The outer ear includes the pinna, the part of the ear you can see, and the ear canal. These structures collect sound waves from the environment and direct them down the ear canal toward the eardrum.

The middle ear is an air-filled space between the eardrum and the inner ear. The middle ear contains three tiny middle ear bones called ossicles. The middle ear bones connect the eardrum to the inner ear.

When sound enters the ear canal, the eardrum vibrates, causing the middle ear bones to move. The movement of the middle ear bones amplifies these vibrations as sends them to the inner ear.

The inner ear includes a tiny coiled tube, called the cochlea, which is the organ of hearing. It also has some other structures that help us maintain our balance.

The cochlea is filled with fluid and thousands of tiny hair cells (sensory cells). 

Movement of the middle ear bones pushes on a little membrane at the entrance of the cochlea called the oval window. This causes the fluid inside the cochlea to move. When this fluid moves, the hairs bend, converting the movement into electrical signals. These electrical signals are passed along the auditory nerve to the brain. The brain interprets this as sound.