When it comes to worker safety, the wearing of proper hearing protection when noise levels are high can diminish the chances of, or eliminate the chance of hearing loss. In the safety industry, this is called hearing conservation…but how loud is too loud?
How Do We Hear?
Sound is collected in our outer ear and then funneled to the eardrum. When these soundwaves hit the eardrum, it vibrates and sends sound to the middle ear. From here, the middle ear amplifies the vibrations and send them to the inner ear. The vibrations stimulate hair cells in the inner ear and create an electrical pulse. This pulse then travels to the brain along the auditory nerve, causing the sensation of sound.
The healthy human ear can hear frequencies ranging from 20 Hz (the lowest note on a Tuba, for example) to 20,000 Hz (so high pitched adults generally lose the ability to hear this high).
Different groups of hair cells are responsible for different frequencies. Over time, if enough of these hairs get damaged, hearing loss will result.
Who Determines ‘Too Loud?’
OSHA has defined what they call the permissible exposure limit for noise. Often referred to as the PEL for noise. It is located in 29 CFR 1910.95.
The permissible exposure limit is 90 decibels averaged over eight hours. Hearing protection is required when noise exceed the PEL.
OSHA’s action level is 85 decibels averaged over eight hours. Hearing conservation training is required with annual audiograms and hearing protection must be made available at this lever.
Let’s put this in perspective for you. A bulldozer that is idling – not actively bulldozing, but just sitting on the side idling – is loud enough at 85 decibels that it can cause permanent hearing damage after only one workday. 8 hours.
Protect Your Hearing
There are many types of safety equipment out there specifically designed to protect your hearing.
- Ear Muffs
- Ear Plugs
- Ear Canal Caps
Each type of device has an NRR, noise reduction rate. The higher the number, the more protection the device. So, make sure your NRR is appropriate for the type of work you are doing and the type of noise you are being exposed to.
Sensory hearing loss, the type caused by excessive noise from equipment or processes, is damage to the inner ear, auditory nerve or the brain. These are not treated medically or surgically. Once that hearing is gone, it is gone.
So prevention is the only cure.