HPD Attenuation
Attenuation refers to the damping or decrease of noise levels as a result of wearing HPDs. Attenuation requirements include the following:
- HPDs must attenuate employee exposure to at least an eight hour time-weighted average (TWA) of 90 dBA. [29 CFR 1910.95(j)(2)]
- The employer must have a hearing conservation program whenever employee noise exposures equal or exceed an 8-hour time-weighted TWA of 85 decibels measured on the A scale (slow response) or a dose of fifty percent.
- For employees who have experienced a standard threshold shift (STS), HPDs must attenuate exposure at or below the action level of 85 dBA-TWA.
- The adequacy of the HPDs must be re-evaluated whenever employee noise exposures increase to the extent that they may no longer provide adequate attenuation.
- The employer understands the methods for estimating HPD attenuation.
Noise Reduction Ratings (NRR)
Most employers use the Noise Reduction Rating (NRR) that represents the protector’s ability to reduce noise under ideal laboratory conditions. The employer then adjusts the NRR to reflect noise reduction in the actual working environment.
Noise Reduction Rating
According to EPA regulation, the NRR must be shown on the hearing protector package. The NRR is then related to an individual worker's noise environment in order to assess the adequacy of the attenuation of a given hearing protector.
ANSI published a new test method (subject-fit) for measuring the actual ear attenuation of hearing protectors (ANSI S12.6-2016). This method provides more representative estimates of the real world performance of hearing protectors.
The National Institute for Occupational Safety and Health (NIOSH) has developed a Sound Level Meter app to help measure sound levels with a mobile iOS device.
Knowledge Check Choose the best answer for the question.
4-8. Hearing protection devices must attenuate employee exposure to at least _____.
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