Hearing (sense) – Dayna, Laura, Melanie, Tanya and Jina

HEARING

How the ear works (video)

The ear is an extraordinary organ; it picks up the sound and translates it into nerve impulse – the type of signal that the brain can understand.  The peculiar thing about hearing is that it is a completely mechanical process. Other senses such as vision, taste, and smell involve chemical reactions. Hearing, however, is based solely on physical movement.

First of all, the sound travels as a vibration of air compressions. Pinna is a part of the outer ear which catches the sound; it has a number of curves which help to determine where the sound comes from. To find out the horizontal position of the sound one’s brain compare the signals that come from both ears.

When the sound waves travels into the ear canal and hit the ear drum (a tightly stretched membrane), the pressure they create is converted into vibrations of the same frequency. The ear drum is positioned between the ear canal (outer ear) and middle ear; it is also connected to the throat via Eustachian tube which allows maintaining the same atmospheric pleasure in the middle ear as in the outer ear.

Ossicles are a group of small bones in the middle ear designed to transmit the sound signal from ear drum to the fluid in the cochlea. Ossicles also amplify the signal so it can go through the liquid in the inner ear and be translated to the nerve impulses (more about the system of amplification).

The function of the cochlea, which is considered to be an inner ear, is to transform the mechanical sound signal into nerve impulses. The cochlea is filled with fluid, through which the vibration passes, and is lined with hair-like nerve cells which vary in length and degree of resilience so that the different cells will be sensitive to specific frequencies. These hear cells transform the vibrations into nerve signals  which are then sent to the brain by the auditory nerve (More about how hair cells work – video).

For more information see:

http://health.howstuffworks.com/human-body/systems/ear/hearing.htm

http://www.avatar.com.au/courses/PPofM/index.html

http://www.unmc.edu/physiology/Mann/mann8.html

http://www.physicsclassroom.com/class/sound/u11l2d.cfm

http://www.ndt-ed.org/EducationResources/HighSchool/Sound/hs_sound_index.htm

Images:

http://www.freedomscope.com/wireless_stethoscope_for_the_hearing_impaired.htm

http://health.allrefer.com/pictures-images/ear-anatomy.html

http://www.cartoonstock.com/directory/s/selective_hearing.asp



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