The work presented in this thesis is concerned with the relationships between the perceived tone quality of classical guitars and the vibrational behaviour of the guitar body.Anumerical model is described which calculates the sound pressure response of a guitar when a sinusoidal force is applied to one of its strings. The response of the body is described in terms of its modes of vibration, each mode being characterised by four parameters: a resonance frequency, an efective mass, an efective monopole area and a Q-value. Coupling between the string, top plate and fundamental modes of the back plate and air cavity is included. The output of the model represents the sound of a plucked note as heard by a listener at a given distance in front of the guitar. Using notes synthesised from the model, psychoacoustical listening tests are performed which examine the e ect on tone quality of a variety of changes to the mode parameters.
The thesis is divided into nine chapters. Chapter 1 outlines the aims and methods of the research. Chapter 2 reviews the literature relating to stringed musical instruments. Chapter 3 presents a description of the processes that occur in the guitar during sound production. Chapter 4 outlines the theory for the numerical model. Chapter 5 describes experimental measurements of the frequency responses of two guitars and the curve- tting techniques used to obtain values of the four mode parameters for a number of body modes. Chapter 6 describes experimental measurements of the coupling between string and body. Chapter 7 describes the four psychoacoustical listening tests. Chapter 8 discusses the results of the listening tests, and establishes connections between the properties of the body modes and certain characteristics of tone quality. Chapter 9 presents a brief summary of the conclusions reached, and also outlines topics for future work.