The sound waves of frequency greater than 20 kHz are called ultrasonic waves. These sound waves are not audible to the human ear. The term sonic applies to ultrasound waves of very high amplitude.
Animals like dolphins and bats rely on ultrasound waves to live. Bats make sounds that have the frequency of ultrasound. These sounds get transmitted and the bat receives its echo. From the time interval between the transmitted sound and the echo received, as well as the angle of the echo received, they can find the distance of the target. Similarly, dolphins use ultrasound to understand the surrounding conditions and communicate with their peers.
Property 1: Ultrasonic waves vibrate at a frequency greater than the audible range for humans (20 kilohertz).
Property 2: They have smaller wavelengths. As a result, their penetrating power is high.
Property 3: They cannot travel through vacuum.
Property 4: Ultrasonic waves travel at the speed of sound in the medium. They have maximum velocity in a denser medium.
Property 5: In a homogeneous medium, they travel at a constant velocity.
Property 6: In low viscosity liquids, ultrasonic waves produce vibrations.
Property 7: They undergo reflection, refraction and absorption.
Property 8: They have high energy content. They can be transmitted over a large distance without much loss of energy.
Property 9: They produce intense heat when they are passed through objects.
Property 10:Like sound waves, ultrasonic waves are longitudinal waves that produce alternate compressions and rarefactions.