Hearing loss: causes, symptoms and next steps

What is hearing loss?

Hearing loss is any reduction in your ability to detect or make sense of sound compared with typical hearing. Sound normally travels a three-stage path: the outer ear funnels air pressure waves down the canal to the eardrum; three small bones in the middle ear amplify that movement mechanically; and the cochlea in the inner ear converts it into nerve signals that the brain interprets as speech, music or a smoke alarm. Damage anywhere along that path causes hearing loss, and where the damage sits determines both the type of loss and whether it can be medically corrected or is better managed with amplification. The World Health Organization estimates more than 1.5 billion people live with some degree of hearing loss worldwide.¹

Two details matter more than most people expect. First, hearing loss is almost never uniform across pitches — most age-related loss takes the high frequencies first, which is exactly where the consonants that distinguish “cat” from “hat” live. That is why people describe speech as mumbled rather than quiet. Second, the brain adapts to gradual loss, so the person losing hearing is usually the last to notice; family members typically raise it first.

What are the three types of hearing loss?

Where the breakdown occurs decides what can be done about it. For a longer treatment of the same three categories, see our guide to types of hearing loss.

How is hearing loss measured?

A hearing test produces an audiogram: the quietest sound, in decibels hearing level (dB HL), that you can reliably detect at each pitch. Your threshold is then described in bands from mild to profound. The number is not a percentage of hearing “lost” — it is the volume a sound has to reach before you notice it, so a 50 dB HL threshold means everything quieter than 50 dB is effectively inaudible to you. The tool below moves a threshold across those bands and shows which everyday sounds fall above and below it.

What are the early signs of hearing loss?

Because loss accumulates over years, the reliable signals are behavioural rather than sensory — the workarounds you have quietly adopted. Tick anything that sounds like your recent experience.

What causes hearing loss?

Most adult hearing loss in Canada comes down to two causes acting over decades — ageing and noise — with a longer tail of medical and structural causes that a clinician needs to rule out. Age-related loss (presbycusis) is a gradual, symmetrical, high-frequency sensorineural loss reflecting cumulative wear on cochlear hair cells. Noise-induced loss is caused by exposure to sound intense enough to damage those same cells, whether in one blast or across years of occupational exposure; risk rises with prolonged exposure above roughly 85 dB(A), and it is the one major cause that is almost entirely preventable.¹

• Ageing (presbycusis) — gradual and usually symmetrical, taking high frequencies first.
• Noise exposure — occupational (trades, agriculture, manufacturing, music) or recreational (firearms, power tools, personal audio at volume).
• Earwax and obstruction — a common, entirely reversible conductive cause, and the first thing worth ruling out.
• Middle-ear infection or fluid — the most frequent cause in children, and a recurring conductive cause in adults.
• Ototoxic medication — certain antibiotics, chemotherapy agents and high-dose salicylates can damage the inner ear; never stop a prescribed drug on your own, but do raise hearing changes with the prescriber.
• Otosclerosis and other structural conditions — abnormal bone growth stiffening the middle ear, often surgically treatable.
• Genetics and family history — influences both congenital loss and susceptibility to age-related loss.
• Head injury, barotrauma or sudden idiopathic loss — abrupt onset, and a reason to seek care immediately rather than wait.

What happens when you get your hearing checked?

A hearing assessment is painless, takes under an hour, and produces a document you keep. A clinician starts with your history and a look inside the ear canal with an otoscope, which is often where an easily removed wax blockage is found. Testing then establishes your thresholds pitch by pitch through headphones, adds a bone-conduction comparison to separate conductive from sensorineural loss, and usually includes a speech-in-noise measure — the closest thing to the situation people actually struggle with. You leave with an audiogram, an explanation of which bands your thresholds fall into, and a recommendation: medical referral, monitoring with a repeat test, or a discussion about hearing aids. Our guide to what to expect at a hearing test walks through the appointment and your audiogram in more detail.

In Canada, a physician-referred diagnostic hearing assessment is covered by public health insurance in every province and territory, though the referral rules and the age groups covered differ — the details for your province are summarised on each provincial clinic page. Funding for the hearing aids themselves is a separate question with a very different answer province to province.

Where to go next

Common questions

This guide is general information about hearing health, not medical advice, and it cannot substitute for an assessment by a qualified hearing professional. If you are concerned about your hearing, book an appointment with an audiologist, hearing instrument practitioner or your physician.