EXTERNAL EAR The external ear is composed by auricle and the auditory canal. The auricle is the structure that surrounds the opening of the ear; the auditory canal is a chamber carved into the temporal bone of the skull (Marieb, 2012). MIDDLE EAR It is a cavity that contains the eardrum, two openings (oval and round windows) and the three smallest bones in the body Malleus, Incus, and Stapes (Marieb, 2012). INTERNAL EAR The internal ear is like a labyrinth of bony chambers which is located behind the eye socket. It has three divisions the cochlea, the vestibule and the semicircular canals. The labyrinth contains a fluid called perylimph which suspended in this fluid there are membrane sacs which also contains a thicker fluid called endolymph (Marieb, 2012). HOW DO WE HEAR? Sound waves enter the external ear where they travel to the auditory canal to the eardrum. The eardrum makes vibrations with the incoming sound and sends these vibrations to the malleus, incus, and stapes in the middle ear.
The bones in the middle ear function as an amplifier with the sound vibrations and they send them to the cochlea in the internal ear. The hair receptors found in the cochlea are activated by the sound vibrations which in turn release neurochemical messengers. The auditory nerve takes the electrical signal to the brain which makes the translation into sound we can understand. ANATOMY OF THE AUDIOMETER Oscillator: The function of the oscillator is to generate electronically frequencies of 125, 250, 500, 750, 1000, 1500, 2000, 3000, 4000, 6000 and 8000 Hz (Khandpur, 2003). ??FW''WFW"7v?F6??F??26????V?B?2???'F?B&V6W6Rv?V???R&R&W6V?FVBv?F?F??RF?B?26??F??V?W2f?"W&??B?bF??R??RF??( ?B??F?6RF?R???V?Bv?V?F?RF??R?2?????vW"F?W&R?6??B?V6W76'?F??fR7v?F6?F??fRF?RF??W2???"?fb?WV??F???6?&7V?C?F??2fVGW&R?27V6?f?6??F?F?W7BF?Rg&WVV?6?W2F?6W'F??&?vRW7V??&?V?B"????&V6W6RF?R?V??V"?2??7B6V?6?F?fRBF??2g&WVV?7??