Fig 1. Animation of the response of a square plate to impulse excitation
Fig 1. illustrates the natural response of simply-supported square plate to impulse excitation composed from the first 5 modal shapes. Visually speaking, “waves” of different wavelengths, corresponding to different “modal shapes” travel across the plate surface in various directions, overlap one another and “reflect” themselves from plate boundaries while decaying in time.
Very similar processes occurs on a surface of guitar soundboard following each and every pluck of a string : deformation waves of different wavelengths, corresponding to modal shapes, travel across the soundboard in various directions, overlap one another while gradually dissipating in time. It is important to realise that all modal shapes are present in this wave movements after each and every pluck of a string, albeit in different proportions for each note and each articulation.
