Think back to the last time you went to a rock 'n' roll concert or a fireworks display. Do you remember that peculiar ringing in your ears after the show stopped? The noises around you were muffled briefly, replaced with a buzzing inside your head, almost as if your ears were screaming. In a way, they were.
Noise levels louder than a shouting match can damage parts of our inner ears called hair cells. Hair cells act as the gatekeepers of our hearing. When sound waves hit them, they convert those vibrations into electrical currents that our auditory nerves carry to the brain. Without hair cells, there is nothing for the sound to bounce off, like trying to make your voice echo in the desert.
Hair cells reside in the inner ear inside the shell-shaped cochlea. Bundles of hair-like extensions, called stereocilia, rest on top of them. When sound waves travel through the ears and reach the hair cells, the vibrations deflect off the stereocilia, causing them to move according to the force and pitch of the vibration. For instance, a melodic piano tune would produce gentle movement in the stereocilia, while heavy metal would generate faster, sharper motion. This motion triggers an electrochemical current that sends the information from the sound waves through the auditory nerves to the brain.
When you hear exceptionally loud noises, your stereocilia become damaged and mistakenly keep sending sound information to the auditory nerve cells. In the case of rock concerts and fireworks displays, the ringing happens because the tips of some of your stereocilia actually have broken off. You hear those false currents in the ringing in your head, called tinnitus. However, since you can grow these small tips back in about 24 hours, the ringing is often temporary [source: Preuss].
Read on to find out exactly how something invisible like sound can harm our ears, how you can protect those precious hair cells and what happens when the ringing never stops.
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 grow 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 about 20 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.
More Great Links
- American Tinnitus Association. "Understanding the Facts." (March 1, 2016) http://www.ata.org/abouttinnitus/index.php
- Goldberg, Jeff. "The Quivering Bundles That Let Us Hear." Seeing, Hearing and Smelling the World. 1997. Howard Hughes Medical Institute. (Feb. 15, 2008)http://www.hhmi.org/senses/c120.html
- Hudspeth, James. "Hair cells of the inner ear." The Rockefeller University. (Feb. 15, 2008) http://www.rockefeller.edu/labheads/hudspeth/hairCells.php
- Mayo Clinic. "Tinnitus." Aug. 2, 2006. (Feb. 13, 2008)http://www.mayoclinic.com/health/tinnitus/DS00365
- MedLine Plus. "Tinnitus." Feb. 19, 2007 (Feb. 13, 2008)http://www.nlm.nih.gov/medlineplus/ency/article/003043.htm
- National Institute for Occupational Safety and Health. "Noise Meter." (March 1, 2016) http://www.cdc.gov/niosh/topics/noise/noisemeter.html
- National Institute on Deafness and Other Communication Disorders. "The Noise in Your Ears: Facts about Tinnitus." February 2001. (Feb. 13, 2008)http://www.nidcd.nih.gov/health/hearing/noiseinear.asp
- National Institute on Deafness and Other Communication Disorders. "Noise-Induced Hearing Loss." May 2007. (Feb. 13, 2008)http://www.nidcd.nih.gov/health/hearing/noise.asp
- The Royal National Institute for Deaf People. "Look after your ears." April 2005. (Feb. 13, 2008) http://www.rnid.org.uk/VirtualContent/84927/look_after_your_ears.pdf