Abstract
The work described in this thesis comprises three parts: devising an original method capable of making absolute measurements of acoustic impedance (both modulus and phase) for brass instruments; developing formal subjective assessment procedures enabling the subjective dimensions of trombone quality to be quantified; discovering the extent to which the acoustic impedance of an instrument may be used to predict its subjective quality. The impedance measurement systems of various authors are reviewed, and the limitations imposed by such systems discussed. The computer controlled system devised by the author, which uses a hotwire anemometer to measure particle velocity, is then described in detail including transducer calibration and measurement accuracy. The factors governing the subjective quality of trombones, based on interviews with players, are introduced, and the techniques used to quantify subjective characteristics (Semantic Differential Scaling and Multidimensional Scaling) are presented together with a discussion of the advantages and disadvantages of each method. The results of a series of subjective experiments are given. Several hypotheses relating the subjective quality of an instrument to its impedance are discussed. For the trombone, the degree of harmonicity of the impedance maxima and the envelope of the impedance curve are shown to have an important effect on players' assessment.