Development and Evaluation of a Hybrid Wind Instrument

Buys, Kurijn (2018). Development and Evaluation of a Hybrid Wind Instrument. PhD thesis The Open University.



A hybrid wind instrument generates self-sustained sounds via a real-time interaction between a computed excitation model (such as the physical model of human lips interacting with a mouthpiece) and a real acoustic resonator. Attempts to produce a hybrid instrument have so far fallen short, in terms of both the accuracy and the variation in the sound produced. The principal reason for the failings of previous hybrid instruments is the actuator which, controlled by the excitation model, introduces a fluctuating component into the air flow injected into the resonator.

In the present thesis, the possibility of using a loudspeaker to supply the calculated excitation signal is evaluated; the loudspeaker is placed at the entrance of the resonator (a clarinet-like tube), along with a microphone. This work focusses particularly on two possibilities: using the instrument as a new musical instrument and using it as a tool to carry out wind instrument research.

First, a theoretical study facilitates the modelling of the loudspeaker-resonator system and the design of a feedback and feedforward filter to successfully compensate for the presence of the loudspeaker.

The prototype is then evaluated using physical models of a single-reed, a lip-reed and a bow-string interaction and using a purely mathematical “polynomial” excitation model. For the design of excitation models, the usefulness of dimensionless and reduced parameter forms is outlined, and a sound prediction theory is presented, enabling the pre-estimation of both amplitude and spectral related features of the self-sustained sounds.

The resulting self-sustained sounds are evaluated by a mapping of their sound descriptors to the input parameters of the excitation models, both for sustained and attack sounds. For all excitation models, the sounds produced by the hybrid instrument are shown to match those predicted by simulation. However, the hybrid instrument is more easily destabilised for certain extreme parameter states.

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