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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
151

Evaluating the use of adaptive transform acoustic coding (ATRAC) data compression in acoustic phonetics

Nash, Carlos Marcelo January 2001 (has links)
In linguistic research, current practices of recording audio data involves a mixture of analogue and digital technologies giving little forethought to methodological issues and insight into the consequences of using one technology over the other. Analogue recorders are inherently flawed and are not ideal for acoustic analysis. With the introduction of digital recorders into the consumer market, it is difficult to decide which recorder is best suited for linguistic and acoustic analysis. The MiniDisc, introduced by Sony in 1992, is a magneto-optical recorder that offers 'CD-like' quality, in a compact and shock-resistant system, thus making it a potential tool for linguistic field research. However it is not known how the psycho-acoustically based compression system, ATRAC, affects the spectrum of speech sounds. This thesis compares the MiniDisc with a DAT recorder and analyses the differences using spectral and spectrographic analyses. In addition, this thesis tries to establish sound practices for using the MiniDisc in linguistic research.
152

The Effect of Nest Acoustics on the Begging Calls of Nestling Tree Swallows

Fairhurst, Elizabeth 06 December 2010 (has links)
Animals’ long-distance acoustic signal structure minimizes habitat-specific attenuation and distortion, but it is unknown how environmental acoustics shape the signals of dependent young, or short-range signals generally. I investigated the influence of the nest environment on nestling tree swallows’ begging calls by relating nest reverberation and resonance to nest structure; relating call features to nest reverberation, resonance and structure; and testing whether call structure reduced distortion in the home nest. Reverberation was stronger in wider cavities with intact ceilings. Nestlings used shorter calls in more reverberant cavities, and longer calls with higher middle frequency and lower minimum frequency in wider cavities with smoother walls, but did not adjust call frequency in relation to resonance. Calls originally produced in a given nest did not transmit with less distortion than calls originally produced in other nests. These findings suggest that the nest environment may shape the structure of begging calls.
153

Q estimates from local coda waves

Duckworth, Robert Michael 05 1900 (has links)
No description available.
154

Collinear acousto-optic interactions in optical fibers using laser generated flexural acoustic waves

Yu, Jefferey C. H. January 1989 (has links)
No description available.
155

Classification trees for acoustic models : variations on a theme

Lazaridès, Ariane. January 1997 (has links)
One of the most important problems to be faced when building a speech recognizer is the lack of sufficient training data to estimate all of the parameters of the system. One of the most successful techniques addressing this problem is to decrease the number of parameters in the system by the use of classification-tree based acoustic models. In this thesis, several variations on this theme will be presented, the first few ones dealing with trees classifying whole HMMs (tree units), the others with trees classifying states of HMMs (tree states). Results obtained on the Air Travel Information System (ATIS) task show that using classification trees produces systems with up to 90% less models (and proportionally less parameters to estimate) with no loss of performance.
156

Ultrasonic monitoring of die-casting process using clad buffer rod sensor

Moisan, Jean-Francois. January 2001 (has links)
In-line monitoring of die-casting of aluminum (A356, A357, 86S), magnesium (AZ91) and a metal matrix composite (Gra-NiRTM 6S:3G) will be monitored using the reflection coefficient obtained by using an ultrasonic technique, the pulse/echo. For each of the materials enumerated above, the average temperature of the mold through its thickness, the end of filling of the part, the solidification of the part in the cavity of the mold, the gap and/or the detachment of the part, the sound velocity and the attenuation of the material will be measured by this ultrasonic technique during the process. / For the materials the melt temperature will not exceed 600°C because the casting is made at the semi-solid state, between the solidus and liquidus, of the materials. A novel high performance buffer rod with a cooling system is integrated into the die. Therefore, ultrasonic measurements can be carried out with high signal-to-noise ratio at elevated temperatures.
157

Measurement of the time dispersion due to multiple path trajectories in the shallow underwater acoustic channel

Clark, Leah 12 1900 (has links)
No description available.
158

Analysis of nonsymmetric effects in finite amplitude sound beams

Miao, Hsu-Chiang 12 1900 (has links)
No description available.
159

Design of laser-induced-heating configurations for generation and control of underwater sound beams

Hsieh, Hsiao-an 05 1900 (has links)
No description available.
160

Characterization of a three-phase medium with a large and negative parameter of nonlinearity

Pauly, Olivier 05 1900 (has links)
No description available.

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