Prestress effects on the eigenfrequencies of the soundboards: experimental results on a simplified string instrument.

This paper presents an experimental study of the effects of prestresses on the vibration behavior of string instruments. These prestresses are created by gluing ribs (crowning) and tensioning string (downbearing). The effects of these prestresses were previously studied numerically for a piano soundboard by Mamou-Mani et al. [J. Acoust. Soc. Am. 123, 2401-2406 (2008)] and analytically for simplified models by Mamou-Mani et al. [Acta Acust. Unit. Acust. 95, 915-926 (2009)]. In the present study, a specified test bench is designed, including a simplified soundboard (a rectangular plate), a bridge, and a single string. The plate is subjected to in-plane and transverse loads. Vibrational eigenmodes are identified using nearfield acoustical holography (NAH) measurement. The evolution of eigenfrequencies with these specific prestresses is studied. The results show the effectiveness of NAH for this purpose and a very good qualitative concordance with previous numerical and analytical calculus.

Restoration of a 17th-century harpsichord to playable condition: a numerical and experimental study.

The Music Museum in Paris recently acquired a harpsichord made by Ioannes Couchet in Antwerp in 1652. This instrument is considered to be a masterpiece and is protected as a "National Treasure." It was restored with the aim to be played again in concert. An experimental and numerical study of the vibraoacoustic behavior of this harpsichord is presented. A numerical modal analysis was performed with a finite element model. For the experimental part, impact nearfield acoustical holography was used. Experimental eigenmodes are compared to literature and to the finite element results. An application of the model for restoration studies is also proposed.

Numerical simulation of a piano soundboard under downbearing.

A finite element model of a piano soundboard is used to study the effect of the strings tension (downbearing) on its vibration, considering the ribs, the bridges and the crown. The downbearing is modeled with the prestress theory. Prestress calculation with linear and nonlinear models including geometric rigidity are compared in terms of the modal frequencies. The effects of the downbearing in modal frequencies and mobility are investigated and the importance of the crown on these results is evaluated. A simple phenomenological law is exhibited, which characterizes the evolution of eigenfrequencies with downbearing, including the initial crown.