Effects of Visual and Auditory Cues About Threat 

Location on Target Acquisition and Attention to 

Auditory Communications 

by Monica M. Glumm, Kathy L. Kehring, and Timothy L. White 

ARL-TR-3560 August 2005 

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Army Research Laboratory 

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ARL-TR-3560 August 2005 

Effects of Visual and Auditory Cues About Threat 

Location on Target Acquisition and Attention to 

Auditory Communications 

Monica M. Glumm, Kathy L. Kehring, and Timothy L. White 

Human Research and Engineering Directorate, ARL 

Approved for public release; distribution is unlimited. 
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 Effects of Visual and Auditory Cues About Threat Location on Target 

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13. SUPPLEMENTARY NOTES 

14. ABSTRACT 

This study examined the effects of visual, spatial language and three-dimensional (3-D) audio cues about target location on 

target acquisition performance and the recall of information contained in concurrent radio communications. Two baseline 

conditions were also included in the analysis: no cues (Baseline 1) and target presence cues only (Baseline 2). In modes in 

which target location cues were provided, 100% of the targets presented were acquired, as compared to 94% in Baseline 1 

and 95% in Baseline 2. On average, targets were acquired 1.4 seconds faster in the visual, spatial language, and 3-D audio 

modes than in the baseline conditions, with times in the visual and 3-D audio modes being 1 second faster than those in 

spatial language. Overall workload scores were lower in the 3-D audio mode than in all other conditions except the visual 

mode. Less information (23%) was recalled from auditory communications in Baseline 1 than in the other four conditions 

where attention could be directed to communications between target presentations. 

15. SUBJECT TERMS

 display; sensory modalities; target acquisition 

16. SECURITY CLASSIFICATION OF:

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 Monica M. Glumm 

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Prescribed by ANSI Std. Z39.18
iii 

Contents 

List of Figures v

List of Tables v

Acknowledgments vii

1. Introduction 1

2. Objectives 4

3. Method 4

3.1 Participants ......................................................................................................................4 

3.2 Apparatus.........................................................................................................................5 

3.2.1 Control Station and Target Scenario ...................................................................5 

3.2.2 Target Location Cues ..........................................................................................5 

3.2.3 Radio Communications and Questionnaires .......................................................7 

3.2.4 The National Aeronautics and Space Administration (NASA) Task Load 

Index (TLX) ........................................................................................................7 

4. Procedures 8

4.1 Experimental Design .......................................................................................................8

4.2 Training ...........................................................................................................................9 

4.3 Testing...........................................................................................................................10 

5. Results 10

5.1 Target Acquisition.........................................................................................................10 

5.2 Secondary Task Performance (scores on SITREP questionnaire) ................................14 

5.3 Subjective Workload .....................................................................................................15 

5.4 Participants’ Preferences and Comments......................................................................16 

6. Discussion 17

7. Conclusions and Recommendations 19
iv 

8. References 21

Appendix A. Situation Report (SITREP) Example 23

Appendix B. SITREP Questionnaire (Example) 25

Appendix C. NASA-TLX 27

Distribution List 31 
v 

List of Figures 

Figure 1. Dismounted enemy soldier within sight image. ............................................................. 6 

Figure 2. Icon providing directional cue in the visual modality.................................................. 6 

Figure 3. Mean time to first shot.................................................................................................. 11 

Figure 4. Mean time to target hit. ................................................................................................ 11 

Figure 5. Time to first shot and time to target hit by target location. .......................................... 12 

Figure 6. Mean degrees off target center at first shot. ................................................................. 13 

Figure 7. Mean degrees off target center at target hit.................................................................. 13 

Figure 8. Percentage of target hits. .............................................................................................. 14 

Figure 9. Mean scores on SITREP questionnaire. ....................................................................... 14 

Figure 10. Overall workload scores............................................................................................. 15 

List of Tables 

Table 1. Mean difference between modes in time to first shot.................................................... 12 

Table 2. Mean difference between modes in time to hit.............................................................. 12 

Table 3. Mean difference between modes in scores on SITREP questionnaires......................... 15 

Table 4. Mean difference between modes in overall workload scores........................................ 15 
vi 

INTENTIONALLY LEFT BLANK
vii 

Acknowledgments 

The authors would like to express their appreciation to the following colleagues and friends at 

the U.S. Army Research Laboratory who assisted in the conduct of this research: 

 SGM Enoch Godbolt and MSG Lamar Garrett for their assistance in the recruitment of 

the military participants, 

 Tim Mermagen, Theo Feng, and Dr. Ellen Haas for their assistance in the development 

and recording of the spatial language and three-dimensional audio cues, 

 Dr. Paula Henry for providing hearing tests to the participants, 

 Mike Lattin for his assistance in the development of the situation report, and 

 Ron Carty for providing photographic support. 

Last, but never least, the authors would like to thank the Soldiers who participated in this 

research for their enthusiasm and dedication to the research tasks. We would also like to express 

our sincere gratitude to their sergeant major for allowing the Soldiers time away from their 

normal duties and to the members of his staff for their support in coordinating their visits. 
viii 

INTENTIONALLY LEFT BLANK
1 

1. Introduction 

This study was conducted in support of a situational understanding Army technology objective 

(ATO). The objective of this ATO is to “develop, demonstrate, and transition unit of action 

Soldier information system interface guidelines that facilitate Soldiers gaining situational 

understanding and enable planning and acting within the adversary’s decision cycle.” 

The strategy selected to achieve this objective involved the development of models of Soldieroperator functions and tasks via the Improved Performance Research Integration Tool 

(IMPRINT). The IMPRINT models helped to identify the frequency at which workload levels 

exceeded a specified threshold, the tasks that contributed most often to these workload peaks, 

and the mental resources for which concurrent tasks competed. Interviews were conducted with 

experienced vehicle commanders and gunners to discuss suspected problem areas and potential 

solutions that might reduce workload and enhance situational awareness (SA). Questionnaires 

were also administered to derive a prioritized list of critical information requirements (CIRs). 

Candidate solutions related to the design of the information display were identified based on 

principles of attention management (Wickens & Hollands, 2000). This study is one of a series of 

investigations designed to evaluate these potential solutions and a first step in iterative analyses 

(i.e., modeling and experimentation), which will be performed to assess the effects of these 

interventions on SA and decision cycle time. 

The rationale for the present study was based on the results of an IMPRINT model and analyses 

of the functions and tasks of the two-person crew (commander-gunner and driver) and squad 

leader in the infantry carrier vehicle (ICV) (Mitchell, Samms, Glumm, Krausman, Brelsford, & 

Garrett, 2004). Multiple runs of the model consistently indicated that the commander-gunner 

frequently experienced instances of high workload. The greatest of these workload peaks were 

caused by conflicts between tactical communications and other tasks that might be shared by 

crew members in three- and four-person systems. Conflicting tasks included those associated 

with maintaining an awareness and understanding of the situation inside and outside the vehicle, 

such as the task of scanning for threats via the periscope or the battlefield display. According to 

the Soldiers surveyed, information about the strength, activity, and location of dismounted 

enemy infantry will be most critical to the commander-gunner of the ICV, as it is to the 

commander and the gunner of the Bradley fighting vehicle (BFV) (Mitchell et al., 2004). In a 

line-of-sight environment, the closer the enemy is, the more critical the information. 

Communications and scanning tasks are the primary means for obtaining this information. 

Digital communications, which employ the same resources used to perform the scanning task 

(i.e., visual, motor, and cognitive), were found to overload the commander-gunner more often 

than voice communications that do not rely on visual resources. Although voice messages would 
2 

be the most likely mode of communication during engagements and other periods of high 

activity, digital communications containing critical information are also likely to be exchanged. 

Discussions with Soldiers confirmed that communications often conflict with target acquisition 

and engagement tasks in the BFV. The Soldiers claimed that, as in the BFV, when the 

commander-gunner of the ICV becomes overloaded, he will most likely ignore those tasks he 

considers less important and will focus on the task of highest priority. Some Soldiers added that 

during engagements, they turn off their radio. In such instances, information critical to a present 

or subsequent engagement might be lost. Providing information about the presence and location 

of threats in a manner that will facilitate target acquisition rather than compete for mental 

resources is expected to enhance SA and reduce decision cycle time. 

Directional cues on target location might be provided auditorily, visually, or tactilely. Auditory 

cues can be presented verbally in spatial language (e.g., “5 o’clock”) or in 3-D audio sounds that 

appear to emanate from the clock position of the target. However, some of the Soldiers 

interviewed expressed concern that auditory cues might be lost amid the din and frequent verbal 

exchanges that are typical of a combat vehicle environment. The Soldiers were also skeptical 

about the effectiveness of tactile cues in conveying position information while they are being 

tossed about their moving vehicle. Some Soldiers preferred visual cues that could be integrated 

into the sight picture in such a manner as to avoid distraction and obstruction of the scene being 

scanned. 

Auditory cues have been found to be useful in supplementing visual information or alerting the 

listener to critical information within a visual display (Shinn-Cunningham, Lehnert, Kramer, 

Wenzel, & Durlach, 1997), but the use of auditory cues in providing spatial information about 

target location in ground combat vehicles has not been adequately explored. For the most part, 

research on spatialized audio has focused on its use in aircraft where 3-D audio displays have 

scored a number of successes. Studies have shown that listeners who must monitor multiple 

radio communications can selectively attend to one message at a time if messages are presented 

in different spatial locations. In these studies, dismounted Soldiers (Haas, dePontbriand, Mello, 

Patton, & Solounias, 2000) and helicopter pilots (Haas, Gainer, Wightman, Couch, & Shilling, 

1997) were found to identify and respond to multi-channel radio communications more quickly 

and accurately with 3-D audio than with existing monaural displays. In the latter study, pilots 

scored fewer points on a radio communications-identification task when some speech messages 

were presented to one ear and other messages presented to the opposite ear (i.e., dichotic 

presentation). Even fewer points were scored when all speech messages were sent to both ears 

(i.e., diotic presentation). 

Spatial information about target location has been found to have positive effects on target 

acquisition performance and perceptions of workload (Begault, 1993; McKinley, Erickson, & 

D’Angelo, 1994; McKinley et al., 1995). In one study, commercial airline crew members 

acquired targets faster using a 3-D audio display than did crew members using a one-earpiece 
3 

headset; however, no significant differences were found between these auditory displays in the 

number of targets acquired (Begault, 1993). In another investigation, 3-D audio cues alone did 

not improve target localization, but when paired with visual cues, the 3-D cues resulted in 

improvements in time and accuracy, reduced head movement, and lower subjective ratings of 

workload (Tannen, 2001). 

Many studies that have compared the effects of auditory (e.g., 3-D audio and spatial language) 

and visual cues in the localization of targets during navigation have focused primarily on 

differences in spatial updating (i.e., the ability of people to keep track of the location of a target 

mentally without concurrent perceptual cues). In one such study, Loomis, Klatsky, Philbeck, and 

Golledge (1998) found that distance perception was more accurate with visual cues than with 

auditory cues, but spatial updating was performed well in both modalities. In another study with 

blind and blindfolded sighted observers, Loomis, Lippa, Klatzky, and Golledge (2002) again 

found greater error in distance perception with 3-D audio than with spatial language (e.g., 

“5 o’clock, 10 meters”) for the latter participant group. However, directional errors were greater 

in the spatial language condition than in the 3-D audio mode. Here, too, spatial updating 

performance was nearly the same for both auditory conditions. The researchers concluded that 

once a target location is encoded or represented internally, the representation can be updated as 

well with either modality. In their report about the results of this research, Loomis and her 

associates present a two-process model of the task of navigating to a target using the two 

auditory modes. The two processes they identify are stimulus encoding and spatial update. 

According to the researchers, encoding of 3-D audio sound involves two substages: perception 

of the spatial location of the source and then the creation of a spatial image of the source 

location. Encoding of a spatial language stimulus may or may not require more than one 

substage, depending on whether a spatial image is formed in the process of converting the verbal 

directions into meaning. However, regardless of whether the location of the target is cued with 

3-D audio sound or a verbal description, the result of encoding these stimuli is a spatial image 

that continues to exist after the stimulus is no longer present. 

The objective of the present investigation was to measure and compare the effects of auditory 

(speech and non-speech) and visual cues about target location on target acquisition performance 

and attention to auditory communications. During the study, the participants performed target 

acquisition tasks while monitoring radio communications in each of five cue conditions: (1) 

Baseline 1, (2) Baseline 2, (3) Visual, (4) Spatial Language, and (5) 3-D Audio. Baseline 1 

represented current limitations in targeting information. In this condition, the participant was not 

provided any information about the presence or location of targets. In Baseline 2, the participant 

was provided an auditory alert (bell) when a target was presented but he did not receive any 

information about where the target was located. In the Visual mode, target location cues were 

provided by an icon that resembled a one-handed clock without numbers. In the Spatial 

Language mode, cues were presented verbally in clock positions (e.g., “Target ...3 o’clock”). 
4 

In the 3-D Audio mode, target location was cued by two broadband audio tones that appeared to 

emanate from the position of the target. 

For the current study, it was hypothesized that target detection times would be significantly faster 

in modes in which information about target location was provided. These improvements in target 

acquisition performance, however, were expected to be greatest in the Visual mode for two 

reasons. First, the process of converting the 3-D audio and spatial language stimuli into spatial 

images may involve more substages than the visual stimulus. Second, auditory resources used in 

listening to radio communications would not compete for the visual resources used in the 

perception of the visual cues. Thus, for the same reason, it was also expected that the participants 

would be able to attend better to radio communications in the Visual mode. The verbal cues 

provided in Spatial Language were expected to be more disruptive to this latter task than the 3-D 

Audio cues that were conveyed in sounds and not words. 

2. Objectives 

The objective of this study was to measure and compare the effects of auditory (speech and nonspeech) and visual cues about target location on target acquisition performance and attention to 

auditory communications. 

3. Method 

3.1 Participants 

The participants were 20 male Soldiers who ranged in age from 22 to 41 years (mean = 30.6 years; 

standard deviation [SD] = 6.5 years) with from 1.9 to 22.2 years of time in service (mean = 

11.1 years; SD = 6.2 years) and a similar amount of time in their military occupational specialty 

(MOS). Most of the participants were commanders or gunners of the BFV or the M1 tank with an 

MOS of 19D or 19K, respectively. Fifteen of the 20 participants had seen combat during 

Operation Desert Storm and/or Operation Iraqi Freedom. 

All the participants passed tests of color vision and met visual acuity requirements of 20/20 in 

one eye and 20/30 in the other eye, corrected or uncorrected. The hearing threshold levels (HTL) 

of the participants corresponded to Army physical profile H2 which specifies an average HTL of 

no more than 30 dB, no individual HTL greater than 35 dB at 500, 1000, and 2000 Hz, and no 

HTL greater than 55 dB at 4000 Hz (U.S. Army, 1991). The participants had otoscopically 

normal ears (i.e., no blockage or infection), and no history or otologic pathology (i.e., hearing 

problems) as reported by the participant. 
5 

The voluntary, fully informed consent of the persons used in this research was obtained as 

required by 32 Code of Federal Regulations 219 and Army Regulation (AR) 70-25. The 

investigators have adhered to the policies for the protection of human subjects as prescribed in 

AR 70-25. 

3.2 Apparatus 

3.2.1 Control Station and Target Scenario 

The participant’s control station consisted of 17-inch1

 Trinitron monitor manufactured by Dell 

and a joystick manufactured by Saitek (Cyborg 3-D Rumble Force Stick). The participant was 

seated approximately 25 inches from the monitor (i.e., seat reference point to screen). The 

monitor presented a 10-degree horizontal field of view (FOV)1 of the 360-degree field around an 

imaginary vehicle in which the participant was operating. The joystick controlled the movement 

of the scene behind crosshairs that were fixed in the center of the visual display. The participant 

scanned the terrain around the vehicle by twisting the joystick to the left or the right. The farther 

the hand control was twisted, the faster the movement of the target scene. Movement of the 

scene behind the crosshairs was limited to the horizontal plane. Each target was an individual 

dismounted Soldier who was presumed to be an enemy (see figure 1). This choice of target type 

was based on a prioritized list of CIRs and related threats identified by Soldiers. All personnel 

targets were situated at a distance of 75 meters from the participant’s vehicle. The targets were 

equal in size and presented along the vertical centerline of the visual display. A hit on the target 

was recorded when the trigger on the joystick was pulled while the crosshairs were on any 

portion of the target. The target fell to the ground to indicate to the participant that a hit had 

been scored. The DiGuy Scenario2 (Version 5.2.3) developed by Boston Dynamics was used in 

the development of the target scenarios, the presentation of the target location cues, the 

interpretation of the input from the joystick, and data collection. 

3.2.2 Target Location Cues 

Cues about the location of targets were provided in the visual, spatial language (speech), and 3-D 

audio (non-speech) modes. All cues were 2.5 seconds in duration and their presentation was 

controlled by a computer. Target location cues were presented once, relative to the 12-o’clock 

position at each target presentation. The following paragraphs describe these cues and the 

apparatus that was used to present them. 

 1This was based on discussions with United Defense Limited Partnership (UDLP) who is responsible for the 

design of the crew station in the ICV. UDLP provided information about the FOV of the commander’s independent 

viewer (daylight TV sensor) in the BFV A3 (i.e., wide FOV [WFOV]: 10 degrees x 7.5 degrees) and best guess 

about the FOV of the sight in the ICV (WFOV: 9 degrees circular). At the time of this study, there had not been any 

decision regarding the FOV of the commander-gunner’s sight in the ICV or the size of the flat panel on which the 

sight image would be displayed. A best guess was that the sight image would be presented on one of the main 15-

inch square flat panel displays and, if desired, on a smaller square flat panel called the Crewman’s Remote Interface 

System (CRIS).

2DiGuy Scenario is a trademark of Boston Dynamics.
6 

Figure 1. Dismounted enemy soldier within sight image. 

 (1) Visual. The visual cues about target location were provided by an icon that resembled a 

one-handed clock without numbers (see figure 2). The direction in which the hand on the clock 

was pointing indicated the location of the target within the 360-degree field about the vehicle 

platform. The directions were incremented in hours in the same manner as those cues presented in 

3-D audio (non-speech) and spatial language (speech). Ten clock positions were used. No targets 

were presented at the 12- or the 6-o’clock positions, partly because of front-back reversals that can 

occur when these cues are presented in the 3-D audio mode (Begault, 1991). The visual icon was 

2.5 x 2.5 inches in size and centered at the bottom of the scene displayed on the 17-inch monitor. 

Figure 2. Icon providing 

directional cue in 

the visual modality. 

 (2) Spatial Language (speech). These cues about target location were verbal and were 

presented in a clock-type format. An example of this type of cue is “Target!...5 o’clock.” 

As with the 3-D audio cue, the total duration of each cue in the spatial language mode was 

2.5 seconds. The first and second parts of the cue were each approximately 1.0 second in 
7 

duration, separated by 0.5-second pause. All directional cues were pre-recorded in a female 

voice in contrast to the radio communications that were presented in a male voice. 

 (3) 3-D Audio (non-speech). These cues about target location were broadband nonspeech audio signals. Each audio signal consisted of two 1-second tones that were presented 

approximately 0.5 second apart for a total duration of 2.5 seconds. The tones were spatialized 

with a 3-D virtual audio localization (3-DVALS) system manufactured by Veridian Engineering 

and played on a computer with a generic head-related transfer function recorded on a Kelso 

electronic mannequin for auditory research (KEMAR) acoustic head. 

All cues about the presence and location of targets and other auditory communications were 

presented to both ears of the participant through stereo earphones manufactured by Sony. All 

were normalized to 21 dB and noise reduction was applied. The intensity levels of the auditory 

cues about target location, as measured through an artificial ear, were 73 peak decibels for the 

Spatial Language cue and 78 peak decibels for the 3-D audio cue. The decibel peaks for the 

auditory communications ranged from 65 to 70. 

3.2.3 Radio Communications and Questionnaires 

During each target run in each cue condition, the participant was presented communications 

through his headphones that simulated tactical information transmitted from command 

headquarters. These communications were in the form of a situation report (SITREP), although 

much longer and more detailed than normal. An example of this SITREP is provided in 

appendix A. The pre-recorded SITREP was the same duration as the target run (i.e., 2.5 minutes) 

and contained 27 different facts. Ten of the 27 facts were changed at each presentation of the 

SITREP. A total of 25 SITREPs was prepared and pre-recorded: 20 SITREPs for testing (i.e., 

four target runs in each of the five experimental conditions) and five SITREPs for training (i.e., 

two target runs in each condition). After the completion of each target run, the participant was 

asked to complete a questionnaire that consisted of ten questions pertaining to the information 

contained in the SITREP. The answers to each question were written and required a one- or twoword response. Each answer was worth two points. If the participant did not provide an answer to 

a question or the answer was wrong, the participant scored zero points. If the participant omitted a 

word from an answer that required two words or if one of the words in the answer was wrong, the 

participant scored one point. The participant had a maximum of 3 minutes to answer the ten 

questions. The SITREPs and associated questionnaires presented after each run were counterbalanced among the five experimental conditions. An example of the SITREP is provided in 

appendix B. 

3.2.4 The National Aeronautics and Space Administration (NASA) Task Load Index (TLX) 

The NASA-TLX was used to assess the participant’s experience of workload (Hart & Staveland, 

1988). This technique uses rating scales to assess mental, physical, and temporal demands, 

performance, effort, and frustration. Initially, each of these six workload factors is assigned a 
8 

weight, based on the responses of the participant to pairwise comparisons. In these comparisons, 

the six factors are presented in 15 possible pairs, and for each pair, the participant is asked to 

circle the factor that s/he perceived contributed most to his or her workload experience. The 

participant then completes rating scales that provide a measure of the magnitude of the workload 

for each factor. Those factors perceived by the participant to have contributed most to his or her 

workload experience are given more weight in the computation of an overall workload score. 

The paired comparisons worksheets and the workload rating scale are provided in appendix C. 

4. Procedures 

4.1 Experimental Design 

The study was a repeated measures, fixed factor design. Five cue conditions were evaluated. 

These conditions and the independent variables in this study were (1) Baseline 1 (2) Baseline 2 

(3) Visual (4) Spatial Language, and (5) 3-D Audio. Cues about target location were provided in 

the Visual, Spatial Language, and 3-D Audio modes but not in the two baseline conditions. 

Baseline 1 represented current limitations in targeting information where the participant 

continuously scanned the terrain around the vehicle for threats without knowing whether threats 

were present or where they might be located. In Baseline 2, the participant was provided an 

auditory alert (bell) when a target was presented, but he did not receive any information about 

the location of the target. The primary purpose of the second baseline condition was to 

determine if the mere knowledge of the presence of a target would affect performance of the 

target acquisition task and perceptions of workload. In all conditions except for Baseline 1, the 

participant’s crosshairs automatically returned to the 12-o’clock position after each target 

presentation. The participant could not move his crosshairs from that position until cued about 

the presence or location of another target. 

The primary task of the participants was to find and engage targets as quickly as possible. Their 

secondary task was to attend to tactical information contained in SITREPs that were presented 

auditorily throughout each target run. The dependent variables in this study included measures 

of primary and secondary task performance and subjective ratings of workload. In the target 

acquisition task, the dependent variables were time to first shot, the degrees off target center at 

first shot, and the percentage of hits. For those targets hit, time to hit and the degrees off target 

center at hit were also recorded. The time to first shot and the time to hit were calculated from 

the time at which the target was presented to the time of trigger pull. The dependent variable in 

the secondary task was the total number of points scored on the SITREP questionnaires that were 

administered after each target run in each condition. Overall workload scores were derived with 

the NASA-TLX. 
9 

One participant was trained and tested at a time. The duration of training and testing for each 

participant was approximately 4.0 hours. The procedures that were followed for each participant 

are described in section 4.2. 

4.2 Training 

Each volunteer was briefed about the purpose of the investigation, the procedures to be followed 

during the study, and any risks involved in participation. The investigator read a volunteer 

agreement affidavit aloud to the participant who followed along. If the participant agreed to 

participate in the investigation, he completed the information requested in the consent form and 

signed it. 

Each participant then completed a demographic questionnaire to obtain pertinent background 

information. A vision tester manufactured by Titmus Optical Company, Inc. was used to assess 

the participant’s vision at near and far distances to ensure that the participant met visual acuity 

requirements of 20/20 in one eye and 20/30 in the other eye, corrected or uncorrected. The 

participant was also required to pass a test for color vision. A hearing test was administered by 

an audiologist with an AC40 clinical audiometer manufactured by Interacoustics A/S. The 

participants were required to have an HTL corresponding to Army physical profile H2 (U.S. 

Army, 1991) or better, otoscopically normal ears, and no history of otologic pathology. 

The participant received training in all tasks to be performed during the study in each of the five 

experimental conditions, including instruction in rating his workload experience using the 

NASA-TLX. Training also included practice in localizing the 3-D audio cues presented at the 

ten clock positions. During this portion of the training, the investigator presented 3-D audio 

tones at each of ten clock positions, starting at the 1-o’clock position and ending at 11 o’clock. 

After each tone, the investigator stated the clock position at which the tone was presented. This 

process was repeated two more times. The investigator then presented the 3-D audio tones at 

each clock position in a randomized order to the participant who identified the clock position of 

each tone. This process was repeated two additional times. 

During training in each of the five experimental conditions, the participant was reminded that his 

primary task was to find and engage all targets as quickly as possible. If the target did not fall at 

trigger pull, the target had not been hit and the participant was required to re-engage. The 

participant was told that his secondary task was to attend to the information contained in the 

SITREP. He was informed that some of the details in the SITREP would change and that he 

should not rely on his memory of information contained in previous SITREPs. 

Training in each condition included the completion of two target runs, each followed by the 

questionnaire that assessed the participant’s knowledge of the information contained in the 

SITREP. At the conclusion of training, the participant received practice in rating his workload 

experience using the NASA-TLX. The order in which the participant received training in each 
10 

condition was counterbalanced and presented in the same order in which the conditions would be 

presented to him during the testing period. 

4.3 Testing 

After a 15-minute rest break, the participant completed four runs in each of the five experimental 

conditions. Each run consisted of five targets for a total of 20 target presentations. Each of the 

20 targets was presented twice at each of the ten clock positions in a random order. Five 

different random orders of target locations were developed and the presentation of these orders 

was counterbalanced across the five experimental conditions. 

All targets were individual dismounted Soldiers and all represented enemy personnel. Each 

target was presented for a maximum time of 15 seconds. If a hit was scored, the target fell to the 

ground to indicate to the participant that the target had been successfully engaged. The target 

disappeared from the screen after the 15 seconds had elapsed, regardless of whether a hit was 

scored. The time at which the first target was presented at the start of a target run and the time 

between subsequent target presentations was varied to reduce expectancy. The time intervals 

between target presentations were 5, 10, 15, 20, and 25 seconds and the order in which these 

intervals occurred was counterbalanced. The start of a time interval between target presentations 

began 15 seconds after the preceding target had been presented, regardless whether or when the 

participant had scored a hit on that target. Each target run was therefore 2.5 minutes in duration. 

Each target run was followed by the questionnaire that assessed the participant’s knowledge of 

information contained in the radio communications. Immediately after testing in each condition, 

the participant was asked to rate his workload experience using the NASA-TLX. 

At the conclusion of testing in all five conditions, the participant was asked to provide his 

opinions and preferences with regard to the conditions evaluated. 

5. Results 

5.1 Target Acquisition 

It had been hypothesized that target acquisition times in the Visual, Spatial Language, and 3-D 

Audio modes would be significantly faster than target acquisition times in the two baseline 

conditions (Baseline 1 and Baseline 2) where no information was provided about target location. 

These improvements in target acquisition performance were expected to be greatest in the Visual 

mode for two reasons. First, the process of converting the Spatial Language and 3-D Audio cues 

into spatial images about target location may involve more substages than the visual stimulus, 

resulting in an increase in response time and thus time to acquire the target. Second, auditory 
11 

resources used in attending to radio communications are less likely to compete for visual 

resources used in capturing visual cues about target location. 

To test this hypothesis, separate linear mixed effects model analyses were performed on time to 

first shot and time to hit. Each analysis included the order of presentation of the cue conditions. 

The mean times to first shot and mean times to target hit for each of the five experimental 

conditions are shown in figures 3 and 4, respectively. The similarity between time to first shot 

and time to hit within each condition merely suggests that, if found, most targets were hit on the 

first shot. 

The results of the analysis on time to first shot indicated a significant main effect of mode (F 

(4, 472) = 55.596, p <.001). The analysis on time to target hit also revealed differences between 

cue conditions (F (4, 472) = 55.837, p <.001). 

0

2

4

6

8

10

12

Cue Condition

Time to First Shot (seconds)

Series1 7.55 8.40 5.78 6.81 5.83

Baseline 1 Baseline 2 Visual Spatial 3-D Audio

Figure 3. Mean time to first shot. 

0

2

4

6

8

10

12

Cue Condition

Time to Hit (seconds)

Series1 7.69 8.48 5.83 6.87 5.93

Baseline 1 Baseline 2 Visual Spatial 3-D Audio

Figure 4. Mean time to target hit. 
12 

The results of post hoc analyses using the least significant difference (LSD) method are provided 

for time to first shot and time to hit in tables 1 and 2, respectively. These analyses revealed that, 

as hypothesized, time to first shot and time to target hit were significantly faster in the Visual, 

Spatial Language, and 3-D Audio modes than in either of the two baseline conditions. Time to 

first shot and time to target hit were slower in the Spatial Language mode than in the Visual and 

3-D Audio conditions, but no significant differences were found between the Visual and the 3-D 

Audio modes. The analyses also suggested that time to first shot and time to hit were 

significantly faster in the Baseline 1 condition than in Baseline 2. 

Table 1. Mean difference between modes in time to first shot. 

Mode Baseline 2 Visual Spatial Language 3-D Audio 

Baseline 1 -0.857 (p < .001) 1.766 (p < .001) 0.741 (p = .001) 1.712 (p < .001) 

Baseline 2 2.623 (p < .001) 1.598 (p < .001) 2.569 (p < .001) 

Visual -1.025 (p < .001) -0.054 (p = .800) 

Spatial Language 0.971 (p < .001) 

Bold blocks indicate significant differences. 

Table 2. Mean difference between modes in time to hit. 

Mode Baseline 2 Visual Spatial Language 3-D Audio 

Baseline 1 -0.793 (p < .001) 1.854 (p < .001) 0.819 (p < .001) 1.756 (p < .001) 

Baseline 2 2.647 (p < .001) 1.612 (p < .001) 2.548 (p < .001) 

Visual -1.035 (p < .001) -0.098 (p = .647) 

Spatial Language 0.936 (p < .001) 

Bold blocks indicate significant differences. 

Figure 5 shows the mean time to first shot and the mean time to hit based on the distance (clock 

position) of the target from the 12-o’clock position across the five conditions. Generally, the 

farther the target was from the 12-o’clock position, the farther the slewing distance and thus the 

longer the time to acquire targets. 

0

2

4

6

8

10

Target Location (Clock Position)

Time (seconds)

First Shot

Hit

First Shot 5.71 6.56 6.87 7.43 7.81

Hit 5.8 6.64 6.95 7.52 7.9

11 or 1 10 or 2 9 or 3 8 or 4 7 or 5

Figure 5. Time to first shot and time to target hit by target location. 
13 

The mean degrees off target center at first shot and the mean degrees off target center at hit for 

each of the five experimental conditions are shown in figures 6 and 7, respectively. The results 

of the linear mixed effects model analyses that were performed on these data did not reveal 

significant differences between cue conditions for either the mean degrees off target center at 

first shot (F (4, 472) = 2.139, p =.075), or for the mean degrees off target center at hit 

(4, 72) = .924, p =.445). 

-0.1

-0.05

0

0.05

0.1

Cue Condition

Degrees Off Target at First 

Shot

Series1 -0.001 0.036 -0.01 -0.02 -0.015

Baseline 1 Baseline 2 Visual Spatial 

Language 3-D Audio

Figure 6. Mean degrees off target center at first shot. 

-0.1

-0.05

0

0.05

0.1

Cue Condition

Degrees Off Target at Hit

Series1 -0.002 0.009 -0.009 -0.008 -0.014

Baseline 1 Baseline 2 Visual Spatial 

Language 3-D Audio

Figure 7. Mean degrees off target center at target hit. 

The percentage of hits achieved in each of the five cue conditions is shown in figure 8. The 

results of the linear mixed effects model analysis indicated a significant difference between 

modes on this measure of target acquisition performance (F (4, 72) = 5.220, p =.001). Post hoc

analyses indicated that the percentage of hits achieved in the Visual, Spatial Language, and 3-D 

Audio modes (100%) was greater than that achieved in Baseline 1 (94%) and Baseline 2 (95%). 
14 

No significant differences were found between Baseline 1 and the Baseline 2 conditions or 

between the Visual, Spatial Language, and 3-D Audio modes. 

85.0

90.0

95.0

100.0

Cue Condition

Target Hits (%)

Series1 94.0 95.0 100.0 100.0 100.0

Baseline 1 Baseline 2 Visual Spatial 

Language 3-D Audio

Figure 8. Percentage of target hits. 

5.2 Secondary Task Performance (scores on SITREP questionnaire) 

It had been hypothesized that the participants would achieve higher scores on questionnaires about 

information contained in the SITREP in the Visual mode because the visual cues about target 

location would not compete for auditory resources used when the Soldiers attended to the radio 

communications. The verbal cues provided in the Spatial Language mode were expected to be more 

disruptive to the secondary task than 3-D Audio cues that were conveyed in sounds and not words. 

To test this hypothesis, a linear mixed effects model analysis was performed on the total number of 

points scored on the SITREP questionnaires in each of the five experimental conditions. The results 

of the analysis revealed a significant difference between cue conditions (F (4, 72) = 3.467, p =.012). 

Post hoc analyses indicated that significantly less information was recalled from the SITREPs in 

Baseline 1 than in the other four cue conditions (see table 3). No differences were found between 

Baseline 2 and the Visual, Spatial Language, or 3-D Audio modes. 

0

10

20

30

40

50

60

Mean Scores on SITREP

Questionnaire

Series1 30 36.6 36.55 37.6 37.25

Baseline 1 Baseline 2 Visual Spatial 

Language 3-D Audio

Figure 9. Mean scores on SITREP questionnaire. 
15 

Table 3. Mean difference between modes in scores on SITREP questionnaires. 

Mode Baseline 2 Visual Spatial Language 3-D Audio 

Baseline 1 -6.60 (p = .008) -6.55 (p = .008) -7.60 (p = .002) -7.25 (p = .004) 

Baseline 2 0.05 (p = .983) -1.00 (p = .678) -0.65 (p = .787) 

Visual -1.05 (p = .663) -0.70 (p = .771) 

Spatial Language 0.35 (p = .885) 

Bold blocks indicate significant differences. 

5.3 Subjective Workload 

The results of a linear mixed effects model analysis on subjective ratings of workload on each of 

the six workload dimensions of the NASA-TLX (i.e., mental, physical, and temporal demand, 

performance, effort, and frustration) did not reveal a significant difference between any of the five 

cue conditions. However, significant differences were found between modes on overall workload 

scores computed from the weighted ratings on the six workload dimensions (F (4, 72) = 3.036, 

p =.023). The mean overall workload score for each condition is shown in figure 10. The results 

of post hoc analyses, shown in table 4, revealed that overall workload scores were significantly 

lower in the 3-D Audio mode than in all other conditions except the Visual mode. 

0

20

40

60

80

100

Overall Weighted Workload Scores

Series1 64.6 62.99 59.49 62.77 58.19

Baseline 1 Baseline 2 Visual Spatial 

Language 3-D Audio

Figure 10. Overall workload scores. 

Table 4. Mean difference between modes in overall workload scores. 

Mode Baseline 2 Visual Spatial Language 3-D Audio 

Baseline 1 1.61 (p = .459) 5.11 (p = .021) 1.83 (p = .400) 6.41 (p = .004) 

Baseline 2 3.50 (p = .110) 0.22 (p = .919) 4.80 (p = .030) 

Visual -3.28 (p = .134) 1.30 (p = .550) 

Spatial Language 4.58 (p = .038) 

Bold blocks indicate significant differences. 
16 

5.4 Participants’ Preferences and Comments 

When asked about which condition they thought was best for acquiring targets while they 

attended to radio communications, more than half of the participants (53%) selected the Visual 

mode. The preferences of the remaining participants were split among the 3-D Audio (18%), 

Spatial Language (12%), Baseline 1 (12%), and the Baseline 2 (5%) conditions. Most of those 

who preferred the Visual mode believed that the visual cues were more straightforward, required 

less thought in determining target location, and did not interfere with the radio communications. 

The reasons some gave for preferring the Spatial Language mode were that it “gets your 

attention” or that “it is what I’m used to.” The latter reason was also given by one participant 

who preferred the Baseline 1 condition. 

When asked about which condition they thought to be the worst for acquiring targets while they 

attended to the radio communications, half of the participants (50%) selected the Baseline 1 

condition. Eighteen percent of the participants believed the Spatial Language mode was the 

worst, and another 18% chose Baseline 2. Six percent of the participants thought the Visual 

mode was the worst, and another 6% chose the 3-D Audio mode. Many of those who thought 

the Baseline 1 condition was the worst noted the lack of information about target location and the 

need to scan continuously for targets. Most who disliked the Baseline 2 condition also noted the 

lack of information about target location. Some considered the auditory alert to be “useless,” 

claiming that they found themselves merely waiting for the auditory alert and not focusing on the 

radio transmissions. Others claimed that there were times when they were slow in responding to 

the alert. Interference with the radio transmissions and distraction was the reason given most 

often for their disliking the Spatial Language and 3-D Audio cues. Participants also expressed a 

lack of confidence in their ability to localize the 3-D Audio sounds to specific clock positions, 

although all but one participant performed well in pre-tests. One participant who believed the 

Visual mode was the worst claimed that determining the location of the target “took too many 

steps” and required him to “look and process before taking action.” 

Many participants believed that cues about target location should be provided visually and 

auditorily, not only for backup in case a cue should fail but also when a visual display is 

unavailable, as would be the case when the commander-gunner is seated with his head outside 

the vehicle. When the commander-gunner is outside the vehicle, the participants believed that 

cues about the location of targets should be provided relative to the orientation of his head. 

When the commander-gunner is seated inside the vehicle, visual cues about target location 

should be based on the azimuth orientation of the main gun. A number of participants preferred 

that the auditory cues be provided in 3-D Audio rather than in Spatial Language, but they 

expressed concern that two speakers were needed to provide the 3-D Audio cues. They claimed 

that the speakers in their headsets tend to fail and replacements are not readily available. 

According to the Soldiers, it is not uncommon for crew members to have a headset with only one 

speaker that works. Speakers are often swapped between crew members to ensure that each has 

at least one functional speaker. 
17 

6. Discussion 

In this study, participants hit 100% of the targets presented in the Visual, Spatial Language, and 

3-D Audio modes by comparison to 94% in Baseline 1 and 95% in Baseline 2. As hypothesized, 

target acquisition times were faster in modes where information about target location was 

provided than in either of the two baseline conditions. On the average, time to first shot in the 

Visual, Spatial Language, and 3-D Audio modes was 1.4 seconds faster (19%) than in Baseline 1 

and 2.3 seconds faster (27%) than in Baseline 2. No difference was found between the Visual 

and 3-D Audio modes in time to first shot or time to hit, but target acquisition times were 

1.0 second faster (15%) in these modes than in the Spatial Language condition. Similarly, no 

differences were found between the 3-D Audio and Visual modes in overall workload scores, but 

scores in the 3-D Audio mode were lower than scores in all other cue conditions. On the 

average, 23% less information was recalled from the SITREPs in Baseline 1 than in the other 

four cue conditions where attention could be directed to communications between target 

presentations. No differences were found between Baseline 2 and the Visual, Spatial Language, 

or 3-D Audio modes in the performance of this secondary task. 

Differences found between cue conditions in target acquisition performance might best be 

compared with the results of an investigation by Simpson et al. (2004). In this latter study, the 

researchers measured times to visually acquire targets in a simulated flight task in four display 

conditions that were like those assessed in the current investigation. One of the four conditions 

provided no information about the presence or location of targets (no display), as in Baseline 1. In 

a second condition, an auditory alert was provided to signal the presence of a target (as in 

Baseline 2) but was also accompanied by a visual display that showed target direction and relative 

elevation (Visual + Audio Alert). In the remaining two conditions, the visual display was 

supplemented by a non-spatialized verbal cue (Visual + Clock-Coordinate) or a spatialized audio 

cue (Visual + 3-D Audio). As in the present investigation, Simpson et al. (2004) found that target 

acquisition times were slower in the first two conditions which were also the only conditions in 

which targets went undetected. However, pairing the auditory alert about the presence of a target 

with the visual display showing target location significantly reduced target acquisition times over 

the “no-display” condition. By themselves, the auditory alerts about the presence of a target 

provided in the present study were considered “useless” by some participants who observed that on 

a number of occasions, they were slow in responding to these alerts. 

On average, target acquisition times in the Visual and 3-D Audio modes were 24% faster than in 

Baseline 1 and 31% faster than in Baseline 2. By comparison, Simpson et al. (2004) found an 

average 25% reduction in target acquisition time between the Visual + 3-D Audio mode and the 

other conditions they studied. The 1-second difference in target acquisition time found between 
18 

the Spatial Language condition and the 3-D Audio and Visual modes in the current investigation 

was also similar to the difference found between the Visual + 3-D Audio mode and the Visual + 

Clock Coordinate condition in Simpson et al. (2004). In this latter investigation, the researchers 

did not present any concurrent verbal communications that could potentially interfere with the 

perception of the verbal cues about target location. Therefore, for the present study, it is 

believed that the increase in target acquisition time in the Spatial Language condition might be 

attributable to other factors. First, the 1-second delay in target acquisition time may have been 

influenced by the structure of the verbal cue. In both studies, words that defined the location of 

the target were presented in the latter half of the cue, preceded by a verbal alert (e.g., “Target -- 9 

o’clock” or “Traffic -- 9 o’clock high...”). A 1-second delay in the receipt of information about 

the location of a target might be expected to result in a similar delay in the time to acquire the 

target. However, it is also likely that the encoding of the Spatial Language cue required an 

additional cognitive step that involved the conversion of the verbal cue about the clock position 

of the target into a spatial image. 

In a more recent study by Haas, Pillalamarri, Stachowiak, and Lattin (in press), target location 

information was also prefaced by a verbal alert, but the location of the target was presented in 

plus and minus degrees rather than in clock positions (e.g., “Target -- minus 15 degrees”). 

Unlike the results of the present investigation, no differences were found between the verbal and 

3-D audio cueing techniques in target acquisition time or perceived workload. It is believed that 

the spatial language cues employed by Haas et al. (in press) may have provided a more 

immediate indication of whether the target lay to the right or left of 0 degrees, as did the Visual 

and 3-D Audio cues used in the present study. Here, any additional time and effort spent in the 

transformation of the Spatial Language cue into meaning may not only have contributed to 

increases in target acquisition time but also may have offset any potential reductions in perceived 

workload over baseline conditions. 

In the present investigation, no differences were found between the Visual and 3-D Audio modes 

in either target acquisition performance or workload. The location of the target with respect to 

the 12-o’clock position was more readily discerned in these modes than in the Spatial Language 

condition. Given that targets were easy to detect, even at high slew rates, participants may not 

have felt compelled to localize the target to a specific clock position. Rather, they may have 

merely slewed in the direction indicated. 

Without reliable information about the existence or location of targets, commander-gunners must 

spend more time scanning the terrain around their vehicle in search of potential threats. The task 

of detecting and identifying targets can impose significant demands on cognitive resources and 

attention. Thus, in this study, it was anticipated that while the participants were searching for 

targets, less attention would be available for acquiring information contained in radio transmissions. Improvements in the performance of this secondary task were expected in conditions where 

attention could be directed to communications between target presentations. Additionally, it had 

been hypothesized that improvements would be greater in the Visual mode because the visual cues 
19 

about target location would not compete for auditory resources used by Soldiers in attending to the 

radio transmissions. The verbal cues provided in the Spatial Language mode were expected to be 

more disruptive to this secondary task than the 3-D Audio cues that were conveyed in sounds and 

not words. However, although many of the participants complained that the auditory cues 

interfered with the SITREPs, no differences were found between the Visual, Spatial Language, or 

3-D Audio modes in the performance of the communications task. Generally, the analysis of 

secondary task performance appeared to suggest that the less time Soldiers spend scanning for 

targets, the more time would be available for them to attend to communications between target 

engagements. 

It is believed that if targets had been less conspicuous than they were in the present investigation, 

target acquisition times in all conditions would have been greater than those that were found. 

Target acquisition times would still be expected to be faster in modes where target location cues 

are provided. However, the time to acquire a target would become increasingly dependent on the 

fidelity of the target location due and the extent to which the cue enables the commander-gunner 

to narrow the focus of his search. The more time and resources Soldiers spend in the search for 

targets, the less time and fewer resources they will have available to perform a secondary 

communications task. 

7. Conclusions and Recommendations 

In this study, cues that merely signaled the presence of a target did not provide any benefit in target 

acquisition performance. However, as might be expected, targets were acquired significantly 

faster when cues were provided about their location. Target acquisition times were faster in the 

Visual and 3-D Audio modes than they were in the Spatial Language condition, but the advantage 

that 3-D Audio cues provided in reductions in target acquisition performance and overall workload 

were not clearly distinguishable from those provided by cues in the Visual mode. Less information was recalled from SITREPs in Baseline 1 than in the other four cue conditions where attention 

could be directed to the communications task between target presentations. However, contrary to 

expectations, no differences were found between Baseline 2 and the Visual, Spatial Language, or 

3-D Audio modes in the performance of this secondary task. 

The results of this investigation are preliminary. Additional studies are needed to explore the 

advantages and disadvantages of the information presentation techniques assessed in this study 

and other display alternatives, particularly in the noise and vibration conditions that are typical of 

the combat vehicle environment. Studies that follow will include an assessment of the effects of 

tactile displays on target acquisition performance and attention to communications. The 

modality in which these communications are presented (i.e., auditory and visual) will be included 

as a factor in these analyses. In these studies, targets will be more embedded in the surrounding 
20 

terrain to provide a better indication of the fidelity of the target location cues and the effects 

these cues have on primary and secondary task performance. 

The technology that will provide information about target location has not currently been 

defined, although work is under way to demonstrate such a capability. It cannot be assumed, as 

it was here, that such a technology will detect 100% of targets with no false alarms. The 

translation of information from sensors and other intelligence sources into reliable, high fidelity 

sensory cues about enemy position poses a significant challenge. The potential impact of cue 

reliability on target acquisition performance and workload with the use of these and other display 

techniques will need to be explored. 
21 

8. References 

Begault, D. R. Challenges to the successful implementation of 3-D sound. Journal of the Audio 

Engineering Society 1991, 39 (11), 864-870. 

Begault, D. R. Head-up auditory displays for traffic collision avoidance system advisories: A 

preliminary investigation. Human Factors 1993, 35 (4), 707-717. 

Haas, E.; Gainer, C.; Wightman, D.; Couch, M.; Shilling, R. Enhancing system safety with 3-D 

audio systems. Proceedings of the Human Factors and Ergonomics Society 41st Annual 

Meeting, 868-872, Albuquerque, NM, 1997. 

Haas, E.; dePontbriand, R.; Mello, R.; Patton, J.; Solounias, A. The effect of auditory display 

type and physical load on message intelligibility for the dismounted soldier. Proceedings of 

the Human Factors and Ergonomics Society 44th Annual Meeting, 706 - 709, San Diego, 

CA, 2000. 

Hart, S. G.; Staveland, L. E. Development of a multi-dimensional workload rating scale: 

Results of empirical and theoretical research. In P.A. Hancock & N. Meshkati (Eds.). 

Human Mental Workload. Amsterdam, The Netherlands: Elsevier, 1988. 

Loomis, J. M.; Klatzky, R. L.; Philbeck, J. W.; Golledge, R. G. Assessing auditory distance 

perception using perceptually directed action. Perception and Psychophysics 1998, 60, 966–

980. 

Loomis, J. M.; Lippa, Y.; Klatzky, R. L.; Golledge, R. G. Spatial updating of locations specified 

by 3-D sound and spatial language. Journal of Experimental Psychology: Learning, 

Memory, and Cognition 2002, 28, 335-345. 

McKinley, R. L.; Erickson, M. A.; D’Angelo, W. R. 3-dimensional auditory displays: 

Development, applications, and performance. Aviation, Space, and Environmental Medicine 

1994, 5, A31 – A38. 

McKinley, R. L.; D’Angelo, W. R.; Haas, M. W.; Perrot, D. R.; Nelson, W. T.; Hettinger, L. J.; 

Brickman, B. J. An initial study of the effects of 3-dimensional auditory cueing on visual 

target detection. Proceedings of the Human Factors and Ergonomics Society 39th Annual 

Meeting, 119-124, Santa Monica, CA, 1995. 

Mitchell, D. K.; Samms, C.; Glumm, M.; Krausman, A.; Brelsford, M.; Garrett, L. Improved 

performance research integration tool (IMPRINT) model analyses in support of the 

situational understanding as an enabler for unit of action maneuver team soldiers science 

and technology objective (STO) in support of future combat systems (FCS); ARL-TR-3405; 

U.S. Army Research Laboratory: Aberdeen Proving Ground, MD, 2004. 
22 

Shinn-Cunningham, B.; Lehnert, H.; Kramer, G.; Wenzel, E.; Durlach, N. Auditory displays. In 

Gilkey, R. H., & Anderson, T. A. (Eds.). Binaural and Spatial Hearing in Real and Virtual 

Environments. (pp. 611–633). New Jersey: Lawrence Erlbaum Associates, Inc, 1997. 

Simpson, B. D.; Brungart, D. S.; Gilkey, R. H.; Cowgill, J. L.; Dallman, R. C.; Green, R. F.; 

Youngblood, K. L.; Moore, T. J. 3-D audio cueing for target identification in a simulated 

flight task. Proceedings of the Human Factors and Ergonomics Society 48th Annual 

Meeting, 1836-1840, Santa Monica, CA, 2004. 

Tannen, R. Multimodal displays for target localization in a flight test; AFRL-HE-WP-TR-2001-

0102; Air Force Research Laboratory: Wright Patterson Air Force Base, OH, 2001. 

U.S Army. Hearing Conservation. U.S. Army Pamphlet 40-501, Washington, DC: Department 

of Defense, 1991. 

Wickens, C. D.; Hollands, J. G. Attention, time-sharing and workload. Engineering Psychology 

and Human Performance. New Jersey: Prentice Hall, 2000. 
23 

Appendix A. Situation Report (SITREP) Example 

Attention! Some aspects of the current situation have changed that will affect your mission. The 

following is the latest from Command Headquarters. 

The friendly country of Dodge has been overthrown by insurgent religious extremists. The 

United States has deployed the 3rd STRYKER Brigade Combat Team of the 2nd Infantry 

Division. This team will link up with and support the remaining elements of the government. 

The team is currently assembled 3 kilometers west of the airport in the capital city of Aberdeen. 

The team will conduct reconnaissance operations around the airport prior to securing it for the 

entry of heavy U.S. forces. Your platoon will proceed to Objective Brown which is 500 meters

east of your current assembly point. Other STRYKER platoons will proceed northeast and 

southeast to their objectives to encircle the airport. You are to arrive at your objective at 0500 

hours tomorrow morning. Potential threats on the way to your objective include an ambush 

along Phaseline Washington. The insurgents have captured tanks from the defense forces and 

have deployed them around the perimeter of the airport. Your closest supporting unit is 

dismounted infantry located 100 meters south of the objective. The call sign of this supporting 

unit is Charlie 1. A friendly artillery unit is currently 2 kilometers north of the airport. The call 

sign of this unit is Zulu 3. They will await your signal to provide support as needed. Air support 

will be provided by a squadron of Apache helicopters. Their call sign is Eagle 1. The drop off 

point for your squad is Peach Hill which is 100 meters south of the objective. The closest enemy 

unit to the objective is armor, located 200 meters east of the objective. This armor unit is a 

company-size unit and is currently re-supplying. Dismounted enemy infantry are located 

throughout the countryside and are armed with RPGs. They have placed landmines near your 

objective along Church Road. 
24 

INTENTIONALLY LEFT BLANK
25 

Appendix B. SITREP Questionnaire (Example) 

Participant # : ______ Run : ___ Target Set : ___ 

Please answer the following questions based on the SITREP you heard during this last target set. 

Each answer is one or two words. The number in parentheses after the question indicates the 

number of words in the answer. Examples of one-word answers are “armor” or “NBC.” Examples 

of two-word answers are “mechanized infantry” or “Charlie Company.” An answer which 

requires two words can also include a number. Examples of two-word answers with a number are 

“200 meters” or “Charlie 35.” Each answer is worth 2 points. If you do not provide an answer to a 

question, or the answer is wrong, you will lose 2 points. If you omit a word from an answer that 

requires two words, or if one of the words in your answer is wrong, you will lose 1 point. 

Question Answer (Please PRINT)

 (1) What is the name of the country that has been 

 overthrown? (1) ________________________ 

 

 (2) In what direction is the STRYKER team from 

 the airport? (1) ________________________ 

 

 (3) How far is your objective from your current 

 assembly point? (2) ________________________ 

 (4) At what time is your platoon to arrive at the 

 objective? (2) ________________________ 

 (5) What have the insurgents captured from the 

 country’s defense forces? (1) ________________________ 

 

 (6) What is the call sign of the friendly unit located 

 north of the airport? (2) ________________________ 

 

 (7) What is the name of the drop off point for the 

 squad? (2) ________________________ 

 

 (8) How far is the closest enemy unit from the 

 objective? (2) ________________________ 

 

 (9) In what activity is the enemy unit closest to your 

 objective currently engaged? (1) ________________________ 

 

(10) What is the name of the road near your objective 

 where the enemy infantry has placed obstacles? (1) ________________________ 
26 

INTENTIONALLY LEFT BLANK
27 

Appendix C. NASA-TLX 

RATING SCALE DEFINITIONS 

 Title Endpoints Descriptions 

MENTAL Low/High How much mental and perceptual 

DEMAND activity was required (e.g. thinking, 

deciding, calculating, remembering, 

looking, searching, etc.)? Was the task 

easy or demanding, simple or complex, 

exacting or forgiving? 

PHYSICAL Low/High How much physical activity was 

DEMAND required (e.g. pushing, pulling, 

turning, controlling, activating, etc.)? Was 

the task easy or demanding, slow or brisk, 

slack or strenuous, restful or laborious? 

TEMPORAL Low/High How much time pressure did you 

DEMAND feel due to the rate or pace at 

which the task or task elements occurred? 

Was the pace slow and leisurely or rapid 

and frantic? 

PERFORMANCE Perfect/Failure How successful do you think you 

were in accomplishing the goals of the 

task set by the experimenter (or yourself)? 

How satisfied were you with your 

performance in accomplishing these 

goals? 

EFFORT Low/High How hard did you have to work 

(mentally and physically) to accomplish 

your level of performance? 

FRUSTRATION Low/High How insecure, discouraged, 

LEVEL irritated, stressed and annoyed 

versus secure, gratified, content, 

relaxed and complacent did you 

feel during the task? 
28 

Effort

or 

Performance

Temporal Demand

or 

Frustration

Temporal Demand

or 

Effort

Performance

or 

Frustration

Physical Demand

or 

Performance

Physical Demand

or 

Frustration

Physical Demand

or 

Temporal Demand

Temporal Demand

or 

Mental Demand

Effort

or 

Performance

Temporal Demand

or 

Frustration

Temporal Demand

or 

Effort

Performance

or 

Frustration

Physical Demand

or 

Performance

Physical Demand

or 

Frustration

Physical Demand

or 

Temporal Demand

Temporal Demand

or 

Mental Demand
29 

Frustration 

or 

Effort

Performance

or 

Mental Demand

Performance

or 

Temporal Demand

Mental Demand 

or 

Physical Demand

Frustration 

or 

Mental Demand

Mental Demand

or 

Effort

Effort 

or 

Physical Demand

Frustration 

or 

Effort

Performance

or 

Mental Demand

Performance

or 

Temporal Demand

Mental Demand 

or 

Physical Demand

Frustration 

or 

Mental Demand

Mental Demand

or 

Effort

Effort 

or 

Physical Demand
30 

RATING SCALE SHEET

Low High 

MENTAL DEMAND 

Low High 

PHYSICAL DEMAND 

Low High 

TEMPORAL DEMAND 

Good Poor 

PERFORMANCE 

Low High 

EFFORT 

Low High 

FRUSTRATION 
31 

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