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Objective: To design and develop a Portable Auditory Localization Acclimation Training (PALAT) system capable of producing psychoacoustically accurate localization cues; evaluate the training effect against a proven full-scale, laboratory-grade system under three listening conditions; and determine if the PALAT system is sensitive to differences among electronic level-dependent hearing protection devices (HPDs). Background: In-laboratory auditory localization training has demonstrated the ability to improve localization performance with the open (natural) ear, that is, unoccluded, and while wearing HPDs. The military requires a portable system capable of imparting similar training benefits as those demonstrated in laboratory experiments. Method: In a full-factorial repeated measures design experiment, 12 audiometrically normal participants completed localization training and testing using an identical, optimized training protocol on two training systems under three listening conditions (open ear, TEP-100, and ComTac™ III). Statistical tests were performed on mean absolute accuracy score and front-back reversal errors. Results: No statistical difference existed between the PALAT and laboratory-grade DRILCOM systems on two dependent localization accuracy measurements at all stages of training. In addition, the PALAT system detected the same localization performance differences among the three listening conditions. Conclusion: The PALAT system imparted similar training benefits as the DRILCOM system and was sensitive to HPD localization performance differences. Application: The user-operable PALAT system and optimized training protocol can be employed by the military, law enforcement, and various industries, to improve auditory localization performance in conditions where auditory situation awareness is critical to safety. [ABSTRACT FROM AUTHOR]

Objective: This study was designed to determine the effects of hearing loss, aviation headset type, flight workload complexity, and communication signal quality on pilots' performance in an army rotary-wing flight simulator.Background: To maintain flight status, army aviators who do not meet current audiometric standards require a hearing loss waiver, which is based on speech intelligibility in quiet conditions. Because hearing loss characteristics of hearing-impaired aviators can vary greatly, and because performance is likely also influenced by degree of flight workload and communication demand, it was expected that performance among hearing-impaired aviators would also vary.Method: Participants were 20 army helicopter pilots. Pilots flew three flights in a full motion-based helicopter simulator,with a different headset configuration and varying flight workload levels and communication signal quality characterizing each flight. Objective flight performance parameters of heading, altitude, and airspeed deviation and air traffic control command read-backs were measured.Results: Statistically significant results suggest that high levels of flight workload, especially in combination with poor communications signal quality, lead to deficits in flight performance and speech intelligibility.Conclusion: These results support a conclusion that factors other than hearing thresholds and speech intelligibility in quiet should be considered when evaluating helicopter pilots' flight safety. The results also support a recommendation that hearing-impaired pilots use assistive communication technology and not fly with strictly passive headsets.Application: The combined effects of flight environment with individual hearing levels should be considered when making recommendations concerning continued aviation flight status and those concerning communications headsets used in high-noise cockpits. [ABSTRACT FROM AUTHOR]

Objective: This study was designed to determine the effects of hearing loss, aviation headset type, flight workload complexity, and communication signal quality on pilots’ performance in an army rotary-wing flight simulator. Background: To maintain flight status, army aviators who do not meet current audiometric standards require a hearing loss waiver, which is based on speech intelligibility in quiet conditions. Because hearing loss characteristics of hearing impaired aviators can vary greatly, and because performance is likely also influenced by degree of flight workload and communication demand, it was expected that performance among hearing-impaired aviators would also vary. Method: Participants were 20 army helicopter pilots. Pilots flew three flights in a full motion-based helicopter simulator, with a different headset configuration and varying flight workload levels and communication signal quality characterizing each flight. Objective flight performance parameters of heading, altitude, and airspeed deviation and air traffic control command read-backs were measured. Results: Statistically significant results suggest that high levels of flight workload, especially in combination with poor communications signal quality, lead to deficits in flight performance and speech intelligibility. Conclusion: These results support a conclusion that factors other than hearing thresholds and speech intelligibility in quiet should be considered when evaluating helicopter pilots’ flight safety. The results also support a recommendation that hearing-impaired pilots use assistive communication technology and not fly with strictly passive headsets. Application: The combined effects of flight environment with individual hearing levels should be considered when making recommendations concerning continued aviation flight status and those concerning communications headsets used in high-noise cockpits. [ABSTRACT FROM AUTHOR]

Objective: General aviation (GA) pilot performance utilizing a mixed-modality simulated data link was objectively evaluated based on the time required in accessing, understanding, and executing data link commands. Additional subjective data were gathered on workload, situation awareness (SA), and preference. Background: Research exploring mixed-modality data link integration to the single-pilot GA cockpit is lacking, especially with respect to potential effects on safety. Methods: Sixteen visual flight rules (VFR)-rated pilots participated in an experiment using a flight simulator equipped with a mixed-modality data link. Data link modalities were text display, synthesized speech, digitized speech, and synthesized speech/text combination. Flight conditions included VFR (unlimited ceiling and visibility) or marginal VFR flight conditions (clouds 2,800 ft above ground level, 3-mile visibility). Results: Statistically significant differences were found in pilot performance, mental workload, and SA across the data link modalities. Textual data link resulted in increased time and workload as compared with the three speech-type data link conditions, which did not differ. SA measures indicated higher performance with textual and digitized speech data link conditions. Conclusion: Textual data link can be significantly enhanced for single-pilot GA operations by the addition of a speech component. Application: Potential applications include operational safety in future GA systems that incorporate data link for use by a single pilot and guidance in the development of flight performance objectives for these systems. [ABSTRACT FROM AUTHOR]

Objective: We examined the willingness and ability of general aviation pilots to execute steep approaches in low-visibility conditions into nontowered airports.Background: Executing steep approaches in poor weather is required for a proposed Small Aircraft Transportation System (SATS) that consists of small aircraft flying direct routes to a network of regional airports.Method: Across two experiments, 17 pilots rated for Instrument Flight Rules at George Mason University or Virginia Tech flew a Cessna 172R simulator into Blacksburg, Virginia. Pilots were familiarized with the simulator and asked to fly approaches with either a 200- or 400-foot ceiling (at approach angles of 3 degrees, 5 degrees, and 7 degrees in the first experiment, 3 degrees and 6 degrees in the second). Pilots rated subjective workload and the simulator recorded flight parameters for each set of approaches.Results: Approaches with a 5 degree approach angle produced safe landings with minimal deviations from normal descent control configurations and were rated as having a moderate level of workload. Approaches with 6 degree and 7 degree approach angles produced safe landings but high workload ratings. Pilots reduced power to control the speed of descent and flew the aircraft slightly above the glide path to gain time to control the landing.Conclusion: Although the 6 degree and 7 degree approaches may not be practical for routine approaches, they may be achievable in the event of an emergency.Application: Further work using other aircraft flying under a wider variety of conditions is needed before implementing SATS-type flights into airports intended to supplant or complement commercial operations in larger airports. [ABSTRACT FROM AUTHOR]

An experiment was conducted wherein masked thresholds (using ascending method of limits) for a backup alarm were obtained in pink and red noise at 85 and 100 dBA for 12 participants immersed in a probability monitoring task and wearing a conventional passive hearing protection device (HPD, an earmuff or a foam earplug), an active noise reduction (ANR) headset, or no HPD at all (only in 85 dBA noise). Results revealed statistically significant between-HPD differences in red noise (from 2.3 to 3.1 dB) and in the 100-dBA noise level (from 2.6 to 4.3 dB). An additional finding, which corroborates other studies using different protocols, was that masked thresholds in 85-dBA noise were significantly lower (from 3.2 to 4.4 dB) for the occluded conditions (wearing an HPD) than for the open-ear (unoccluded) condition. This result refutes the belief among many normal-hearing workers that the use of HPDs in relatively low levels of noise compromises their ability to hear necessary workplace sounds. Actual or potential applications of this research include (a) the selection of appropriate HPDs for low-frequency-biased noise exposures wherein signal detection is important and (b) gaining insight into the appropriateness of ANR-based HPDs for certain industrial noise environments. [ABSTRACT FROM AUTHOR]

This on-road field investigation employed, for the first time, a completely automated trigger-based data collection system capable of evaluating driver performance in an extended-duration real-world commercial motor vehicle environment. The study examined the use of self-assessment of fatigue (Karolinska Sleepiness Scale) and temporal separation (minimum time to collision, minimum headway, and mean headway) as indicators of driver fatigue. Without exception, the correlation analyses for both the self-rating of alertness and temporal separation yielded models low in associative ability; neither metric was found to be a valid indicator of driver fatigue. In addition, based upon the data collected for this research, preliminary evidence suggests that driver fatigue onset within a real-world driving environment does not appear to follow the standard progression of events associated with the onset of fatigue within a simulated driving environment. Application of this research includes the development of an on-board driver performance/fatigue monitoring system that could potentially assist drivers in identifying the onset of fatigue. [ABSTRACT FROM AUTHOR]

Objective: General aviation (GA) pilot performance utilizing a mixed-modality simulated data link was objectively evaluated based on the time required in accessing, understanding, and executing data link commands. Additional subjective data were gathered on workload, situation awareness (SA), and preference.Background: Research exploring mixed-modality data link integration to the single-pilot GA cockpit is lacking, especially with respect to potential effects on safety.Methods: Sixteen visual flight rules (VFR)-rated pilots participated in an experiment using a flight simulator equipped with a mixed-modality data link. Data link modalities were text display, synthesized speech, digitized speech, and synthesized speech/text combination. Flight conditions included VFR (unlimited ceiling and visibility) or marginal VFR flight conditions (clouds 2,800 ft above ground level, 3-mile visibility).Results: Statistically significant differences were found in pilot performance, mental workload, and SA across the data link modalities. Textual data link resulted in increased time and workload as compared with the three speech-type data link conditions, which did not differ. SA measures indicated higher performance with textual and digitized speech data link conditions.Conclusion: Textual data link can be significantly enhanced for single-pilot GA operations by the addition of a speech component.Application: Potential applications include operational safety in future GA systems that incorporate data link for use by a single pilot and guidance in the development of flight performance objectives for these systems. [ABSTRACT FROM AUTHOR]