Hearing and Hearing Loss
What causes hearing loss?
Hearing loss is caused by damage to any of the parts of the ear above or by interruption to the pathway of sound through the auditory system. Congenital or hereditary hearing loss is present at birth or soon after. Acquired hearing loss is developed later in life resulting from injury, trauma or illness. When describing hearing loss, we look at three factors, the type of hearing loss, the degree of hearing loss and the configuration of the hearing loss.
Type of Hearing Loss
Hearing loss can be categorized by which part of the auditory system is damaged. There are three basic types of hearing loss;
Conductive Hearing Loss
Conductive hearing loss results from some disruption of the outer or middle ear system and can occur for a number or reasons including;
- Cerumen (wax) build up in the ear canal
- Foreign body in the ear canal
- Perforation of the tympanic membrane (ear drum)
- Damage to the bones in the middle ear by trauma or disease (otosclerosis).
- Effusion in the middle ear space (glue ear)
- Absence or malformation of the outer ear, ear canal, or middle ear
Conductive hearing loss can sometimes be managed medically and requires review by a GP and/or ENT Specialist.
Sensorineural Hearing Loss
Sensorineural hearing loss results from damage to the inner ear or neural auditory pathways and can occur for a number of reasons including;
- Genetic factors such as a family history of hearing loss or associated syndrome
- Trauma such as head injury or acoustic shock
- Illness such as measles or meningitis
- Ototoxic damage such as certain medications and chemicals
- Prolonged noise exposure
Once damage has occurred to the inner ear or neural auditory pathway, it is usually permanent and cannot be treated medically, with one of the main management options being the use of hearing aids (link to hearing aid page) or assistive listening devices.
Mixed Hearing Loss
Sometimes a conductive hearing loss occurs in combination with a sensorineural hearing loss. In other words, there may be damage in the outer or middle ear and in the inner ear (cochlea) or auditory nerve. When this occurs, the hearing loss is referred to as a mixed hearing loss.
Degrees of hearing loss:
After your hearing assessment your Audiologist will be able to accurately determine the degree of hearing loss. The severity of your hearing loss is measured in terms of its functional impact on your quality of life.
Mild: 21–45 dB
Difficulty hearing soft speech but able to hear conversations in quiet situations.
Moderate: 46–65 dB
Difficulty hearing normal conversational speech especially in the presence of background noise.
Severe: 66–90 dB
Normal conversational speech is inaudible and you will rely heavily on facial cues and lip reading.
Profound: 91 dB +
Normal conversational speech is inaudible and you will rely heavily on facial cues and lip reading. There is a big variation in the success of these clients with hearing aid fitting.
Configuration of Hearing Loss:
The configuration, or shape, of the hearing loss refers to the degree and pattern of hearing loss across the frequency range. For example, a hearing loss that only affects the high frequencies would be described as a high-frequency loss.
Other descriptors associated with the configuration of the hearing loss are;
• Bilateral versus unilateral
Bilateral means hearing loss in both ears. Unilateral means hearing loss in one ear.
• Symmetrical versus asymmetrical
Symmetrical means the hearing loss is the same in each ear. Asymmetrical means the hearing loss is different in each ear.
• Progressive versus sudden hearing loss
Progressive means that hearing loss becomes worse gradually over time. Sudden means hearing loss that happens quickly.
• Fluctuating versus stable hearing loss
Fluctuating means hearing loss that changes over time—sometimes getting better, sometimes getting worse.