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 Class500 Hz1000 Hz2000 Hz3000 Hz4000 Hz6000 Hz 1/1A /2F/3/ 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 One-part radio command Ex. “Turn right heading 270°.” Read-back task during maneuver Medium workload Two-part radio command Ex. “Turn right heading 290°, climb and maintain 2500’.” Read-back task during maneuver High workload 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 1Group 2 Age range Age median Age mean Flight hours range75-12,0001,100-11,000 Flight hours median Flight hours mean

Mean Hearing Levels RIGHT250Hz500Hz1kHz2kHz3kHz4kHz6kHz8kHz Group Group LEFT250Hz500Hz1kHz2kHz3kHz4kHz6kHz8kHz Group Group

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