If you think you have grown used to a loud noise, it probably has damaged your ears, and there is no treatment - no medicine, no surgery, not even a hearing aid that truly corrects your hearing once it is damaged by noise.
Is your workplace noisy?
- Do you have to shout to make yourself heard?
- Do you go home with ringing in your ears?
- Do any of the tools / equipment you use makes loud noise?
How Does Hearing Loss Occur?
Any source of sound sends vibrations or sound waves into the air. These funnel through the ear opening, down the ear canal, and strike the eardrum, causing it to vibrate. The vibrations are passed to the small bones of the middle ear, which transmit them to the hearing nerve in the inner ear. There, the vibrations become nerve impulses and go directly to the brain, which interprets the impulses as sound. As the exposure to loud noise increases, more nerve endings are destroyed. As the number of nerve endings decreases, so does the hearing.
Intensity of sound is measured in decibels (dB). Habitual exposure to noise above 85 dB will cause a gradual hearing loss in a significant number of individuals, and louder noises will accelerate this damage.
Temporary hearing loss (Temporary Threshold Shift)
Normal hearing will usually return after a rest period away from all sources of intense or loud noise. The recovery period may be minutes, hours, a day or perhaps even longer.
It is believed that a temporary hearing loss occurs when hair cells in the inner ear have been bent by vibrations and need time to bounce back,or when the fluid in the inner ear has changed chemically because of over-stimulations,and need time to revert to its original composition.
Permanent Hearing Loss (Permanent Threshold Shift)
Permanent hearing loss is the result of hair cells or nerve destruction within the cochlea. Once these important parts of the hearing process are destroyed, they can never be restored of regenerated. The resulting permanent hearing loss also referred to as permanent threshold shift (PTS), can range from slight to total hearing loss.
The following factors determine the degree and extent of hearing loss:
- Type and intensity of noise: continous, intermittent, impact, high or low frequency
- Duration of exposure: length of time, subjected to noise
- Type of noise environment: enclosed, open, reflective surfaces
- Distance from ears to the source of noise: earphones in the ear, centimetres from the ear
- Physical position / posture relative to the noise source
- General health and age of listener
- Individual susceptibility
|Examples of decibel levels in different surroundings|
|Approximate Decibel Level||Examples of surroundings|
|0||The quietest you can hear|
|30||Whisper, quiet library|
|60||Normal conversation, sewing machine, typewriter|
|90||Lawnmower, shop tools, truck traffic, 8 hours per day is the maximum exposure (protects 90% of people)|
|100||Chainsaw, pneumatic drill, snowmobile; 2 hours per day is the maximum exposure without protection|
|115||Sandblasting, loud rock concert, auto horn; 15 minutes per day is the maximum exposure without protection|
|140||Gun muzzle blast, jet engine; noise causes pain and even brief exposure injures unprotected ears. Maximum allowed noise with hearing protector|
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