Do employees who wear hearing aids still need to have a baseline hearing test?

Yes. A March 26, 1984 Letter of Interpretation (LOI) clarifies that baseline audiograms must be established even if medical problems exist. Another LOI dated August 3, 2004 says that the Occupational Noise Exposure Standard applies to all employees, and that there is no exception for employees who have diminished capacity to hear or for employees who have been diagnosed as deaf. The LOI also states:

“Employees with a diminished capacity to hear cannot satisfy the requirement to wear hearing protection simply by turning off their hearing aids when working in a high noise area. Hearing aids are not hearing protectors. Employees should actually leave their hearing aids on and wear ear muffs with sufficient attenuation to reduce all workplace noise below 85 dBA TWA. Employees need to be protected from excess noise, but should also be able to hear any machine noises or warning signals necessary. Even employees who have been diagnosed with severe or profound deafness may still hear some noise and need to be protected from additional loss.”