Hearing loss explained

Hearing loss

What hearing loss is, in plain terms

Hearing loss means sound is not reaching the brain as completely as it once did. It is common, it has many different causes, and it is not one single condition. This guide explains how hearing works, what can go wrong at each point, and what the words you will hear actually mean.

How hearing works

Hearing happens in stages, and each stage hands over to the next.

The outer ear collects sound and funnels it down the ear canal to the eardrum. The eardrum vibrates, and passes that vibration to three small bones in the middle ear. Those bones pass it into the cochlea, a fluid-filled spiral in the inner ear lined with thousands of tiny hair cells. The cochlea turns the vibration into nerve signals, and the auditory nerve carries them to the brain, which does the work of making them into meaning.

That last part matters more than people expect. Hearing is not only about the ear — it is about what the brain receives and what it can make sense of. It is why two people with similar test results can find conversation very different in practice.

Cross-section diagram of the human ear showing the outer ear and ear canal, the eardrum and three middle ear bones, and the cochlea and auditory nerve in the inner ear

Sound enters the outer ear, vibrates the eardrum and three small bones, and is converted to nerve signals in the cochlea. Damage at different points causes different types of hearing loss.

The types of hearing loss

Hearing loss is usually grouped by where in that chain the problem sits, not by how severe it is.

Conductive — something in the outer or middle ear is stopping sound getting through, such as wax or fluid.
Sensorineural — the inner ear or the hearing nerve is not converting or carrying sound as it should.
Mixed — both of the above at the same time.

Some health authorities list a fourth category. The US Centers for Disease Control and Prevention, for example, separates out auditory neuropathy spectrum disorder, where sound reaches the inner ear normally but is not passed on to the brain in an organised way.

What causes hearing loss

Health New Zealand describes ageing as the most common cause of gradual hearing loss in adults. It usually affects both ears, and typically affects high-pitched sounds first — which is why speech can start to sound mumbled before it sounds quiet.

A build-up of wax in the ear canal
Fluid behind the eardrum
Exposure to loud sound over a long period
Conditions affecting the outer, middle or inner ear, or the hearing nerve

Sometimes no cause is found. More on causes.

Some causes are reversible

This is worth knowing before you assume anything is permanent. Wax blocking the canal and fluid behind the eardrum are both things that can change — and both are conductive, meaning the inner ear may be working perfectly well underneath.

That is one of the reasons a hearing test starts with someone looking in your ear. A blockage found in the first two minutes changes what the rest of the appointment is for.

What people usually notice first

If your hearing drops suddenly, or gets noticeably worse over a short time, contact a healthcare provider urgently rather than waiting for a routine appointment. Health New Zealand advises an urgent ear examination in that situation.

Gradual hearing loss is genuinely hard to notice in yourself, because there is no moment when it changes. Health New Zealand lists these among the common signs:

Mishearing what people say
Feeling that people are mumbling
Asking people to repeat themselves
Wanting the television or radio louder than others in the room do
Finding conversation hard when there is background noise

None of these on their own means you have hearing loss — they are simply the things people tend to notice. A hearing test is what answers the question. More on the signs.

How hearing loss is measured

Hearing is measured across a range of pitches, in each ear separately, and the results are plotted on a chart called an audiogram. The chart shows the quietest sound you responded to at each pitch.

Results are then described with words like mild, moderate, severe and profound. Those words correspond to decibel ranges — but the exact ranges differ between classifications, which is why two reports can label the same hearing differently. We explain the chart and the labels here.

What can be done

It depends entirely on the cause and on what the test shows. A conductive problem such as wax or fluid is dealt with differently from a permanent inner-ear change.

Where hearing loss is permanent, hearing aids are one of the options discussed, and cochlear implants are considered for some people with severe or profound loss that hearing aids do not adequately address. There are also practical communication strategies that make a real difference regardless of what device is or is not involved.

We explain devices separately and without recommending anything: hearing aids explained. For communication strategies, the New Zealand Audiological Society publishes a practical guide.

Common questions about hearing loss

Is hearing loss a normal part of getting older?

Age-related change is common — Health New Zealand describes ageing as the most common cause of gradual hearing loss in adults. Common is not the same as unimportant, and it is not a reason to avoid having it measured. Being able to describe what is happening is useful whatever you decide to do next.

Can hearing loss be reversed?

Some causes can change and some cannot. Wax blocking the ear canal and fluid behind the eardrum are both things that can be addressed. Changes in the inner ear are generally permanent. Which one you are dealing with is exactly what a hearing test is for.

Why is it harder to follow conversation in a noisy room?

Age-related change usually affects high-pitched sounds first, and much of the detail that separates one consonant from another sits in those higher pitches. In a quiet room there is enough context to fill the gaps. In a cafe, with several voices and background noise competing, there is not.

Does hearing loss always affect both ears?

Not always. Age-related change usually affects both ears fairly similarly, but hearing loss can affect one ear only, or affect the two ears differently. This is one of the reasons each ear is tested separately.

What does it mean if only some pitches are affected?

It is very common. Hearing is not a single volume setting — you can hear some pitches normally and others poorly, which is why an audiogram plots a curve across pitches rather than giving one number.

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This page is general information. A hearing test measures your own hearing and is the only way to know where yours sits.

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Sources

This page is general information, not a diagnosis or individual advice.