No description available.

The absolute measurement of acoustic particle velocity using Laser Doppler Anemometry (LDA) provides the basis for a method of microphone calibration. In this thesis, after the current standardized calibration method (called reciprocity) is explained, the application of LDA to the determination of sound pressure acting on a microphone is discussed. From a measurement of the output voltage for a given sound pressure, the sensitivity of the microphone can be calculated. In LDA, there are two different techniques for detecting and analysing the Doppler signal generated by acoustic particle motion: continuous detection followed by frequency or time domain analysis, and photon correlation. After a brief discussion of the theory of both methods, their application to measurements within a standing-wave tube is investigated. Velocity measurements extracted from Doppler signals are used to derive values of sound pressure, which are compared with probe microphone measurements. The continuous detection and photon correlation LDA systems are used to measure particle velocity amplitude in a standing wave for frequencies between 660 Hz and 4kHz and velocities between 1 mms⁻¹ and 18 mms⁻¹. LDA is applied to the measurement of microphone sensitivity. The frequency response of the probe microphone is characterized relative to the response of a reference microphone. From the frequency response information, the output voltage of the probe microphone, and the LDA derived sound pressure in a standing wave the sensitivity of the reference microphone is established. Using the continuous detection system, the microphone sensitivity is measured to within ±0.1 dB of the sensitivity obtained by reciprocity calibration for frequencies between 660 Hz and 2 kHz. Using the photon correlation system, the sensitivity is measured to within ±0.2 dB for the same frequency range. Initial measurements were performed in a free field environment, using the photon correlation system, to demonstrate the potential for further development of the LDA calibration technique.

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).

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This dissertation presents the characterization and modeling of crosstalk noise based on the theory of coupled microstrip lines. An equivalent circuit model used in this work comprises of the addition of mutual inductances and mutual capacitances to the fundamental transmission line model. Characterization of crosstalk noise along adjacent lines, current-voltage characteristics, characteristic impedance, effective dielectric impedance, and maximum crosstalk are performed analytically. Computer simulations and computations of these parameters are also performed. The circuits are realized experimentally, and an investigation of crosstalk noise using time domain and frequency domain measurement techniques is conducted. The results illustrate that the computation matched closely the experimental data and explained the physical phenomena better. / Ph. D.

The concept of mounting a loudspeaker on one end of a sound-absorbing tube has existed since at least 1936. Surprisingly, a detailed mathematical analysis of the configuration has not been performed, nor has a design method been established. This configuration, known as a transmission line loudspeaker, has received little consideration in the reviewed literature. Instead, it has become frequently featured in magazines for audio hobbyists, where it is experimentally designed with rules seemingly derived from hearsay and described with terms of high praise. In this dissertation, an electro-acoustical model of a fiberglass-filled transmission line is presented. This model represents the transmission line as two separate lines -- a mechanical line that models the mechanical motion of the fiberglass and an acoustical line that models the motion of the air. The lines are linked by the flow resistance of the fiberglass. From the model, solutions for the acoustic pressure, acoustical volume velocity of the air, mechanical velocity of the fiberglass fibers, and mechanical force on the fiberglass in the line are obtained. The fiberglass is characterized and empirical formulas that describe its characteristics are found. It is shown that the modeled input impedance to the transmission line is a good fit to measured data. The performance of the system is assessed by comparing it with the performances of typical loudspeaker mountings, i.e., the infinite baffle, the closed box, and the vented box. Finally, an example is shown of how the equations derived from the model can be used to evaluate the design of a transmission line loudspeaker system.

Thesis (M.A.)--University of Wollongong, 2005. / Typescript. Includes audio disc in back pocket. Includes bibliographical references: leaf 65-66.

The purpose of this study is to investigate the occurrences of electroacoustic content in and its relation to cinematic film. Key research questions include: What pioneering techniques and aesthetic positions used by creators of early electroacoustic music have found their way into mainstream cinema? Where and when have they been developed? In which films do they appear, and how are they distributed among film genres? The findings of this study assert the idea that many techniques that are part of sound design of contemporary cinematic film (the process and result of mixing and manipulating sounds) come directly from pioneers of electroacoustic music. Electroacoustic techniques and aesthetics play an important role in the history of sound film in making fundamental contributions to production processes, the relation between directors and sound makers, and film sound theory. On an aesthetic level, electroacoustic music in film has reformed the role of sound in film: a film score can contain 'noise', while speech and sound effects can actually serve as music. The findings also assert that electroacoustic techniques and aesthetics can be found in cinematic film from the beginning of sound film in the late 1920s. Once established, techniques have largely remained the same, regardless of the carrier media and their transformation from analog to digital: modern, digital techniques are refinements of their analog predecessors. Aesthetics have developed along with techniques, albeit much slower; their potential and exploration is far from being exhausted. The use of electroacoustic content for a particular element of film sound is not unusual and often genre-specific (for example in science fiction and thriller). However fully electroacoustic scores are rare. A portfolio of selected original compositions by the author complements this study. Acoustic and electroacoustic pieces for film and multimedia highlight different aesthetics, techniques and practices of film sound and film music.

Thesis (D.Tech.: Electronic Engineering)-Dept. of Electronic Engineering, Durban University of Technology, 2007 vii, 150 leaves / Detecting and minimising distortion in audio signals is an important aspect of sound engineering. Distortion of a signal passing through an audio system may be caused by a number of factors and it is necessary to detect these effects for optimal sound. The problem is of interest to users and operators of high quality audio equipment and transmission facilities. The objective of this thesis was the development of techniques for the blind identification of distortion in a high quality audio signal using digital signal processing techniques. The techniques developed are based on digital signal processing techniques and statistical analysis of a recorded audio signal, which is treated as a random, non-stationary signal.

Thesis (D.Tech.: Electronic Engineering)-Dept. of Electronic Engineering, Durban University of Technology, 2007 vii, 150 leaves / Detecting and minimising distortion in audio signals is an important aspect of sound engineering. Distortion of a signal passing through an audio system may be caused by a number of factors and it is necessary to detect these effects for optimal sound. The problem is of interest to users and operators of high quality audio equipment and transmission facilities. The objective of this thesis was the development of techniques for the blind identification of distortion in a high quality audio signal using digital signal processing techniques. The techniques developed are based on digital signal processing techniques and statistical analysis of a recorded audio signal, which is treated as a random, non-stationary signal.