How hearing works

Our ability to hear and understand sounds around us depends on the inner ear (the cochlea) converting sounds to electrical signals that are interpreted by the brain. 

Sounds waves are channeled into the ear and down the ear canal, where the eardrum and three tiny ear bones convert those sound waves into a form of mechanical energy that is transmitted to the cochlea in the inner ear. 

The cochlea of the inner ear encodes this mechanical energy into an electrical signal that is transmitted via nerve fibers to the brain. This process happens because the cochlea contains highly specialized hair-like cells that allow complicated sound vibrations to be converted with perfect fidelity into electrical signals that get sent to the brain. 

Multiple parts of the brain are involved in decoding the signal from the ear, and this primarily takes place in portions of the brain’s temporal lobe (the part of the brain on either side of your head that sits above the ears). 

To put it another way, your ear encodes sounds into an electrical signal, and your brain then decodes the signal into actual meaning.

Watch Hearing 101: How Hearing Works

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Why hearing changes 

Everyone’s hearing changes over time. This is because the structures in the inner ear that process sound break down from the effects of aging, noise exposure, and other causes and no longer convert sound precisely into neural signals for the brain.  Unlike other cells of the body, when the highly specialized hair-like cells and other components of the inner ear become damaged over time, they can’t regenerate. When this happens, the inner ear can still transmit a signal to the brain, but it will no longer be clear. Spoken words may often sound garbled or like the speaker is mumbling. 

This gradual loss of hearing can impact our lives and isolate us from the people and world around us. The Cochlear Center studies the impact that hearing loss in older adults has on public health and develops and implements public health strategies and solutions for hearing loss.

Watch Hearing 101: What Happens to Hearing As We Get Older

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Why hearing matters

Hearing loss isn’t just an inconvenience that comes with getting older—it’s a critical public health issue that is now the focus of national and international initiatives coming from the National Academies, the White House, and the World Health Organization. This global attention to hearing loss is the result of our growing understanding of the impact that hearing loss can have on the risk of dementia, cognitive decline, greater healthcare costs, and other adverse outcomes. Strategies to treat hearing loss are vastly underutilized around the world, and could help reduce the risk of these outcomes and optimize the health of older adults.

An older, bespectacled white man smiles in profile, showing his hearing aid

The world’s population is aging. 

The World Health Organization estimates that by 2050, the number of people 60 years and older will double to 2.1 billion, while the number of people 80 years or older is expected to triple to 426 million.  (WHO Fact Sheet, Ageing and Health, Oct 2022)

FAQ About Hearing and Hearing Loss

Sound is funneled down the ear canal and converted into a form of mechanical energy that is transmitted to the inner ear. There, the highly specialized hair-like cells of the cochlea encode this mechanical energy into an electrical signal that is transmitted via nerve fibers to the brain. 

The brain then decodes the signal from the ear into meaning. 

As we age, structures in the inner ear needed for sound processing begin to break down from the effects of aging, noise exposure, and other causes. Our ability to hear clearly is reduced because sounds in the inner ear are no longer being converted precisely into neural signals for the brain. Spoken words may sound garbled or as if the speaker is mumbling.

No. Once the highly specialized hair-like cells and other components of the inner ear become damaged over time, they can’t regenerate.

Our ability to hear and understand others is what connects us to the world. Researchers and physicians now know that age-related hearing loss can impact mental, emotional, physical, and cognitive health.

Hearing loss can lead to social isolation and loneliness. Individuals who are lonely are much more likely to develop a range of poor health outcomes, including depression, dementia, and even earlier death.

Hearing loss may also be linked to a decline of physical function. Hearing loss can also increase the risk of losing balance or having a fall.

Hearing loss is the biggest potentially treatable risk factor for dementia, accounting for more cases of dementia in the world than other risk factors such as high blood pressure, smoking, or low education.


There are three main mechanisms that may explain why hearing loss may be associated with dementia.

First, with hearing loss, speech, and sound are garbled by the time they reach the brain, which requires the brain to use extra effort for processing and deciphering this speech and sound. The brain then has fewer resources for activities like memory and executive function, which can eventually lead to cognitive impairment.

Second, with hearing loss, the parts of the brain that are stimulated by speech and sound are now under-stimulated, which can lead to atrophy and changes in brain structure and function.

Third, hearing loss can make communicating with others more difficult, which can lead to social isolation, another risk factor for dementia.

This is a question that Cochlear Center researchers and collaborators are examining in the ACHIEVE study. Learn more in our fact sheet on Hearing Loss and Dementia.

Changes to our hearing happen very gradually over time, so many individuals may not even be aware of hearing problems if they haven’t had a hearing test. Getting a hearing test every 1-2 years is reasonable and something that a person could get by seeing an audiologist. Depending on the insurance type, the individual may or may not need a physician referral to see an audiologist. 

Alternatively, individuals can also self-test their hearing with a compatible smartphone. The website takes people through how to do this. The website is part of the Know Your Hearing Number public health campaign created by the Cochlear Center to introduce an easy way to understand and talk about hearing.  Knowing their Hearing Number and tracking it over time can help people know when their hearing changes and guide them toward strategies that can help improve their hearing and communication.

Begin by getting a professional hearing test or using a smartphone-based hearing test to understand hearing ability. 

Simple communication strategies can improve sound quality or give visual or contextual information to help hearing: Get close and speak with people face-to-face. Avoid background noise by turning down ambient sounds. Minimize reverberation - soft surfaces can help muffle noisy echoes.  

Everyday technologies like VOIP (voice over internet protocol) services, such as Skype, Google Voice, WhatsApp, and FaceTime, offer better sound quality than regular phone lines, which can improve phone communication. Smartphones offer customization options that let people adjust the sound to their needs. 

Addressing hearing loss with hearing aids and other strategies comes with virtually no health risks and could only have positive upsides for the ability to communicate and engage with others and possibly even benefits for cognitive health.  Hearing care professionals such as audiologists and hearing aid specialists can dispense prescription hearing aids.  Over-the-counter hearing aids offer a new accessible, and affordable category of hearing aids and do not require a professional consultation to purchase