Sound waves enter the outer ears, moving into the ear canals setting the eardrums into mechanical vibration. This mechanical sound energy moves from the eardrum to the middle ear bones (hammer, anvil and stirrup) setting them into motion.
The bones in the middle ear amplify, or increase the sound vibrations and send them to the inner ear or cochlea, a snail-shaped structure filled with fluid. An elastic partition runs from the beginning to the end of the cochlea, splitting it into an upper and lower part. This partition is called the basilar membrane because it serves as the base, or ground floor, on which key hearing structures sit. These microscopic hearing structures are called ‘otocilia’ or hair cells.
Once the vibrations cause the fluid inside the cochlea to ripple, a traveling wave forms along the basilar membrane. Hair cells—sensory cells sitting on top of the basilar membrane -move with the sound wave. Hair cells near the wide end of the snail-shaped cochlea detect higher-pitched sounds, such as an infant crying. Those closer to the center detect lower-pitched sounds, such as a large dog barking.
As the microscopic hair cells move up and down, microscopic hair-like projections (known as stereocilia) that perch on top of the hair cells bump against an overlying structure and bend. Bending causes pore-like channels, which are at the tips of the stereocilia, to open up. When that happens, chemicals rush into the cells, creating an electrical signal and mechanic sound energy is converted to electrical sound energy.
The auditory or hearing nerve carries this electrical sound signal to the brain’s auditory cortex or hearing centre, which processes the sound and assigns meaning to it so that we recognize and understand what we hear.
Types of Hearing Loss
Conductive Hearing Loss: Conductive hearing loss results when there is a problem in sound being transmitted from the outer ear to the inner ear or cochlea. Common reasons for conductive hearing loss include a wax blockage of your ear canal, a hole in your ear drum, problems with three small bones in your ear, or fluid in the space between your ear drum and cochlea. Fortunately with treatment, most cases of conductive hearing loss can be improved.
Some causes of Conductive hearing loss:
- Excessive earwax blocking up the ear canals.
- Hole in the ear drum—A hole in the ear drum (called the tympanic membrane) can be caused by trauma, infection,
- Swimmer’s ear, also called otitis externa, is an infection in the ear canal often related to water exposure, or cotton swab use.
- Foreign object —This is typically a problem in children who may put common objects including beads and beans in their ears but can also be seen in adults most often by accident, such as when a bug gets into the ear.
- Bony growth—These are non-cancerous growths of bone in the ear canal often linked with cold water swimming.
- Middle ear fluid or infection
- Damage to the middle ear bones—This may result from trauma, infection, cholesteatoma (growth), or a retracted ear drum.
- Otosclerosis—This is an inherited disease in which the stapes or stirrup bone in the middle ear fuses with bones around it and fails to vibrate well. It affects slightly less than one percent of the population, occurring in women more often than men.
Sensori-Neural Hearing Loss
SNHL happens when there is damage to tiny hair cells in the cochlear and/or the hearing nerve. Sound energy reaches the cochlea, but damaged hair cells are unable to convert sound waves into neural signals that pass through the hearing nerve to the brain. Noise induced hearing loss and age related hearing loss is the most common causes of sensori-neural hearing loss.
Some causes of Sensor-neural hearing loss:
- Sudden hearing loss—may be caused by a virus; an urgent referral is made for these patients to see an ENT (ear, nose, and throat) specialist, or otolaryngologist, for urgent treatment that could help recover some hearing
- Aging—gradual SNHL that cannot be reversed (most common)
- Noise induced hearing loss—exposure to loud noises (e.g., industrial/machinery or explosion/gunfire close to the ear; can be prevented with proper hearing protection)
- Autoimmune inner ear disease—the body’s immune system attacks the inner ear and causes progressive hearing loss in both ears
- Ménière’s disease—a condition characterized by fluctuating hearing loss, dizziness, ear fullness, or ringing in the ears (called tinnitus)
- Central nervous disease—damage caused by a condition such as multiple sclerosis
- Cochlear otosclerosis—abnormal bone growth in the inner ear
- Benign tumor—called “vestibular schwannoma,” this is a noncancerous tumor on the adjacent balance nerve that compresses the hearing nerve that connects the inner ear to the brain, causing SNHL
Mixed Hearing Loss
Sometimes a conductive hearing loss occurs in combination with a sensorineural hearing loss (SNHL). This results in a disruption to the transmission of sound through the outer and middle ear as well as damage to the hair cells in the inner ear.
Some causes of mixed hearing loss:
*Causes of a conductive hearing loss or SNHL can lead to a mixed hearing loss.
- Genetic factors/family history
- Over-exposure to loud noise
- Certain medications
- Aging process and a history of middle ear infection
- Ear surgery (Cholesteatoma)
- Chronic ear infections
- Head injuries/skull base fracture
- Large Vestibular Aqueduct Syndrome (LVAS) resulting in enlargement of the canal between the inner ear and the cranial cavity.
Jenevieve’s patient centred approach is the real point of differentiation of Midland Hearing Care from other providers. She believes in a patient first and product based intervention later approach.
Midland Hearing Care offers the following services;
You can find out more by clicking on the links below:
Outer Ear Examination (Otoscopy)
Middle Ear Health Check (Tympanometry)
Comprehensive Hearing Assessment (Children age 4+)
Hearing Assessment (Adults)
Tinnitus Assessment (Noise in the Ears)
Microsuction and Ear Irrigation Wax Removal
Specialist Custom Hearing Protection
Hearing Aid Consultation
E-Audiology (Remote Support Now Available)