Listen up: Want to keep your ears healthy and prevent hearing loss? First it's important to understand what these complex organs really are.

How hearing works
Human ears are sound-collecting machines designed to gather noise (through the ear canal) and convert it into vibrations (in the eardrum) that are sent via the tiny bones of the middle ear (hammer, anvil, stirrup) to the coiled cochlea of the inner ear. But this is only half of what it takes for us to hear the world. The rest of the work is done in the brain. 

"In the past 10 years, there has been a recognition that we don't hear just with the ears. We hear with the brain," says Barbara Cone, a professor of speech, language, and hearing sciences at the University of Arizona, in Tucson.

The brain's job is not only to receive sound but also to reduce background noise and home in on the things we most want to hear -- quite often, other people's voices. Human ears are particularly attuned to the frequency range used in conversation. And our large brains and long life spans enable us to use our experiences to differentiate an extraordinary variety of sounds. 

For example, says Jan Schnupp, a research leader at the University of Oxford Auditory Neuroscience Group, in England, "I can instantly recognize and distinguish the sound of an elephant from that of an owl from that of a shopping trolley rattling over a bumpy pavement."

Our ears are about as sensitive as those of other mammals. Unlike cats, we cannot move them independently to collect sound from one direction or another (a cat has more than 20 different muscles to move each ear like a radar receiver), but we are able to sense when a sound reaches one ear before the other one or is louder in one ear than the other, and this helps us tell where sounds come from.

Structures deep inside our ears called semicircular canals also help us feel balanced and oriented in space. The movement of fluid within the canals keeps the brain aware of head motion, so that if we look up, sway from side to side, bend over, or stand on our heads, we don't (necessarily) feel dizzy or fall over.

During medical checkups at every age, we have our ears inspected. The doctor sets his otoscope in the opening of each ear and takes a quick look, just to see that things are pretty clean, that there's no puncture in the eardrum and no swelling of tissue. But problems arise now and then, from the earaches and infections of childhood to the loss of hearing that can come in late life. Here's what to look out for.

Ear Infection 
Children younger than 5 are prone to ear infections, in part because their immune systems are still developing and often are not strong enough to fight off the viruses and bacteria that reach, and inflame, the middle ear. 

By adulthood, such infections are rare, but grown-ups are still prone to infections of the outer ear and ear canal, caused by swimming in not-so-clean water (swimmer's ear), for example, or by inserting objects into the ear, usually in a misguided attempt to clean out wax.

To prevent swimmer's ear, avoid polluted lakes and rivers or pools with poor chlorine and pH control, and dry your ears after swimming.