ULTRASONIC SENSOR

PROBLEM TO BE SOLVED: To suppress reverberant vibration in an ultrasonic sensor.SOLUTION: An ultrasonic sensor 1 includes a vibrator 2 for receiving and transmitting an ultrasonic wave, a driving circuit 3 for transmitting the ultrasonic wave from the vibrator 2, and a reverberant vibration suppression circuit 7 for suppressing the reverberant vibration of the vibrator 2. The driving circuit 3 boosts voltage of a transmission signal for transmitting the ultrasonic wave by a transformer 32, and supplies the transmission signal of the boosted voltage to the vibrator 2. The reverberant vibration suppression circuit 7 includes the vibrator 2, a secondary coil (first inductive element) 34 of the transformer 32, a coil (second inductive element) 41, a resistor 42, and a capacitor (capacitive element) 43. The capacitor 43 and the resistor 42 are connected in series to each other, and connected in parallel to the coil 41. An LCR circuit including the resistor 42, the capacitor 43, and the coil 41 is connected between the vibrator 2 and the secondary coil 34. The reverberant vibration suppression circuit 7 absorbs the reverberant vibration of the vibrator 2 by using a resonance phenomenon at a plurality of different resonance frequencies.