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Types and Causes of Hearing Loss
Some hearing loss is permanent and some is fixable in a single visit. Which one you have depends entirely on where in the ear the problem sits, and that is the first thing a hearing test establishes.
IN SHORT
There are three types of hearing loss. Sensorineural loss involves the inner ear or hearing nerve and is permanent, usually caused by aging or noise. Conductive loss involves the outer or middle ear and is often reversible, commonly caused by wax, fluid or infection. Mixed loss is both together. A hearing test distinguishes them, which matters because the treatments are completely different.
The three types
Sound has to travel through the outer ear, be transmitted by the middle ear, and be converted to nerve signals by the inner ear. A problem at any stage causes hearing loss, but the type, the treatment and the outlook are entirely different.
Most common in adults
Sensorineural
Where the problem is: The inner ear (cochlea) or the hearing nerve
The hair cells that convert sound into nerve signals are damaged. They do not regenerate, so this is permanent. It usually affects high frequencies first, which is why speech becomes unclear rather than merely quiet.
Common causes
- Aging, known as presbycusis
- Noise exposure over time
- Genetics and family history
- Ototoxic medication
- Sudden idiopathic loss
- Head injury
Treatment: Permanent. Hearing aids for most people, or a cochlear implant for profound loss.
Often fixable
Conductive
Where the problem is: The outer or middle ear
Sound is blocked or poorly transmitted before it reaches a working inner ear. The inner ear itself is fine, which is why treating the blockage frequently restores hearing completely.
Common causes
- Impacted earwax
- Fluid behind the eardrum
- Middle ear infection
- Perforated eardrum
- Otosclerosis, a stiffening of the tiny bones
- Eustachian tube dysfunction
Treatment: Often reversible with medical or surgical treatment. See a physician before considering hearing aids.
Both at once
Mixed
Where the problem is: Inner ear and outer or middle ear together
Sensorineural loss with a conductive problem layered on top. Common in someone with age-related loss who also has wax impaction or middle ear fluid.
Common causes
- Any sensorineural cause, plus
- wax, fluid, infection or perforation
- Chronic ear disease
- Previous ear surgery
Treatment: Treat the conductive part first, then amplify whatever loss remains underneath.
Degrees of hearing loss
Type tells you where the problem is. Degree tells you how much. Your audiogram reports thresholds in decibels hearing level, and this is one commonly used clinical classification of what those numbers mean.
| Degree | Threshold | What it means day to day |
|---|---|---|
| Normal | 25 dB HL or better | Conversation is comfortable, including in mild background noise |
| Mild | 26 to 40 dB | Quiet speech and soft consonants are missed. Restaurants become work |
| Moderate | 41 to 55 dB | Normal conversation is difficult without help. Television needs turning up |
| Moderately severe | 56 to 70 dB | Loud speech is needed. Group conversation is largely inaccessible unaided |
| Severe | 71 to 90 dB | Shouting close to the ear may be heard. Hearing aids are essential |
| Profound | 91 dB or more | Speech is not heard through air conduction. Cochlear implant assessment is appropriate |
Degree is not the whole story
Two people with identical mild loss can have very different experiences, because how well you resolve speech at a comfortable volume is measured separately. That is your word recognition score, and it predicts how much hearing aids will help better than the audiogram alone does. It is why we test both.
What causes hearing loss
Aging. Presbycusis is the most common cause in adults. Hair cells in the cochlea wear out over decades, starting with the ones that respond to high frequencies, which is why speech clarity goes before speech volume. It is gradual, symmetrical and painless.
Noise. The one entirely preventable cause. It can be a lifetime of machinery or a single gunshot, and it is cumulative and permanent. Noise damage has a recognizable signature on an audiogram, described below.
Genetics. Family history matters, both for age-related loss and for rarer inherited conditions. If your parents needed hearing aids in their sixties, get a baseline in your fifties.
Medical conditions. Middle ear disease, otosclerosis, Meniere’s disease, autoimmune conditions, and in rare cases a benign tumour on the hearing nerve. Diabetes and cardiovascular disease are both associated with higher rates of hearing loss.
Medication. Some drugs are ototoxic, meaning they can damage hearing. This is worth knowing about rather than worrying about, and is covered below.
Infection and injury. Meningitis, mumps, measles, severe ear infections, head trauma and barotrauma from pressure changes.
Sudden idiopathic loss. Hearing that drops over hours or a day with no identifiable cause. This is a medical emergency, not a hearing aid appointment.
Medications that can affect hearing
Several classes of medication are known to be ototoxic. Most are prescribed because the condition being treated is more serious than the risk, so this is information for a conversation with your prescriber rather than a reason for alarm.
- Aminoglycoside antibiotics such as gentamicin and tobramycin. Effects are usually permanent
- Platinum chemotherapy such as cisplatin and carboplatin. Often permanent, and baseline testing before treatment is standard practice
- Loop diuretics such as furosemide, particularly at high doses. Usually temporary
- High-dose aspirin and some NSAIDs. Usually temporary and reversible when the dose is reduced
- Quinine and related compounds. Usually temporary
Never stop a prescribed medication on the strength of a web page
Including this one. If you are taking something on this list and have noticed a change in your hearing or new ringing, tell the doctor who prescribed it. They can weigh the options in a way we cannot, and in many cases monitoring rather than stopping is the right answer. If you are about to start platinum chemotherapy, ask about a baseline hearing test first.
Noise damage leaves a fingerprint
One of the more interesting things about an audiogram is that the shape of the loss often reveals the cause.
Age-related loss typically slopes gently downward as frequency rises, worst at the top. Noise damage does something different: it produces a characteristic notch around 3,000 to 6,000 hertz, with hearing recovering slightly above it. When we see that notch in someone who spent thirty years around machinery, the audiogram is confirming the history.
Conductive loss tends to be flatter across frequencies and shows a gap between air conduction and bone conduction thresholds, which is the specific measurement that tells us the inner ear is working and something before it is not.
What can be reversed, and what cannot
| Cause | Reversible? | What happens |
|---|---|---|
| Impacted earwax | Yes | Removed in one visit, hearing returns immediately |
| Fluid behind the eardrum | Usually | Medical treatment, sometimes drainage. See a physician |
| Middle ear infection | Usually | Medical treatment. Hearing generally recovers fully |
| Otosclerosis | Often | Surgery or hearing aids, depending on the case |
| Perforated eardrum | Often | Many heal alone, some need surgical repair |
| Sudden sensorineural loss | Sometimes, if treated fast | Steroids within days give the best chance. Urgent |
| Age-related loss | No | Permanent. Hearing aids are the treatment |
| Noise-induced loss | No | Permanent. Protection prevents any further damage |
This table is the reason we look in your ear before we talk about devices. Selling hearing aids to someone whose problem is a plug of wax would be both useless and indefensible.
Common questions
What are the three types of hearing loss?
Sensorineural, involving the inner ear or hearing nerve and permanent. Conductive, involving the outer or middle ear and often reversible. And mixed, which is both together.
What is the most common type of hearing loss?
Sensorineural, and within that age-related loss known as presbycusis. It accounts for the large majority of adult hearing loss.
Can hearing loss be reversed?
Conductive loss from wax, fluid or infection frequently can be. Sensorineural loss from aging or noise cannot, because inner ear hair cells do not regenerate. This is why identifying the type first matters so much.
What is presbycusis?
The medical term for age-related hearing loss. Hair cells in the cochlea wear out over decades, starting with those responding to high frequencies, which is why clarity fades before volume does.
How do I know which type I have?
A hearing test distinguishes them by comparing air conduction and bone conduction thresholds. It takes about 45 minutes.
Can medication cause hearing loss?
Yes. Aminoglycoside antibiotics and platinum chemotherapy agents can cause permanent damage, and loop diuretics, high-dose aspirin and quinine can cause temporary changes. Never stop a prescribed medication without speaking to your prescriber.
Is hearing loss hereditary?
Family history is a genuine risk factor for both age-related and rarer inherited hearing loss. If your parents needed hearing aids in their sixties, it is worth getting a baseline in your fifties.
Can hearing loss happen in only one ear?
Yes, and one-sided loss always warrants medical evaluation rather than going straight to a hearing aid, because the causes that produce it include some that need treatment.
Find out which type you have
A hearing test distinguishes the types and tells you whether your loss is the fixable kind. About 45 minutes, no referral needed.