliable wind resource and that does not reside near populated areas is becoming extremely scarce, particularly in Europe. This decline in available space then results in a heightened need for wind turbine designs to be optimized for both acoustic emission and power-performance. Due to highly variable operating conditions, wind turbine acoustic noise emission may deviate from design levels, causing irritation to local residents and requiring reduced power production of the contributing turbines. The ...


Fast Band-Structure Computation For Phononic And Electronic Waves In Crystals, Dimitri Krattiger 2017 University of Colorado at Boulder

Fast Band-Structure Computation For Phononic And Electronic Waves In Crystals, Dimitri Krattiger

Aerospace Engineering Sciences Graduate Theses & Dissertations

The band structure is a frequency/energy versus wave vector/momentum relationship that fundamentally describes the nature of wave motion in a periodic medium. It is immensely valuable for predicting and understanding the properties of electronic, photonic, and phononic materials, and is typically computed numerically. For materials with large unit cells, such as nanostructured supercells for example, band-structure computation is very costly. This inhibits the ability to feasibly analyze new material systems with potentially extraordinary properties. This thesis describes a novel unit-cell model-reduction technique for band-structure calculations that is capable of lowering computational costs by one or two orders of ...


An Investigation Into Wind Turbine Acoustic Noise Variability, Steven Redford Buck 2017 University of Colorado at Boulder

An Investigation Into Wind Turbine Acoustic Noise Variability, Steven Redford Buck

Aerospace Engineering Sciences Graduate Theses & Dissertations

Wind turbine acoustic noise has been the subject of significant research in recent decades due to rapid growth in the wind energy industry. Available space with a reliable wind resource and that does not reside near populated areas is becoming extremely scarce, particularly in Europe. This decline in available space then results in a heightened need for wind turbine designs to be optimized for both acoustic emission and power-performance. Due to highly variable operating conditions, wind turbine acoustic noise emission may deviate from design levels, causing irritation to local residents and requiring reduced power production of the contributing turbines. The ...


On A Time Domain Boundary Integral Equation Formulation For Acoustic Scattering By Rigid Bodies In Uniform Mean Flow, Fang Q. Hu, Michelle E. Pizzo, Douglas M. Nark 2017 Old Dominion University

On A Time Domain Boundary Integral Equation Formulation For Acoustic Scattering By Rigid Bodies In Uniform Mean Flow, Fang Q. Hu, Michelle E. Pizzo, Douglas M. Nark

Mathematics & Statistics Faculty Publications

It has been well-known that under the assumption of a uniform mean flow, the acoustic wave propagation equation can be formulated as a boundary integral equation. However, the constant mean flow assumption, while convenient for formulating the integral equation, does not satisfy the solid wall boundary condition wherever the body surface is not aligned with the assumed uniform flow. A customary boundary condition for rigid surfaces is that the normal acoustic velocity be zero. In this paper, a careful study of the acoustic energy conservation equation is presented that shows such a boundary condition would in fact lead to source ...


Multi-Modal And Short-Range Transmission Loss In Ice-Covered, Near-Shore Arctic Waters, Miles B. Penhale 2017 Michigan Technological University

Multi-Modal And Short-Range Transmission Loss In Ice-Covered, Near-Shore Arctic Waters, Miles B. Penhale

Dissertations, Master's Theses and Master's Reports

In the past century, extensive research has been done regarding the sound propagation in arctic ice sheets. The majority of this research has focused on low frequency propagation over long distances. One of the most commonly used excitation methods for air-ice-water layers has been explosives. However, environmental regulation has become more stringent, disallowing the use of almost all explosive excitation types. Due to changing climate conditions in these environments, new experimentation is warranted to determine sound propagation characteristics in, through, and under thin ice sheets, in shallow water, over short distances. In April, 2016 several experiments were conducted approximately 2 ...


Development Of A High-Fidelity Model And Kalman Filter Based State Estimator For Simulation And Control Of Nox Reduction Performance Of A Scr Catalyst On A Dpf, Venkata Rajesh Chundru 2017 Michigan Technological University

Development Of A High-Fidelity Model And Kalman Filter Based State Estimator For Simulation And Control Of Nox Reduction Performance Of A Scr Catalyst On A Dpf, Venkata Rajesh Chundru

Dissertations, Master's Theses and Master's Reports

Reduction of emissions and improving the fuel consumption are two prime research areas in Diesel engine development. The present after-treatment systems being used for emissions control include diesel oxidation catalyst (DOC) for NO, HC and CO oxidation along with catalyzed particulate filters for PM (particulate matter) and selective catalytic reduction (SCR) for controlling NOx emissions. Recently an after-treatment system called SCR catalyst on a DPF capable of simultaneously reducing both NOx and PM emissions has been developed in order to reduce the overall size of the after-treatment system.

The goal of this proposed research is to create a state estimator ...


Performance Of Hard Disk Drives In High Noise Environments, Trinoy Dutta 2017 Michigan Technological University

Performance Of Hard Disk Drives In High Noise Environments, Trinoy Dutta

Dissertations, Master's Theses and Master's Reports

Digital information stored in rotational media, such as Hard Disk Drives (HDD) needs to be reliable and readily accessible. Various studies have been performed on the modal analysis of HDDs and the noise emitted during operation. Analysis performed by Siemens Corporation, IBM and Tyco Fire Protection Products show that HDDs are sensitive to noise. This report initially focusses on identifying the critical frequency ranges and the levels of noise where the performance of the drives reduces. A series of tests have been performed using pink noise at one-third octave frequency bands at sound pressure levels ranging from 80 dB to ...


Fast Band-Structure Computation For Phononic And Electronic Waves In Crystals, Dimitri Krattiger 2017 University of Colorado at Boulder

Fast Band-Structure Computation For Phononic And Electronic Waves In Crystals, Dimitri Krattiger

Aerospace Engineering Sciences Graduate Theses & Dissertations

The band structure is a frequency/energy versus wave vector/momentum relationship that fundamentally describes the nature of wave motion in a periodic medium. It is immensely valuable for predicting and understanding the properties of electronic, photonic, and phononic materials, and is typically computed numerically. For materials with large unit cells, such as nanostructured supercells for example, band-structure computation is very costly. This inhibits the ability to feasibly analyze new material systems with potentially extraordinary properties. This thesis describes a novel unit-cell model-reduction technique for band-structure calculations that is capable of lowering computational costs by one or two orders of ...


Evaluation Of Impedance Control On A Powered Hip Exoskeleton, Punith condoor 2017 University of Massachusetts Amherst

Evaluation Of Impedance Control On A Powered Hip Exoskeleton, Punith Condoor

Masters Theses

This thesis presents an impedance control strategy for a novel powered hip exoskeleton designed to provide partial assistance and leverage the dynamics of human gait. The control strategy is based on impedance control and provides the user assistance as needed which is determined by the user’s interaction with the exoskeleton. A series elastic element is used to drive the exoskeleton and measures the interaction torque between the user and the device. The device operates in two modes. Free mode is a low impedance state that attempts to provide no assistance. Assist mode increases the gains of the controller to ...


Simulation Of Horse-Fence Contact And Interaction Affecting Rotational Falls In The Sport Of Eventing, Gregorio Robles Vega 2017 University of Kentucky

Simulation Of Horse-Fence Contact And Interaction Affecting Rotational Falls In The Sport Of Eventing, Gregorio Robles Vega

Theses and Dissertations--Mechanical Engineering

Rotational falls, or somersault falls, have led to serious and fatal injuries during the cross-country phase of Eventing competitions. Research to improve the safety of the sport began in 2000 after five fatal injuries occurred in the 1999 Eventing season. These efforts led to safety devices such as air jackets, improved helmets, and frangible/deformable fences. The focus of this thesis is to develop a more complete understanding of the horse-fence interaction as the approach motion transitions to a rotational fall. To achieve this, a large distribution of inertial properties was compiled through the development of a cylinder-based inertia approximation ...


Development Of An Excel® Rocket Simuator For Application In Middle School, High School, And University Stem Education, Melvin Lee Hortman 2017 Central Washington University

Development Of An Excel® Rocket Simuator For Application In Middle School, High School, And University Stem Education, Melvin Lee Hortman

All Master's Theses

Water rocket activities are one of the most popular STEM activities used in primary, secondary, and higher education yet are void of engineering, though engineering is heavily implied in the STEM acronym. This study investigated the amount of engineering present in water rocket activities, and options for emphasizing engineering more in water rocket activities using an open-platform flight simulator for use by educators to enable students to predict flight parameters of a water rocket they designed, and test those predictions against experimental data. The simulator was constructed in Excel® with many functions, but the function validated in this study was ...


Utilization Of Empirical Models To Determine The Bulk Properties Of Compressed Sound Absorptive Materials, Ruimeng Wu 2017 University of Kentucky

Utilization Of Empirical Models To Determine The Bulk Properties Of Compressed Sound Absorptive Materials, Ruimeng Wu

Theses and Dissertations--Mechanical Engineering

Empirical models based on flow resistivity are commonly used to determine the bulk properties of porous sound absorbing materials. The bulk properties include the complex wavenumber and complex characteristic impedance which can be used directly in simulation models. Moreover, the bulk properties can also be utilized to determine the normal incidence sound absorption and specific acoustic impedance for sound absorbing materials of any thickness and for design of layered materials. The sound absorption coefficient of sound absorbing materials is measured in an impedance tube using wave decomposition and the measured data is used to determine the flow resistivity of the ...


Advances In Multi-Agent Flocking: Continuous-Time And Discrete-Time Algorithms, Brandon Wellman 2017 University of Kentucky

Advances In Multi-Agent Flocking: Continuous-Time And Discrete-Time Algorithms, Brandon Wellman

Theses and Dissertations--Mechanical Engineering

We present multi-agent control methods that address flocking in continuous-time and discrete-time settings. The method is decentralized, that is, each agents controller relies on local sensing to determine the relative positions and velocities of nearby agents. In the continuous-time setting, each agent has double-integrator dynamics. In the discrete-time setting, each agent has the discrete-time double-integrator dynamics obtained by sampling the continuous-time double integrator and applying a zero-order hold on the control input. We demonstrate using analysis, numerical simulations, and experimental demonstrations that agents using the flocking methods converge to flocking formations and follow the centralized leader (if applicable).


Impedance-To-Scattering Matrix Method For Large Silencer Analysis, Peng Wang 2017 University of Kentucky

Impedance-To-Scattering Matrix Method For Large Silencer Analysis, Peng Wang

Theses and Dissertations--Mechanical Engineering

Large silencers used in the power generation industry usually have a very large cross section at the inlet and outlet. Higher-order modes will populate the inlet and outlet even at very low frequencies. Although the silencer itself is often modeled by a three-dimensional analysis tool such as the boundary element method (BEM) or finite element method (FEM), a direct computation of the transmission loss (TL) from the BEM or FEM model can be challenging without incorporating certain forms of modal expansion.

A so-called “impedance-to-scattering matrix method” is proposed to extract the modes at the inlet and outlet from the BEM ...


Noise Reduction Mechanisms Due To Bio-Inspired Airfoil Designs, Andrew Bodling, Anupam Sharma 2017 Iowa State University

Noise Reduction Mechanisms Due To Bio-Inspired Airfoil Designs, Andrew Bodling, Anupam Sharma

Aerospace Engineering Conference Papers, Presentations and Posters

This paper presents numerical analysis of an airfoil geometry inspired by the down coat of the night owl. The objective is to understand the mechanisms of airfoil trailing edge noise reduction that has been observed with such designs in previous experiments. The bioinspired geometry consists of an array of “fences” that are applied near the trailing edge of the NACA-0012 baseline airfoil. Wall-resolved large eddy simulations are performed over the baseline and the bioinspired airfoil geometries and the aeroacoustic performance of the two geometries are contrasted. Both models are simulated at chord-based Reynolds number Rec = 5 × 105 , flow ...


Audio-Based Productivity Forecasting Of Construction Cyclic Activities, Chris A. Sabillon 2017 cs10852

Audio-Based Productivity Forecasting Of Construction Cyclic Activities, Chris A. Sabillon

Electronic Theses and Dissertations

Due to its high cost, project managers must be able to monitor the performance of construction heavy equipment promptly. This cannot be achieved through traditional management techniques, which are based on direct observation or on estimations from historical data. Some manufacturers have started to integrate their proprietary technologies, but construction contractors are unlikely to have a fleet of entirely new and single manufacturer equipment for this to represent a solution. Third party automated approaches include the use of active sensors such as accelerometers and gyroscopes, passive technologies such as computer vision and image processing, and audio signal processing. Hitherto, most ...


Electroencephalographic Signal Processing And Classification Techniques For Noninvasive Motor Imagery Based Brain Computer Interface, Md Erfanul Alam 2017 Georgia Southern University

Electroencephalographic Signal Processing And Classification Techniques For Noninvasive Motor Imagery Based Brain Computer Interface, Md Erfanul Alam

Electronic Theses and Dissertations

In motor imagery (MI) based brain-computer interface (BCI), success depends on reliable processing of the noisy, non-linear, and non-stationary brain activity signals for extraction of features and effective classification of MI activity as well as translation to the corresponding intended actions. In this study, signal processing and classification techniques are presented for electroencephalogram (EEG) signals for motor imagery based brain-computer interface. EEG signals have been acquired placing the electrodes following the international 10-20 system. The acquired signals have been pre-processed removing artifacts using empirical mode decomposition (EMD) and two extended versions of EMD, ensemble empirical mode decomposition (EEMD), and multivariate ...


Quantitative Ultrasonic Coda Wave (Diffuse Field) Nde Of Carbon-Fiber Reinforced Polymer Plates, Richard Livings 2017 Iowa State University

Quantitative Ultrasonic Coda Wave (Diffuse Field) Nde Of Carbon-Fiber Reinforced Polymer Plates, Richard Livings

Graduate Theses and Dissertations

The increasing presence and applications of composite materials in aerospace structures precipitates the need for improved Nondestructive Evaluation (NDE) techniques to move from simple damage detection to damage diagnosis and structural prognosis. Structural Health Monitoring (SHM) with advanced ultrasonic (UT) inspection methods can potentially address these issues. Ultrasonic coda wave NDE is one of the advanced methods currently under investigation. Coda wave NDE has been applied to concrete and metallic specimens to assess damage with some success, but currently the method is not fully mature or ready to be applied for SHM. Additionally, the damage diagnosis capabilities and limitations of ...


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