No description available.

Thesis (M.E.) -- University of Adelaide, Department of Mechanical Engineering, 1977.

This thesis provides an analysis of an acoustic imaging technique using holography and the interaction of acoustic and light waves at a liquid-gas interface. Real time optical images of objects that have been transilluminated with ultrasonic waves in a liquid medium can be obtained. The liquid surface acts as a detector of the ultrasonic energy. When coherent light is reflected off the liquid surface an optical image of the object is obtained. An analysis is presented of the mechanisms involved including an analysis of the transient motion of the liquid surface. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2005. / Includes bibliographical references.

No description available.

Thesis (Ph. D.)--University of Canterbury, 2006. / Typescript (photocopy). "August 2006." Includes bibliographical references (p. [167]-179) and index. Also available via the World Wide Web.

Orientador: Jose Maria Campos dos Santos / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-25T04:25:40Z (GMT). No. of bitstreams: 1 Colinas_NiltonGilber_M.pdf: 6668829 bytes, checksum: 0f5fe00364a351d5d5859c9c042c161c (MD5) Previous issue date: 1999 / Resumo: Neste trabalho procurou-se explorar a técnica de Holografia Acústica de Campo Próximo (Nearfield Acoustic Holography - NAB), que tem se mostrado como uma forma de análise para problemas vibroacústicos. A holografia é um processo que permite determinar as características de um campo de ondas acústicas usando a Transformada de Fourier Discreta (Discrete Fourier Transform - DFT), a partir de uma grade de pontos de medições regularmente espaçados obtidos em um ambiente acústico onde a função de Green é conhecida. O presente trabalho apresenta uma breve revisão dos princípios desta técnica com uma aplicação na reconstrução de propriedades vibroacústicas de estruturas. O campo de pressão, campo de velocidade das partículas e intensidade acústica gerados por um elemento estrutural vibrante foram as grandezas reconstruídas através da técnica NAH em diferentes posições do espaço. A fim de minimizar os problemas de leakage oriundos do processamento dos sinais, a Série de Fourier Discreta Regressiva (Regressive Discrete Fourier Series - RDFS) foi utilizada como alternativa às técnicas de janelamento do sinal. Resultados obtidos para uma estrutura do tipo placa são analisados, validados e comparados com previsões teóricas / Abstract: In this work, the Nearfield Acoustic Holography technique - NAH was explored as an way to analyze vibroacoustic problems. Holography is a process that allows to determine acoustic fields characteristics using a Discrete Fourier Transform - DFT, from a regular grid of measurements obtained in an acoustic environment for which the Green' s function is known. This work presents a brief principle's review of this technique with an application on the reconstruction of the vibroacoustic properties of structures. The pressure field, particle velocity field and acoustical intensity generated by a vibrating structural element were reconstructed through the NAH technique in different spatial positions. ln order to minimize spatial leakage problems from signal processing a Regressive Discrete Fourier Series ¿ RDFS was utilized as an alternative to windowing techniques. Results obtained from a plate type structure were analyzed, validated and compared with theoretical predictions / Mestrado / Mecanica dos Solidos / Mestre em Engenharia Mecânica

Acoustical-based imaging techniques have found merit in determining the behavior of vibrating structures. These techniques are commonly used in numerous applications to obtain detailed noise source information and energy distributions on source surfaces. This thesis focuses on the continued development of the nearfield acoustic holography (NAH) approach. Conventional NAH consists of first capturing pressure data on a two-dimensional conformal measurement contour in the nearfield of the radiating source. These data are then propagated back to the vibrating structure to obtain the normal velocity profile on the source surface. With the source surface velocity profile known, the acoustic pressure, particle velocity, and intensity generated by the source can be reconstructed anywhere in space. The precision of source reconstruction is reliant upon accurate measurement of the pressure field at the hologram surface. For complex acoustic fields this requires fine spatial resolution and therefore demands large microphone arrays. In this thesis, a technique is developed for performing NAH using energy-based measurements. Recent advancements in the area of acoustic sensing technology have made particle velocity field information more readily available. Because energy-based measurements provide directional information about the field, a more accurate measurement of the pressure field is obtained. It is proposed that an energy-based system will significantly reduce the number of measurements required to perform NAH without sacrificing accuracy. Significantly reducing the number of measurements required to perform NAH will reduce the time, and therefore the expense, of using NAH as an analysis tool. Many potential applications exist for an improved NAH measurement method in the automobile and aerospace industries. These industries provide numerous large-scale applications where employing time-consuming scanning methods is not cost-effective. This is especially the case for airplane in-flight passenger noise tests, where the expense of operating the airplane is extremely high. Therefore, even a small savings in data acquisition time would be very beneficial.

Thesis. 1976. Sc.D.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering. / Microfiche copy available in Archives and Engineering. / Vita. / Includes bibliographical references. / by Paul R. Donavan. / Sc.D.

Laryngectomy, as a treatment for malignant laryngeal lesions, requires the patient to seek a substitute method of producing speech. Three types of alaryngeal speech were described: esophageal, Asai, and artificial larynx. One consideration in deciding which mode of speech is best for the patient is how closely each type of alaryngeal speech approximates normal. This investigation was an objective examination of esophageal, Asai, and artificial larynx speech as compared with normal in males and females.