How hearing works.
The anatomy of the hearing system can be divided into four components for our convenience in remembering the parts and associating these parts with their function.
These divisions are the:
1. outer ear
2. middle ear
3. inner ear
4. central auditory pathways
1. 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.
2. Middle ear
The eardrum (tympanic membrane) is a membrane at the inner end of the ear canal. On that 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.
3. The inner ear
The inner ear has two divisions: one for hearing, the other for balance. The hearing division consists of the cochlea and the nerve of hearing. The cochlea is snail-shaped, bony structure that contains the sensory organ for hearing called the organ of 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.
4. 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.
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!
Does this sound familiar?
What is the nature of your hearing problem? Do any of these symptoms or situations sound familiar?
- Difficulty understanding or comprehending what is being said.
- Turning up the volume on TV to ever-higher levels.
- Discomfort in meetings or social settings where many people are speaking.
- Being told by a loved one that you’re not listening.
- A feeling that you’re missing important parts of conversations.
- A tendency to avoid social situations that you used to like.
- Concern for the future of your career.
If you are experiencing any of these symptoms, you can likely benefit from a thorough hearing evaluation. The ADVENT Hearing Center begins by listening to you, understanding your hearing problem and how it is affecting your relationships, work, and enjoyment of life. We also discuss your goals for treatment and what is most important for you to hear.