Relations between the geometry and acoustics of brass instruments

• Main Author: Goodwin, John Christopher
• Published: University of Surrey 1981
• Subjects: 534; Acoustics & noise analysis
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.256171

This thesis examines the role of the bore shape in brass instruments. Difficulties in finding the precise nature of the bore shape in an assembled instruments are discussed. Several measurement methods employed to overcome these are developed, and the overall bore shape found. A model is developed whereby input impedance and pressure transfer function of an instrument may be predicted from the bore shape, and the musically important effect of temperature investigated. Good agreement with experimental measurements of instruments under similar conditions is found. Time domain measurements using a computer controlled impulse source and digital signal acquisition are given which illustrate the effect of small discontinuities of the bore upon the impulse response. Synthesis of bore shape from acoustic data is discussed with reference to reflections from such features. The methods currently employed by manufacturers to design new instruments are discussed, and an iterative process combining the prediction of acoustic properties from bore shape, synthesis, and psychometric techniques postulated.