why can't most people hear ultra sonic waves?

Answer 1

Most people cannot hear ultrasonic waves because they are above the frequency range of human hearing. The human ear is only able to detect frequencies between 20 Hz to 20,000 Hz, whereas ultrasonic waves have frequencies higher than 20,000 Hz. Additionally, the structures in the inner ear that are responsible for detecting sound vibrations are not designed to pick up on frequencies outside of the audible range.