Robert S. Bolia

A speech corpus for multitalker communications research

A database of speech samples from eight different talkers has been collected for use in multitalker communications research. Descriptions of the nature of the corpus, the data collection methodology, and the means for obtaining copies of the database are presented.

Aurally aided visual search in three-dimensional space

We conducted an experiment to evaluate the effectiveness of spatial audio displays on target acquisition performance. Participants performed a visual search task with and without the aid of a spatial audio display. Potential target locations ranged between plus and minus 180° in azimuth and from -70° to +90° in elevation. Independent variables included the number of visual distractors present (1, 5, 10, 25, 50) and the spatial audio condition (no spatial audio, free-field spatial audio, virtual spatial audio). Results indicated that both free-field and virtual audio cues engendered a significant decrease in search times. Potential applications of this research include the design of spatial audio displays for aircraft cockpits and ground combat vehicles.

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.

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.

EVALUATING ADAPTIVE MULTISENSORY DISPLAYS FOR TARGET LOCALIZATION IN A FLIGHT TASK

This study was designed to determine the efficacy of providing target location information via head-coupled visual and spatial audio displays presented in adaptive and nonadaptive configurations. Twelve United States Air Force pilots performed a simulated flight task in which they were instructed to maintain flight parameters while searching for ground and air targets. The integration of visual displays with spatial audio cueing enhanced performance efficiency, especially when targets were most difficult to detect. Several of the interface conditions were also associated with lower ratings of perceived mental workload. The benefits associated with multisensory cueing were equivalent in both adaptive and nonadaptive configurations.

Effects of Automated Cueing on Decision Implementation in a Visual Search Task

A visual search paradigm was used to examine the effects of status information automation cueing in a target detection task. Manual and information automation conditions were manipulated with the size of the distractor set. Participants were required to respond to the presence or absence of a target in a time-limited trial. In the information automation condition, status information regarding target presence was presented to the participant. The participants were informed that the information automation was not perfectly reliable. A significant detection performance improvement was observed with the addition of the information automation. This improvement was more marked in the condition with the higher number of distractors. Additionally, detection performance declined when the information automation was invalid, without a corresponding increase in subjective measures of workload or confidence. Implications of the results and future studies are discussed.

Asymmetric performance in the cocktail party effect: implications for the design of spatial audio displays.

An experiment was conducted to determine the extent to which hemispheric specialization is manifested in the performance of tasks in which listeners are required to attend to one of several simultaneously spoken speech communications. Speech intelligibility and response time were measured under factorial combinations of the number of simultaneous talkers, the target talker hemifield, and the spatial arrangement of talkers. Intelligibility was found to be mediated by all of the independent variables. Results are discussed in terms of the design of adaptive spatial audio interfaces for speech communications. Actual or potential applications of this research include the design of adaptive spatial audio interfaces for speech communications.

EFFECTS OF HEARING PROTECTORS ON AUDITORY LOCALIZATION IN AZIMUTH AND ELEVATION

An experiment was conducted to determine the effects of two types of hearing protectors on auditory localization performance. Six listeners localized a 750--ms broadband noise from loudspeakers ranging in azimuth from -180° to +180° and in elevation from -75° to +90°. Independent variables included the type of hearing protector and the elevation of the source. Dependent measures included azimuth error, elevation error, and the percentage of trials resulting in a frontback confusion. Performance on each of the dependent measures was found to be mediated by one or more of the independent variables. Actual or potential applications include the generation of improved design guidelines for hearing protectors and workplace alarms.

Spatial Audio Displays for Speech Communications: A Comparison of Free Field and Virtual Acoustic Environments

The ability of listeners to detect, identify, and monitor multiple simultaneous speech signals was measured in free field and virtual acoustic environments. Factorial combinations of four variables, including audio condition, spatial condition, the number of speech signals, and the sex of the talker were employed using a within-subjects design. Participants were required to detect the presentation of a critical speech signal among a background of non-signal speech events. Results indicated that spatial separation increased the percentage of correctly identified critical speech signals as the number of competing messages increased. These outcomes are discussed in the context of designing binaural speech displays to enhance speech communication in aviation environments.

Applying Adaptive Control and Display Characteristics to Future Air Force Crew Stations

The Human Effectiveness Directorate of the Air Force Research Laboratory is developing and evaluating human-machine interface concepts to enhance overall weapon system performance by embedding knowledge of the operators state inside the interface, enabling the interface to make informed, automated decisions regarding many of the interfaces information management display characteristics. Some of these characteristics include information modality, spatial arrangement, and temporal organization. By increasing the ability of the interface to respond, or adapt, to the changing requirements of the human operator in real time-in essence closing the loop-the interface provides intuitive information management to the operator and provides real-time human engineering.