First, it is important to understand the definition of sound. Let's see two
definitions of sound:
Simple definition: Sound is the perception of vibrations stimulating
the ear
Scientific definition of sound: sound is a periodic disturbance in
fluids density, or in the elastic strain of a solid, generated by a vibrating
object. These waves (vibrations) propagate in two basic ways: longitudinal waves
and transverse waves.
Simple ultrasound definition
Ultrasound is sound with a frequency over 20,000 Hz, which is about
the upper limit of human hearing. Human beings cannot hear ultrasound
