What frequency range is considered ultrasonic?

In the field of physics, the term ultrasonics refers to vibrations with frequencies greater than the upper limit of the human audible range, which is approximately 20 kilohertz (20,000 hertz).12

While this threshold marks the beginning of the ultrasonic range, applications can extend to much higher frequencies. For instance, medical diagnostic imaging often utilizes pulses of ultrasound generally above one megahertz, and specialized acoustic microscopes can operate at frequencies as high as 2,000 megahertz. Conversely, sound waves with frequencies exceeding ${10}^{13}$ hertz are categorized as hypersound (also known as microsound or praetersound).31