HEARING PROTECTION

Damage to the complex human hearing mechanism can be permanent. Hearing loss can be prevented, f you protect yourself by using muffs or plugs, or both.  

The Human Hearing Mechanism

The human hearing mechanism consists of three important components:

  • The outer ear – Sound waves from the outside world are collected and channeled into the ear canal.
  • The middle ear – here, sound waves hit the eardrum (tympanic membrane) causing it to vibrate. The vibrations then pass through 3 tiny connected bones and on to the middle ear. These 3 bones are the smallest bones in the body. They are called the stirrup, anvil and stapes.
  • The inner ear – has a fluid filled organ called the cochlea. It looks like a seashell. Inside the cochlea are tiny hair cells that change the vibrations into nerve impulses that are transmitted to the brain which interprets the impulses as sounds.

When the tiny hair cells in the cochlea are exposed to excessively high sound levels, they are damaged. With continued exposure, cochlea hair cells lose their ability to heal or recover, and the damage (hearing loss) becomes permanent.

OSHA’s Hearing Conservation Standard

To protect workers from hearing loss, OSHA has issued a hearing conservation standard.  If sound exposure exceeds an 8-hour average of 85 decibels, your employer (in this case UNM) is required, by 29 CFR 1910.95, to implement a hearing conservation program.
OSHA’s time limits for average exposures will shift as noise levels vary. For example:

  • It is permissible to be exposed up to 90 decibels (dBA) for up to 8 hours.
  • It is permissible to be exposed up to 100 dBA – for a maximum of 2 hours.
  • It is permissible to be exposed up to 115 dBA – for a maximum of 15 minutes.
  • No exposure to any noise above 115 dBA is permitted for any length of time.

Elements of a Hearing Conservation Program

  • All UNM employees, who may be exposed to loud sounds, will be given a baseline audiogram at Employee Occupational Health Services. You are required by OSHA to have this audiogram every year (annually).  
  • The annual testing will determine if any significant change in your hearing has occurred.
  • Loud sounds in your work area can be monitored using a dosimeter. Contact Industrial Hygiene to perform the testing (277-2753).

Sound Level Reduction in the Workplace

Sound levels in your work place can be reduced or eliminated by administrative controls, engineering controls or by personal action on your part.

  • Administrative Controls – means a supervisor only allows use of loud machines or tools when fewer people are present or by rotating workers in and out of a noisy area to reduce their noise exposure time.
  • Engineering Controls – means isolating a loud machine in a sound absorbing area or room. Using carpet, sound dampening walls, foam, egg containers or baffles. Sound bounces off of hard surfaces and reflects back at you. You want some means of absorption or defection.
  • Action – you are personally responsible for the protection of your own hearing, and to properly wear and maintain your personal protective equipment (i.e, ear muffs, ear plugs, etc.).

Personal Protective Equipment

Ear Plugs

  • Are soft foam and conform to fit the shape of your ear canal
  • They must be properly inserted and positioned in the ear canal to effectively seal it off from noise
  • They are disposable or reusable
  • Make sure your hands and earplugs are clean before insertion. If dirt, moisture or bacteria get into your ear, it can cause an infection. You can wash them with warm soap and water. Dry them thoroughly and put them into a clean baggie.

Ear Muffs

  • Ear cushions and cups are attached to a headband
  • Your entire ear should fit within the cup
  • The headband should fit snugly against the top of your head
  • Be sure your hair is pulled back and out of the way so that it does not affect the seal of the muff. Make sure that anything else, such as earrings or hair clips, are removed so they don’t adversely affect the seal.
  • Hard hats and glasses can affect the seal. If you are wearing these, make sure you position them correctly to obtain an optimal fit

For your best protection use plugs and muffs together. Muffs and plugs usually have a noise reduction factor of 25 and 35 decibels, respectively. Used together, they can provide an additional 10-15 decibel reduction.