Ultrasonic waves have greater frequency (more than 20000 Hz). Ordinary sound has lower frequency than ultrasonic wave.
Due to their high frequencies,
(i) they have high power.
(ii they can penetrate anywhere to a large extent.
(iii) they are able to travel along well-defined straight paths, even in the presence of obstacles.
Applications of ultrasound are
(i) To detect the flaw or defect in metal.
(ii) In the diagnosis of diseases.