Which frequencies must be tested to assess hearing loss for certification?

The frequencies that must be tested to assess hearing loss for certification are 500 Hz, 1000 Hz, and 2000 Hz. These frequencies are crucial as they correspond to the speech frequencies that are most important for communication. Testing at these specific frequencies allows medical examiners to evaluate an individual's ability to hear conversational speech and detect potential hearing impairments that could affect their ability to perform tasks safely in a driving context.

The choice of these frequencies is grounded in audiological research that highlights their relevance to understanding the functional aspects of hearing loss. A loss in these ranges can lead to difficulties in understanding speech, which is essential for safe operation of commercial motor vehicles. Thus, focusing on 500, 1000, and 2000 Hz provides a reliable measure of the hearing capabilities relevant to certification requirements for drivers in safety-sensitive positions.