The human auditory system. The cochlea is the seashell-shaped part of the ear that houses the hair cells.

Photo courtesy of NASA

How can sound hurt you?

Imagine cramming the power of an electric guitar solo into something smaller than a marble, and you'll understand how incredibly strong, yet delicate, our auditory system is. Sound travels in waves that enter our bodies through our ear canals. The waves cause our eardrum in the outer ear to vibrate, passing the sensory information along to the bones in the middle ear where that sound is amplified. It then moves to the inner ear and the pea-sized cochlea, where the hair cells come in, as we discussed earlier. The force of those vibrations can snap the tips of the cells' hair-like extensions and cause the lingering ring, signaling that the noise was too loud.

­Repeated exposure to loud noises can kill the hair cells entirely. So what? We have 16,000 of them in each cochlea, but that number pales in comparison to the eye's 100 million photoreceptors, which do to light what hair cells do to sound. In addition, once those hair cells die, we cannot growth them back. This is why protecting your ears is essential.

How loud is too loud? Sound is measured in units called decibels. Decibels measure the power of sound, rather than the amount. Safe sound levels are considered below 85 decibels. Here's another rule of thumb: If you have to shout to hear someone an arm's length away, the sound is probably above that safety threshold.

Repeatedly crossing that 85-decibel threshold can have unpleasant consequences. While the ringing in your ears from a loud noise is usually brief, for more than 12 million Americans, it never stops [source: American Tinnitus Association]. Chronic tinnitus can be a symptom of infections, high blood pressure and compacted earwax, but it is commonly associated with noise-related hearing loss.

­There are a few simple ways to safeguard your hearing. First, be aware of the noise levels around you. If you know you're going to be in a loud environment, such as a rock concert, wear earplugs. Also, notice how close you are to the source of loud noises and how long you're exposed to them. And pay attention to the ringing in your ears. Our bodies are sometimes more fragile than we think.

What's that? Still curious about how your hearing works? Visit the related links on the next page.