Auditory Fitness for Duty
Tufts, Vasil, and Briggs (2009) described the concept and factors impacting "Auditory Fitness for Duty" (AFFD). AFFD can be defined as possessing hearing ability sufficient for safe and effective job performance. Occupations impacted by AFFD are vast and include military personnel, miners, police officers, fire-fighters, pilots, air traffic controllers, etc. Clearly, not hearing well in these (and other) "hearing critical" occupations would be a significant liability. Additionally, people with hearing impairment appear to be under more stress than normal hearing peers. The authors note a 2006 article stating that hearing impaired workers take five times as much "sick time" due to mental distress.
The authors cite multiple reports supporting the concept and need for greater attention with regard to AFFD. For example, one study from Denmark indicated hearing loss (greater than 20 dB hearing loss at 4000 Hz) was one of the three main risk factors for injury at a shipping yard. Another study reported people with normal hearing can detect footsteps in leaves at 100 meters, but given a sloping mild to moderately-severe hearing loss, the same sounds would not be perceived until they were less than a meter away. Thus, warning time from auditory cues can be diminished significantly. The authors state that as communication difficulty (from hearing loss) increases, the mean time to identify the sound source (i.e., target) increased, as did the percentage of communication errors and other negative consequences.
When a person does meet AFFD standards for a given job, there is often little (or no) validation, which demonstrates the specific standard (usually based only on a pure-tone audiogram) has been rigorously validated. Thus, the major question is "what degree of hearing loss is handicapping for a specific job" and quite often, AFFD pass-fail criteria do not provide an answer. Further, although pure-tone hearing thresholds may be reasonable indicators of a person's ability to hear in quiet, as hearing loss increases, people with sensorineural hearing loss (SNHL) need additional and increasingly beneficial signal-to-noise (SNR) ratios to understand speech clearly. Further, the mean SNR for signal detection increases as hearing thresholds increase. Signal detection is noise is rarely assessed clinically and is even more rare in AFFD protocols, despite the obvious importance of these measures. Clearly, people with SNHL experience increased difficulty understanding speech in noisy backgrounds and the exact degree of difficulty varies tremendously and is not predictable based solely on pure-tone thresholds.
The authors note in most cases pure-tone only AFFD assessments are simply no longer defensible. AFFD protocols should not be "one size fits all." Rather, they should be job-specific and should include audiometric measures beyond pure tone thresholds--which would be beneficial and are recommended.
For More Information, References, and Recommendations:
Tufts JB, Vasil KA, Briggs S. (2009) Auditory Fitness for Duty: A Review. Journal of the American Academy of Audiology 20(9):539-557.