When Employees Need Protection
Your workplace must have a hearing-conservation program when employees are exposed to noise levels that are equal to or greater than 85 decibels averaged over an eight-hour period (dBA), known as the "Time-Weighted Average" (TWA). This represents the average noise exposure during a workday, considering both the noise level and the duration of exposure.
Measure Noise Levels: Use a sound level meter to measure the noise level (in decibels, dB) at various times and locations within the employee's work environment.
Determine Exposure Times: Document the duration of time the employee is exposed to each level of noise. This should be performed for every distinct noise level encountered throughout the employee's workday.
Calculate the TWA: The TWA is calculated using the following formula:
Interpret the Result: Compare the TWA to relevant occupational noise exposure limits set by regulatory bodies such as OSHA. If the TWA exceeds these limits, it indicates that the noise exposure is excessive, and steps should be taken to reduce the noise level or the duration of exposure.
If noise levels in your workplace exceed those listed in the table below, you must use engineering or administrative controls to reduce employee exposures. If these controls are not adequate, employees must also use hearing protectors to reduce exposures to safe levels.
Permissible Noise Exposures*
| Duration Per Day | Maximum Exposure Level (dB) |
|---|---|
| 8 | 90 |
| 6 | 92 |
| 4 | 95 |
| 3 | 97 |
| 2 | 100 |
| 1 1/2 | 102 |
| 1 | 105 |
| 1/2 | 110 |
| 1/4 or less | 115 |
*Exposure to impulsive or impact noise should not exceed 140 dB peak sound pressure level.
Knowledge Check Choose the best answer for the question.
7-5. If employees are exposed to noise levels that are equal to or greater than _____ averaged in an eight-hour period, your employer needs a hearing conservation program.
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