Extracting vibration characteristics of a guitar using finite element, modal analysis, and digital image correlation techniques

The sound quality generated by the guitar depends on the vibration characteristics (i.e. natural frequencies and mode shapes) of this instrument. Thus, it is of particular interest to the guitar manufacturers to be able to obtain global information about the characteristics of the guitar. Traditional sensors can only measure at discrete locations. However, digital image correlation (DIC) can measure full-field data on the surface of the structure. In the current paper, a finite element (FE) model of a guitar with free boundary configurations was developed using quadratic solid elements. An eigensolution was performed on the FE model to determine its natural frequencies and mode shapes. In order to validate the numerical results, a modal impact hammer test was performed on the instrument in a free configuration. Furthermore, a measurement was performed on the guitar using the DIC technique. In this measurement as well, the guitar was suspended in a free configuration, but was driven using a broadband acoustic excitation generated by a sound source. The response of the guitar to the excitation was recorded using a pair of high-speed cameras. The recorded images were processed to extract the natural frequencies and mode shape of the guitar.