The only way to simplify and promote the effective use of an alerting system that must be comprehensive in its coverage of hazardous or non-normal conditions is to convey top level information that provides an indication of criticality and identity. In an attempt to reduce the number of aural alerting signals presented in aircraft flight decks, this investigation pursued advances toward the development of a simple aural alert categorization scheme that provides flight deck function and urgency level information. In Experiment 1, 20 subjects having "normal" hearing threshold levels provided magnitude estimation urgency ratings for a series of aural alerts. These ratings revealed that subjects perceived low, moderate, and high urgency levels within each of four equally urgent aural alerting sets. In Experiment 2, 12 subjects having "normal" hearing threshold levels participated in a brief training session and then performed a sound identification task in conjunction with an automated and manual tracking task. Sound identification data revealed that subjects correctly identified the alerting set (i.e., major flight deck function) and urgency level associated with each of 12 aural alerts in 96.53% of the trials occurring during automated tracking and in 95.83% of the trials occurring during manual tracking; furthermore, subjects correctly identified each alerting set, urgency level, and aural alert equally often during each tracking task condition. Electroencephalogram (EEG) data recorded throughout the performance of each tracking task condition revealed that manual tracking required a significantly higher level of attentional engagement than automated tracking. Subjective assessments of workload collected after the performance of each tracking task condition revealed that a significantly higher level of workload was experienced during the manual condition of the tracking task than during the automated condition of the tracking task. Collectively, this investigation's results indicated that acoustic parameter manipulations can be used to create four distinctive alerting sets that each convey three levels of urgency and that these alerting sets and urgency levels can be accurately identified when two levels of workload and attentional engagement are experienced. / Ph. D.

The only way to simplify and promote the effective use of an alerting system that must be comprehensive in its coverage of hazardous or non-normal conditions is to convey top level information that provides an indication of criticality and identity. In order to prevent the continued proliferation of aural alerting signals presented in the flight deck, a simple aural alert categorization scheme that provides flight deck function and urgency level information was proposed and evaluated in this study. Specifically, the present investigation examined the ability of a population having "normal" hearing to: 1) distinguish among four sets of aural alerting signals having distinctive rhythmic patterns and pitch contours, 2) perceive three urgency levels having distinctive tempos within each alerting set, and 3) associate each alerting set and its related urgency levels with one of the four major flight deck functions. Magnitude estimation ratings revealed that subjects perceived differences between low urgency level alerts and moderate urgency level alerts and between low urgency level alerts and high urgency level alerts. Pair comparison ratings of similarity revealed that subjects differentiated among the four within of the alerting sets relatively well after participating in a brief training session. alerting sets. A sound identification task revealed that subjects were able to associate functional categories with four aural alerting sets and were also able to simultaneously distinguish among and perceive three urgency levels within each of the alerting sets relatively well after participating in a brief training session. / Master of Science