Spatial release from speech-on-speech masking in the median sagittal plane.

Several studies have described a release from speech-on-speech masking associated with separation of target and masker sources in the median sagittal plane. Some have excluded the possibility that small differences between target and masker interaural time disparities can fully account for this release. This study explored the mechanisms underlying the spatial release from speech-on-speech masking that can be obtained in the absence of such differences. In one condition, interaural time disparities were removed from the nominal median-sagittal-plane, head-related impulse responses used to generate the virtual auditory space within which competing sentences were presented. In other conditions, interaural level and spectral disparities also were manipulated by presenting competing sentences monaurally or diotically after convolution with one ear's head-related impulse responses. It was found that substantial spatial release from masking can be obtained in the absence of any interaural disparities and that such disparities probably make a relatively minor contribution to spatial release from speech-on-speech masking in the median sagittal plane. It is argued that this release from masking is driven primarily by a reduction in informational masking that occurs when monaural information at one, or both, of the listener's ears facilitates differentiation of competing sentences that emanate from spatially separated sources.

Characterizing team performance in network-centric operations: philosophical and methodological issues.

The recently promulgated doctrine of network-centric warfare suggests that increases in shared situation awareness and self-synchronization will be emergent properties of densely connected military networks. What it fails to say is how these enhancements are to be measured. The present article frames the discussion as a question of how to characterize team performance, and considers such performance in the context of its hypothetical components: situation awareness, workload, and error. This examination concludes that reliable measures of these constructs are lacking for teams, even when they exist for individual operators, and that this is due to philosophical and/or methodological flaws in their conceptual development. Additional research is recommended to overcome these deficiencies, as well as consideration of novel multidisciplinary approaches that draw on methodologies employed in the social, physical, and biological sciences.

The impact of hearing protection on sound localization and orienting behavior.

The effect of hearing protection devices (HPDs) on sound localization was examined in the context of an auditory-cued visual search task. Participants were required to locate and identify a visual target in a field of 5, 20, or 50 visual distractors randomly distributed on the interior surface of a sphere. Four HPD conditions were examined: earplugs, earmuffs, both earplugs and earmuffs simultaneously (double hearing protection), and no hearing protection. In addition, there was a control condition in which no auditory cue was provided. A repeated measures analysis of variance revealed significant main effects of HPD for both search time and head motion data (p < .05), indicating that the degree to which localization is disrupted by HPDs varies with the type of device worn. When both earplugs and earmuffs are worn simultaneously, search times and head motion are more similar to those found when no auditory cue is provided than when either earplugs or earmuffs alone are worn, suggesting that sound localization cues are so severely disrupted by double hearing protection the listener can recover little or no information regarding the direction of sound source origin. Potential applications of this research include high-noise military, aerospace, and industrial settings in which HPDs are necessary but wearing double protection may compromise safety and/or performance.

Target acquisition with UAVs: vigilance displays and advanced cuing interfaces.

Vigilance and threat detection are critical human factors considerations in the control of unmanned aerial vehicles (UAVs). Utilizing a vigilance task in which threat detections (critical signals) led observers to perform a subsequent manual target acquisition task, this study provides information that might have important implications for both of these considerations in the design of future UAV systems. A sensory display format resulted in more threat detections, fewer false alarms, and faster target acquisition times and imposed a lighter workload than did a cognitive display format. Additionally, advanced visual, spatial-audio, and haptic cuing interfaces enhanced acquisition performance over no cuing in the target acquisition phase of the task, and they did so to a similar degree. Thus, in terms of potential applications, this research suggests that a sensory format may be the best display format for threat detection by future UAV operators, that advanced cuing interfaces may prove useful in future UAV systems, and that these interfaces are functionally interchangeable.