Of the five senses, hearing is one of the most important. The hearing of audible sounds cannot be easily shut down or avoided unlike the other senses. Audible sounds also have a significant effect on how we feel. The human ear is an organ of complex design and function.
The hearing mechanism in the ear is sensitive enough to detect even small pressure waves. A healthy, young person can hear sounds with frequencies from roughly 20 to 20,000 Hz. The sound of human speech is mainly in the range 300 to 3,000 Hz. Movements of the ear drum as small as the diameter of a hydrogen atom can be audible!