Speaker
Description
The soundboard is a key element in an acoustic guitar. It both makes the instrument radiate as a result of the strings’ motion, and withstands the static stress induced by their tension. Made out of a thin wooden plate with wooden stiffening bars glued on its back (the bracing), it plays a dominant role in the instrument’s sound profile. This way, a large variety of bracing patterns have been created through the ages, giving the guitar a substantial sound palette available to this day.We show here an alternative soundboard structure, in which the bracing is redesigned into a multilayer geometrical network, whose vibrational behavior can be controlled by varying two geometrical parameters, using recent concepts and manufacturing processes such as architectured materials and laser cutting. Determining the vibrational behavior by a direct method for such a structure would be too computationally expensive, so we need to develop reduced equivalent homogeneous models. Two methods are presented here: one exploiting the dispersion relation of a thin homogeneous orthotropic plate (Kirchhoff-Love), the other adjusting the generalized stiffnesses of a thick plate model (Reissner-Mindlin).The results show the relevance of these models, both with simulated or experimental data. This novel structure thus aims to facilitate the soundboard dynamical behavior optimization, hence potentially widen the sound palette of the acoustic guitar thanks to spatial modulation of the network’s geometrical parameters, giving luthiers an additional tool to design their instruments.