About Hearing Loss
How Sound Travels Through a Healthy Ear
- Sound is transmitted through the air as sound waves from the environment. The sound waves are gathered by the outer ear and sent down the ear canal to the eardrum.
- The sound waves cause the eardrum to vibrate, which sets the three tiny bones in the middle ear into motion.
- The motion of the three bones causes the fluid in the inner ear, or cochlea, to move.
- The movement of the fluid in the inner ear causes the hair cells in the cochlea to bend. The hair cells change the movement into electrical impulses.
- These electrical impulses are transmitted to the hearing (auditory) nerve and up to the brain, where they are interpreted as sound.
Types of Hearing Loss
Hearing loss is described by varying degrees, not percentages. Hearing loss may be mild, moderate, moderately-severe, severe or profound and vary across pitches. It is determined by a simple hearing test as the amount of volume loss you experience compared to the average adult listener with a normal auditory system.
Sensorineural Hearing Loss
Sensorineural (sen-sory-nuhral) hearing loss mainly occurs as a result of an abnormality or damage to the hair cells in the cochlea. This abnormality prevents sound from being transmitted to the brain normally, resulting in a hearing loss.
The hair cells may have been abnormal since birth (congenital), damaged as a result of genetics, infection, drugs, trauma or over-exposure to noise (late-onset or acquired), or damaged as a result of the aging process, a kind of hearing loss known as presbycusis (pres-be-cue-sis).
Sensorineural hearing losses are generally permanent and may stay stable or worsen over time. Routine hearing tests are needed to monitor the hearing loss. Amplification, such as hearing aids is the most common treatment that is recommended.
Individuals with sensorineural hearing loss may report muffled speech, ringing in the ears (tinnitus), difficulty hearing in background noise or that others do not speak clearly.
Conductive Hearing Loss
Conductive hearing loss occurs when there is a problem with the way sound is conducted to the inner ear or cochlea. The problem may lie in the outer ear (pinna or ear canal), eardrum (tympanic membrane), or the middle ear (ossicles and Eustachian tube). The inner ear remains unaffected in this type of hearing loss.
Some causes of conductive hearing loss can include outer or middle ear infections, complete earwax blockage, deterioration of the middle ear bones (ossicles), fixation of the ossicles (otosclerosis), a hole in the tympanic membrane, or absence of the outer ear or middle ear structures.
Conductive hearing losses may be temporary or permanent, depending on the source of the problem. Medical management can correct some cases of conductive hearing loss, while amplification may also be a recommended treatment option in more long-standing or permanent cases.
Individuals with conductive hearing loss may report that sounds are muffled or quiet. Generally, when sounds are made louder, these individuals can hear well again.
Mixed Hearing Loss
Mixed hearing loss occurs when a person has an existing sensorineural hearing loss in combination with a conductive hearing loss. This means there is a problem in the inner ear as well as in the outer or middle ear. The conductive hearing loss may be temporary or permanent, depending on the source of the problem.
Mixed hearing loss can sometimes be treated with medical management, and hearing aids are a common treatment recommendation.