How We Hear.
We may be biased but this is the coolest of the five senses. It is the first sense to develop in the womb, too, so it is very robust complex.
What a toddler points to when you ask, “where is your ear?”. The outer ear is actually called the pinna or auricle. It captures sound waves and acts like a funnel. The sound pressure waves move through the ear canals to the middle ear.
The middle ears start with the tympanic membrane (eardrum). Behind this dynamic membrane are the three smallest bones in your body- the maleus (hammer) incus (anvil), and stapes (stirrup). The sound waves vibrate the tympanic membrane and that energy is transferred through the three bones in a lever action where it is enhanced and sent to the inner ear.
This houses the cochlear (organ of hearing) and the vestibular system (balance). The inner ear is encased in bone and filled with a fluid called endolymph. There are thousands of microscopic hair cells (not really “hair”) that sit in this fluid within the cochlea. The hair cells detect the movement of the fluid from the movement of the bones in the middle ear and fire to the auditory nerve.
The auditory nerve of each ear is connected to mutiple parts of your brain, most importantly the auditory cortex. This is truly how we ear because the brain is what interprets the input from your ears.
A lot has to go right for the ears to work as they were designed to. “Hearing loss” is the widely accepted term for when one of these systems is not working as expected causing difficulty.
Sensorineural Hearing Loss
90-95% of hearing loss falls in this category. Something is affecting the inner ear’s ability to do it’s nature job. That may be from damage to the hair cells, absence of the hair cells, changes to the nerve endings, or changes to how the inner ear and the brain communicates. This is typically permanent and may be progressive depending on the cause and intervention. Medical intervention is typically unnecessary. Causes: Aging (presbycusis), genetics, excessive noise exposure, impulse noise (explosion, etc.), certain strong medications, illnesses, trauma, repeated loud exposure to music, power tools, machinery, and much more.
Conductive Hearing Loss
Something is affecting the outer or middle ear’s ability to perform their jobs. This can cause a temporary or permanent hearing loss. When identified, medical intervention may be recommended. Causes: impacted wax, ear infections, congenital or acquired malformations, otosclerosis, etc.
Mixed Hearing Loss
A combination of both sensorineural and conductive hearing losses.