Thesis (M.S.)--Boston University

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This research proposes the unsound object and intimate space as new approaches to listening to, writing about and performing creative sound works. The writing and the practical works sketch new territory around these two terms to pluralise sound art histories, with the aim of opening up practical discourse between artistic fields. The research begins with musique concrète and Pierre Schaeffer’s sound object, but draws on Mladen Dolar’s voice object, Christof Migone’s unsound and Six Years, Lucy Lippard’s account of conceptual art, instead of a strict acousmatic music narrative. A deliberate ‘wandering across borders’ is maintained throughout, to unpick the unsound object and intimate space through live work and ‘writing through’ of texts. My practice shifts between object based sound works, live art performance presentations, and open-ended text works. It tilts at intimate space by operating from the tabletop, from just beyond the page; my practice is made more uncertain and less fixed by its investigation of the unsound object. The project offers this as a positive outcome. In this project, I draw connections between the art object and the sound object, between mesostics and live art practice, between writing and space. These are tentatively offered as overlapping histories, as overlapping methods. Not as fixed Venn diagrams, or word clouds, but part of a flickering, oscillating unmethod that allows for both abstract and concrete, for waves and particles. The unmethod proposed in this project uses words like unshackling, unfixing, unpicking, and untethering to unsettle my practice and writing. The project suggests that destabilising existing definitions offers the potential of sound in silent media, and music beyond sound.

A simple computer model is described that takes a novel approach to the problem of accounting for perceptual coherence among successive pure tones of changing frequency by using simple physiological principles that operate at a peripheral, rather than a central level. The model is able to reproduce a number of streaming phenomena found in the literature using the same parameter values. These are: (1) the build-up of streaming over time; (2) the temporal coherence and fission boundaries of human listeners; (3) the ambiguous region; and (4) the trill threshold. In addition, the principle of excitation integration used in the model can be used to account for auditory grouping on the basis of the Gestalt perceptual principles of closure, proximity, continuity, and good continuation, as well as the pulsation threshold. The examples of Gestalt auditory grouping accounted for by the excitation integration principle indicate that the predictive power of the model would be considerably enhanced by the addition of a cross-channel grouping mechanism that worked on the basis of common on sets and offsets, as more complex stimuli could then be processed by the model.

This practice-as-research study documents the development of a sonic arts approach to film sound design. An interdisciplinary conceptual framework that combines selected theories of electroacoustic music and apposite perspectives from film soundtrack studies informs the approach. Over the course of the research, a broadening practical knowledge of theoretical applications influenced the development of the sound design approach and its conceptual framework. The term 'sonic arts' characterises the compositional tenets of the sound design approach, which takes the form of an inter-modal strategy based on the interdependence of two compositional modes. The intersonic compositional mode corresponds to sound-object design and to the forming of meaningful structural relationships between soundtrack elements. The audiovisual compositional mode corresponds to forming meaningful relationships between soundtrack elements and film images. The overall approach also reflects Walter Murch's concept of sound design as a multifaceted practice endeavour, which includes taking creative responsibility for the soundtrack in post-production (Murch 1995). The presentation of research in this thesis comprises two distinct parts. The first part outlines the sonic arts approach, defines the theoretical basis of its conceptual framework, and identifies potential practice applications. The second part presents three case studies of sound design practice for independent film projects. The case studies document applications of the conceptual framework and critically reflect on acquired practical knowledge of the sonic arts approach. The study concludes that the electroacoustic music theories of spectromorphology and indicative fields (Smalley 1986; 1992; 1997) have useful applications in sound design practice as a perception-based system of analysis. The research also illustrates that sonic landscape theory (Wishart 1986; 1996) constitutes a creatively enabling conceptual framework for sound design when it is applied to the inter-modal compositional strategy.

A model for predicting the response of a system composed of a fluid halfspace, overlying a porous ground layer, resting on an elastic halfspace, to incident plane waves, is developed to include further porous elastic layers within the ground. The dynamic properties of the porous elastic layers are modelled using a modified Biot formulation. Using the same boundary conditions a Fast Field algorithm for Layered Air Ground Systems (FFLAGS) is formulated to predict acoustic propagation and acoustic-seismic coupling in the model layered system due to a point source in a horizontally stratified atmosphere. This is a full wave solution. Results are compared to those of existing propagation prediction methods. FFLAGS has been used to predict (i) the effects of temperature gradients on short range propagation over an asphalt like surface, (ii) sensitivity of received sound pressure levels to ground parameters for various atmospheric conditions, and (iii) the influence of ground parameters on acoustic-seismic coupling. Predictions of acoustic surface waves in the presence of an upward refracting atmosphere using Creeping wave theory and the FFP method have been shown to agree. Dispersion equation based predictions of surface wave types have been assessed. It has been shown that the high velocity surface waves predicted by dispersion equation solutions on porous and elastic ground surfaces are not predicted to be excited by a point source. However several other surface wave modes have been predicted in layered systems, similar to those predicted in visco-elastic media. The influence of ground elasticity on received sound pressure levels is examined. Measurable effects of elasticity of the surface are predicted for low density materials, and measured over a low density polyester foam. Controlled experiments have been performed to study the effect of soil wetting on acoustic to seismic coupling. It is found that the observed effects can be modelled using FFLAGS.

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2009 / In acoustics, pulse echo methods are well known as a means of measuring time of Hight. Traditional techniques for generating acoustic waves in solid ferromagnetic waveguides include piezoelectric, capacitive and magnetostriction. Piezoelectric and capacitive techniques are preferred due to the inefficiency of magnetostriction caused by electro-mechanical coupling losses and the fact that most ferromagnetic materials show low levels of magnetostriction. The aim of this study was to optimise the magnetostrictive effects for sensing applications based on a ferromagnetic waveguide using the pulse echo method. The results obtained were implemented in the design of an acoustic thermometer. Two configurations for signal generation and recovery were examined, the use of a single wound copper coil acting as a transceiver coil, and the use of separate transmit and receive coils. Results obtained using the latter configuration indicated better signal to noise ratio's and provided the flexibility to manipulate the point of signal recovery. The pulse echo method was implemented and optimised. An acoustic thermometer based on an existing design was developed by inducing a partial reflection from a set position in the waveguide, defining a sensing probe. Awareness of the elastic properties of the waveguide material enabled the guaging of its temperature by measuring the acoustic pulse velocity in the probe. The accuracy of the instrument was increased through signal conditioning, examined together with cross correlation and an increased sampling frequency. Systematic errors were resolved through calibration, giving the instrument an overall accuracy of ±O.56"C for the range of temperatures between 2O"C and 400"C.

Thesis submitted in fulfilment of the requirements for the degree Doctor of Technology: Mechanical Engineering in the Faculty of Engineering at the Cape Peninsula University of Technology 2014 / Thermoacoustic heat engines provide a practical solution to the problem of heat management where heat can be pumped or spot cooling can be induced. This is new among emerging technology with a strong potential towards the development of sustainable and renewable energy systems by utilising solar energy or wasted heat. The most inhibiting characteristic of current thermoacoustic cooling devices is the lack of efficiency. Although simple to fabricate, the designing of thermoacoustic coolers involves significant technical challenges. The stack has been identified as the heart of the device where the heat transfer takes place. Improving its performance will make thermoacoustic technology more attractive. Existing efforts have not taken thermal losses to the surroundings into account in the derivation of the models. Although thermal losses can be neglected for large-scale applications, these losses need to be adequately covered for small-scale applications. This work explores the use of a multi-objective optimisation approach to model and to optimise the performance of a simple thermoacoustic engine. This study aims to optimise its geometrical parameters—namely the stack length, the stack height, the stack position, the number of channels and the plate spacing—involved in designing thermoacoustic engines. System parameters and constraints that capture the underlying thermoacoustic dynamics have been used to define the models. Acoustic work, viscous loss, conductive heat loss, convective heat loss and radiative heat loss have been used to measure the performance of the thermoacoustic engine. The optimisation task is formulated as a five-criterion mixed-integer nonlinear programming problem. Since we optimise multiple objectives simultaneously, each objective component has been given a weighting factor to provide appropriate user-defined emphasis. A practical example is provided to illustrate the approach. We have determined a design statement of a stack describing how the design would change if emphasis is placed on one objective in particular. We also considered optimisation of multiple objective components simultaneously and identified global optimal solutions describing the stack geometry using the augmented ε-constraint method. This approach has been implemented in GAMS (General Algebraic Modelling System). In addition, this work develops a novel mathematical programming model to optimise the performance of a simple thermoacoustic refrigerator. This study aims to optimise its geometrical parameters—namely the stack position, the stack length, the blockage ratio and the plate spacing—involved in designing thermoacoustic refrigerators. System parameters and constraints that capture the underlying thermoacoustic dynamics have been used to define the models. The cooling load, the coefficient of performance and the acoustic power loss have been used to measure the performance of the device. The optimisation task is formulated as a three-criterion nonlinear programming problem with discontinuous derivatives (DNLPs). Since we optimise multiple objectives simultaneously, each objective component has been given a weighting factor to provide appropriate user-defined emphasis. A practical example is provided to illustrate the approach. We have determined a design statement of a stack describing how the geometrical parameters described would change if emphasis is placed on one objective in particular. We also considered optimisation of multiple objective components simultaneously and identified global optimal solutions describing the stack geometry using a lexicographic multi-objective optimisation scheme. The unique feature of the present mathematical programming approach is to compute the stack geometrical parameters describing thermoacoustic refrigerators for maximum cooling or maximum coefficient of performance. The present study highlights the importance of thermal losses in the modelling of small-scale thermoacoustic engines using a multi-objective approach. The proposed modelling approach for thermoacoustic engines provides a fast estimate of the geometry and position of the stack for maximum performance of the device. The use of a lexicographic method introduced in this study improves the modelling and the computation of optimal solutions and avoids subjectivity in aggregation of weight to objective functions in the formulation of mathematical models. The unique characteristic of this research is the computing of all efficient non dominated Pareto optimal solutions allowing the decision maker to select the most efficient solution. The present research experimentally examines the influence of the stack geometry and position on the performance of thermoacoustic engines and thermoacoustic refrigerators. Thirty-six different cordierite honeycomb ceramic stacks are studied in this research. The influence of the geometry and the stack position has been investigated. The temperature difference across the stack and radiated sound pressure level at steady state are considered indicators of the performance of the devices. The general trends of the proposed mathematical programming approach results show satisfactory agreement with the experiment. One important aspect revealed by this study is that geometrical parameters are interdependent and can be treated as such when optimising the device to achieve its highest performance. The outcome of this research has direct application in the search for efficient stack configurations of small-scale thermoacoustic devices for electronics cooling.

The performance of reflectors and diffusers used in auditoria have been evaluated both objectively and subjectively. Two accurate systems have been developed to measure the scattering from surfaces via the cross correlation function. These have been used to measure the scattering from plane panels, curved panels and quadratic residue diffusers (QRDs). The scattering measurements have been used to test theoretical prediction methods based on the Helmholtz-Kirchhoff integral equation. Accurate prediction methods were found for all surfaces tested. The limitations of the more approximate methods have been defined. The assumptions behind Schroeder's design of the QRD have been tested and the local reacting admittance assumption found to be valid over a wide frequency range. It was found that the QRD only produces uniform scattering at low frequencies. For an on-axis source the scattering from a curved panel was as good as from a QRD. For an oblique source the QRD produced much more uniform scattering than the curved panel. The subjective measurements evaluated the smallest perceivable change in the early sound field, the part most influenced by reflectors and diffusers. A natural sounding simulation of a concert hall field within an anechoic chamber was used. Standard objective parameters were reasonable values when compared to values found in real halls and subjective preference measurements. A difference limen was measured for early lateral energy fraction (.048 ± .005); . inter aural cross correlation (.075 ± .008); clarity index (.67 ± .13 dB); and centre time (8.6 ± 1.6ms). It was found that; (i) when changes are made to diffusers and reflectors, changes in spatial impression will usually be larger than those in clarity; and (ii) acousticians can gain most by paying attention to lateral sound in auditoria. It was also found that: (i) diffuse reflections in the early sound field are not perceived differently from specular reflections; and (ii) the initial time delay gap is not significant to listener preference.

This paper is about the sound iconicity of the Late Middle Chinese entering tone in two of Du Fu's long narrative poems, "The Journey to the North" and "Singing my Heart out in Five Hundred Characters on the Way from the Capital to Fongxian County", as well as Du Fu's grammar of poetry in these two poems. In poetry, rhyme is an arbitrary and 'visible' figure reiterated with regulation which forms an axis of sequence, and this axis will work jointly with all the other poetic elements—semantics, images, and grammar to form the whole of a poem. In these two poems, all the rhyme characters carry a voiceless —t ending, which is classified with —k and —p endings as the entering tone in Late Middle Chinese reconstructed by Edwin Pulleyblank. These voiceless stops are short, tense, and uncomfortable to utter; when they are repeated fifty and seventy times at the end of each couplet, it naturally brings about a strong, rough, and uncomfortable feeling which correlates with the feeling of suffering in both poems. It is sound iconicity, because an icon resembles the object it stands for in an immediate and concrete manner, and the —t ending rhyme characters do have the characteristics to make the reader grasp the feeling of suffering when she reads the poems. In terms of Du Fu's grammar of poetry, I used Jakobsonian methodology and found how Du Fu's poeticity was created with lexical meaning and grammar. Although Classical Chinese does not have a huge grammatical repertoire (e.g., person, case, gender, finite, non-finite . . .) which can figure in a poem, this language still has its own obligatory categories that will provide for the 'grammar of poetry'. Classical Chinese is already known for its grammatical parallelism in poetry, because this language is extremely isolating and analytical. However, grammatical parallelism is little in these two poems, but there are different kinds of grammatical tropes. They are mainly anti-syntactic inversions interacting with semantics. I found Du Fu a fascinating artist of grammar; he may be anti-grammatical but never agrammatical. / Arts, Faculty of / Asian Studies, Department of / Graduate