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

• 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 ceiling6 SM visibility

Low visibility, fog1.75 SM visibility

Instrument Meteorological

Conditions (IMC)0 SM visibility

Independent Variable – Flight Workload (Psychomotor)

Low workloadStraight and level flight followed by turns to various headings

Medium workloadStraight 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 workloadOne-part radio commandEx. “Turn right heading 270°.” Read-back task during maneuver

Medium workload

Two-part radio commandEx. “Turn right heading 290°, climb and maintain 2500’.”Read-back task during maneuver

High workloadThree-part radio commandEx. “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 PerformanceAltitude deviation – Interaction effect of workload/signal quality

Flight PerformanceAirspeed deviation – Interaction effect of

workload/signal quality

Flight PerformanceAirspeed deviation – Interaction effect of

group/headset

Communications IntelligibilityATC readbacks – Interaction effect of

workload/signal quality

Communications Intelligibility

ATC readbacks – Interaction effect of group/headset

WorkloadModified Cooper-Harper – Interaction effect of signal

quality/workload

WorkloadModified Cooper-Harper – Interaction effect of

group/headset

WorkloadModified Cooper-Harper – Interaction effect of

group/workload

Situation AwarenessSART – Interaction effect of group/headset

Situation AwarenessSART – 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. CastoU.S. Army Aeromedical Research Laboratory

Ft. Rucker, Alabamakristen.casto@us.army.mil