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Objective: The effects of talker sex and voice style of verbal cockpit warnings on performance were investigated to help make warning messages distinct from speech on the flight deck. Background: Auditory warnings are used in aircraft to alert the crew to hazards and their associated levels of danger. Failing to comply with a warning has led to aviation incidents and accidents. Methods: Participants were required to monitor the auditory channel and identify the verbal warning while simultaneously performing a visual pursuit tracking task. A male and a female actor annunciated the warning words in three styles: monotone, urgent, and whisper. In Experiment 1, warning words were presented in quiet, and in Experiment 2, they were presented in a background of speech babble that simulated cockpit radio communication. Results: Experiment 1 showed that the monotone and urgent styles resulted in the fastest identification response time (RT) regardless of the talker and listener's sex. Experiment 2 showed that the male talker annunciating in either the monotone or the urgent style resulted in the largest proportion correct and fastest identification RT regardless of the listener's sex. Both experiments showed effects of word semantics on performance. Conclusion: Effective use of speech parameters and word semantics can increase the saliency of verbal cockpit warnings. Application: Potential applications of this research include improving the attention-getting capability of an alerting system, which could lead to increased warning compliance, potentially resulting in fewer incidents and accidents.

Objective: The viability of a three-dimensional (3-D) auditory display for improving signal detection of passive sonar signals was investigated. Background: Sonar operators usually have difficulty detecting targets because the sound received by the hydrophone has a low signal-to-noise ratio when coupled with the operator's headset that does not isolate well against the ambient noise. Methods: Release from masking was assessed by pairing a recording of a torpedo with diotic broadband pink noise that served as a masker, and a 400 Hz tone with the masker. Masked thresholds were measured for seven signal durations when each signal was presented dioticly and in 3-D auditory space at three positions on the horizontal plane. Results: The spatial separation of signal and masker yielded a significant improvement in detection. Conclusion: A 3-D auditory display is a viable technology that could lead to a significant improvement in release from masking. The magnitude of the masking level difference will vary with respect to the characteristics of the hydrophone signal and masker and the synthesis capability of the 3-D auditory display. Application: Potential applications of this research include enhanced auditory displays for processing passive sonar signals, leading to earlier detection of enemy targets.

Objective: Performance and mental workload were observed for the administration of a rest break or exogenous vibrotactile signals in auditory and visual monitoring tasks. Background: Sustained attention is mentally demanding. Techniques are required to improve observer performance in vigilance tasks. Method: Participants ( N = 150) monitored an auditory or a visual display for changes in signal duration in a 40-min watch. During the watch, participants were administered a rest break or exogenous vibrotactile signals. Results: Detection accuracy was significantly greater in the auditory than in the visual modality. A short rest break restored detection accuracy in both sensory modalities following deterioration in performance. Participants experienced significantly lower mental workload when monitoring auditory than visual signals, and a rest break significantly reduced mental workload in both sensory modalities. Exogenous vibrotactile signals had no beneficial effects on performance, or mental workload. Conclusion: A rest break can restore performance in auditory and visual vigilance tasks. Although sensory differences in vigilance tasks have been studied, this study is the initial effort to investigate the effects of a rest break countermeasure in both auditory and visual vigilance tasks, and it is also the initial effort to explore the effects of the intervention of a rest break on the perceived mental workload of auditory and visual vigilance tasks. Further research is warranted to determine exact characteristics of effective exogenous vibrotactile signals in vigilance tasks. Application: Potential applications of this research include procedures for decreasing the temporal decline in observer performance and the high mental workload imposed by vigilance tasks.