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Hahn, Casey BernardDesign and Validation of the New Jet Facility and Anechoic Chamber
Master of Science, The Ohio State University, 2011, Mechanical Engineering

The jet facility and anechoic chamber at the Gas Dynamics and Turbulence Laboratory (GDTL) at The Ohio State University have been redesigned and rebuilt to significantly improve their capabilities. The new jet facility is capable of jets of 2-inch diameter—twice the size of the old jets. The new and much larger anechoic chamber can handle the larger jet and enables the measurements of shock noise generated by the jet of tactical aircraft. Free-field qualification requirements of ISO 3745 standard are met, and the chamber has a cutoff frequency of 160 Hz. A few improvements were incorporated into the new facility including thicker, acoustically-treated walls and an acoustically transparent grating floor above the floor anechoic wedges. Tests showed that very minor variations in the spectra are introduced by the grating floor panels.

Two additional microphones were added to the new facility with three within the upstream region of the acoustic field (a maximum polar angle of 130° compared to the maximum of 90° of the old facility). The radial distances of the microphones were increased, and far-field tests show that the microphones are safely within the far-field of 1-inch and 1.5-inch jets. For a 2-inch jet, some microphones are likely within the transition region of the acoustic field but could be moved farther outward to locate them within the far-field, as there is more room within the chamber. The stagnation chamber diameter was increased from 3.068 inches to 5.047 inches to handle the larger mass flow rate of a 2-inch jet. Initially, spectra suffered from narrowband cavity tones generated by ports upstream. The ports were modified, and a second perforated plate was added to eliminate these tones.

Acoustic data of the new and old jets are compared, and some minor differences in the high frequency content of the spectra are found. Early guesses point to internal rig noise created by flow through the second perforated plate. Work will continue to remove these differences. Finally, PIV results of the old and new jets are compared. The Mach number decay and spreading rates of a new Mach 0.9 jet compare well to an old Mach 0.9 jet. The old Mach 0.9 jets had slightly lower levels of turbulent kinetic energy. A new Mach 1.3 jet compares well with an old Mach 1.3 jet all these statistics.

Committee:

Mo Samimy, PhD (Advisor); Datta Gaitonde, PhD (Committee Member)

Subjects:

Acoustics; Aerospace Engineering; Engineering; Experiments; Fluid Dynamics; Mechanical Engineering

Keywords:

jet facility; anechoic chamber; aeroacoustics

Zelnio, Anne M.Detection of Small Aircraft using an Acoustic Array
Master of Science in Engineering (MSEgr), Wright State University, 2009, Electrical Engineering
Detection of small aircraft visually or with radar sensors is difficult due to its small size, low-velocity, and low radar cross section. This effort investigates the detection and localization of small aircraft using an acoustic array. The acoustic array was fabricated using low-cost commercial off-the shelf (COTS) hardware that is mobile and can adapt to different signatures and deployment environments. A cross-correlation method for calibration and delay-and-sum beamforming was performed. A generalized likelihood ratio test (GLRT)-based energy detector and a GLRT-based sinusoidal signal detector was applied after beamforming. Detection was also performed using various subpace adaptive beamforming techniques including MUSIC, min-norm, and SSMUSIC which first performed sinusoidal filtering followed by adaptive beamforming. Constant false alarm rate (CFAR) detectors were used to compare all algorithms.

Committee:

Brian Rigling, PhD (Advisor); Fred Garber, PhD (Committee Member); Mike Bryant, PhD (Committee Member)

Subjects:

Acoustics; Electrical Engineering

Keywords:

acoustic array; signal processing; detection theory

Zachariah, Cherian RenilStatistical Model for Predicting Multiple Sclerosis Cortical Lesion Detection Rates with Ultra High Field Imaging
Master of Science, The Ohio State University, 2011, Electrical and Computer Engineering
Pathology studies indicate that cortical demyelination can be extensive in Multiple Sclerosis (MS) and may contribute significantly to the disease process. Imaging of cortical lesions by MRI is hampered by their small size and low contrast. Ultrahigh field MRI with high spatial resolution and sequences maximizing cortical contrast were employed. SWI (Susceptibility Weighted Imaging) sequence was employed to capture the differences in magnetic susceptibility between tissues. WHAT (White Matter Attenuated) sequence was used to suppress signal from white matter while enhancing signal from the gray matter. Formalin-fixed brain tissue from MS patients was imaged with SWI and WHAT. The specimen was subsequently processed for immunohistochemical labeling. Histological sections were evaluated for number and size (measured as the smallest diameter) of cortical demyelinating lesions. Lesions were scored by two readers on high and low resolution of both sequences. A statistical model based on logistic regression was developed for estimation of cortical lesion detection rates. This model was derived from comparison of MRI data with histology of MS brain specimens. The results give the probability of detecting lesions based on lesion size, MR contrast and resolution.

Committee:

BRADLEY CLYMER, DR. (Committee Chair); PETRA SCHMALBROCK, DR. (Committee Co-Chair)

Subjects:

Acoustics; Biomedical Research; Electrical Engineering

Keywords:

Multiple Sclerosis; Cortical Lesion

Gadziola, Marie AAuditory Responses in the Amygdala to Social Vocalizations
PHD, Kent State University, 2013, College of Arts and Sciences / School of Biomedical Sciences
GADZIOLA, MARIE A., Ph.D., December 2013 BIOMEDICAL SCIENCES AUDITORY RESPONSES IN THE AMYGDALA TO SOCIAL VOCALIZATIONS (166 pp.) Director of Dissertation: Jeffrey J. Wenstrup, Ph.D. The underlying goal of this dissertation is to understand how the amygdala, a brain region involved in establishing the emotional significance of sensory input, contributes to the processing of complex sounds. The general hypothesis is that communication calls of big brown bats (Eptesicus fuscus) transmit relevant information about social context that is reflected in the activity of amygdalar neurons. The first specific aim analyzed social vocalizations emitted under a variety of behavioral contexts, and related vocalizations to an objective measure of internal physiological state by monitoring the heart rate of vocalizing bats. These experiments revealed a complex acoustic communication system among big brown bats in which acoustic cues and call structure signal the emotional state of a sender. The second specific aim characterized the responsiveness of single neurons in the basolateral amygdala to a range of social syllables. Neurons typically respond to the majority of tested syllables, but effectively discriminate among vocalizations by varying the response duration. This novel coding strategy underscores the importance of persistent firing in the general functioning of the amygdala. The third specific aim examined the influence of acoustic context by characterizing both the behavioral and neurophysiological responses to natural vocal sequences. Vocal sequences differentially modify the internal affective state of a listening bat, with lower aggression vocalizations evoking the greatest change in heart rate. Amygdalar neurons employ two different coding strategies: low background neurons respond selectively to very few stimuli, whereas high background neurons respond broadly to stimuli but demonstrate variation in response magnitude and timing. Neurons appear to discriminate the valence of stimuli, with aggression sequences evoking robust population-level responses across all sound levels. Further, vocal sequences show improved discrimination among stimuli compared to isolated syllables, and this improved discrimination is expressed in part by the timing of action potentials. Taken together, these data support the hypothesis that big brown bat social vocalizations transmit relevant information about the social context that is encoded within the discharge pattern of amygdalar neurons ultimately responsible for coordinating appropriate social behaviors. I further propose that vocalization-evoked amygdalar activity will have significant impact on subsequent sensory processing and plasticity.

Committee:

Jeffrey Wenstrup (Advisor); Brett Schofield (Committee Member); Shobhana Sivaramakrishnan (Committee Member); J.G.M. Hans Thewissen (Committee Member); Aaron Jasnow (Committee Member)

Subjects:

Acoustics; Anatomy and Physiology; Behavioral Sciences; Biology; Communication; Neurobiology; Neurosciences

Keywords:

acoustic communication; bat; Eptesicus fuscus; electrocardiogram; heart rate; persistent firing; response duration; behavioral context

Mieskoski, RandyCapturing and Modeling a Three-Dimensional Stationary Noise Source Directivity Pattern with a Dynamic Array in the Near Field
Master of Science (MS), Wright State University, 2013, Physics
The author has studied several legacy landmark methodologies to develop an original measurement technique. Spherical harmonics modeling practices were leveraged to accurately represent a source directivity pattern. In this thesis a lightweight microphone measurement array that was manually maneuvered around a static noise source was employed. The measurement technique consisted of inserting a head-tracker sensor onto the microphone array to allow the location of the captured acoustic Sound Pressure Level (SPL) to be investigated. By leveraging the historical methodologies the acoustic SPL and location data collected with this technique were processes to represent a directivity pattern of the compressor source chosen. The results indicated that the measurement technique is valid for capturing acoustic SPL and location data of a static noise source with a dynamic array. Propagation techniques yielded a ten decibel difference between the measured and predicated SPLs. The dynamic measurement technique and method for characterizing the three-dimensional acoustic directivity of a static noise source is further presented in this thesis.

Committee:

Frank Mobley, Ph.D. (Advisor); Doug Petkie, Ph.D. (Committee Chair); Ivan Medvedev, Ph.D. (Committee Member)

Subjects:

Acoustics; Physics

Keywords:

acoustic modeling and modeling; spherical harmonics; source directivity pattern; microphone array; acoustic Sound Pressure Level -SPL; propagation techniques; static noise source

Kearney-Fischer, Martin A.The Noise Signature and Production Mechanisms of Excited High Speed Jets
Doctor of Philosophy, The Ohio State University, 2011, Mechanical Engineering

Following on previous works showing that jet noise has significant intermittent aspects, the present work assumes that these intermittent events are the dominant feature of jet noise. A definition and method of detection for intermittent noise events are devised and implemented. Using a large experimental database of acoustically subsonic jets with different acoustic Mach numbers (Ma = 0.5 – 0.9), nozzle exit diameters (D = 2.54, 5.08, & 7.62 cm), and jet exit temperature to ambient temperature ratios (ETR = 0.84 – 2.70), these events are extracted from the noise signals measured in the anechoic chamber of the NASA Glenn AeroAcoustic Propulsion Laboratory. It is shown that a signal containing only these events retains all of the important aspects of the acoustic spectrum for jet noise radiating to shallow angles relative to the jet axis, validating the assumption that intermittent events are the essential feature of the peak noise radiation direction. The characteristics of these noise events are analyzed showing that these events can be statistically described in terms of three parameters (the variance of the original signal, the mean width of the events, and the mean time between events) and two universal statistical distribution curves. The variation of these parameters with radiation direction, nozzle diameter, exit velocity, and temperature are discussed.

A second experimental database from the Ohio State University Gas Dynamics and Turbulence Laboratory of far-field acoustic data from an excited subsonic jet with hydrodynamic Mach number of 0.9 (Mj = 0.9) at various total temperature ratios (TTR = 1.0 - 2.5) is analyzed using the same process. In addition to the experimental acoustic database, conclusions and observations from previous works using Localized Arc Filament Plasma Actuators (LAFPAs) are leveraged to inform discussion of the statistical results and their relationship to the jet flow dynamics. Analysis of the excited jet reveals the existence of a resonance condition. When excited at the resonance condition, large amounts of noise amplification can occur – this is associated with each large-scale structure producing a noise event. Conversely, noise reduction occurs when only one noise event occurs per several large-scale structures. One of the important conclusions from these results is that there seems to be a competition for flow energy among neighboring structures that dictates if and how their dynamics will produce noise that radiates to the far-field.

Utilizing the results from both databases, several models for noise sources addressing different aspects of the results are discussed. A simple model for this kind of noise signal is used to derive a relationship between the characteristics of the noise events and the fluctuations in the integrated noise source volume. Based on the known flow-field dynamics and the acoustic results from the excited jet, a hypothetical model of the competition process is described. These various models speculate on the dynamics relating the noise sources to the signal in the far-field and, as such, the present work cannot provide a definitive description of jet noise sources, but can serve as a guide to future exploration.

Committee:

Mo Samimy, PhD (Advisor); Igor Adamovich, PhD (Committee Member); James Bridges, PhD (Committee Member); Michael Dunn, PhD (Committee Member); Walter Lempert, PhD (Committee Member)

Subjects:

Acoustics; Aerospace Engineering; Fluid Dynamics; Mechanical Engineering

Keywords:

Jet Noise; Aeroacoustics; Active Flow Control; Turbulence

Jayasankaran, KathikSTRUCTURE-BORNE NOISE MODEL OF A SPUR GEAR PAIR WITH SURFACE UNDULATION AND SLIDING FRICTION AS EXCITATIONS
Master of Science, The Ohio State University, 2010, Mechanical Engineering
This study presents an improved gear noise source model with surface undulation or roughness as the main excitation while taking into account the sliding frictional contacts between meshing teeth. This model extends the prior linear time-varying model that predicted the surface roughness-induced air-borne noise source. The structure-borne noise source is examined in this study by employing a six degree of freedom linear time-varying model. Gear contact mechanics is used to determine the mesh stiffness variation and also to relate the surface undulation to an equivalent static transmission error over a range of torques. Four alternate dynamic sliding friction models are also compared. Sound pressure radiated by the casing via structure-borne noise path is predicted using experimental partial pressure to acceleration transfer functions given pinion and gear accelerations in the line of action and the off-line of action direction. Linear time-invariant models are also developed by assuming that the mesh stiffness, moment arm and coefficient of friction do not vary with time. Sinusoidal, periodic and random tooth surface undulations are examined and sound pressures at gear mesh harmonics are predicted; the random undulation also generates off gear mesh frequency components. Both linear time-varying and linear time-invariant models are utilized to quantify the structure-borne noise sources and to understand the role of mesh stiffness, moment arm and coefficient of friction variations. The effects of torque, surface undulation amplitude, coefficient of friction and speed are also examined by using the linear-time varying model. Noise predictions (especially the trends) are compared with prior literature and some plausible explanations regarding the dominant sources are provided.

Committee:

Dr. RAJENDRA SINGH (Advisor); Dr. AHMET KAHRAMAN (Committee Member)

Subjects:

Acoustics; Engineering; Mechanical Engineering

Keywords:

gear noise; surface undulation; static transmission error; mesh stiffness; random undulation; structure-borne; line of action; off-line of action; linear time-varying; linear time-invariant; sliding friction

Kozlosky, Kenneth MichaelPerception of Parkinsonian speech: Ratings by self and listeners vs. acoustic measures
Master of Science (MS), Bowling Green State University, 2009, Communication Disorders/Speech-Language Pathology
Parkinson Disease (PD) has been found to have significant effects on speech production, including deficits in phonation and prosody. Studies of self-perception of speech and voice by individuals with PD suggested that individuals with PD may be unaware of their own speech deficits. It was also hypothesized previously that caregivers (or other non-neurologically impaired listeners) would show awareness of the speech deficits associated with PD. However, neither the claim that individuals with PD are unaware of their deficits, nor the claim that caregivers are aware of deficits have been comprehensively examined. The current study examined ten individuals with PD (speakers) their primary caregivers. Individuals with PD completed a paragraph reading and both those individuals and their caregivers were asked to rate the speech across six perceptual measures. Trained listeners also rated the paragraph reading across the same six perceptual measures. Perceptual measures were correlated with acoustic measures, and perceptual measures were studied for significant differences across listener types. Results showed five correlations between trained perceptions and acoustics, three (one meaningful) correlations between self-perceptions and acoustics, and no correlations between caregiver perceptions and acoustics. Across listener type, trained listener perceptions were found to be significantly higher when compared to self-perceptions on three speech characteristics, and were significantly higher than caregiver perception on one speech characteristic. Although no significant differences were found between self-ratings and caregiver ratings, descriptive analysis of the correlation results may indicate caregivers underestimate the effects of PD on speech and voice. Clinical implications are discussed, including the impact this finding may have on PD patients and caregivers regarding their abilities to seek and attend treatment for speech and voice.

Committee:

Alexander M. Goberman, PhD (Advisor); Elizabeth I. Burroughs, PhD (Committee Member); Rodney M. Gabel, PhD (Committee Member)

Subjects:

Acoustics; Communication; Health Care; Neurology; Personal Relationships; Speech Therapy

Keywords:

Parkinson; speech; voice; phonation; prosody; self-perception; listener perception; acoustic;

Szostak, ChristineIndividual Differences in Working Memory Capacity Influence Spoken Word Recognition
Doctor of Philosophy, The Ohio State University, 2013, Psychology
Prior work has shown that when speech is unclear, listeners show a greater dependence upon semantic than on acoustic information to aid word identification when distracting stimuli (e.g., other talkers) are present. The current project extended this work to explore whether individual differences in working memory capacity (WMC) would influence the likelihood that listeners will depend on the biasing information when distracted. In five experiments, participants heard sentences that contained an early target word with or without noise at its onset and a subsequent word that was semantically biased in favor of the target word or one of its lexical competitors (e.g., The wing had an exquisite set of feathers or The wing had an exquisite set of diamonds where diamonds would be semantically associated with ring). The sentences were presented in the presence of distracters ranging in their degree of signal-similarity to that of the sentence (e.g., another speaker vs. an everyday nonspeech sound). Participants made target word identification and sentence sensibility judgments for each sentence they heard. The findings showed that those with lower WMC were more likely to depend upon biasing than on acoustic signal information, but only when the signal was masked by noise. In contrast, those with higher WMC showed less dependence upon the biasing information than those with lower WMC, even when the signal was masked by noise. Although performance across distracter similarity was not influenced by WMC, the likelihood of being able to anticipate what distraction would be heard was shown to influence performance as a function of WMC. A discussion of the role of WMC in spoken word recognition, especially during distraction, is provided and the potential mechanisms involved in this process are considered.

Committee:

Pitt Mark, Ph.D. (Advisor); Per Sederberg, Ph.D. (Committee Member); Simon Dennis, Ph.D. (Committee Member); Eric Healy, Ph.D. (Committee Member)

Subjects:

Acoustics; Behaviorial Sciences; Cognitive Psychology; Experimental Psychology; Language; Linguistics; Psychology

Keywords:

spoken word recognition; working memory capacity; subsequent context; dichotic listening; individual differences

Durand, ChristopherValidation of a CAA Code for a Case of Vortical Gust-Stator Interaction
Master of Science, University of Toledo, 2016, Mechanical Engineering
In this work, the solution of the NASA Glenn Research Center Broadband Aeroacoustic Stator Simulation (BASS) Computational Aeroacoustics (CAA) code to a benchmark problem has been presented. The test case used for this work is the Category 3 problem from the NASA Second CAA Workshop on Benchmark Problems, which is a 2D gust--cascade problem involving the interaction of an incident vortical gust with a row of infinitely thin stator blades. It has been found that BASS accurately predicts the magnitude of the cut-on acoustic modes that result from the gust impinging on the blades for both the low frequency and the high frequency benchmark case. Spurious reflections from the upstream and downstream boundaries are present in the solution due to limitations of the boundary conditions. Absorbing layers were used to minimize reflections from the boundary, with favorable results achieved by both using absorbing layers and increasing the axial length of the computational domain. Results also have been presented that suggest that dispersion-relation-preserving (DRP) spatial differencing schemes may not accurately resolve the decay rate of decaying acoustic waves with an economical number of grid points per wavelength. This work does not suggest a solution to this issue, but provides a general overview of the problem in order to help form a basis for future research.

Committee:

Ray Hixon, Ph.D (Committee Chair); Sorin Cioc, Ph.D (Committee Member); Mehdi Pourazady, Ph.D (Committee Member)

Subjects:

Acoustics; Aerospace Engineering; Mechanical Engineering

Keywords:

CAA; computational aeroacoustics; gust-cascade; vortical gust; drp; absorbing boundary layer; stator

Thompson, Shannon C.Resonance in Tongue Drums
Master of Science (MS), Ohio University, 2015, Physics and Astronomy (Arts and Sciences)
The purpose of this experiment was to test and improve the sound quality of tongue drums. In this experiment two different tongue drums were tested to find the frequency of the tongues compared to the resonances of their respective cavities. In preliminary testing the frequency of each tongue was found, then the modes of frequency were found for the dimensions of the box. In order to lengthen the duration of the tone emitted by a given tongue, a hollow tube with an adjustable slide was inserted into the side of the box. After testing a variety of lengths the long tongue with a constant frequency of 279.3 Hz on the large drum was amplified by changing the length of the drum to 0.61 m for resonant frequency. In order to continue testing ways to find the resonant frequency for different tongue drums, a computer simulation was created to model the experiment. The simulation could be used in the lab to model data. In addition, it could be used in a classroom setting to allow students to test and analyze tongue drums.

Committee:

Martin Kordesch, Dr. (Advisor); Mark Lucas, Dr. (Committee Member)

Subjects:

Acoustics; Physics

Keywords:

resonance; tongue drums

Pawar, AsawariQUANTIFICATION OF FLOW PARAMETERS IN COMPLEX VASCULATURE FLOW PHANTOMS USING CONTRAST-ENHANCED ULTRASOUND METHOD
Master of Science in Biomedical Engineering, Cleveland State University, 2015, Washkewicz College of Engineering
Currently, there are few simple-to-construct in vitro, wall-less phantoms that have accurate acoustic properties while mimicking the complex normal and neoplastic geometries and flow of the vascular network. The purpose of this study was to develop agar-based tissue-mimicking phantoms (TMP) to model such flow networks and to quantify the mean intensity and slope measurements of the ultrasound flow. Three types of vascular networks were developed; (1) single vessel, (2) multi-vessel with artery bifurcations and (3) multi-vessel with artery bifurcations and structural abnormalities typical of disease (tumor) vascular networks. Bolus injections of ultrasound contrast agents (UCAs) were performed under varying flow conditions relevant to our ongoing work in developing techniques to simultaneously quantify both the total volume and flow measurements within a tumor phantom The correlation coefficient between the mean slope measurements and the least squares fitted line was all higher than 0.95, indicating a good linear relationship between the mean slope and the flow-rates. For all single-vessel flow phantom data, the mean proportional difference of the slope measurements and flow-rate was 0.695 ± 0.18 (mean ± SD). It was found that the correlation coefficient between the mean slope measurements and the least squares fitted line is 0.90, indicating a good linear correlation between the single-vessel and Multi-vessel flow phantoms. However, the parameters obtained from tumor region 1, 2 and 3 did not show any significant flow pattern and correlation after contrast injection of UCAs. Finally, the slope measurements of intensity at the tumor regions inflow and outflow demonstrated the nonlinear and undefined relationship between the measured intensity and varied flow rates. Ideally, most information could be obtained when intensities at both the input and the output of the tumor periphery are measured. For further studies, alternative modeling of the problem is required as in physiology, microvasculature flow system has multiple input vessels and multiple output vessels. Developing new time-intensity-based techniques is the focus of future research.

Committee:

Gregory Clement, PhD (Committee Chair); Joanne Belovich, PhD (Committee Member); Chandra Kothapalli, PhD (Committee Member)

Subjects:

Acoustics

Keywords:

Quantification of Blood Flow, Contrast-enhanced ultrasound, Tumor vasculature flow phantoms

Seeman, Scott E.Informational Masking and Sensorineural Hearing Loss
Doctor of Philosophy, The Ohio State University, 2009, Speech and Hearing Science
A simulation was developed to examine the role reduced frequency selectivity has in explaining why hearing impaired listeners often have difficulty communicating in noise. This difficulty is the hallmark complaint of sensorineural hearing loss. More specifically, this simulation addresses the impact of poor spectral resolution on informational masking for multiple-burst stimuli. Perception of these complex tonal signals likely involves the same processing necessary for comprehending speech in complex listening environments (i.e., auditory stream segregation). Reduced frequency selectivity was simulated by restricting the frequency range of the masker pool in multiple-burst same (MBS) and multiple-burst different (MBD) informational maskers. MBS maskers have the same components in each burst of a sequence, while MBD maskers have different frequencies in each burst. In normal hearing listeners, MBS is a more effective masker, where signal and masker streams perceptually fuse, while MBD signal-masker streams are more easily segregated. Large differences in masker effectiveness for MBS and MBD are not seen for hearing impaired listeners however. A reduced difference in masking between MBS and MBD and increased effectiveness for MBD maskers in the hearing impaired has been attributed to deficits in frequency selectivity. Results for the simulation (in normal hearing subjects) confirm that restricting the masker range has demonstrative effects on multiple-burst IM. Reduced spectral resolution at restricted masker ranges results in greater MBD masking and reduced differences between MBS and MBD compared to results at wider masker ranges. Furthermore, results in hearing impaired listeners also show a reduced MBS-MBD difference, yet overall masking is reduced for both MBD and MBS. Predictions based on simulation experiments at an equal sensation level (26 dB SL) in normal hearing subjects are on average within 6 dB of hearing impaired data when frequency selectivity (i.e. psychophysical three-point tuning curves) estimates are taken into account. Results are both consistent with the reduced sensation level and the reduced frequency selectivity hypotheses in explaining multiple-burst informational masking in the hearing impaired.

Committee:

Lawrence Feth, PhD (Advisor); Christina Roup, PhD (Committee Member); Gail Whitelaw, PhD (Committee Member)

Subjects:

Acoustics

Keywords:

Informational Masking Sensorineural Hearing Loss Frequency Selectivity

Sorosiak, Eric J.Numerical Simulation and Active Noise Control of Vehicle Interior Acoustics
MS, University of Cincinnati, 2008, Engineering : Mechanical Engineering
Vehicle noise, vibration and harshness (NVH) problems can be analyzed using numerical methods such as finite element and boundary element analysis approaches, which are generally complex and time consuming. In order to speed the analysis and reduce the calculation burden, an enhanced, simplified numerical acoustic cavity formulation is developed, used and verified for the analysis of several vehicle NVH problems. The simplified model can incorporate multiple acoustic cavities joined by flexible panels to represent adjacent vehicle compartments. Several models are created with different cavity and panel configurations, and transfer functions predicted by these models are compared with corresponding transfer functions from measured vehicle data. The comparison results show that the developed simplified model provides reasonable accuracy for the analysis and simulation of vehicle compartment acoustics. While the initial goal of the simplified model was to develop a tool to observe general trends and effects associated with perturbations in the dimensions and configurations of joined vehicle compartments, results show sufficient accuracy for the model to be used for more detailed analyses as well. Additionally, an active noise control (ANC) system is proposed for tuning vehicle interior response, whereas traditional vehicle ANC is intended to suppress unwanted vehicle response. The proposed concept is adapted from the basic filtered-x least mean squares (FXLMS) algorithm and is studied numerically, utilizing simulated control input speakers inside the passenger compartment. An optimal configuration of these speakers is determined in order to maximize the effectiveness of the ANC system and then the proposed approach is demonstrated using a powertrain noise example in which individual engine firing orders are targeted for shaping either by reducing or enhancing the spectral content.

Committee:

Teik Lim, PhD (Committee Chair); Randall Allemang, PhD (Committee Member); Jay Kim, PhD (Committee Member)

Subjects:

Acoustics; Engineering; Mechanical Engineering

Keywords:

vehicle; interior; passenger compartment; cabin; cavity; modeling; active noise control; FXLMS; acoustics

Finet, Marc A.Sensor Hardening Through Translation of the Detector from the Focal Plane
Master of Science (M.S.), University of Dayton, 2012, Electro-Optics
The defense industry has numerous detectors that provide critical imaging capability on tactical and reconnaissance platforms and have been shown to be susceptible to permanent damage from high energy pulsed lasers in both laboratory and field testing. Much of the materials research into this involves two different methods of providing pulsed laser damage protection: extrinsic limiter implementation and intrinsic detector hardening. This thesis focused on what gains could be made using another method: system defocus and detector redundancy. The work of this thesis revolved around hardening a camera system through defocusing the focal plane array (FPA) and then using image restoration algorithms to regain the image quality of the degraded images. This system, a three channel image splitting prism with lens mount, provided a unique opportunity to test multiple images of an identical scene with slight spatial misalignments, varying sensor defocus and precisely measured optical degradation as measured by the Point Spread Function. These defocused images were then restored using filters that utilized information from only a single channel (the Wiener Filter, Regularized Least Squares Filter, and Constrained Least Squares Filter) and across multiple channels (Multichannel Constrained Least Squares Filter). Results from the single channel filters were excellent and allowed significant sensor hardening without image degradation when compared to the unfiltered image. Results from the multichannel RLS filter as tested were disappointing when compared to those from the single channel however and could be expanded upon in future work.

Committee:

Russell Hardie (Advisor)

Subjects:

Acoustics; Electrical Engineering; Optics

Keywords:

Image Restoration; multichannel; prism;

Saborse, Jacob A.Cultural Breakdown of Learned Avian Alarm Calls: Implications to Management and Conservation
Master of Science in Biological Sciences, Youngstown State University, 2011, Department of Biological Sciences
Mobbing is a common response of prey birds to aggressively displace potential predatory birds. This behavior transcends lineages and empirical evidence indicates that auditory cues from one species elicit mobbing responses in the same and/or different species. The black-capped chickadee (Pocile atricapillus) varies the number and length of D notes in the "chick-a-dee" mobbing call to denote information about the threat level a potential predator poses, with more numerous, shorter D notes designating a high threat. However, their limited natal dispersal may result in restricted transmission of culturally important vocalizations, which are known to quickly diminish in songbird populations that become isolated or are small in size, potentially exacerbating their decline. Whereas the black-capped chickadee and associated mixed flock members are common, we use this system as a model to study the cultural transmission of information important to prey survivorship and as a model of cultural breakdown in bird populations that are threatened by isolation. This project was replicated in areas containing persistent populations of Eastern screech owls (Megascops asio) and in those historically lacking them to assess whether black-capped chickadee alarm calls have a site-specific learned cultural component. Regional dialects are not hard-wired but learned in many songbirds, and locale-specific calls may uniquely convey information to members of the same mixed flock. Our data show that “chick-a-dee” warning calls differ in response to eastern screech owl presence. Where black-capped chickadees co-occurred with eastern screech owls, the average number of D notes was 5.25 but in areas lacking them, the average number of D notes was 2.25. Moreover, the length of the first D note was 40% shorter in areas with a persistent screech owl population. This indicates a breakdown in their vocal culture and suggests management that increases the connectivity of otherwise isolated populations can be of strong conservation value to many songbirds in decline.

Committee:

Ian Renne, PhD (Advisor); Thomas Diggins, PhD (Committee Member); John Usis, PhD (Committee Member)

Subjects:

Acoustics; Animals; Biology; Ecology

Keywords:

antipredator behavior; cultural transmission; ornithology; conservation

Zhang, WenbinSoft Fullerene Materials: Click Chemistry and Supramolecular Assemblies
Doctor of Philosophy, University of Akron, 2010, Polymer Science
Fullerenes are fascinating carbon nanostructures with outstanding structural and functional properties, which critically rely on their spatial arrangements. However, their strong aggregation makes them difficult to pack into ordered structures in different dimensions and across multiple length scales. The purpose of this research is to develop “soft fullerene materials,” in particular, using self-assemblies of polymers as templates to manipulate their order and symmetry. Synthesis of fullerene polymers with high purity and well-defined structure has been difficult due to the reactive nature of fullerene towards various reaction intermediates and the often unavoidable multiple additions. To address this, a “click chemistry” approach has been developed, as demonstrated by the model reaction between azide-functionalized polystyrene (PS-N3) and highly reactive alkyne-functionalized fullerene (Fulleryne01). fullerynes with different structures and reactivities have been designed and synthesized. Combined with living/controlled polymerization techniques, the method has been successfully extended to fullerene polymers based on poly(ethylene oxide) (PEO) and poly(ethylene oxide)-block-polystyrene (PEO-b-PS) with controlled molecular weight and narrow polydispersity. The C60 was placed at the chain-end [PEO-C60 and PEO-b-PS-C60], or at the junction point between two blocks [PEO-(C60)-PS], or randomly tethered along one block [PEO-b-PS/C60]. The self-assembly of these polymers, such as crystallization from dilute solution, micellization in selective solvent, and phase separation in bulk or thin films, have been studied. Preliminary results have shown that they could template the spatial arrangements of C60. For example, the single crystals of PEO-C60 have been grown to generate PEO single crystal lamellae with C60 tethered to the surface, forming a 2D C60 molecular sheet. The alternating, epitaxial growth of PEO and PEO-C60 single crystals might lead to near-1D ring patterns of C60. The diblock copolymers, PEO-(C60)-PS and PEO-b-PS-C60, were found to form micelles in DMS/water mixed solvent, in which C60 was either confined to the interface between the core and corona, or inside the core. The bulk self-assembly of PEO-(C60)-PS has shown an unusual decrease in d-spacing, as compared to its parent polymer PEO-(N3)-PS; whereas both PEO-b-PS-C60 and PEO-b-PS/C60 showed increase in d-spacing. This drastic difference was due to the location of C60 in the final structure. This study has demonstrated the concept and the promising future of “soft fullerene materials.” In addition, during the development of these materials, a “retro-functional analysis” approach has been proposed as the molecular design principle for advanced materials. It could allow efficient and modular development of functional molecular materials with engineered hierarchical structure across different length scales to exhibit a specific macroscopic property. Being function-oriented rather than synthesis-oriented, it fuels innovation in molecular design and provides future targets for material research.

Committee:

Dr. Stephen Cheng (Advisor); Roderic Quirk, PhD (Committee Chair); George Newkome, PhD (Committee Member); Ali Dhinojwala, PhD (Committee Member); Chrys Wesdemiotis, PhD (Committee Member)

Subjects:

Acoustics; Chemistry; Physics; Polymers

Keywords:

Fullerene; soft materials; click chemistry; supramolecular assemblies; self-assembly; ordered structure; retro-functional analysis

Cardinale, Luke AAutomating the Subjective Analysis of Knock during Hot Engine Starts
Master of Science, The Ohio State University, 2016, Mechanical Engineering
The engine start serves a crucial point of interaction with the end user of a vehicle. It is a unique operating condition for a motorist in that there is no requirement to focus on anything outside of the engine starting. This provides the opportunity for the motorist to gauge the state of reliability. A good engine start brings maintains confidence in the vehicle. A short crank, followed by a quiet roar of the exhaust and the motorist can be on their way without concern. Any indicator of unreliability during the start of the engine, however, may influence the motorist’s decision on whether to depart on their journey or to halt and schedule maintenance. Evaluation of engine starts is thus highly subjective in nature. This creates a challenge in the task of calibration. The present investigation focuses on developing a method to translate subjective assessment practices for calibration into measureable objective metrics. Knock during hot engine starts is selected for detailed demonstration of the method, however the method was also applied to additional aspects of hot engine starts. In practice, the subjective requirements for this set of aspects is used to tune a calibration table referenced to mitigate hot engine start knock. A full factorial experiment was performed with respect to the calibration table. The recorded data was evaluated using the scoring method and compared to a manually tuned calibration with satisfactory results.

Committee:

Shawn Midlam-Mohler, Dr. (Advisor); Giorgio Rizzoni, Dr. (Committee Member)

Subjects:

Acoustics; Automotive Engineering; Engineering; Mechanical Engineering

Keywords:

Knock;Engine Knock;Start;Engine Start;Hot Start;Subjective Analysis;Marketability;Subjective;Subjective Mapping;key-on

Dehner, Richard D.An Experimental and Computational Study of Surge in Turbocharger Compression Systems
Doctor of Philosophy, The Ohio State University, 2016, Mechanical Engineering
The objective of the present study is to predict compression system surge instabilities, including discrete sound peaks at low frequencies and their amplitudes at key locations. One-dimensional (1D) gas dynamics models were created for a turbocharger stand and a twin, parallel turbocharged V6 gasoline turbocharged direct injection (GTDI) engine, which have a common turbocharger design. In addition, a three-dimensional (3D) computational fluid dynamics (CFD) model was developed for the compression system of the turbocharger stand, and prediction results are utilized to study the details of compressor flow-field breakdown and the resulting instabilities at reduced flow rates. The turbocharger stand isolated surge from engine airborne pulsations, thereby providing a simplified bench-top environment for in-depth studies of pertinent physics and model development. Two different compression system configurations were studied on the turbocharger stand. The first configuration incorporated a plenum (large volume), which produced surge as the flow rate was reduced. To facilitate surge predictions, a compressor performance map from an extended flow range small volume system (second configuration) was incorporated into a 1D model of the large volume configuration. Mild and deep surge predictions were completed with the 1D model of the large volume turbocharger stand compression system and the dominant sound peaks of simulations agreed reasonably well with the corresponding measurements. Engine experiments and modeling were carried out in two phases, where the first phase was steady-state, full load operation at low engine speeds and the second phase perturbed one of the compressors into surge. The engine model incorporated loss coefficients from flow bench experiments with induction system components, and modified air cleaner box and charge air cooler models that accurately captured the frequency dependent interaction of pressure waves. Steady-state engine data confirmed the accuracy of predicted performance, pressure drops, and wave dynamics in the induction system. Once the models for compressor surge and stable engine operation were independently validated with experimental data from the turbocharger stand and engine dynamometer, respectively, the engine model was then utilized for predictions with the right-bank compressor in both mild and deep surge. The mild surge prediction provided reasonable agreement with experimental data, and the accuracy of predictions improved as the load was increased and the right-bank compressor entered deep surge. Simulations with a 3D CFD model were initially performed during stable operation with a domain that was confined to the compressor with short inlet and outlet duct extensions. Resulting predictions agreed well with measurements from the turbocharger stand, including compressor performance and the onset of temperature rise near the inducer blade tips. Next, the computational domain was expanded to include the (full) large volume turbocharger stand compression system. As the compressor flow rate was reduced below that at the peak pressure ratio, rotating stall cells formed near the shroud-side diffuser wall. A further reduction in flow rate resulted in the system entering mild surge, where two cycles were simulated. Mild surge predictions from this CFD model provided good agreement with compressor inlet and outlet pressure measurements, in terms of reproducing the amplitude and frequency.

Committee:

Ahmet Selamet (Advisor); Jen-Ping Chen (Committee Member); Sandip Mazumder (Committee Member); Junmin Wang (Committee Member); Philip Keller (Committee Member)

Subjects:

Acoustics; Aerospace Engineering; Automotive Engineering; Engineering; Experiments; Fluid Dynamics; Mechanical Engineering; Transportation

Keywords:

turbocharger; automotive; internal combustion engine; engine; centrifugal compressor; compressor; instabilities; surge; rotating stall; one-dimensional model; three-dimensional computational fluid dynamics; 3D CFD

Longenecker, Ryan JamesDifferential Pathologies Resulting From Sound Exposure: Tinnitus Vs. Hearing Loss
PHD, Kent State University, 2015, College of Arts and Sciences / School of Biomedical Sciences
Longenecker, Ryan J, Ph.D., December 2015 DIFFERENTIAL PATHOLOGIES RESULTING FROM SOUND EXPOSURE: TINNITUS VS HEARING LOSS (104 pp.)Director of Dissertation: Alexander V. Galazyuk, Ph.D. The first step in identifying the mechanism(s) responsible for tinnitus development would be to discover a neural correlate that is differentially expressed in tinnitus-positive compared to tinnitus negative animals. Previous research has identified several neural correlates of tinnitus in animals that have tested positive for tinnitus. However it is unknown whether all or some of these correlates are linked to tinnitus or if they are a byproduct of hearing loss, a common outcome of tinnitus induction. Abnormally high spontaneous activity has frequently been linked to tinnitus. However, while some studies demonstrate that hyperactivity positively correlates with behavioral evidence of tinnitus, others show that when all animals develop hyperactivity to sound exposure, not all exposed animals show evidence of tinnitus. My working hypothesis is that certain aspects of hyperactivity are linked to tinnitus while other aspects are linked to hearing loss. The first specific aim utilized the gap induced prepulse inhibition of the acoustic startle reflex (GIPAS) to monitor the development of tinnitus in CBA/CaJ mice during one year following sound exposure. Immediately after sound exposure, GIPAS testing revealed widespread gap detection deficits across all frequencies, which was likely due to temporary threshold shifts. However, three months after sound exposure these deficits were limited to a narrow frequency band and were consistently detected up to one year after exposure. This suggests the development of chronic tinnitus is a long lasting and highly dynamic process. The second specific aim assessed hearing loss in sound exposed mice using several techniques. Acoustic brainstem responses recorded initially after sound exposure reveal large magnitude deficits in all exposed mice. However, at the three month period, thresholds return to control levels in all mice suggesting that ABRs are not a reliable tool for assessing permanent hearing loss. Input/output functions of the acoustic startle reflex show that after sound exposure the magnitude of startle responses decrease in most mice, to varying degrees. Lastly, PPI audiometry was able to detect specific behavioral threshold deficits for each mouse after sound exposure. These deficits persist past initial threshold shifts and are able to detect frequency specific permanent threshold shifts. The third specific aim examined hyperactivity and increased bursting activity in the inferior colliculus after sound exposure in relation to tinnitus and hearing loss. Spontaneous firing rates were increased in all mice after sound exposure regardless of behavioral evidence of tinnitus. However, abnormal increased bursting activity was not found in the animals identified with tinnitus but was exhibited in a mouse with broad-band severe threshold deficits. CBA/CaJ mice are a good model for both tinnitus development and noise-induced hearing loss studies. Hyperactivity which was evident in all exposed animals does not seem to be well correlated with behavioral evidence of tinnitus but more likely to be a general result of acoustic over exposure. Data from one animal strongly suggest that wide-spread severe threshold deficits are linked to an elevation of bursting activity predominantly ipsilateral to the side of sound exposure. This result is intriguing and should be followed up in further studies. Data obtained in this study provide new insights into underlying neural pathologies following sound exposure and have possible clinical applications for development of effective treatments and diagnostic tools for tinnitus and hearing loss.

Committee:

Alexander Galazyuk, Ph.D. (Advisor); Jeffrey Wenstrup, Ph.D. (Committee Member); Yong Lu, Ph.D. (Committee Member); Angelo DeLucia, Ph.D. (Committee Member); Gary Koski, Ph.D. (Committee Member)

Subjects:

Acoustics; Behavioral Sciences; Biomedical Research; Neurobiology; Neurosciences

Keywords:

tinnitus; noise-induced hearing loss; neurophysiology; acoustic startle reflex; prepulse inhibition; inferior colliculus; hyperactivity; burst firing

Whitfield, Jason A.Speech Motor Sequence Learning in Parkinson Disease and Normal Aging: Acquisition, Consolidation, and Automatization
Doctor of Philosophy (Ph.D.), Bowling Green State University, 2014, Communication Disorders
Motor learning relies on the integrity of sensorimotor circuits in the brain, which are largely affected in individuals with Parkinson disease (PD). Additionally, data suggest normal aging can affect various stages of motor learning. Though data are available on the nature of non-speech motor learning, fewer studies have examined how adults with and without motor speech disorders learn speech articulatory sequences. The aim of the current investigation is to examine speech motor sequence learning in normal aging and PD. A speech motor sequence learning task was developed and implemented to examine acquisition, consolidation, and automatization over two days. On Day 1, participants learned a sequence of six monosyllabic nonwords to examine acquisition. This speech motor sequence was re-tested on Day 2 in single- and dual-task conditions to evaluate consolidation and automatization, respectively. Learning was inferred from gains in speed and accuracy of the speech motor sequence. There were no observed effects of aging or PD on speech motor sequence acquisition, as all groups exhibited comparable gains in speed and accuracy on Day 1. However, aging and PD were observed to affect speech motor consolidation following night-time sleep. Specifically, at the Day 2 re-test, young adults exhibited offline gains in speed and accuracy, older adults maintained speed and accuracy (without offline gains), and individuals with PD exhibited offline losses in speed. Only younger adults demonstrated automatization, exhibiting negligible dual-task effects when concurrently performing the speech motor sequence with a visuo-motor task. Conversely, both older adults and individuals with PD exhibited significantly poorer performance of the speech motor sequence in the dual-task condition, with individuals with PD experiencing the largest degree of bidirectional dual-task interference. Overall, the current findings suggest that speech motor learning is affected by both Parkinson Disease and normal aging. Data from the current investigation are largely in line with findings in the non-speech motor sequence learning literature, suggesting that speech and non-speech motor learning may rely on similar neural circuits. As the individuals with PD exhibited deficits in the consolidation and automatization phases of learning, these data may hold important implications for the speech rehabilitation in PD.

Committee:

Alexander Goberman, Ph.D. (Advisor); Ronald Scherer, Ph.D. (Committee Member); Miriam Krause, Ph.D. (Committee Member); Howard Cromwell, Ph.D. (Committee Member); Patricia Sharp, Ph.D. (Committee Member)

Subjects:

Acoustics; Behavioral Sciences; Cognitive Psychology; Neurosciences; Speech Therapy

Keywords:

Speech Motor Sequence Learning; Parkinson disease; Aging; Motor Sequence Learning; Consolidation; Automatization; Automaticity; Dual-task; Sleep Quality; Speech Acoustics; Basal Ganglia

Suresh, SaurabhTransmission Loss Analysis of Laminated Glass with Porous Layers using Transfer Matrices for Automotive Applications
MS, University of Cincinnati, 2011, Engineering and Applied Science: Mechanical Engineering
This study analyzes the sound transmission characteristic of various laminated glass designs with application to motor vehicles. The laminated glasses contain a combination of solid, air and/or porous layers. The porous interlayer is filled with Polyvinyl Butyral (PVB) that serves as an acoustic damper. To model the physics behind the sound transmission losses of the fluid, solid and porous layers, acoustic noise transfer matrices that relate the dynamic characteristics of two interlayer points are used for modeling each medium in the laminated glass. The porous model also includes the effect of the variation in porosity on Poisson’s ratio. The Poisson’s ratio is used in calculations involving the wave number as well as the bulk modulus and hence the variation in the Poisson’s ratio affects the acoustic wave propagation through the porous layer. Furthermore, an interface matrix is introduced, which defines the dynamic interaction at the interface of every layer. A viscoelastic model is used for the solid layers and the Biot’s theory is applied to describe the flow through the porous layer. The addition of a fluid layer, like air, yields an interesting phenomenon of two coincidence dips in the laminated structure. The lower frequency dip is due to the air layer acting as part of the system damping medium and the other higher frequency dip occurs where air acts as a separation medium and decouples the layers in the glass. The analysis reveals difference in the effects of porosity on the behaviors of the low and high frequency dips Finally, a set of parametric studies are performed to observe the transmission loss characteristic due to changes in glass thickness and porous layer.

Committee:

Teik Lim, PhD (Committee Chair); Jeffrey Kastner, PhD (Committee Member); David Thompson, PhD (Committee Member)

Subjects:

Acoustics

Keywords:

Transmission Loss;Laminated Glass;Wind Noise;Porous Layer;Coincidence Frequency;Transfer Matrix

Horstemeyer, MarkThe Determination of Failure Mechanisms in the Fatigue of Unidirectional Composites by the Use of Acoustic Emissions
Master of Science, The Ohio State University, 1987, Mechanical Engineering
The fatigue failure mechanisms of three unidirectional laminated composite material systems (consisting of a common fiber in three varying matrices) were investigated. Static tension tests of the composites, in both axial and transverse directions, and of the resins were used along with acoustic emissions to evaluate fatigue test data. The resins with the highest strain energy and ultimate strain were best in fatigue. Hence, unidirectional glass-polymer composites possessed a matrix dominated failure mode. But when fatigue curves for the resins and composites were compared, interface debonding was shown to be a failure mechanism. Acoustic emissions also showed that interface debonding was a major failure mechanism involved in fatigue. Acoustic Emissions also gave insight into the intermediate failure mechanisms during the fatigue life. The important aspect of the analysis is that matrix cracking and interface debonding are both involved in determining the major failure mechanism.

Committee:

George Staab (Advisor); Brian Harper (Advisor)

Subjects:

Acoustics

Ingraham, DanielVerification of a Computational Aeroacoustics Code Using External Verification Analysis (EVA)
Master of Science in Mechanical Engineering, University of Toledo, 2010, College of Engineering
As Computational Aeroacoustics (CAA) codes become more complex andwidely used, robust Verification of such codes becomes more and more important. Recently, Hixon et al. proposed a variation of the Method of Manufactured Solutions of Roache especially suited for Verifying unsteady CFD and CAA codes that does not require the generation of source terms or any modification of the code being Verified. This work will present the development of the External Verification Analysis (EVA) method and the results of its application to some popular model equations of CFD/CAA and a high-order nonlinear CAA code.

Committee:

Ray Hixon, PhD (Committee Chair); Douglas Oliver, PhD (Committee Member); Chunhua Sheng, PhD (Committee Member)

Subjects:

Acoustics; Mechanical Engineering

Keywords:

Computational Aeroacoustics; Computational Fluid Dynamics; Code Verification; External Verification Analysis; Method of Manufactured Solutions; CAA; CFD; EVA; MMS

KULKARNI, PRASHANT M.EXPERIMENTAL FORMULATION OF FOUR-POLE PARAMETERS FOR ANALYTICAL-EXPERIMENTAL HYBRID MODELING OF ACOUSTIC SYSTEMS
MS, University of Cincinnati, 2003, Engineering : Mechanical Engineering
Experimental implementation and validation of the method for formulation of pressure response functions based on the four-pole method is the main focus of this thesis. Four-pole formulation provides a very convenient way to model and analyze acoustic systems; however the concept has been applied mainly to systems composed of one-dimensional or lumped parameter elements because of the difficulty to obtain four poles of three-dimensional systems. In this work an experimental procedure based on measured pressure response functions is proposed to measure four pole parameters. Being an experimental method, four pole parameters of any general systems can be obtained as long as they are connected to other systems one-dimensionally. Combined with the cascading property of the four poles, the method enables hybrid modeling of acoustic systems; models of different parts of the system can be formulated analytically, numerically or experimentally, depending on the needs, then combined to obtain the system model. The technique to be developed utilizes simultaneous measurement of signals from three microphones, which allows obtaining two pressure response functions at a time. The proposed experimental procedure is applied to a one-dimensional pipe, which allows comparisons with exact four poles and experimental four poles for validation of the proposed method. Procedures are also explained for practical applications of this four-pole based hybrid modeling. This study will result in important advancement of modeling techniques in analysis of complicated acoustic systems.

Committee:

Dr. Jay Kim (Advisor)

Subjects:

Physics, Acoustics

Keywords:

acoustics; four pole method; sound; impedance; muffler

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