The ear has three main sections--the outer ear which captures sound waves, the middle ear which begins the process of transmitting these vibrations to the inner ear, which is the final step in the process of capturing sound before it is passed along via the auditory nerves to the brain. Each section plays a vital role in determining how we perceive and interpret the sounds emanating from our immediate environment and the learning process involved in the development of speech.
Anatomy
On their webpage, the Partners in Assistive Technology Training and Services (PATTS), provides a comprehensive look at the anatomy of the ear. The middle ear is composed of the eardrum (tympanic membrane) which separates it from the outer ear, three bones (ossicles), the smallest bones in the body, that are named for their shapes---the malleus (hammer), the incus (anvil) and the stapes (stirrup), and the Eustachian tube which connects the throat to the ear.
Function
Part of the function of the middle ear, also described by PATTS, involves the process of chewing and swallowing. This causes the Eustachian tube to open and close, moving air in and out of the middle ear to maintain stable pressure on the both sides of the eardrum. When sounds enter the outer ear (auditory canal), the eardrum begins to vibrate. The vibration passes through the malleus, which rests against the eardrum, causing all three ossicles to begin vibrating. The vibrations then travel through another membrane, the oval window, via the end of the stapes (called the footplate) and they enter the inner ear. When these vibrations encounter the fluid contained within the inner ear, they are transformed into chemical impulses. Moving along the nerves, located in the inner ear, their journey ends when the chemical impulses reach the portion of the brain that interprets sound.
Speech Impairment
The California Ear Institute informs us that normal middle ear function during the first 12 years of a child's life is necessary for the proper development of speech. Childhood infections or allergies can cause fluid to develop in the middle ear, which is normally an air-filled chamber. Left untreated, fluid remaining in the middle ear can cause sound distortion. The development of normal speech patterns depends upon unimpaired sound reception within the ears. One of the treatments used to correct this problem is the insertion of a tympanostomy tube into the ear to drain the fluid.
Ruptured Eardrum
According to University of Wisconsin Department of Neurophysiology, any injury to the eardrum can cause a rupture of this membrane and result in conductive hearing loss, an interruption in normal hearing as the result of the inability to maintain normal air pressure on the outer ear side and middle ear side of the eardrum. When this function is interfered with, it alters each successive step in the normal hearing process. The energy from the sound vibrations filtered through the air-filled chamber of the middle ear to the fluid-filled chamber of the inner ear is diminished in intensity and results in a hearing disorder proportional to the degree of the injury sustained. The hearing loss is compounded if the injury involves the ossicles as well.
Types of Hearing Loss
On their website, the University of Alabama describes the four different types of hearing loss as conductive, sensorineural, central deafness and mixed hearing loss. Conductive hearing loss results from problems in the functioning of the outer and/or middle ear involving the way sound vibrations are processed and interpreted. Sensorineural hearing impairment involves problems within the inner ear and the auditory nerve leading to the brain. One of the reasons for central deafness is an injury to the area of the brain involved in the auditory process. Mixed hearing problems stem from a combination of the three previous types described.
Tags: hearing loss, air-filled chamber, central deafness, chemical impulses, development speech, eardrum When