Guitar timbre modification through active vibration control – preliminary results

The analysis and modification of instrument timbre is a topic of discussion in both luthier and musician literature as well as in scientific publications. The need for versatility in an instrument's timbre characteristic is particularly visible in the acoustic guitar and the multitude of common types in which it is produced, which differ in size, body shape, top plate bracing and many other factors. Depending on the required loudness as well as the expected spectral and temporal characteristics different models are used. It is worth considering whether the ability to modify an existing guitars timbre would not be valuable, allowing for greater customizability and avoiding the requirement for a vast instrument collection. This paper presents preliminary research into the modification of an acoustic guitar's timbre through application of active vibration control to its top plate. A system making use of a piezoelectric sensor-actuator pair is created, capturing the vibration at a point of the plate, performing signal processing inside a feedback loop and running the resulting signal through the actuator. The goal of this work is to present the measurement results of the acoustic guitars top plate vibration characteristic, the created system and the initial test results into the capability of such a system with regards to timbre modification. The work concludes with a summary of the observed effects and a discussion of the viability of this technology.