Hearing Conservation

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OSHA’s Hearing Conservation Program is a topic that continues to cause confusion. In response to this, CS Consulting has compiled this summary of the standard to hopefully clarify a somewhat confusing topic.

Hearing Conservation & Occupational Noise Exposure:

The purpose of the OSHA’s Hearing Conservation Standard is to ensure that employers are taking measures to prevent employees from being exposed to dangerous levels of noise. Noise can have varying effects on the body including hearing loss, fatigue, disorientation, and even heart conditions depending on the levels and timeframes of exposures. Employers as required to take protective measure to prevent or limit employee exposure to these stresses.

The start of a hearing conservation program is with determining what levels of noise employees are exposed to. This is done through a process called dosimetry. Dosimetry is a process of taking periodic samples of noise and averaging the samples throughout the day. Dosimetry equipment typically will take a sample every second and automatically calculate the average, along with other useful data. 85 Decibels on the A scale (abbreviated dBA) is the OSHA action point for hearing conservation. Employees whose working environments do not every exceed 85 dBA are considered to be safe, and thus do not fall under the regulations of this standard. To ensure this exclusion, employers must prove that all areas employees work in do not exceed the action point. This means multiple samples might be required for each job or working environment.

All employees who exceed the action point would be considered “at risk” and would fall under the requirements of the standard. The major requirements of the plan are audiometric (hearing loss) testing for all employees subject to the standard. Once determination is made that employees are subject to the standard, they must wear hearing protection until they have had an initial or baseline audiogram. This hearing protection must reduce noise exposures to below the action point until this testing has been completed. Once the baseline audiogram has been conducted, employees will need to complete annual audiograms to determine if the employee has suffered substantial hearing loss. Depending on the results of follow-up audiometric testing, employees may be subject to more frequent audiometric testing.

While audiometric testing is required at 85 dBA, this is not the required starting point for hearing protection. The following table outlines the durations of time employees can be exposed to without hearing protection. Exceeding the contents of this table will automatically require hearing protection.

Duration of Exposure (Hours)Permitted Sound Levels
890 dBA
692 dBA
495 dBA
397 dBA
2100 dBA
1.5102 dBA
1105 dBA
0.5110 dBA
0.25115 dBA









Any exposure above 140 dBA will also require hearing protection for any duration of time. Medical professionals might also require hearing protection be required on specific employees based on the results of audiometric testing.

Hearing protection devices are rated with an NRR or Noise Reduction Rating. The NRR is determined by the EPA and essentially outlines the level of protection a device provides. While the number for the NRR literally specifies a numeric reduction of decibels, it does so on the C scale. Since OSHA’s standard is based on the A scale for noise, one must convert the NRR to the A scale. To do this one must subtract 7 from the NRR, then divide the difference by 2. For example, hearing protection with an NRR of 33 would protect against 13 dBA (33-7=26. 26÷2=13).  If employees are exposed above the levels listed on the table above, they must have protection that reduces their exposure below the levels on the table. For example, if employees are going to be exposed to 120 decibels for 8 hours, hearing protection with an NRR of 33 would not provide adequate protection as it would only reduce exposure to 103 decibels. Employees would have to restrict exposure to 15 minutes or less per day, double up on hearing protection (i.e. plugs and muffs), or implement engineering controls to reduce the noise levels in the working environment.

In addition to dosimetry and audiometric testing, employers whose employees fall under the hearing conservation standard must have a written policy with regards to that company’s hearing conservation program, as well as training for those affected.

*Unless specific citations are shown, all answers are based on interpretations provided by authorized officials. As such, all information is deemed reliable, but not guaranteed.