Parts of Human Ear:
The human ear can be divided into three main parts, viz. external ear, middle ear and internal ear.
Visible, External or Outer Ear: This part of the ear is outside the body and is also called pinna. It extends into the ear canal.
Middle Ear: The middle ear is an air-filled cavity responsible for perceiving sound waves from the outer ear in the form of pressure waves, it is composed of the eardrum or tympanum and the bone ossicles. There are three bone ossicles, viz. the hammer, the anvil and the stirrup.
Inner ear, Labyrinth or Internal Ear: The internal ear is composed of a cochlea and three semi-circular canals. The cochlea makes the hearing apparatus and the auditory nerve from it goes to the brain. It is filled with a water-like substance and comprises both hearing and balancing organs.
How we hear sounds: The external ear perceives sound waves and channelizes them to the eardrum, via the ear canal. During compression, the pressure increases outside the eardrum which forces the eardrum to move inwards. During rarefaction, the pressure decreases outside the ear drum which forces the eardrum to move outwards. Thus, a vibration is produced in the eardrum. Further, the three bones amplify the sound wave, by vibrating in turns. In the inner ear, the vibrations are converted into electrical signals. These signals are transmitted by the auditory nerve to the brain. Finally, the brain interprets those signals as sound.