The aim of this PhD research project is to provide digital control over the timbre of stringed musical instruments, creating new sound palettes and ways of interacting with strings while maintaining the innate benefits of acoustic musical instruments. Custom optical sensors installed on a string precisely measure how it is vibrating, and powerful piezo stack actuators at the ends of the string expand and contract to change the vibration.
Using a feedforward control strategy first developed to suppress vibration in flexible spacecraft structures and oil rigs, an array of sensors is used to sense the precise shape of a wave travelling along the string towards the actuator. The actuator is then displaced by the same amount, in theory completely absorbing the wave and allowing the shape of the reflected wave to be controlled arbitrarily. This technique affords unprecedented control of the musical properties (i.e pitch, dynamics and timbre) of the sound emitted by the vibrating string.