The effects of different levels of task complexity on three vocal measures.

Interactive voice query and control systems are being considered as an alternative method of interfacing pilots with aircraft systems in high performance aviation environments. Before engineers integrate interactive voice systems into aircraft, knowledge is needed concerning what types of vocal changes, if any, are likely to occur as a result of environmental and task-induced stress. Recordings of the vocal utterances of 20 subjects, obtained as the subjects performed psychomotor and dichotic listening tasks, were subjected to acoustical analyses to evaluate the effects of task complexity on three measures: fundamental frequency (fo), peak amplitude (intensity), and word duration. The analyses revealed significant increases in fo (p less than 0.05) and amplitude (p less than 0.01) and a significant decrease in word duration (p less than 0.01) as a function of increased task complexity. These findings suggest that task-induced vocal changes must be considered in the design of voice recognition systems for use in complex, high performance aviation environments.