What are the Different Types of Hearing Loss – Explained by an Audiologist.

senior man with eyeglasses holding his ear to hear better

Tens of millions in the United States suffer from some form of hearing impairment, according to the Hearing Loss Association of America. Hearing loss describes a wide range of experiences that vary greatly depending on the root cause.

This guide will explore the different types of hearing loss and how to determine which one you have.  

Types Of Hearing Loss

Hearing loss is categorized according to multiple dimensions, including:

  • Location: Hearing impairment is classified based on where the disorder occurs. Conductive hearing loss can be traced to the outer ear or the middle ear, while sensorineural hearing loss is a problem in the inner ear. Mixed hearing loss is a combination, and auditory spectrum disorders are rooted in the brain.
  • Intensity: Hearing symptoms are classified as mild, moderate, severe, and profound.
  • Laterality: Symptoms are described as unilateral or bilateral depending on if they occur in one ear or both.
  • Symmetry: If hearing loss is more pronounced in one ear, it is asymmetrical and symmetrical if both are the same.
  • Onset: Some hearing loss is gradual and progressive. Other forms appear suddenly. Hearing loss can be present from birth or develop later in life.
  • Consistency: Symptoms may be stable or fluctuate.  
  • Duration: Some types of hearing loss are temporary and reversible through medical treatment or surgery. However, many conditions cause permanent hearing loss.

Correctly classifying hearing symptoms is crucial to determining the correct cause and treatment.

Where Does the Hearing Loss Occur?

There are four types of hearing loss based on the place in the body where the hearing loss occurs.

Conductive Hearing Loss

The conductive component of the ear comprises the parts of the outer or middle ear that carry the sound to your inner ear, including:

  • External ear
  • Ear canal
  • Middle-ear bones or ossicles
  • Tympanic membrane or eardrum

Conductive hearing loss occurs when a problem in the middle or outer ear interferes with your ear’s ability to transmit sound.

Possible causes of conductive hearing loss include:

  • Ruptured eardrum
  • Impacted earwax
  • A foreign body blocking the ear canal
  • Buildup of fluid in the eustachian tube or the middle ear
  • Ear infection

Sensorineural Hearing Loss

Sensorineural hearing loss is caused by damage to inner ear structures, such as:

  • Sensory hair cells
  • Cochlea
  • The eighth cranial nerve, also known as the hearing nerve or auditory nerve
  • Semi-circular canals

Causes of sensorineural hearing loss include:

  • Exposure to loud noise
  • Autoimmune disease
  • Head trauma
  • Congenital inner ear defects

Mixed Hearing Loss

Mixed hearing loss combines elements of conductive and sensorineural hearing loss. Typically, it occurs when a person with one type of chronic hearing impairment develops an acute form of the other type due to an illness or health condition.

For example, a person might use hearing aids to treat their age-related hearing loss, and daily use of hearing aids leads to an earwax impaction, causing conductive hearing loss.

Alternatively, a person might have chronic conductive hearing loss from abnormal growths in their middle ear bones and develop sudden sensorineural hearing loss from a viral infection.

Causes of mixed hearing loss include:

  • Toxic reaction to a medication
  • Noise exposure
  • Genetic conditions
  • Ear trauma
  • Tumors.

Auditory Neuropathy Spectrum Disorder

In auditory neuropathy spectrum disorder, there are no problems with the inner ear. The outer ear and middle ear are both normal, as well. The brain can’t process messages transmitted via the auditory nerve.

People with the condition have difficulty understanding speech, indicating a brainstem problem.

In Auditory Neuropathy Spectrum Disorder, the brain does not register messages from the ear.

Severity

Audiologists use pure-tone audiometry and other hearing tests to quantify hearing impairment using a metric called hearing loss in decibels (dB HL). They will then classify your symptoms according to intensity.

Mild

A 25 to 40 dB HL score on a hearing test is considered mild hearing impairment in adults. The threshold is 15 dB HL for children. People with mild hearing symptoms can manage conversations just fine, but they may misunderstand a few words or misinterpret consonant sounds, especially in the presence of background noise.

Moderate

A score of 41 to 55 dB HL is classified as moderate. Those with a moderate hearing impairment might have trouble conversing on the phone or in person. You start to lose the ability to distinguish both consonant and vowel sounds at this level. People in this category could benefit from a hearing aid, but they might be able to manage without them.

Severe

A score between 56 to 70 dB HL signifies severe hearing loss. These folks can only hear loud sounds, and normal conversation is challenging. They can only hear if someone speaks loudly or shouts. At this point, hearing aids become essential.

Profound

Profound hearing loss is a score of 71 dB HL or higher. These people can only hear sounds that are incredibly loud but no speech. Once hearing loss has progressed to this stage, hearing aids might not help. The person may need to learn lip-reading or get a cochlear implant surgically implanted in their inner ear.  

Laterality and Symmetry

During a hearing test, an audiologist will test each ear separately to determine whether there is impairment in one or both ears and if the severity is the same across ears. This crucial diagnostic information helps pinpoint the cause.

Unilateral

Hearing impairment is unilateral if it only affects one ear. Some causes include:

  • Meniere’s disease
  • Cerebellopontine angle tumors
  • Outer, middle or inner ear abnormality
  • Head trauma
  • Earwax impaction

Bilateral

When both ears have hearing problems, the condition is considered bilateral. Causes of bilateral hearing loss include:

  • Age-related hearing loss
  • Long-term exposure to loud noises
  • Exposure to substances and medications that are harmful to the ear

Configuration

Hearing impairment is also categorized according to whether it’s more pronounced in one ear or the other. It’s symmetrical if both ears have the same degree of loss.

If one of them has a greater impairment, it’s considered asymmetrical. Age-related hearing loss is an example of symmetrical hearing impairment.

Onset and Course

Hearing loss is classified based on the speed at which it develops as well as the point in a person’s life when it appears. It might also be labeled according to the variability of symptoms.

Time of Onset

The onset of hearing impairment is divided into three categories based on when and how a person develops symptoms:

  • Congenital: You have symptoms from birth due to a genetic disorder or a defect caused by your environment.
  • Acquired: You develop a hearing impairment later in life due to exposure to noise, infection or age-related degradation.
  • Delayed onset: Some genetic conditions do not produce hearing symptoms at birth, but the symptoms start to present a few years later, before or after a child learns to speak.

Speed of Onset

Hearing loss can develop instantly or slowly over time.

Progressive hearing loss gradually gets worse. One’s hearing degrades incrementally so it’s often not noticeable until it starts interfering with a person’s daily life. Causes of progressive hearing loss include:

  • Age
  • Noise exposure

Progressive hearing loss occurs due to aging and prolonged noise exposure.

Sudden hearing loss appears almost instantly minutes or hours after being exposed to the cause of the condition. Causes include:

  • Anti-cancer medications
  • Bacterial and viral infections
  • Head or ear trauma
  • Sudden changes in air pressure

Many forms of temporary hearing loss, such as earwax blockages, occur suddenly, but they can be treated medically and reversed.

Course

Hearing health professionals classify hearing loss based on its consistency. If the course of the hearing loss remains the same over time, it’s called stable hearing loss.

There is also fluctuating hearing loss, which waxes and wanes over time. Fluctuating hearing loss is seen in:

  • Auditory neuropathy
  • Perilymphatic fistulas
  • Enlarged vestibular aqueduct syndrome.

What Type of Hearing Loss Do You Have?

You may probably be wondering what type of hearing loss you have. Here are a few questions to ask yourself:

  • When did the hearing loss start?
  • Did it happen slowly or suddenly?
  • Was there an inciting event?
  • Did you have it from birth?
  • Is it one-sided? If yes, which one?
  • Is it getting worse?
  • Are you having trouble understanding conversations?
  • Is it similar on both sides?
  • Do you take over-the-counter pain medicines or other medications?
  • Do you work around loud noises or listen to loud music?
  • Are you exposed to toxic fumes, solvents, and chemicals?

Answering these questions should give you some good clues, but you need to see a doctor to get a definitive diagnosis. Having this information handy will help.  

If the cause of your hearing loss can’t be treated with something simple like antibiotics or ear drops, your doctor will send you to an audiologist for a hearing test. If necessary, a hearing specialist will refer you for a hearing aid fitting or cochlear implants.  

Conclusion

Discovering the type of hearing loss you have is the first step to getting help. With a proper diagnosis, hearing professionals can identify and treat the underlying causes or recommend helpful technologies and strategies to make everyday life easier for you.

Citations

1. Reiss M, Reiss G. Zur Differentialdiagnose der einseitigen Schwerhörigkeit [Differential diagnosis of unilateral hearing loss]. Praxis (Bern 1994). 2000;89(6):241-247.

2. Zahnert T. The differential diagnosis of hearing loss. Dtsch Arztebl Int. 2011;108(25):433-444. doi:10.3238/arztebl.2011.0433

3. Shearer AE, Hildebrand MS, Smith RJH. Hereditary Hearing Loss and Deafness Overview. 1999 Feb 14 [Updated 2017 Jul 27]. In: Adam MP, Ardinger HH, Pagon RA, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2021. Figure 2. [Causes of prelingual hearing loss in developed countries]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK1434/figure/deafness-overview.F2/