Finite element modeling of guitar top plates

Here we describe the results of finite element method modeling of the resonant vibrations of a guitar top plate in various stages of construction using COMSOL. These models were completed in parallel with electronic speckle pattern interferometry ESPI measurements on three different top plates made of Engleman spruce purchased from Stewmac. The modeling was first set up for a thin piece of wood in a rectangular shape. Subsequent modeling was done at each step as the bode shape was cut, then a tone hold cut, and finally bracing was added. Care was taken to rotate the stiffness matrices for the braces in the model. Normal mode eigenfrequencies and mode shapes were calculated at each step in the fabrication process. Good agreement between the model and the measured data was obtained at low frequencies, but the model deviated from the measured results at higher frequencies.