Sound is an invisible sound wave formed by different air pressures, which can be perceived by the human ear. The seemingly simple ear is actually a big family. Exposed outside, we usually call the ear pinna, which is an open door.
Why can people's ears hear sound? What is the principle that the ear can hear sound?
Sound waves enter the ear canal from the auricle and vibrate the eardrum. The tympanic membrane is a tight skin, and sound waves make it vibrate. The tympanic membrane is connected to a small bone called the malleus, and the vibration wave is transmitted from the malleus to the other two small bones, the incus and stapes, and then into the cochlea.
The cochlea is a snail shaped tube filled with fluid. The fluid in the cochlea fluctuates and pushes the cilia out of the rows of hair cells in the fluid, which are usually only visible under a microscope. Ciliary movement produces nerve signals, which are transmitted to the brain through a structure similar to a telephone line - nerves in the human body. So we heard the sound.