The acoustic correlates of psychological stress have largely been examined through artificial means. Task overloads and loud noise have been used to generate changes in a person's voice which, it has been hoped, are similar to actual changes found in an operational environment. Purely artificial approaches such as pretending to be angry have also been used. These approaches offer no guarantee that the measured changes are indeed the changes found in the real situation.

An audio tape of pilot's speech during a serious aircraft malfunction, engine failure of the single-engine F-16 was obtained and analyzed. The tape records speech both before and after the incident. Analyses were made of the linguistic structure of the speech and acoustics. Acoustic measures included pitch, spectral slope and formant frequencies. Additionally, time-warped versions of pre- and post-incident examples of the same words were compared using a cepstral-distance measure, in an effort to determine how stress might effect recognition performance.