Ultrasound definition

First, it is important to understand the definition of sound. Let's see two definitions of sound:

1. Simple definition: Sound is the perception of vibrations stimulating the ear
2. 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