Abstract
In the research of the tone quality of a classic guitar, the control of the vibration modes on the surface board is important. The couple bending modes on the front and rear face cause the "glottal sound " which is unsuitable for the guitar sound. The glottal sound has the rapid damping wave shape by the diffusion of the vibration energy with creating the sound strongly. It is occasioned by the dynamic change of the guitar acoustical room volume. We can find the higher sound pressure level on the sound hole of the guitar.. In the main case, there are the opposite phase vibration modes between the front face and the rear face.
