Acoustics, Dynamics, and Controls Commons^™

Experimental Studies On The Determination Of Acoustic Bulk Material Properties And Transfer Impedance, Wanlu Li

Theses and Dissertations--Mechanical and Aerospace Engineering

Soft trim absorbing parts (i.e., headliners, backwalls, side panels, etc.) are normally comprised of different layers including films, adhesives, foams and fibers. Several approaches to determine the complex wavenumber and characteristic impedance for porous sound absorbing materials are surveyed and the advantages and disadvantages of each approach are discussed. It is concluded that the recently documented three-point method produces the smoothest results. It is also shown that measurement of the flow resistance and the use of empirical equations is sufficient for many common materials. Following this, the transfer impedance of covers, adhesives, and densified layers are measured using an impedance …

Optimization Of Wind Fence Enclosures For Infrasonic Wind Noise Reduction, Johnpaul Russell Abbott

Electronic Theses and Dissertations

A large porous wind barrier enclosure has been built and tested to optimize wind noise reduction at infrasonic frequencies between 0.01-10 Hz in order to develop a technology that is simple, cost effective, and improves upon the limitations of pipe and porous hose arrays. The effects of varying the fence's porosity, modifying its top condition and bottom gap, doubling the height and diameter, and adding a secondary wind barrier were investigated. A simple mathematical model which estimates the wind noise measured at the center of the enclosure was derived based on the measured turbulence and velocity profiles measure outside the …

Visualizing Interior And Exterior Jet Aircraft Noise, Manmohan Singh Moondra

Wayne State University Dissertations

In today's competitive aerospace industry, the quest for quiet has drawn significant attention to both the interior and exterior design of an airplane. Understanding the noise generation mechanisms of a jet aircraft is a crucial first step toward developing the most cost-effective noise and vibrations abatement methods. In this investigation, the Helmholtz Equation Least Squares (HELS) based nearfield acoustic holography will be used to understand noise transmission caused by jet engine and turbulence into the fuselage of a jet aircraft cruising at 30,000 ft.

Modern propulsive jet engines produce exterior noise sources with a high amplitude noise field and complicated …

Neuromodulation Based Control Of Autonomous Robots On A Cloud Computing Platform, Cameron Muhammad

College of Graduate Studies: Theses & Dissertations

In recent years, the advancement of neurobiologically plausible models and computer networking has resulted in new ways of implementing control systems on robotic platforms. The work presents a control approach based on vertebrate neuromodulation and its implementation on autonomous robots in the open-source, open-access environment of robot operating system (ROS). A spiking neural network (SNN) is used to model the neuromodulatory function for generating context based behavioral responses of the robots to sensory input signals. The neural network incorporates three types of neurons- cholinergic and noradrenergic (ACh/NE) neurons for attention focusing and action selection, dopaminergic (DA) neurons for rewards- and …