The evolutionary purpose of the pinna is to collect sound. It does so by acting as a funnel, amplifying the sound and directing it to the ear canal. While reflecting from the pinna, sound also goes through a filtering process which adds directional information to the sound (see sound localization, head-related transfer function, pinna notch). The filtering effect of the human pinna preferentially selects sounds in the frequency range of human speech.
Amplification
Amplification of sound by the pinna, tymphanic membrane and middle ear structures create a sound 20 dB greater than the sound entering the pinna. This amplification is an important factor in inner eartrauma resulting
from elevated sound levels.
Anatomy
The diagram shows the shape and location of these components:
Anthelix (antihelix) forms a 'Y' shape where the upper parts are:
*Superior crux (to the left of the fossa triangularis in the diagram)
*Inferior crux (to the right of the fossa triangularis in the diagram)
Antitragus is below the tragus
Auricular sulcus is the depression behind the ear next to the head
Concha is the hollow next to the ear canal
Conchal angle is the angle that the back of the concha makes with the side of the head
