Ultrasound uses sound waves above 20 kilohertz. As this frequency is above the limit of the frequency range that the human ear can detect, it is called ultra sound. Ultra sound waves can penetrate matter and by analyzing the sound waves at the other end it is possible to determine what is inside the object that is being analyzed.
Ultrasound is now used on a large scale to have a look inside the human body and conduct scans without having to make any cuts or incisions. The fact that there is no injury caused makes ultrasound perfect for seeing the growth of the fetus and to detect any problems. Apart from this body scans of other organs are also used as diagnostic tools.
Ultrasound in the frequency range 2 – 10 megahertz is used for non destructive industrial testing to detect for any mechanical flaws. Ultrasound frequencies in the range 15 – 40 kilohertz are used in the welding of plastics. Apart from these, ultrasound is used for many other purposes.