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Browsing by Subject "Acoustics"

Now showing 1 - 9 of 9
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    Acoustic and Perceptual Measurements of 3- and 4-Year Old Children's Productions of Word-Initial /ɹ/ and /w/
    (2023-05-18) Ancel, Elizabeth E; Smith, Michael L; Rao, V. N. Vimal; Munson, Benjamin; ancel014@umn.edu; Ancel, Elizabeth E; University of Minnesota Studies in the Applied Sociolinguistics of Speech and Language Lab
    This data contains acoustic and perceptual measurements of 3- and 4-year-old children's productions of /ɹ/- and /w/- initial words. Young children's production of the /ɹ/ sound is highly variable and often inaccurate, with [w] as the most common substitution error. One acoustic indicator of the goodness of children’s /ɹ/ productions is the difference between the frequency of the second formant (F2) and third formant (F3), with a smaller F3-F2 difference being associated with a perceptually more adult-like /ɹ/. This data contains both automatically extracted F3-F2 differences for the full set of 117 children, as well as manual measurements of a subset of the children (n=14). Additionally, this data contains untrained listeners' perceptual measurements of the children's productions for comparison.
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    Comparing Ship-based to Multi-Directional Sled-based Acoustic Estimates of Pelagic Fishes in Lake Superior
    (2019-05) Grow, Ryan
    Ship-based down-looking acoustic surveys are commonly used to determine the biomass and population density of commercially important fish species for resource managers and scientists, particularly in the Great Lakes and marine systems. However, there are some limitations and biases inherent in traditional down-looking surveys. I examined the use of multi-directional sled mounted acoustics equipped with up, side, and down-looking capabilities to overcome these limitations while examining the Lake Superior pelagic fish community. In the western arm of Lake Superior, I concurrently deployed the sled mounted acoustics during traditional down-looking surveys to directly compare the fish densities obtained from each gear, which I then followed with a mid-water trawl to inform my acoustic data with species composition. My findings from a two-way ANOVA showed a significant difference between fish densities detected by the sled-based survey and the ship-based down-looking survey indicating 60% of the pelagic fish community was missed by the traditional down-looking survey. This study also sought to provide a baseline for future research looking to discover which species in aquatic systems are most effected by traditional survey biases, as well as future work into using alternate forms of acoustic sampling to inform fisheries management and research.
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    High enthalpy Effects on two boundary layer disturbances in supersonic and hypersonic flow.
    (2012-05) Wagnild, Ross Martin
    The fluid flow phenomenon of boundary layer transition is a complicated and difficult process to model and predict. The importance of the state of the boundary layer with regard to vehicle design cannot be understated. The high enthalpy environment in which high speed vehicles operate in further complicates the transition process by adding several more degrees of freedom. In this environment, the internal properties of the gas can stabilize or destabilize the boundary layer as well as modify the disturbances that cause transition. In the current work, the interaction of two types of disturbances with the high enthalpy flow environment are analyzed. The first is known as a second mode disturbance, which is acoustic in nature. The second type is known as a transient growth disturbance and is associated with flows behind roughness elements. Theoretical analyses, linear stability analyses, and computation fluid dynamics (CFD) are used to determine the ways in which these disturbances interact with the high enthalpy environment as well as the consequences of these interactions. First, acoustic wave are directly studied in order to gain a basic understanding of the response of second mode disturbances in the high enthalpy boundary layer. Next, this understanding is used in interpreting the results of several computations attempting to simulate the flow through a high enthalpy flow facility as well as experiments attempting to take advantage of the acoustic interaction with the high enthalpy environment. Because of the difficulty in modeling these experiments, direct simulations of acoustic waves in a hypersonic flow of a gas with molecular vibration are performed. Lastly, compressible transient growth disturbances are simulated using a linear optimal disturbance solver as well as a CFD solver. The effect of an internal molecular process on this type of disturbance is tested through the use of a vibrational mode. It is the goal of the current work to reinforce the critical importance of accurately capturing the physics of the "real" gas effects in the high enthalpy flow environment in order to understand and predict transition on high speed vehicles.
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    Musical Gestures between Scores and Acoustics: A Creative Application to Orchestra
    (2017-05) Mannone, Maria
    Musical gestures connect symbolic scores to physical sounds, and they can be mathematically investigated. Mathematics can also be used to transform images into music and vice versa. The two approaches work together if we consider a visual shape as the result of a drawing gesture. We present here a piece for orchestra, soprano, and piano as a creative application of the mathematical research on musical gestures and music/visual arts.
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    Numerical and Theoretical Studies of Air Entrainment and Bubble Acoustics under Breaking Waves
    (2021-12) Gao, Qiang
    Bubbles and breaking waves play a critical role in many physical processes. However, bubble formation mechanism, trajectories, and their acoustic signatures are still poorly understood due to the complex process of breaking waves. To study the bubble transport dynamics and their formation mechanism, a technique for Lagrangian tracking of bubbles and detecting their time-evolution behaviors is developed. Five possible behaviors are considered: formation, extinction, continuity, binary fragmentation, and binary coalescence. The technique is based on establishing a network of mappings between bubbles identified at adjacent time instants. The accuracies for continuity, binary fragmentation, and binary coalescence are estimated to be 99.5%, 90%, and 95%, respectively. The algorithm is proved to be accurate and robust by extensive validations using the breaking wave cases. Bubble entrainment mechanism and bubble trajectory are investigated. Air filaments and cavities in plunging breaking waves, generically cylinders, produce bubbles through an interface instability. A generalized dispersion relation is obtained that spans the Rayleigh–Taylor and Plateau–Rayleigh instabilities as cylinder radius varies. The analysis provides insight into the role of surface tension in the formation of bubbles from filaments and cavities. Small filaments break up into bubbles through a Plateau–Rayleigh instability driven through the action of surface tension. Large air cavities produce bubbles through a Rayleigh–Taylor instability driven by gravity and moderated by surface tension, which has a stabilizing effect. Surface tension, interface curvature, and gravity are all important for cases between these two extremes. Bubble trajectories and their interaction with breaking wave flow fields are also studied here. A simulation framework for bubbly flow and the sound radiated by breaking waves is presented. It consists of a two-phase flow solver, an algorithm to track bubbles and bubble creation rates, and a module to compute the sound generated by newly-formed bubbles. The sounds from breaking, third-order Stokes waves of 0.25m wavelength and two slopes are calculated. The results show encouraging agreement with existing laboratory observations and identify the importance of air cylinder breakup in bubble creation.
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    A Palette of Transmasculine Voices
    (2023-10-26) Dolquist, Devin V.; Munson, Benjamin; munso005@umn.edu; Munson, Benjamin; Studies in the Applied Sociolinguistics of Speech and Language (SASS) Laboratory, Department of Speech-Language-Hearing Sciences, College of Liberal Arts; Center for Applied and Translational Sensory Sciences
    The growing practice of gender-affirming voice in Speech-Language Pathology often overlooks the voices of transmasculine people. Previous research in this topic focuses primarily on obtaining acoustic information that will help trans folks assimilate to cis-sounding voices. This is a new corpus of voices from a diverse set of 20 masculine-identifying people, including transmasculine men, cisgender men, and transmasculine nonbinary people. The corpus includes recordings of materials commonly used in speech-language pathology (the rainbow passage [Dietsch et al, 2003], the CAPE-V sentences [Kempster et al., 2009]) and a set of 27 sentences created for this project. The corpus contains individual audio files for all of the materials, and Praat TextGrids for the novel sentences. This corpus can be used in clinical services to model different male-sounding voices, and in clinical and preprofessional education in speech-language pathology
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    Prediction and Examination of Rotor Sound using Computational Fluid Dynamics
    (2019-02) Keller, Jacob
    Rotors are extensively used in aerodynamic applications, e.g., propellers, helicopter rotors, wind turbines, and fans. They are a large source of unwanted noise. The sound produced by low speed rotors has received less attention in the literature than sound produced by high speed rotors. These differences in speed and environment can be described by the Mach number, typically defined as the ratio of total tip speed of the rotor to the speed of sound. This dissertation discusses the implementation of a general numerical methodology for the prediction of sound using computational fluid dynamics and examines the production of noise by a low Mach number, marine propeller operating at design conditions. To simulate the fluid flow, the Navier–Stokes equations of fluid motion are solved using both large–eddy simulation and direct numerical simulation. Incompressible and compressible simulations based on the finite-volume methods of Mahesh et al. and Park and Mahesh are conducted. These methods have been used to successfully predict flowfields across a variety of problems in the past. The simulation results are used in conjunction with the Ffowcs-Williams and Hawkings acoustic analogy to predict the sound generated from the simulated flowfield. Within this dissertation, the general acoustic prediction tool is developed. Sound waves are inherently a compressible phenomena, and while the governing equations are well known, the prediction of sound (across Mach numbers) is still a very active field of research. Computationally, it becomes difficult to capture the range of spatial and temporal scales in many acoustic problems. Compressible simulations can require large domains that are highly resolved to capture sound waves. Incompressible simulations do not suffer from these adverse effects, however, it is important to ensure that the acoustic prediction remains accurate when the simulation does not capture the acoustic wave propagation. Hence the tool is applied to predict sound from the flowfield of the canonical pulsating sphere. Results predicted from both compressible and incompressible simulations are discussed. Noise generation is known to be exacerbated by the pressence of a geometric surface singularity, such as blade tips, corners, trailing edges. The case of noise generated by a trailing edge is examined directly using a two-dimensional compressible DNS of laminar flow around a NACA 0012 airfoil. The simulations are conducted at a Mach number of 0.4 and a Reynolds number of 50, 000 based on the airfoil chord length. Finally, the method is used to predict sound from an incompressible LES of propeller DTMB 4381 operating at design conditions. The simulations are conducted at a Reynolds number of 894, 000 and an advance ratio of 0.889 based on the propeller diameter. Three distinct source regions are found along the propeller blade: the hub-root region, the blade mid-span, and the blade tip region. Flow separation in the hub boundary layer interacts with the blade-root surfaces to generate a directionally independent, broadband sound field. This interaction decays with increasing radius along the propeller blades. In the blade mid-span, where the blade generates most of its thrust, high levels of sound are created by boundary layer turbulence convecting past the blade trailing edge. The sound source region is confined very close to the blade trailing edge. The highest levels of sound are found to be generated very near the blade tips. The radial truncation of the surface leads to the shedding of an unsteady tip vortex. The locally separated flow near the core of the vortex creates high levels of unsteady surface loading.
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    Sensible Mathematics: The Science of Music in the Age of the Baroque
    (2019-12) Fix, Adam
    In this dissertation I analyze the relations between mathematics, music theory, and experimental sciences from the scientific revolution through the Enlightenment. Music in the early modern period was seen as a mathematical science. More so than other branches of mathematics, music also had a direct connection to human sensory perception. I show that music, interpreted as a kind of “sensible mathematics,” played a crucial though largely underappreciated role in uniting mathematical and empirical European scientific traditions. I describe the upheavals that saw music theory become unmoored and drift away from what came to be known as modern science. During the Enlightenment it landed in the domain of fine arts and aesthetics, a separation we typically see as self-evident today. By elucidating the role of music in the scientific revolution and its aftermath, while emphasizing the shift from premodern musical science to modern physico-mathematical acoustics, I reveal the profound—even paradoxical—tensions between science and the practical arts.
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    Supplemental Material in Support of the Manuscript: “Characterization of Upper Esophageal Sphincter Pressures Relative to Vocal Acoustics.”
    Hoffmeister, Jesse; Konczak, Jürgen; Misono, Stephanie; University of Minnesota Voice Lab
    The supplementary material is a report of results in prose describing the results of statistical sensitivity analyses comparing upper esophageal sphincter across 4 different phonatory conditions, and assessing relationships between upper esophageal sphincter pressure and two acoustic measures (Cepstral Peak Prominence and Low-to-High Spectral Energy Ratio) excluding statistical outliers. No individual or identifying data from participants are included.