Measuring guitar top plate resonances at stages of fabrication

This project investigates how the shape, quality, and boundary conditions of an object affect its normal modes of vibration. Here we report the results of electronic speckle pattern interferometry (ESPI) measurements on several potential guitar top plates in moving from a solid rectangle shape to the final top plate shape with a sound hole and bracing. The measured nodal patterns were similar for two distinct top plates as they were cut and sanded into final form. The measured frequencies of each normal mode were similar with typical variations of less than 10%. The experimental data was compared to theoretical data modeled in COMSOL to test the accuracy of the input parameters characterizing the wood. We found that the model results agree with the experimental data well at low frequencies, but the accuracy of the model decreases when higher frequency modes are considered.