| 摘要 |
PURPOSE:To miniaturize a device with non-directivity and to improve the efficiency by making a diaphragm material and electrode cylindrical and providing a sound shielding layer on a cylindrical outer periphery. CONSTITUTION:Electrodes 12 provided both inner and outer surfaces of a cylindrical diaphragm material 11 consist of electrode element assemblies 12a-12c having areas in proportion to weight of each bit of a digital signal and an electrode 12d. A sound shielding layer 15 for preventing generated sound pressure from emitting to the outer periphery by enveloping the outer periphery of the outer electrode 12d is provided, while an LPF16 for removing components in a high frequency band is provided on openings 14a at both ends. When signals are impressed to the element assemblies 12a-12c, the material 11 expands and contracts in the longitudinal direction due to an piezoelectric effect. However, since both ends of the expanding direction are fixed, said expansion is converted into a vibration in the vertical direction, and a pulse sound is produced. By transmitting the sound through the LPF16, an original sound is reproduced. |
