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Influence of Headset, Hearing Sensitivity, Flight
Workload, and Communication
Signal Quality on Flight Performance and
Communications: An Army Black Hawk
Helicopter Simulator Experiment
Disclaimer
The views, opinions, and/or findings contained in
this report are those of the author(s) and should
not be construed as an official Department of the
Army position, policy, or decision, unless so
designated by other official documentation.
Citation of trade names in this report does not
constitute an official Department of the Army
endorsement or approval of the use of such
commercial items.
Acknowledgments
•
•
•
•
•
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Dr. John Casali
Dissertation committee members
Bose, Corp.
CEP, Inc.
USAARL
Participating pilots
Background
• Challenges to Army rotary-wing pilots
• Noise
• Communication demand
• Flight workload
• Decreased hearing sensitivity
Background
• Current approaches to meeting challenges
• Hearing protection
• Passive earplugs
• Communication devices
• Communications earplug (CEP)
• Active noise reduction (ANR)
• Hearing loss waivers
• Estimated 10% of aviators
Background
Class
500 Hz 1000 Hz 2000 Hz 3000 Hz 4000 Hz 6000 Hz
1/1A
25
25
25
35
45
45
2/2F/3/4
25
25
25
35
55
65
•
•
•
•
•
Pure tone air and bone conduction testing
Tympanometry
Acoustic reflex testing
Speech reception threshold
Speech discrimination, monaurally at 40dBSL, and
binaurally at most comfortable listening level (MCL)
• In-flight evaluation
Independent Variable – Headset
Configuration
David Clark headset
with CEP
Bose Aviation X ANR
headset
Passive David Clark headset
with passive foam earplug
Independent Variable – Flight
Workload (Perceptual)
Visual Meteorological
Conditions (VMC)
No ceiling
6 SM visibility
Low visibility, fog
1.75 SM visibility
Instrument
Meteorological
Conditions (IMC)
0 SM visibility
Independent Variable – Flight Workload
(Psychomotor)
Low workload
Straight and level flight followed by turns to
various headings
Medium workload
Straight and level flight followed by turns to
various headings combined with altitude
changes
High workload
Straight and level flight followed by turns to
various headings combined with altitude
and airspeed changes
Independent Variable – Flight Workload
(Communication)
Low workload
Medium workload
High workload
One-part radio command
Ex. “Turn right heading 270°.”
Read-back task during maneuver
Two-part radio command
Ex. “Turn right heading 290°, climb and
maintain 2500’.”
Read-back task during maneuver
Three-part radio command
Ex. “Turn right heading 270°, climb and
maintain 2500’ while decelerating to 100 knots.”
Read-back task during maneuver
Independent Variable – Signal
Quality
• Three levels
• Earphone output signal quality was manipulated and
quantified with the Speech Intelligibility Index (SII)
method of predicting speech intelligibility
• SII levels
• 0.4 (poor)
• 0.6 (average)
• 0.8 (good)
Blocking Variable – Hearing Levels
1. Audiometric pure-tone air-conduction thresholds
not exceeding 25 dBHL at 500, 1000, or 2000 Hz,
not exceeding 35 dBHL at 3000 Hz, and up to 55
dBHL at 4000 Hz in either ear
2. Audiometric pure-tone air-conduction thresholds
exceeding 25 dBHL at 500, 1000, or 2000 Hz,
exceeding 35 dBHL at 3000 Hz, and exceeding 55
dBHL at 4000 Hz
Dependent Measures
• Flight control performance
• Heading deviation
• Altitude deviation
• Airspeed deviation
•
•
•
•
Communications intelligibility (ATC readbacks)
Subjective workload measure
Subjective situation awareness measure
Subjective ratings of headset comfort and
speech intelligibility
Participants
• Active duty, Department of the Army civilians, and
contract helicopter pilots
• Instrument rated
• Current ‘full flying duties’ flight physical
• Had flown a military helicopter or military
simulator within the past year
Participant Demographics
Group 1
Group 2
Age range
20-51
33-66
Age median
31
52.5
Age mean
33.4
50.2
Flight hours range
75-12,000
1,100-11,000
Flight hours median
200
4350
Flight hours mean
1678.5
4770
Mean Hearing Levels
RIGHT
250Hz 500Hz
1kHz
2kHz
3kHz
4kHz
6kHz
8kHz
Group 1
9.0
7.0
6.0
4.0
9.0
10.5
14.0
11.0
Group 2
13.0
14.5
19.0
29.5
41.0
51.5
51.5
54.5
LEFT
250Hz 500Hz
1kHz
2kHz
3kHz
4kHz
6kHz
8kHz
Group 1
8.5
7.5
7.5
6.0
12.0
17.0
15.5
15.0
Group 2
18.5
19.5
22.5
30.5
54.5
67.5
69.5
69.0
Apparatus
Results
• Flight performance
• Heading deviation
• Altitude deviation
• Airspeed deviation
• Communications intelligibility
• Workload
• Situation awareness
• Headset comfort/speech intelligibility
Flight Performance
Altitude deviation – Interaction effect of workload/signal quality
Flight Performance
Airspeed deviation – Interaction effect of
workload/signal quality
Flight Performance
Airspeed deviation – Interaction effect of group/headset
Communications Intelligibility
ATC readbacks – Interaction effect of
workload/signal quality
Communications Intelligibility
ATC readbacks – Interaction effect of group/headset
Workload
Modified Cooper-Harper – Interaction effect of signal
quality/workload
Workload
Modified Cooper-Harper – Interaction effect of
group/headset
Workload
Modified Cooper-Harper – Interaction effect of
group/workload
Situation Awareness
SART – Interaction effect of group/headset
Situation Awareness
SART – Interaction effect of group/workload
Conclusions
• Workload level, signal quality level, and headset choice
influence pilot performance – significant difference
trends:
–
–
–
–
between low and medium workload
between average and poor signal quality
with high workload/poor signal quality conditions
with hearing impaired group using passive
headset/passive earplug combination
Limitations of Research
• No co-pilot
• Artificially increased primary pilot workload
• Single ATC radio
• Artificially decreased primary pilot communication
workload
• Number of hearing loss categories
• Unable to draw conclusions on level of hearing loss at
which performance degrades
Recommendations for Future
Research
• Similar study in an actual aircraft
• Similar study to examine how variables in this study
affect intra-cockpit coordination
• More narrowly defined hearing ability categories
• Isolated communication workload
• CEP comfort
• ANR technology
• Functional hearing evaluation
LTC Kristen L. Casto
U.S. Army Aeromedical Research Laboratory
Ft. Rucker, Alabama
[email protected]