What is the ultrasonic? Wave can be divided into three kinds, namely, sound, sound waves, ultrasonic. The frequency of the sound of 20 hz; The frequency of the sound waves to 20 hz to 20 KHZ; The frequency of the ultrasound is more than 20 KHZ. The sound and ultrasonic wave to the human ear is generally can't hear. Ultrasonic due to high frequency, wavelength, and therefore the spread of [...]