Noise-induced hearing loss is the second most common cause of sensorineural (and primarily permanent) hearing loss. It is second only behind aging. As much as 15% of the population between the ages of 20 and 70 years has sensorineural hearing loss that may have been caused by noise. Some of this noise exposure occurred at work, some during recreational activities. Industrial work in Terrace and surrounding communities has dominated the workforce for many years, with many of those workers acquiring noise-induced hearing loss. Other occupations that can be unrecognized as risky high-noise environments are workers in restaurants, bars, and pubs, as well as music teachers.
There are obvious recreational activities that are easily associated with noise exposure, like gun shooting and hobbies using home power tools, but there are also musicians and music-appreciators using music players at dangerously loud levels. The American Speech-Hearing Association (ASHA) even warns parents about the dangers of loud toys for young children.
How Does it Happen?
Hearing occurs when sound that is carried as waves through the air around us, is collected by the outer ear, channeled through the ear canal, and sets up vibration at the “eardrum” (tympanic membrane). This is the eardrum that can be seen by your audiologist or physician through an otoscope. The eardrum is attached to 3 tiny (VERY tiny) bones, jointed together in an air-space (middle ear) behind your eardrum. The eardrum and these bones help to “amplify” the sound to pass it onto another membrane (oval window) that leads into the fluid-filled cochlea. Running throughout the cochlea is yet another membrane (basilar membrane) that also carries that vibratory motion. Sitting atop the basilar membrane are tiny (EXTREMELY tiny) cells we call “hair cells”. Atop those are stereocilia (MICROSCOPICALLY tiny), hair-like structures, that are moved through the fluid in the cochlea, by the movement of the basilar membrane. The bending of these stereocilia alters the chemical balance within the hair cells, sending an electrical impulse along the auditory nerve to the brain.
When the sound is too intense, these very delicate hair cells can be permanently damaged by the intense movement of the basilar membrane, and become damaged or die off. This can happen slowly over time when ears are exposed to intense steady-state noise, or it can happen suddenly if the noise is extremely intense even for a very short time period. As more of these cells become damaged and die off, the louder sound has to be before it can be transmitted to the brain. Other more subtle changes occur in the hearing system after hair cell loss, such as a loss of fidelity in hearing music or complex speech patterns, and understanding speech in a background of noise.
How Much is too Much?
The level of the sound considered safe varies with the amount of time exposed in each exposure session: the louder the sound, the shorter the time period of exposure that is considered safe. Gunshots can be as high as 140-170dB SPL, and intense enough to cause immediate injury. Generally, if a sound is 85dB SPL, an 8-hour time period (like a common workday) is too long for this sound to be considered safe.
How to Prevent Noise-Induced Hearing Loss.
It’s very simple. If you can’t reduce the noise, wear hearing protection.
- Wear hearing protect when shooting, every time. It may seem inconvenient, but a lifetime of hearing loss is even less convenient. If the hearing protection you have tried in the past is uncomfortable or inconvenient for you, discuss other options with your audiologist.
- Wear hearing protection if you work in a noisy environment. If hearing protection is recommended in your workplace, wear it faithfully. If it’s uncomfortable or inconvenient, discuss other options with your audiologist. There are many many options for this environment.
- Turn down the music. Really. Your appreciation for the fine details and nuances of music can become permanently impaired by excessive sound levels, and your communication ability can be permanently impaired. Parents, check the website for the manufacturer of your children’s MP3/MP4 players: many have a software add-on that can allow you to install limits on the levels these devices will allow.
- Parents, check your children’s toys. Put it close to your ear (this is where it often is for young children), and set it off. If it’s an uncomfortable sound, remove the batteries or discard the toy.
- If you are a musician, you can use hearing protection without negatively affecting your performance. From specially-filtered custom ear plugs to custom-made protective ear monitors, there is a way for you to protect your precious hearing without affecting your performances. Over time, damage from excessive noise, even from music, can alter your perception of music, and forever change your perception of pitch, tonal quality, and the fidelity of quality music. Why risk what you love? Protect your hearing and keep appreciating for a lifetime.
Joely Viveiros, M.Sc., Aud (C)