An ultrasonic medical device includes a first ultrasonic transmitter, emitting a first ultrasonic with frequency f1, and a second ultrasonic transmitter, emitting a second ultrasonic with frequency f2. The pathways of these ultrasonics overlap at least a portion of each other in one medical treatment area, forming a first composite ultrasonic with frequency f3 in the medical treatment area. Both f1 and f2 are larger than f3. The composite ultrasonic can be used in medical treatment.
