Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 60-61). Also available via the Internet.

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xvi, 195 p.; also includes graphics. Includes bibliographical references (p. 183-195). Available online via OhioLINK's ETD Center

Thesis (M.S.)--University of Alabama at Birmingham, 2009. / Title from PDF t.p. (viewed June 30, 2010). Additional advisors: Stephen A. Watts, Paul A. Richardson, John T. Tarvin. Includes bibliographical references (p. 36-38).

Thesis (Ph. D.)--Drexel University, 2007. / Includes abstract and vita. Includes bibliographical references (leaf 195).

Orientador: Stelamaris Rolla Bertoli / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-23T15:37:09Z (GMT). No. of bitstreams: 1 Thomazelli_Rodolfo_M.pdf: 57345196 bytes, checksum: 3da9f24b7c1ff80c9e4ffefcf62d51ed (MD5) Previous issue date: 2013 / Resumo: A impedância acústica é um dos conceitos importantes para o estudo da propagação de ondas sonoras em dutos, pois por meio de sua determinação, outros parâmetros acústicos são obtidos. É um espectro em freqüências, e pode ser obtida experimentalmente através de um medidor de impedância acústica. Na presente pesquisa foi construído e validado um medidor de impedância acústica. Como objeto de estudo foi utilizados os pífanos - instrumentos de sopro da família das flautas. Dentre os métodos experimentais indicados na literatura, optou-se pelo uso do TMTC (Two Microphones Three Calibrations), devido à acessibilidade aos requisitos práticos e a possibilidade de investigação das flautas. Foram feitas medidas de impedância de dois dutos cilíndricos, de diferentes comprimentos e diâmetros internos constantes, cujos resultados foram comparados com modelos teóricos (etapa de validação). Determinou-se também a impedância acústica de três pífanos de afinações distintas. Da análise dos resultados, verificou-se a eficácia do método adotado e do aparato construído para a investigação da impedância acústica de dutos simples e, em especial, dos pífanos. Discutiu-se também aspectos importantes da construção do aparato, em termos da acessibilidade e complexidade / Abstract: The acoustical impedance is one of the indissociable factors in the studies of sound wave propagation in ducts, once its measuring provides other acoustical parameters. Its values are frequencydependent and can be determined with the use of an acoustical impedance spectrometer. For this research an acoustical impedance spectrometer was designed and validated. The research focused on a Brazilian woodwind instrument called "pífano", from the flute family. The experimental method known as TMTC (Two Microphones Three Calibrations) was chosen, for it provides easy access to practical needs and has wide capacity to interact with flutes. The spectrum from two cylindrical ducts were taken, each duct with a different length but equal inner diameters. The spectrum of three "pífanos" with different tunings, was also measured. The results from the cylindrical ducts were later compared to theoretical models (validation stage). From the results it was possible to ascertain the efficiency of the adopted method and apparatus built to investigate acoustical impedance of regular ducts and "pífano" flutes. Other important aspects of the process of building the apparatus were also discussed, in terms of accessibility and complexity / Mestrado / Arquitetura e Construção / Mestre em Engenharia Civil

Specialized training in English diction for singers became increasingly prevalent in the twentieth century. Along with this growth, a small but significant literature on the subject developed. There are divergent practices recommended for American singers, displayed by nine authors in ten books published between 1900 and 1971. A comparative study yields pedagogies of vowel and consonant production. Issues of sounds in context, including proper linkage and stress, adjustments from speech to song, and practices dictated by musical style, are paramount. The literature demonstrates an increased use of International Phonetic Alphabet symbols as a pedagogical tool. The areas of kinesiology and acoustical research are suggested for further study.

On-device audio recognition, in particular keyword spotting, will be instrumental to realizing the promise of pervasive intelligence. On-device operation demands ultra-low power and compact area. The state of the art in fully-integrated keyword spotting chips reveals that the power and area bottleneck is not the backend keyword spotting classifier, but rather the frontend audio feature extractor, motivating research into frontend audio feature extraction that is both power- and area-efficient. After, first, introducing the topic of ultra-low power audio feature extraction using time-mode analog signal processing circuits, we, second, present an analog audio feature extractor chip that achieves the lowest power/feature and area/feature, as compared, respectively, to the most area-efficient and power-efficient published analog audio feature extractor chips. Despite the chip's state-of-the-art efficiency, competitive keyword spotting accuracy is maintained when interfacing the chip with a standard, small-footprint, software backend neural network. The chip's efficiency is due to a pair of novel circuit techniques we developed. The techniques are based on time-mode analog signal processing. This is a paradigm favored by technology scaling, in which analog information is encoded in the timing of digital edges, enabling digital gates to perform analog signal processing. Third, we present a theory-based analysis of one of the two circuit techniques. Fourth, we present theory- and simulation-based progress towards what would be a novel type of analog filtering, ``Time-Mode Analog Filter." Such a filter would use only the horizontal time axis to represent and process continuous-valued information, and would be built out of nothing more than digital gates. Fifth, and finally, we present a simulation-based study that finds that in state-of-the-art analog audio feature extractor chips, the power consumption of the critical block, the analog filterbank, can be reduced by one-and-a-half orders of magnitude, while degrading downstream keyword spotting accuracy by only a couple percent, paving the way towards more rigorous system-level design of audio recognition systems.

Acoustical-based imaging systems have found merit in determining the behavior of vibrating structures. This thesis focuses on the continued development of the nearfield acoustic holography (NAH) approach. Conventional NAH consists of first measuring the pressure field on a two-dimensional conformal surface and then propagating this data back to the vibrating structure to obtain information about the source, such as the normal velocity distribution. Recent work has been done which incorporates particle velocity information into the traditional NAH measurements to reduce the number of measurements required. This advancement has made NAH a more affordable tool for acoustical imaging and sound field characterization. It is proposed that the inclusion of velocity information into traditional NAH can further increase its usefulness. By propagating the velocity and pressure values independently and recombining them on the reconstruction surface, the pressure field and energy density fields can be predicted at any point in the sound field. It is also proposed that the same NAH measurement can be used to predict farfield directivity. The inclusion of velocity values into the NAH technique also provides a means for predicting energy density (ED) anywhere within the acoustic field. These two developments would allow a single NAH measurement to provide much more information about an acoustic source and its radiated sound field. Experimental testing shows that NAH is successful at predicting the shape of the resulting ED field and directivity pattern with some error in amplitude. The best performance of the technique is with a planer source resulting in an average amplitude error of 18.5% over the entire field.

The scientific community has employed multiple methods to analyze and describe the jet noise emanating from the turbulent exhaust flow from modern military aircraft engines, with the goal that better characterization of the sound radiation will improve noise reduction efforts. This thesis utilizes three different approaches to characterize the noise source region from a static F-22A Raptor. First, the energy flow field along planes near the aircraft and along an arc is measured using a multidimensional vector intensity probe. The resulting vector intensity maps give a clear indication of the directionality of the noise as a function of frequency at different engine conditions. A straightforward ray-tracing method show the utility of vector intensity measurements in source characterization by estimating the region from which the loudest portions of sound are emanating. Second, intensity reconstructions from near-field acoustical holography (NAH) provide an estimate of the three-dimensional radiated energy flow field. The sound field is shown to be dominated by mutually incoherent radiation lobes, which can be partially isolated by a partial decomposition method. Lastly, a wavepacket source model is optimized in light of amplitude-based NAH reconstructions near the jet axis. The wavepacket model successfully fits the NAH-reconstructed partial fields, especially at frequencies above 50 Hz, indicating that the source may be modeled by multiple wave packets at each frequency.

No description available.