Abstract
This study deals with a control of sound directivity by using a piezoelectric speaker, which is thin and lightweight with a simple structure. Influences of the design factors, the shape of vibration board and the position of vibrator, are experimentally investigated. Cylindrical shell structure is applied to the vibration board in order to increase the rigidity. In the experiment, sound directivity of the speaker models is evaluated from the sound pressure contour of axial transverse section by which the frequency response of radiated sound was measured at each angle. The experimental results show that the sound directivity at long side of the rectangle became sharp by using the shell type of piezoelectric speakers. In the high frequency band, especially, the sound directivity had significant changes by the attached position.
