Determining the need to provide hearing protection for employees can be challenging. Employee exposure to excessive noise depends upon a number of factors, including:

• The loudness of the noise as measured in decibels (dB).
  
• The duration of each employee’s exposure to the noise.
  
• Whether employees move between work areas with different noise levels.
  
• Whether noise is generated from one or multiple sources.

Generally, the louder the noise, the shorter the exposure time before hearing protection is required. For instance, employees may be exposed to a noise level of 90 dB for 8 hours per day (unless they experience a Standard Threshold Shift) before hearing protection is required. On the other hand, if the noise level reaches 115 dB hearing protection is required if the anticipated exposure exceeds 15 minutes.

For a more detailed discussion of the requirements for a comprehensive hearing conservation program, see OSHA Publication 3074 (2002), “Hearing Conservation” or refer to the OSHA standard
at 29 CFR 1910.95, Occupational Noise Exposure, section (c).

The table below, shows the permissible noise exposures that require hearing protection for employees exposed to occupational noise at specific decibel levels for specific time periods. Noises are considered continuous if the interval between occurrences of the maximum noise level is one second or less. Noises not meeting this definition are considered impact or impulse noises (loud momentary explosions of sound) and exposures to this type of
noise must not exceed 140 dB. Examples of situations or tools that may result in impact or impulse noises are powder-actuated nail guns, a punch press or drop hammers.

Note: Only federal regulations are noted. State and local variances may require more stringent regulations than the federal mandates.
To find out more about Hearing Conservation (OSHA Publication 3074) click here.

For a Practical Guide to Effective Hearing Conservation Programs in the workplace (DHHS NIOSH Publication 90-120) click here.

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