Reconstruction of an early viola da gamba informed by physical modeling

Abstract

The reconstruction of an early viola da gamba is considered, using virtual prototyping by means of the finite element method. Based on iconographic sources, previous research has postulated an instrument design lacking a soundpost and a bass bar. This led to the hypothesis of a top plate with variable thickness. In order to investigate the acoustic efficiency of such a design, a finite element model of the instrument is formulated. The structural accuracy of the model is qualitatively verified by comparing calculated modal shapes with those of a reconstructed instrument, visualized with the aid of Chladni patterns and electronic speckle pattern interferometry. Furthermore, simulating the interaction between the vibrating surfaces of the instrument and the surrounding air shows that the posited asymmetric design can radiate sound more efficiently than a design involving a symmetric top plate. However, the asymmetry introduced by the gradually thickening top plate is weaker than that usually enforced by the presence of a soundpost and a bass bar. Therefore, low frequency structural modes of the instrument are less easily excited by a force acting parallel to the top plate.