Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 21 for “"impedance tube"”.
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A phase-sensitive system for measuring acoustic pressure in an impedance tube
Thesis: M.S., Massachusetts Institute of Technology, Department of Electrical Engineering, 1949
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Aircraft interior acoustic noise control
… suited for internal aircraft noise reduction. An impedance tube with dimensions of a scaled aircraft was constructed and evaluated, and eleven materials were tested and compared based on their noise reduction properties, weight, and thickness. Polyvinylidene Fluoride was tested for use in active …
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Material property extraction procedure for electromomentum coupled metamaterials
… Eμ coupling of a sample using a water-filled impedance tube. The impedance tube measurement procedure presented in this work is a generalization of existing methods used to infer the frequency-dependent material properties of a sample from measurements of its scattering coefficients and …
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Behavior of low-frequency sound waves in porous media
… was applied to data taken from a vertical impedance tube to determine the propagation and reflection parameters of the materials. Physical characteristics considered include porosity, tortuosity, and flow resistivity.
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Application of cepstral techniques to the automated determination of the sound power absorption coefficient
… mounted in a sample holder at the end of a tube. Jongens and others identified numerous factors that introduced uncertainties into the measurement. These uncertainties fall into two main categories. The first deals with the influences that the links of the measurement chain have on the …
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Acoustic Vector Network Analyser
… of the current “industry standard”, the impedance tube, by using additional microphones and error correcting methods. A vector network analyser (VNA) is used as the data acquisition component with the aim of developing a module to allow the device to measure in the acoustic domain. The …
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Exploring Novel, Hard, Acoustically Absorbent, Materials
… To find a material answer to this desire an impedance tube was used to analyze the mid-frequency octave band absorption coefficients of various re-purposed existing materials and tiles created utilizing 3D print technology and Helmholtz resonators. Additionally, an empirical study of …
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Acoustic metamaterials comprised of dead-end pores and black hole effect for low frequency sound absorption in linear and nonlinear regimes
… is abrupt, while in the second a gradual impedance matching with air is achieved. The structures developed are tested in a range of various experimental set-ups. This includes performing measurements in a conventional impedance tube (linear regime), in a specially modified impedance tube …
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An investigation of the structurally induced acoustic field in a car passenger compartment
… absorption coefficients were measured with an impedance tube.
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Microperforated Panel (MPP) Absorbers for Impulsive and Narrow-Band Noise Control: Design, Simulation, and Experimental Validation
… MPPs, followed by numerical simulations and impedance tube validation. Key design parameters such as hole diameter, perforation ratio, and cavity depth are systematically evaluated to optimize absorption near 1 kHz—the dominant frequency of pickleball noise. A novel parallel MPP configuration …
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Acoustical characteristics of oil palm mesocarp fibres
… 40%. The measurement of SAC was done using an impedance tube method (ITM). Moreover, there were two analytical models which are Delany�Bazley model and Johnson-Champoux-Allard model to validate the experimental outcomes. There were several internal characteristics of the prepared samples …
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Acoustic and non-acoustic performance of coal bottom ash as sound absorptive material for reducing railway noise level
… to absorb more than 30% of sound by conducting impedance tube and reverberation time. In addition, the Noise Reduction Coefficient (NRC) performance for CBA concrete addresses more than 35% of the absorbed railway sound. CBA concrete showed an improvement in acoustic properties compared to …
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Prediction of sound pressure and intensity fields in rooms and near surfaces by ray tracing
… materials were measured using two methods—an impedance tube and the spherical-decoupling method. Using these coefficients, the modified program was compared with experimental data measured in configurations involving one or more surfaces made of these materials, in an anechoic chamber, a …
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The evaluation of acoustic characteristic performance on natural sound absorbing materials from cogon grass waste
… reduction coefficient (NRC) were done by using impedance tube method (ITM). The samples of cogon grass were tested in a way of the untreated and treated with NaOH in varied soaked hours which are one, two, three, four and five hours. Scanning electron microscope (SEM) and density kit were used …
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The evaluation of acoustic characteristic performance on natural sound absorbing materials from cogon grass waste
… reduction coefficient (NRC) were done by using impedance tube method (ITM). The samples of cogon grass were tested in a way of the untreated and treated with NaOH in varied soaked hours which are one, two, three, four and five hours. Scanning electron microscope (SEM) and density kit were used …
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Physical and acoustic properties of petroleum and renewable based polyurethane foam filled with shorea leprosula
… PF sample. PF samples have been tested by using Impedance Tube test, Scanning Electron Microscopy (SEM) and Mettler Toledo Density kit. As a result, the sound absorption coefficient (SAC) shows value at achievable frequency range at low (0-1500 Hz) and high (1501-6000 Hz) frequency absorption …
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The evaluation of acoustic characteristic performance on natural sound absorbing materials from cogon grass waste
… reduction coefficient (NRC) were done by using impedance tube method (ITM). The samples of cogon grass were tested in a way of the untreated and treated with NaOH in varied soaked hours which are one, two, three, four and five hours. Scanning electron microscope (SEM) and density kit were used …
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The effect of Meranti Merah wood fiber loading and sizes to the absorption property of polymer foam composites
… and flakes form. A set of samples for sample tube 100 mm diameter for low frequency of 0 to 1500 Hz, while the small sample tube of 28 mm diameter is to measure the high frequency absorption level of 1500 to 6000 Hz. Furthermore, the samples were irradiated in ultra violet exposure in the UV …
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Nonlinear Mechanical Metamaterial: A Novel Approach Towards Wideband Sound and Vibration Attenuation
… Impacting metamaterials are tested on the impedance tube and found that it can improve the acoustical performance of the light weight partition wall for a wide range of frequencies. A properly tuned graded metamaterial can extend the attenuation bandwidth almost 40% more in the lower …
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