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When playing a brass instrument the lips of the player fulfil a similar role to the cane reeds of wood-wind instruments. The nature of the motion of this lip-reed determines the ow of air through the lips, between the player's mouth and the instrument. It is a complicated feedback system in which the motion of the lips controls the air ow, which itself affects the behaviour of the lips. In recent years several designs of artificial mouth have been developed; these model the human lips using latex rubber tubes filled with water. These artificial mouths are increasingly used in experiments rather than enlisting the services of a musician as they have many advantages including greater accessibility and the stability of the embouchure. In this thesis factors affecting the reproducibility of the embouchure of one such artificial mouth are investigated with reference to the measured resonances of the lips. Using these results, procedures and practical design improvements are suggested. Two examples of comparative studies of historic instruments are presented. In order to provide detailed information on the behaviour of the lips of brass players high speed digital photography is used to image the self-oscillating lipreed. Variation in the lip opening, over a wide range of notes and different players, is investigated, providing experimental evidence to aid the process of reining physical models of the behaviour of the brass player's lips. Particular attention is paid to the relationship between the area and height of the lip opening. Results suggest that during extremely loud playing the lip motion is qualitatively similar to that in quieter notes and therefore is not the origin of the dramatic increase in the levels of the high harmonics of the radiated sound. Investigation of the behaviour at the start of a note has shown evidence relating the lip motion to the transient in the mouthpiece pressure waveform. Comparison is made between the behaviour of the artificial lips and that of the lips of musicians providing evidence of the suitability of the use of the artificial mouth as a model for real brass players. Results show that although differences exist, particularly when looking at behaviour over a wide range of dynamic levels, the general features of behaviour are reproduced by the artificial mouth.

High order finite difference schemes are generally less dispersive, less dissipative and more isotropic than low order schemes. They are, therefore, better suited for the solution of wave propagation problems. High order schemes, however, support spurious numerical waves which have no relationship to the waves of the original partial differential equations. The large stencils associated with the high order schemes also make the implementation of boundary conditions more difficult. A number of fundamental difficulties which occur when high order finite difference schemes are used to solve computational aeroacoustics and flow problems are investigated and resolved. The research work includes: (a) Development of an artificial selective damping technique for the elimination of spurious numerical waves; (b) Formation of a set of solid wall boundary conditions for high order finite difference schemes; (c) Design of a family of multi-domain multiple-time-step high order finite difference algorithms for the solution of acoustics and flow problems with large disparate length scales. A sequence of direct numerical simulations are performed to demonstrate the effectiveness of all the proposed methods. / Source: Dissertation Abstracts International, Volume: 55-07, Section: B, page: 2768. / Major Professor: Christopher K. W. Tam. / Thesis (Ph.D.)--The Florida State University, 1994.

There is now a substantial body of theoretical and experimental evidence that the dominant part of the turbulent mixing noise of supersonic jets is generated directly by the large turbulence structures/instability waves of the jet flow. The relationship between the instability waves and noise of hot jets at moderate supersonic Mach number is examined in Chapters 1 and 2. It is found that the highest sound-pressure-level of the far-field noise occurs at a direction and frequency that closely match the Mach wave radiation direction and frequency of the most amplified instability wave of the jet. The calculations show that for jet Mach number up to 2.0 and jet total temperature to ambient temperature ratio up to 2.5, the Kelvin-Helmholtz instability waves always grow to a higher amplitude than the supersonic instability wave. Numerical results indicate that for hot jets the most amplified wave invariably belongs to the helical mode Kelvin-Helmholtz instability wave. For lower speed hot jets with jet static temperature higher than or equal to the ambient temperature there is also a fair correlation between the Strouhal number at the peak sound-pressure level of the far-field noise and that of the most amplified instability wave. / In Chapters 3, 4, 5 and 6, a broadband jet noise theory is constructed. In this theory, the compressible flow equations with eddy viscosity are used to calculate the wave propagation characteristics of the instability waves. These equations are solved by the method of matched asymptotic expansions. The inner solution is the instability wave solution. The outer solution gives the associated acoustic field. The amplitudes of the instability waves are assumed to be stochastic random functions. The statistical properties of the random amplitude function are determined by the requirement that the wave spectrum at the nozzle exit has no intrinsic length and time scales. The present theory can predict the dominant part of jet mixing noise from first principles up to a single multiplicative constant. The spectra and directivities of a Mach 2 jet at total temperatures of 500K and 1114K are calculated. The numerical results agree favorably with experimental measurements. / Source: Dissertation Abstracts International, Volume: 54-12, Section: B, page: 6317. / Major Professor: Christopher K. W. Tam. / Thesis (Ph.D.)--The Florida State University, 1993.

For the first time an ocean model is used to assimilate oceanic tomography data in an upper ocean model of the northeast Pacific with the goal of estimating the time independent density field, and thus the slow manifold circulation structure. / The assimilation procedure works by minimizing the cost function, which generalizes the misfit between the observations and their model counterparts, in a least-squares sense, plus a penalty term. This minimization is done consistently with the constraint that the model dynamics must be exactly satisfied. The model consists of integrating the model equations forward in time over the period which data are going to be assimilated. Data misfits between the model and the observation are then calculated and the adjoint equations of the model are integrated backward using the data misfits as forcing. It is necessary to determine the gradient of the cost function with respect to the control variables (the density field). The gradient is found using the model and adjoint variables and it is used in a minimization algorithm to determine a new density field. The minimization procedure utilizes a limited memory quasi-Newton method. / The results indicate that the assimilation procedure works very well. For the twin experiments, the final estimated density recovers the Levitus density field as expected and as fast as in 10 iterations. For the experiments with the Navy layered ocean circulation model (NRLM) output, the density can be estimated through the assimilation procedures. The estimated density field improves the the Levitus climatological density data which are biased and makes the subtropical gyre stronger in the northeast Pacific region. / The proof of the identity between the discretization of the continuous adjoint equations and the adjoint equations which are from discretized model equations with the Arakawa C has been carried out. / Source: Dissertation Abstracts International, Volume: 56-07, Section: B, page: 3667. / Major Professor: James J O'Brien. / Thesis (Ph.D.)--The Florida State University, 1995.

<p> The purpose of this thesis is to share the process behind the development of an approach to composing for central Javanese gamelans that utilizes vertical harmony. This paper will include my history with Javanese gamelan, work on the development of a piano tuning that would work with a gamelan, compositional works that led to the development of the system, a study of existing Javanese gamelan tunings, and a presentation of intervallic relationships and cadences that can be utilized with any gamelan. All of this is done with hope that others who may take interest in writing for central Javanese gamelan will have a new tool at their disposal, and to pique the interest of others in the rich world of possibilities that exist within the instruments. </p><p> There is also an explanation of the process of developing a piano tuning to be used with a traditional gamelan to perform the Concerto for PIano And Javanese Gamelan by Lou Harrison. </p><p> There is some brief discussion on the cognition of interval, and how the brain simplifies complex intervals, and begins to hear them as more simple intervals.</p>