Acoustics, Dynamics, and Controls Commons^™

The Development And Evaluation Of A Method For Understanding The Impact Of Transmission Loss On The Overall Noise Attenuation Of Finite Barriers, Ashwin Arvind Upasani

Graduate Theses - Mechanical Engineering

The purpose of this study is to evaluate the impact of transmission loss on the overall noise reduction obtained from finite barriers. The noise attenuation ability of barriers is understood to be a consequence of sound waves diffracting around their edges. Although the presence of transmission loss is acknowledged, its significance in affecting noise attenuation is usually not considered a priority in barrier design. This study incorporates the Fresnel Number concept for predicting theoretical insertion loss of a finite barrier and compares these predictions to experimental observations. The experiments performed in this study offer a method to isolate the transmission …

Noise Control By Structure And Material, Brian Tarling

Thinking Matters Symposium Archive

An acoustic impedance testing tube is designed and constructed to test noise absorption properties of selected materials. The structure will be made to be convenient for demonstration purposes and real testing procedures while following ASTM E1050 standards as closely as possible. An engineering drawing as well as a 3D-­‐CAD model of the structure is developed. Testing is conducted on selected materials; mainly ones that will allow obtained results to be compared to results found by other parties. Various sounds will be generated using Mathematical programming; the types of sound will include single frequency, wide band and narrow band noises. Microphones …

Computational Valve Plate Design, Paul K. Kalbfleisch

Open Access Theses

Axial piston machines are widely used in many industries for their designs compactness, flexibility in power transfer, variable flow rate, and high efficiencies as compared to their manufacturing costs. One important component of all axial piston machines that is a very influential on the performance of the unit is the valve plate. The aim of this research is to develop a design methodology that is general enough to design all types of valve plates and the simple enough not to require advanced technical knowledge from the user. A new style of valve plate designs has been developed that comprehensively considers …

Vibration-Based Health Monitoring Of Rotating Systems With Gyroscopic Effect, Nenad Gavrilovic

Master's Theses

This thesis focuses on the simulation of the gyroscopic effect using the software MSC Adams. A simple shaft-disk system was created and parameter of the sys-tem were changed in order to study the influence of the gyroscopic effect. It was shown that an increasing bearing stiffness reduces the precession motion. Fur-thermore, it was shown that the gyroscopic effect vanishes if the disk of system is placed symmetrically on the shaft, which reduces the system to a Jeffcott-Ro-tor. The second objective of this study was to analyze different defects in a simple fixed axis gear set. In particular, a cracked shaft, …

Estimation Of Outer-Middle Ear Transmission Using Dpoaes And Fractional-Order Modeling Of Human Middle Ear, Maryam Naghibolhosseini

Dissertations, Theses, and Capstone Projects

Our ability to hear depends primarily on sound waves traveling through the outer and middle ear toward the inner ear. Hence, the characteristics of the outer and middle ear affect sound transmission to/from the inner ear. The role of the middle and outer ear in sound transmission is particularly important for otoacoustic emissions (OAEs), which are sound signals generated in a healthy cochlea, and recorded by a sensitive microphone placed in the ear canal. OAEs are used to evaluate the health and function of the cochlea; however, they are also affected by outer and middle ear characteristics. To …

Intelligent Control Of Miniature Holonomic Vertical Take-Off And Landing Robot, Mohammad A. Jaradata, Mohamed Al-Fandia, Omar Alkhatiba, Yousef Sardahi

All Engineering Faculty Research

This paper discusses the development of a fuzzy based controller for miniaturized unmanned aerial vehicle (UAV).This controller is designed to control the center-of-gravity (CoG) in a new configuration of coaxial miniaturized flying robot (MFR). The idea is to shift the CoG by controlling two pendulums located in perpendicular directions; each pendulum ends with a small mass. A key feature of this work is that the control algorithm represents the original nonlinear function that describes the dynamics of the proposed system. The controller model incorporates two cascaded subsystems: PD and PI fuzzy logic controllers. These two controllers regulate the attitude and …

Helmholtz Equation Least Squares Based Near-Field Acoustic Holography With Laser, Wu Zhu

Wayne State University Dissertations

This dissertation presents the HELS based NAH with laser and use normal surface velocity as input in near-field acoustic holography. The conventional HELS based NAH uses acoustic pressure as input to reconstruct sound field quantities, while this modified HELS based NAH with laser utilizes the normal surface velocities measured by LDV to reconstruct the acoustic quantities at interested positions. Theoretical principles of the HELS based NAH with laser have been fully developed and the method has been verified in theoretical perspective. Two theoretical examples verify that HELS based NAH with laser can obtain exactly the same results as analytic solution. …

Vibration Of Steel-Framed Floors Supporting Sensitive Equipment In Hospitals, Research Facilities, And Manufacturing Facilities, Di Liu

Theses and Dissertations--Civil Engineering

Floors have traditionally been designed only for strength and deflection serviceability. As technological advances have been made in medical, scientific and micro-electronics manufacturing, many types of equipment have become sensitive to vibration of the supporting floor. Thus, vibration serviceability has become a routinely evaluated limit state for floors supporting sensitive equipment. Equipment vibration tolerance limits are sometimes expressed as waveform peak acceleration, and are more often expressed as narrowband spectral acceleration, or one-third octave spectral velocity.

Current floor vibration prediction methods, such as those found in the American Institute of Steel Construction Design Guide 11, Floor Vibrations Due to Human …

Temperature Dependence Of Shear Speed In Micellar Fluid, E.G. Sunethra Kumari Dayavansha

Electronic Theses and Dissertations

Wormlike micellar (WM) fluids are viscoelastic and can support shear waves. Phase transitions of the micellar aggregates are temperature dependent and can manifest as sharp changes in the shear wave speed as a function of temperature. Thus, shear waves provide a good tool for detecting the existence of phase transitions. In this work, the variation of shear speed with temperature of 200mM CTAB/NaSal micellar fluid in a 5:3 ratio was studied. The dependence of shear wave speed on time between fluid synthesis and measurement was also investigated. Shear wave propagation through the fluid was observed as a time varying birefringence …

Airborne Path Frequency Based Substructuring Method And Its Applications, Rui He

Theses and Dissertations--Mechanical and Aerospace Engineering

Frequency based substructuring (FBS) is routinely used to model structural dynamics. It provides a framework for connecting structural subsystems together, assessing path contributions, determining the effect of mount modification, and identifying inverse forces. In this work, FBS methods are extended to include acoustic subsystems and connecting pipes and ducts. Connecting pipes or ducts are modeled using the transfer matrix approach which is commonly used for modeling mufflers and silencers below the plane wave cutoff frequency. The suggested approach is validated using boundary element method (BEM) simulation. Applications of the procedure include determining airborne path contributions, the effect of treating ducts …

Development And Validation Of Finite Element Approaches To Determine The Insertion Loss Of Louvered Terminations Including Parametric Investigations, Huangxing Chen

Theses and Dissertations--Mechanical and Aerospace Engineering

Louvers are employed at the ends of HVAC ducts to direct airflow, provide weather protection, and attenuate noise. This details two finite element approaches that can be used to assess the acoustic attenuation from a louvered termination. In the first approach, plane wave propagation is assumed inside of a duct with a non-reflective source. On the receiver side, a baffled termination is assumed and the radiation condition is simulated using a non-reflective boundary condition called an automatically matched layer. In the second approach, a short aperture is placed between two infinite acoustic spaces. On the source side, a diffuse acoustic …

Determination Of Isolator Transfer Matrix And Insertion Loss With Application To Spring Mounts, Shishuo Sun

Theses and Dissertations--Mechanical and Aerospace Engineering

Transmissibility is the most common metric used for isolator characterization. However, engineers are becoming increasingly concerned about energy transmission through an isolator at high frequencies and how the compliance of the machine and foundation factor into the performance. In this study, the transfer matrix approach for isolator characterization is first reviewed. Two methods are detailed for determining the transfer matrix of an isolator using finite element simulation. This is accomplished by determining either the mobility or impedance matrix for the isolator and then converting to a transfer matrix. One of the more useful metrics to characterize the high frequency performance …

A Subsystem Identification Approach To Modeling Human Control Behavior And Studying Human Learning, Xingye Zhang

Theses and Dissertations--Mechanical and Aerospace Engineering

Humans learn to interact with many complex dynamic systems such as helicopters, bicycles, and automobiles. This dissertation develops a subsystem identification method to model the control strategies that human subjects use in experiments where they interact with dynamic systems. This work provides new results on the control strategies that humans learn.

We present a novel subsystem identification algorithm, which can identify unknown linear time-invariant feedback and feedforward subsystems interconnected with a known linear time-invariant subsystem. These subsystem identification algorithms are analyzed in the cases of noiseless and noisy data.

We present results from human-in-the-loop experiments, where human subjects in- teract …

Eigenvector Pruning Method For High Resolution Beamforming, Jorge E. Quijano, Lisa M. Zurk

Electrical and Computer Engineering Faculty Publications and Presentations

This paper introduces an eigenvector pruning algorithm for the estimation of the signal-plus-interference eigenspace, required as a preliminary step to subspace beamforming. The proposed method considers large-aperture passive array configurations operating in environments with multiple maneuvering targets in background noise, in which the available data for estimation of sample covariances and eigenvectors are limited. Based on statistical properties of scalar products between deterministic and complex random vectors, this work defines a statistically justified threshold to identify target-related features embedded in the sample eigenvectors, leading to an estimator for the signal-bearing eigenspace. It is shown that data projection into this signal …

High-Resolution Bottom-Loss Estimation Using The Ambient-Noise Vertical Coherence Function, Lanfranco Muzi, Martin Siderius, Jorge E. Quijano, Stan E. Dosso

Electrical and Computer Engineering Faculty Publications and Presentations

The seabed reflection loss (shortly "bottom loss") is an important quantity for predicting transmission loss in the ocean. A recent passive technique for estimating the bottom loss as a function of frequency and grazing angle exploits marine ambient noise (originating at the surface from breaking waves, wind, and rain) as an acoustic source. Conventional beamforming of the noise field at a vertical line array of hydrophones is a fundamental step in this technique, and the beamformer resolution in grazing angle affects the quality of the estimated bottom loss. Implementation of this technique with short arrays can be hindered by their …

The University Of Akron 2015 Sae Zips Baja Off-Road Racing Team 2015 Suspension System Design, Ryan W. Timura

Williams Honors College, Honors Research Projects

Baja SAE has been an important part of the University of Akron for the last 20 years. In the early stages, Zips Baja won many races and was one of the best Baja teams around. In more recent years, the teams have not been able to keep up the high place finishes. The 2015 Baja team aims to start a new trend of high place finishes for the years to come. With many design leaders returning from the previous year, passed down knowledge, and experience from last year, it should be an attainable goal.

An Axisymmetric Finite Element Model To Study The Earplug Contribution To The Bone Conduction Occlusion Effect, Martin K. Brummund, Franck Sgard, Yvan Petit, Frédéric Laville, Hugues Nélisse

Études primaires

An axisymmetric linear elasto-acoustic finite element (FE) model of an occluded human external ear is proposed to simulate the bone conduction occlusion effect (OE). The model consists of a cylindrical ear canal cavity surrounded by layers of biological tissues (skin, cartilage and bone) in which an earplug is inserted. Geometrical and material properties are taken from the literature. OEs are predicted for foam and silicone earplug FE-models using COMSOL Multiphysics (COMSOL®, Sweden). The FE-model is shown to predict the experimental OE measured in two healthy human reference groups wearing foam or silicone earplugs, satisfactorily. Deviations between model and experiment are …

Networked Heterogeneous Systems In A Ros-Enabled Cloud Environment, Christopher Reid

College of Graduate Studies: Theses & Dissertations

It is important in the development of cloud robotics that the challenges presented by transferring computational loads to networked resources are properly addressed. The challenges include network latency, data integrity, security, and privacy. The objective of the present work is to investigate the issues of latency and data integrity in a representative cloud robotics environment. The present work involves setting up a cloud robotics network in an open-source Robot Operating System (ROS) framework and carrying out investigations on the levels of latency and reduction in data integrity as utilization of the network increases. In this study, a virtual datacenter has …

Control Of Responses Of Smart Plate Structures Under Non-Stationary Random Excitations, Xiaojian Yang

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

This thesis is concerned with an investigation of the control of responses of plate structures with piezoelectric layers and under complicated excitations modeled as a non-stationary random process. The plate structures and piezoelectric layers are both discretized by the mixed formulation finite element method (FEM).

The investigation consists of three parts. The first part is a literature survey and theoretical development. The second part is the eigenvalue solution and computation of uncontrolled response statistics of laminated plate structures under nonstationary random excitations. The final part is the introduction and application of the stochastic central difference (SCD) method that was presented …

Wingtip Dynamics Simulator, Eugene Fox, Nick Rodriguez, Steven Rieber

Mechanical Engineering

Raytheon is a defense contracting company with an electronic warfare division that is developing a radio frequency signal triangulation system. Part of the focus in improving this technology is the need for accurate and real time locational knowledge of the signal receivers, which are located at the tips of aircraft wings. Due to turbulence during flight, the fluttering motion of the wings alter the distance and angle relationships of the two receivers and add noise to the received signal data, which negatively affect the triangulation estimates. To mitigate this error caused by the wing flutter, Raytheon is developing a software …