This work investigates brass instruments in the time domain, rather than the traditional frequency domain, and considers first, impulse measurements and secondly, their analysis. An existing apparatus for measuring the response to an acoustic impulse at the input of a brass instrument has been refined. Problems of impulse inconsistency, ambient temperature variation and source reflections have been resolved. Developments of the above equipment are used to test the quality of brass instruments on a factory production line. A prototype and a test instrument are compared by taking the arithmetical difference of their impulse responses. The equipment has detected small faults missed by normal inspection methods. The usefulness of this technique to brass instrument manufacturers is discussed. Links between the instrument's measured transient response and its bore geometry have been developed. The stages involved are deconvolution and bore reconstruction. Various deconvolution methods have been studied systematicaly by applying them to simulated noiseless and noisy data. Noise introduces errors, particularly at high frequencies, so deconvolution of real measured data is distorted. Techniques to reduce the effects of noise have been investigated. Attempts to employ the Gerchberg restoration algorithm 'to restore high frequency information proved unsuccessful. A new inverse method, based on an iterative z-transform procedure, of reconstructing an instrument's bore shape and damping profile from its transient response has been developed. It produces perfect results for noiseless model data, but even the smallest amount of noise renders the method unstable. Regularisation is therefore required. The corresponding direct process of predicting the transient response from bore and damping data is stable and produces results which compare well with measured responses. The work strengthens relationships between an instrument's shape and its musical quality, and will enhance the design of better instruments. Further research on the link between transient response and subjective quality is recommended.

abstract: Although many of the effects of the flute’s design and mechanisms have been previously studied, the flute’s stopper remains relatively unexplored. Stoppers are traditionally made of cork, are used to seal the upper end of the headjoint tubing, and determine the overall intonation of the flute. However, new stoppers made of different types of materials have been created to serve an additional purpose: to improve various aspects of player performance. These new non-cork stoppers vary in design and material, and claim to improve players’ projection, resonance, response, and other qualities. This research project discusses the history of the flute’s stopper and its functions, usage, and effects to improve general stopper knowledge and assist flutists interested in trying or purchasing non-cork stoppers available today. Because only three small studies have been published on the stopper’s acoustic and perceived effects to date, two single-blind experiments were conducted to determine the stoppers’ potential acoustic and perceived effects on listener and player perception. Five of the most popular stoppers available today were tested: the Bigio Stopper, Celestine Rexonator, Seidman Flute Stopper Plug, Swap-Stopper, and the traditional cork stopper. To determine the stopper’s acoustic effects, which can be quantified, an acoustic experiment was conducted to investigate the stoppers’ effect on intensity in decibels (which correlates with perceived loudness) and spectral centroid in hertz (which correlates with perceived tonal brightness). Perception tests were conducted to examine how both players and listeners perceive the stoppers’ effects on projection, response, tone quality, and timbre. The results of these experiments will help flutists better understand the effects of the stopper and navigate the stopper-makers’ claims about non-cork stoppers available for purchase today. / Dissertation/Thesis / Doctoral Dissertation Music 2020

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