PURPOSE: To enable the receiving of a sound wave with a receiving side electrode without requiring the generation of a sound wave and a delay circuit, by arranging a transmitting side electrode comprises circular electrodes which are arranged between a comb-shaped electrode and circular arc electrodes and the recieving side electrode and connected to a terminal.

CONSTITUTION: A transmitting side electride is made up of circular arc electrodes 11aW11d and 11'aW11'd arranged respectively between a comb-shaped electrodes to which one end of circular arc electrodes 9aW9d and 9'aW9'd arranged parallel on one surface of a piezo-electric substrate 1 is connected in common and the electrode 9aW9d and 9'aW9'd and has a terminal at one end thereof. A receiving side electrode is made up of a plurality of circular arc electrodes arranged respectively between a comb-shaped electrode to which one end of a plurality of circular arc electrodes arranged in the direction opposite to the said circular arc electrodes on the other surface thereof 1 is connected in common and the circular arc electrodes and have a terminal at one end thereof. This enables the generation of a sound wave with a simple mechanism while the sound wave generated can be received sequentially with the receiving side electrode without providing any delay circuit.