The outer ear
is the external portion of the ear
, which consists of the pinna
, and auditory meatus
. It gathers sound energy and focuses it on the eardrum (tympanic membrane
). One consequence of the configuration of the external ear is to selectively boost the sound pressure
30- to 100-fold for frequencies around 3000 Hz. This amplification makes humans most sensitive to frequencies in this range - and also explains why they are particularly prone to acoustical injury and hearing loss near this frequency. Most human speech sounds are also distributed in the bandwidth around 3 kHz.
Pinna, or auricle
The visible part is called the pinna
and functions to collect and focus sound waves. It is composed of a thin plate of yellow fibrocartilage, covered with integument, and connected to the surrounding parts by ligaments and muscles; and to the commencement of the external acoustic meatus by fibrous tissue. Many mammals
can move the pinna (with the auriculares muscles
) in order to focus their hearing in a certain direction in much the same way that they can turn their eyes
. Most humans, unlike most other mammals, do not have this ability.
Ear canal, or external auditory meatus
From the pinna the sound pressure waves
move into the ear canal
, a simple tube running to the middle ear
. This tube leads inward from the bottom of the auricula and conducts the vibrations to the tympanic cavity and amplifies frequencies in the range 3 kHz
to 12 kHz.