Patricia E. Connelly, Ph.D. CCC-A, FAAA New Jersey Medical School Newark, NJ. The anatomy of the hearing system can be divided into four components. These divisions are the: Outer ear, Middle ear, Inner ear, Central auditory pathways.
The Outer Ear
The outer ear is made up of the pinna or auricle and the external auditory canal. The pinna collects and funnels sound down the ear canal. The ear canal is curved, “S” shaped, and about 1 inch long in adults. It has hairs and glands that produce wax called cerumen. Cerumen helps to lubricate the skin and keep it moist.
The Middle Ear
The eardrum (tympanic membrane) is a membrane at the inner end of the ear canal. On the inner side of the tympanic membrane is an air-filled space called the middle ear cavity. The vibrations of the tympanic membrane are transmitted through the malleus (hammer), incus (anvil), and stapes (stirrup), also called the ossicles. The stapes footplate transmits the vibrations into the inner ear.
The Inner Ear
The inner ear has two divisions: one for hearing, the other balance. The hearing division consists of the cochlea and the nerve of hearing. The cochlea is a snail-shaped, bony structure that contains the sensory organ for hearing called the organ Corti. The organ of Corti releases chemical messengers when the vibrations from the stapes activate its tiny hair cells. These then excite the nerves of hearing which carry sound to the brain.
Central Auditory Pathways
The central auditory system is a complex network of neural pathways in the brain that is responsible for sound localization, speech understanding in noisy listening situations and other complex sounds, including music perception. The Process of Hearing Sound is transformed into mechanical energy by the tympanic membrane. It is then transmitted through the ossicles to the inner ear where it is changed again into hydraulic energy for transmission through the fluid-filled cochlea. The cochlea’s hair cells are stimulated by the fluid waves and a neurochemical event takes place that excites the nerves of hearing. The physical characteristics of the original sound are preserved at every energy change along the way until this code becomes one the brain can recognize and process. Hearing loss misleads our brain with a loss of audibility and introduces distortion into the message that reaches the brain. Changes in the effectiveness of the brain to process stimuli, from head trauma, disease or from aging, can result in symptoms that mimic hearing loss. The ears and the brain combine in a remarkable way to process neural events into the sense of hearing. Perhaps it's fair to say that we "hear" with our brain, not with our ears!
Signs of Hearing Loss
The signs of hearing loss can be subtle and emerge slowly, or they can be significant and come on suddenly. Either way, there are common indications of hearing loss. You should suspect hearing loss if you experience any of the signs below. You might have hearing loss if you experience any of these symptoms.
Social hearing loss symptoms
- Require frequent repetition
- Have difficulty following conversations involving more than 2 people
- Think that other people sound muffled or like they’re mumbling
- Have difficulty hearing in noisy situations, like conferences, restaurants, malls, or crowded meeting rooms
- Have trouble hearing children and women
- Have your TV or radio turned up to a high volume
- Answer or respond inappropriately in conversations
- Have ringing in your ears
- Read lips or more intently watch people’s faces when they speak with you
Emotional hearing loss symptoms
- Feel stressed out from straining to hear what others are saying
- Feel annoyed at other people because you can’t hear or understand them
- Feel embarrassed to meet new people or from misunderstanding what others are saying
- Feel nervous about trying to hear and understand
- Withdraw from social situations that you once enjoyed because of difficulty hearing
Medical hearing loss symptoms
- Have a family history of hearing loss
- Take medications that can harm the hearing system (ototoxic drugs)
- Have diabetes, heart, circulation or thyroid problems
- Have been exposed to very loud sounds over a long period or single exposure to explosive noise