Basic Fact of EAR  Ears are used to detect SOUND in environment.  Ears help to detect movement & position.  Ear is divided into Outer Ear, Middle Ear & Inner Ear.

Structure of EAR  Outer Ear: EAR PINNA, EAR CANAL & EAR DRUM.  Middle Ear: EAR BONES  Inner Ear: EUSTACHIAN TUBE & ADENOIDS.

Outer Ear  It is the part which is visible and is made of folds of skin and cartilage.  It leads into the ear canal, which is about one inch long in adults and is closed at the inner end by the eardrum.  The eardrum is a thin, fibrous, circular membrane covered with a thin layer of skin.  It vibrates in response to changes in the air pressure that constitute sound.  The eardrum separates the outer ear from the middle ear.

Middle Ear  It is a small cavity which conducts sound to the inner ear by means of three tiny, linked, movable bones called "ossicles."  These are the smallest bones in the human body and are named for their shape.  The hammer (malleus) joins the inside of the eardrum.  The anvil (incus) has a broad joint with the hammer and a very delicate joint to the stirrup (stapes).  The base of the stirrup fills the oval window which leads to the inner ear.

Inner Ear  The inner ear is a very delicate series of structures deep within the bones of the skull.  It consists of a maze of winding passages, called the "labyrinth".  The front (see cochlea) is a tube resembling a snail's shell and is concerned with hearing.  The rear part is concerned with balance.

Detection of SOUND 1. Sound waves (air vibrations) are collected by the OUTER EAR. 2. Sound waves vibrate the EAR DRUM. 3. Vibrations are amplified by the EAR BONES. 4. Vibrations change the pressure of the FLUID of the INNER EAR. 5. Vibrations are transmitted to signals to the brain via nerve impulses.

Intensity Cues in Stereo  When the volume of two speakers are equal, we will hear the sound as come from the centre.