The Human Ear

The Human Ear

Ears are extremely sensitive device with the help of which we are able to hear.

The ear consists of three basic parts - the outer ear, the middle ear, and the inner ear. Each part of the ear has a specific role in the task of detecting and interpreting sound. The outer ear is called pinna. It collects and transmits the sound to the middle ear through the auditory canal.

Understanding how humans hear is a complex subject involving the fields of physiology, psychology and acoustics. In this part of Lesson 2, we will focus on the acoustics (the branch of physics pertaining to sound) of hearing. We will attempt to understand how the human ear serves as an astounding transducer, converting sound energy to mechanical energy to a nerve impulse which is transmitted to the brain. The ear's ability to do this allows us to perceive the pitch of sounds by detection of the wave's frequencies, the loudness of sound by detection of the wave's amplitude and the timbre of the sound by the detection of the various frequencies which make up a complex sound wave.

At the end of the auditory canal there is a thin membrane called the eardrum or tympanic membrane. The eardrum moves inward and outward as the compression or rarefaction reaches it. In this way the eardrum vibrates. These vibrations are amplified by the three bones namely the hammer, anvil and stirrup in the middle ear.

The middle ear transmits these vibrations to the inner ear. Inside the inner ear, the vibrations or the pressure variations are converted into electrical signals by the cochlea. These electrical signals are sent to the brain via the auditory nerve and the brain interprets them as sound.