Development of a Speech Analysis Protocol for Accident Investigation

Abstract

This paper describes an initial attempt to develop a protocol for speech analysis techniques that might lead to a better understanding of the cognitive and emotional states that underlie the behavior of people involved in accidents. A tape recording of radio transmissions made by a pilot during both routine and emergency flight conditions was analyzed. Five primary speech measures were made for each statement: mean fundamental frequency (f₀), range of fundamental frequencies (Δf₀), duration, mean amplitude and syllable count. Speaking rate (syllables per second) and two other derived measures were computed later. During routine flight, the pilot's f₀ averaged 123.9 Hz, but this increased to an average of 200.1 Hz during emergency conditions. Range of f₀ also increased significantly, while syllable count decreased. These changes may provide a profile of a response to extreme stress that may be useful for gaining insight into situations in which such stress is not otherwise apparent.