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.