Hearing loss is caused by many things but noise-induced hearing loss is permanent hearing loss caused over time by overexposure to loud noise. Rarely, an extremely loud sound such as an explosion can result in an immediate and permanent hearing loss. However, most NIHL builds up over time and usually by the time you realize that you’re not getting what people are saying or that the music doesn’t sound right, it’s too late. The hearing loss is permanent – and there is currently no cure for this type of hearing damage.
What kinds of noise are dangerous?
Click to download in high resolution.
Any kind that is too loud or too long.
Ok, let’s talk decibels and look at the noise chart to see what exactly is too loud, too long. At the simplest level, a decibel is the unit used to compare sound levels. (But it’s actually more complex than that, so if you’re really into math and physics, look it up.) You can download a high resolution version of the chart by clicking on it.
85dB is considered the safe dividing line…anything below 85 decibels is considered safe. Exposure to any sounds louder than 85dB needs to be monitored. A you can see, a lot of everyday noises are actually louder than 85db. Activities such as snowmobiling, hunting, playing in a band or standing next to loud machinery can push you over the safe limit.
In the decibel chart, you can see that the louder things are, the less time you can listen to them safely. In fact, for ever 3dB increase, you cut the safe listening time in half. Really loud noises, such as explosions, or standing next to a speaker at a loud concert, are never considered safe and can damage your hearing immediately.
Yes, but how does NIHL actually happen?
These healthy hair cells are coloured green, the nucleus is coloured blue and the neurons are red. Click on the image to download in high resolution.
Too much loud noise for too long a time…oh, you want a more graphic answer?
Take a look at the image on the left. Those green stems are healthy, undamaged hair cells. The nuclei of the cells are blue and those thin red things are the neurons. The neurons are where the change from cell movement to electric impulse happens.
The spiky things on top of the inner hair cells are called stereocilia. They project into the fluid filled space above the organ of Corti and help to translate waves into sound. Amazing, don’t you think?
Image: How noise damages the hearing mechanisms
Most noise damage takes place in the inner ear, the snail-shaped cochlea which has 15,000 beautiful hair cells.
Scientists believe that, depending on the type of noise, the pure force of vibrations from the noise can cause hearing loss. The violent onslaught of huge sound waves can bend and twist those little beauties into something really horrible. After the tsunami of sound recedes, their traumatic vibrations set off gongs or bells or static electricity in your head. Or worse – sounds and voices are muffled, as if you were hearing from inside your pillow.
After a few hours, maybe even a day or more, your hearing is back to normal. So you think. NIHL builds up over time….all that noise exposure is cumulative. Recent studies also show that exposure to harmful noise levels triggers the formation of molecules inside the ear that damage hair cells and result in NIHL. Over time, the hair cells are traumatized and brutalized to the point that they twist out of shape, break off, and cease to become functional. And when hair cells die, some of your hearing dies too.
How will I know if I have noise damage?
We’ve taken both Ana’s and Jordan’s songs to simulate what moderate hearing damage sounds like. As you can hear, there’s more to hearing loss than loss of volume – the clarity of the music suffers and everythign you hear sounds muffled.
Ana’s version
Jordan’s version
Damaged hair cells (bottom right) look just like a clearcut forest, with the trees cut down.
Sometimes the effects of noise damage are immediate, such as those experienced just after a concert, but this is usually a temporary condition called a temporary threshold shift – although it must be taken as a warning. Usually, most people don’t realize that their hearing is being eaten away, because it happens so slowly, bit by bit, hair cell by hair cell.
But the time may come when a person says to themself, “Hey, I keep asking everybody to speak up, and I can’t hear the high notes, and my girlfriend says I’ve got hearing loss. Oh man, I DO have hearing loss!” And by that time – drum roll, please – it’s too late! The hearing is damaged. Forever, kaput.
You probably won’t be deaf (no hearing whatsoever), but you will have a hearing loss that will seep into and touch every corner, nook and cranny of your life. Such as, your ability to understand what your friends are saying, or being able to to enjoy music the way you used to.
Caroline’s Story
Caroline Cook was born with a 91% hearing loss. Take a look at the video, to see what it is like to live with hearing loss. Watch in high quality for the clearest subtitles.
Who is affected by NIHL?
Age has little do with it hearing loss.
Some babies are born with it, and some elderly people can hear a pin drop! NIHL is no respecter of age; it’s starting NOW in some kids who haven’t even reached double digits (i.e. 10!!) Once anyone exposes themselves to loud noise on a regular basis, they are candidates for NIHL!
People of all ages, including children, teens, young adults, and older people, can develop NIHL.
Approximately 15 percent of Canadians between the ages of 20 and 69 have high frequency hearing loss that may have been caused by exposure to loud sounds or noise at work or in leisure activities. Recreational activities that can put someone at risk for NIHL include listening to music too “loudly and longly”, video arcades, concerts and monster jams, loud buses and subways, traffic, arget shooting and hunting, snowmobiles and motorcycles, woodworking and other hobbies, such as playing in a band.
