Hearing Loss Overview

Each person’s experience of hearing loss is different, but certain commonalities can help us understand our experiences of hearing impairment.


In the simplest terms, hearing loss is a limitation on a person’s ability to connect sensory stimuli—sounds—with the cognitive perception of that sound. Although the same sound waves are all around us, we have trouble turning those patterns of air pressure into recognizable units understood in the mind.

General Types of Hearing Loss

The three major types of hearing loss are conductive hearing loss, sensorineural hearing loss, and mixed hearing loss. Conductive hearing loss is caused by a problem with the outer or middle ear, where sound waves are conducted toward the inner ear. Sensorineural hearing loss is caused by a problem in the inner ear or auditory neural pathway. Mixed hearing loss is, of course, a combination of the two kinds of hearing loss.

Specific Types of Hearing Loss


These general types of hearing loss are categorized according to the location of the damage, whether it is in the outer, middle, or inner ear. However several other specific categorizations are used to designate the type of hearing loss experienced. In the first place, different frequencies of sound, or pitches ranging from low to high, may be more difficult to hear. Higher pitches tend to the be first to go with the normal deterioration of hearing that we experience through life, but some types of hearing loss cause a level distribution at all frequencies.

An audiogram is a visual depiction of the configuration of hearing loss across these frequencies from low to high. Some people with repeated exposure to a particular frequency at a high volume, such as in a factory workplace, may experience targeted hearing loss at that frequency range. Some people do not have even hearing loss from one ear to the other. Bilateral hearing loss includes both ears, while unilateral hearing loss occurs only in one ear. Even within bilateral hearing loss, the type may not be evenly distributed.

It is possible to have asymmetrical hearing loss between the two ears. Finally, the dimension of time is important to consider. Some have stable hearing loss that does not change much or at all over time. For instance, those born with hearing loss may continue at a given level of impairment throughout their lives. Others may have a sudden incident that causes a stable level of impairment from that point onward. On the other hand, many people have progressive hearing loss that deteriorates with time. Constant exposure to loud sound and aging are two ways to think about progressive hearing loss over the lifespan.

Causes of Hearing Loss


What may be more useful to us is to understand the variety of mechanisms that cause hearing loss. Some people are born with hearing impairment or total deafness. Others encounter a severe life event, such as illness or injury, causing sudden hearing loss. Others experience progressive hearing loss through continuous exposure to harmful sounds or substances. Some specific causes of hearing loss include:

A buildup of earwax, or cerumen, in the ear canal

Fluid in the ear canal due to a cold or allergies

Infections such as Otitis Media or Otitis Externa

A hole in the eardrum

Hereditary hearing loss

Aging

A foreign object stuck in the outer or middle ear

Exposure to loud noises

Exposure to ototoxic chemicals or drugs (ones that are harmful to hearing)

Tumors on the hearing nerve

Degrees of Hearing Loss


Hearing loss ranges from slight to profound. These categorizations are based on the volume level necessary to be able to perceive a sound. For instance, some people can hear sounds up to 15 decibels, and this is considered normal hearing. However, those who cannot hear a particular pitch, or frequency, of sound below 16 decibels of volume are thought to have some hearing loss. The following table explains the categories of hearing loss associated with decibels necessary for them to be heard:


Degree of hearing loss Hearing loss range (in decibels)
Normal -10 to 15
Slight 16 to 25
Mild 26 to 40
Moderate 41 to 55
Moderately Severe 56 to 70
Severe 71 to 90
Profound 91+