As you may know that, the limit of hearing of a human ear are 20 hertz to 20000 Hertz.
That is human ear can ear a sound of frequences in the above range the sound are called audible sound.
Our ears cannot hear the sound of frequences lower than 20 hertz and higher than 20000 Hertz. Sound with frequences smaller than 23rd is called infra sound.
Ex. The sound produced by a pendulum and the sound generated by the vibration of the earth crust just before an earthquake are example of infra sound.
The sound waves with frequency is greater than 20 kilohertz or 20000 hertz are called ultrasound.
The ultrasound can heard by dog, mouse, bat dolphin. Dost they can since some noise which are in inaudible to us.
Children under 5 years of age and some creatures and insect can hear waves with frequency up to 25 kilohertz. Bats,nice, dolphins etc can also produced ultrasound.
What are the uses of ultrasonic sound?
Below I have mentioned some of the uses of ultrasonic sound.
- For communication between ships at sea.
- To sterling liquid like mill by killing the bacteria in it so that milk keeps for a longer duration.
- To join plastic surfaces together.
- Eco cardiography which studies heartbeat is based on ultrasonic waves. It is also called as sonography technology.
- To obtain images of internal organs in the human body.
- In industry to clean intricate part of machines where hand cannot reach.
- To locate the crack and fault in the metal blocks .