What is the range of ultrasonic waves in relation to human hearing?

Ultrasonic waves are defined as sound waves that have frequencies above the upper limit of human hearing. The typical range of human hearing is from 20 Hz to 20,000 Hz. Therefore, any frequencies above 20,000 Hz are classified as ultrasonic. This is why the correct choice is that ultrasonic waves are above 20,000 Hz.

In understanding the implications of this frequency range, it is important to note that various applications utilize ultrasonic waves, such as medical imaging and cleaning processes, due to their ability to travel long distances and penetrate different materials without being detected by the human ear.