Contributions to discrete-time methods for room acoustic simulation

The sound field distribution in a room is the consequence of the acoustic properties of radiating sources and the position, geometry and absorbing characteristics of the surrounding boundaries in an enclosure (boundary conditions). Despite there existing a consolidated acoustic wave theory, it is very difficult, nearly impossible, to find an analytical expression of the sound variables distribution in a real room, as a function of time and position. This scenario represents as an inhomogeneous boundary value problem, where the complexity of source properties and boundary conditions make that problem extremely hard to solve. Room acoustic simulation, as treated in this thesis, comprises the algebraical approach to solve the wave equation, and the way to define the boundary conditions and source modeling of the scenario under analysis. Numerical methods provide accurate algorithms for this purpose and among the different possibilities, the use of discrete-time methods arises as a suitable solution for solving those partial differential equations, particularized by some specific constrains. Together with the constant growth of computer power, those methods are increasing their suitability for room acoustic simulation. However, there exists an important lack of accuracy in the definition of some of these conditions so far: current frequency-dependent boundary conditions do not comply with any physical model, and directive sources in discrete-time methods have been hardly treated. This thesis discusses about the current state-of-the-art of the boundary conditions and source modeling in discrete-time methods for room acoustic simulation, and it contributes some algorithms to enhance boundary condition formulation, in a locally reacting impedance sense, and source modelling in terms of directive sources under a defined radiation pattern. These algorithms have been particularized to some discrete-time methods such as the Finite Difference Time Domain and the Digital Waveguide Mesh.Escolano Carrasco, J. (2008). Contributions to discrete-time methods for room acoustic simulation [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/8309Palanci

Development and exploration of a timbre space representation of audio

Sound is an important part of the human experience and provides valuable information about the world around us. Auditory human-computer interfaces do not have the same richness of expression and variety as audio in the world, and it has been said that this is primarily due to a lack of reasonable design tools for audio interfaces.There are a number of good guidelines for audio design and a strong psychoacoustic understanding of how sounds are interpreted. There are also a number of sound manipulation techniques developed for computer music. This research takes these ideas as the basis for an audio interface design system. A proof-of-concept of this system has been developed in order to explore the design possibilities allowed by the new system.The core of this novel audio design system is the timbre space. This provides a multi-dimensional representation of a sound. Each sound is represented as a path in the timbre space and this path can be manipulated geometrically. Several timbre spaces are compared to determine which amongst them is the best one for audio interface design. The various transformations available in the timbre space are discussed and the perceptual relevance of two novel transformations are explored by encoding "urgency" as a design parameter.This research demonstrates that the timbre space is a viable option for audio interface design and provides novel features that are not found in current audio design systems. A number of problems with the approach and some suggested solutions are discussed. The timbre space opens up new possibilities for audio designers to explore combinations of sounds and sound design based on perceptual cues rather than synthesiser parameters