To correct defects of a simple point sound source including lowering of energy density, despite the ability to form a wide angle directional beam in a three-dimensional system using the Walsh function.
A two-dimensional array is formed by nine ultrasonic vibrators 1 surrounded by a dotted line. The central ultrasonic vibrator la of the two-dimensional array is connected to an oscillator 2 and eight ultrasonic vibrators 1 surrounding the central ultrasonic vibrator la are connected to the oscillator 2 through a phase delay circuit 3. By delaying the vibration phase of the surrounding ultrasonic vibrators 1 from the phase of the vibration of the central ultrasonic wave vibrator 1a by inputting oscillation output to the central ultrasonic vibrator 1a from the oscillator 2, and applying oscillation output to the central ultrasonic vibrator 1 from the oscillator 2 through the delay circuit 3, the directionality of ultrasonic waves sent is widely angled around the central ultrasonic vibrator 1a, and acoustic power becomes ninefold.
GOTO SHIGEFUMI
OKADA OSANARI
