Workers have been using hearing protection devices since the 1960’s to protect themselves from high levels of noise. Approximately 30 million workers in the United States are exposed to hazardous noises each year. 10 million of those workers suffer from noise induced hearing loss according to NIOSH.
According to the World Health Organization, noise-induced hearing loss is the most common, permanent and preventable occupational injury in the world. Noise damage is different from most other occupational injuries. It causes no pain or visible trauma, the ears do not bleed when hearing is being damaged, it leaves no visible scares, it is unnoticeable in its earliest stages, it accumulates with each over-exposure, and it generally takes years to diagnose.
Damage occurs as sound waves from high noise levels enter your ear canal and cause the eardrum to vibrate. Small bones behind your eardrum transmission these vibrations to the cochlea. Receptor cells in the cochlea convert these vibrations into electrical impulses and send them to your brain. These vibrations are then interpreted as sound. When high noise levels damage your hearing it does not damage the eardrum or bones. Loud noise damages the receptor cells in the cochlea overtime. Unlike other cells in your body that can regenerate, nerve cells in the cochlea, once damaged… are gone forever.
So how can you tell whether hearing loss is caused by noise?
1. The amount of time exposed to loud noise.
2. It is almost always a high-frequency hearing loss.
3. It usually affects both ears equally.
4. Gradual progression. It usually takes years to notice permanent change in hearing.
5. Appropriate symptoms. Ringing in the ears is a common symptom.
All workers exposure to noise should be controlled below a level equivalent to 85dBA for eight hours to minimize occupational noise induced hearing loss. Damage from noise exposure depends on the loudness and length of exposure. Habitual exposure to noise above 85 dB will cause gradual hearing loss. Hearing protection is required when noise averages more than 90 dB during an 8-hour workday.
Noise Reduction Rating (NRR)
NRR is a single number rating method which describes a hearing protection device based on how much the overall noise level is reduced. The NRR theoretically provides an estimate of the protection that should be met or exceeded by 98% of the wearers. Although a 34 NRR is the highest ever recorded, no manufacturer offers a hearing protector with an NRR over 33.
With smart use of hearing protectors, the right education and a structured hearing conservation program… noise-induced hearing loss is 100% preventable. If you are responsible for the safety of others at work, offer a variety of hearing protection devices, provide employees with the knowledge of the hazards and be proactive in the monitoring of your hearing conservation program.