Military Hearing Protection Devices and TCAPS: Can the Soldier Detect and Identify Gunshots and other Threats? Acknowledgement & Disclaimer

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1 Military Hearing Protection Devices and TCAPS: Can the Soldier Detect and Identify Gunshots and other Threats? Jay E. Clasing, MAJ, U.S. Army Virginia Tech John G. Casali, Ph.D., CPE Virginia Tech John P. Keady, Ph.D., J.D. Innovation R&D Lab National Hearing Conservation Association New Orleans, LA February 23-25, 2012 Acknowledgement & Disclaimer Funded through a grant provided by the Office of Naval Research (ONR). (Kurt Yankaskas, Contract Monitor) Casali and Keady independently designed the experimental protocols for the preliminary detection study. Clasing and Casali designed and conducted the current experimental protocol Selection of HPEDs and auditory threats occurred with input from the Marine Enhancement Program / Gruntworks Squad Integration facility and ONR s NIHL program leadership. Some devices were Export/ITAR controlled items. All devices provided by the manufacturer 2 1

2 Warfighters Require Hearing Protection NIHL and tinnitus are the most common military disabilities (Veterans Health Administration Office of Research and Development, 2010) Over $1.2 billion spent on hearing injuries in : VA dispensed ~ 380,000 hearing aids at ~ $135 million ~ 1/3 of soldiers from Iraq and Afghan theaters have NIHL (Ahroon, 2007) The hearing-impaired warfighter may pose a liability to himself and others in combat operations. Survivability & Lethality implications (Abel, 2008; Casali, Ahroon, & Lancaster, 2009) 3 Warfighters Require Hearing Protection Warfighters who lose their fitness-for-duty due to HL represent a huge $ investment lost. Casali & Talcott (2011), Vause & Grantham (1999) showed more errors in localizing a rifle being fired (Casali) and cocked (Vause) with certain HPDs & HPEDs, compared to open ear. Warfighters have little confidence in, and won t use HPDs that compromise their situational awareness (Casali et al, 2009). 4 2

3 Field Study: Experimental Design S 1-20 S 1-20 S 1-20 S 1-20 S 1-20 S 1-20 S 1-20 S 1-20 S 1-20 S 1-20 S 1-20 S 1-20 S 1-20 S 1-20 S 1-20 S 1-20 S 1-20 S 1-20 Auditory Threats 1. Gunshot 2. AK-47, charging 3. Arabic Hearing Conditions Atlantic Signal s Dominator (Max) (TCAPS) Nacre Quiet- Pro+ (Max) (TCAPS) Peltor Com- Tac II (Max) (TCAPS) Etymotic EB-15 (Hi) Combat Arms (Rocker Open) Open Ear Signals & conditions chosen through collaboration with the Marine Enhancement Program / Gruntworks Squad Integration staff. TCAPS = Tactical Communication and Protective System 5 AK-47 Recording 6 3

4 Atlantic Signal / Phonak Dominator 7 Nacre QuietPro+ 8 4

5 Peltor Com-Tac II Sound Transmission Earmuff (AEARO/3M) 9 Etymotic EB-15 BlastPLG 10 5

6 Combat Arms Earplug: Rocker Switch Version (AEARO/3M) 11 Subjects and Sessions Age: years, x = 21; 20 males, 18 cadets, 2 active duty, all Army or Marine (20) Normal hearing (as defined by us): Each ear: < 25 dbhl at 250 Hz to 6000 Hz Symmetry: < 15 dbhl difference between ears Attended 2 sessions: Screening: PT audiogram, informed consent Experimental (3-5 hrs.) 12 6

7 Stepwise Protocol - Experimental Session 1) Subject (S) receives signal demonstration. 2) S fit by E with HPED (counterbalanced) and both move to starting position; S faces towards signal, E stands besides. 3) E prompts S to listen and initiates signal. 4) E asks if S detects signal. E & S advance until detection occurs. E records the detection distance. 5) Once detection has occurred, the S is asked to positively identify the signal and advances until identification occurs. The E records the identification distance. 6) Once identification has occurred, the S advances 50 ft., then faces away from the signal and advanced until detection is lost. The E records the detection-lost distance. 7) Repeat steps 3-6 for each auditory signal. 8) S performs ratings of HPED/OE condition after conclusion of all 3 auditory signals. 9) Repeat of steps 2-8 for all listening conditions. 13 Field Experimental Site: VT s Kentland Farm 14 7

8 Field Experimental Site: 15 Results 1. Detection Distance on Approach and Detection Lost on Retreat per listening condition 1. Identification Distance per listening condition 2. Subjective Rankings 16 8

9 Approach Detection Detection Lost on Retreat DOMINATOR QUIET PRO+ COMTAC II EB15 (HI SETTING) COMBAT ARMS (OPEN) OPEN EAR TCAPS 17 Approach Detection Detection Lost on Retreat DOMINATOR QUIET PRO+ COMTAC II EB15 (HI SETTING) COMBAT ARMS (OPEN) OPEN EAR TCAPS 18 9

10 Approach Detection Detection Lost on Retreat DOMINATOR QUIET PRO+ COMTAC II EB15 (HI SETTING) COMBAT ARMS (OPEN) OPEN EAR TCAPS 19 DOMINATOR QUIET PRO+ (MAX GAIN) COMTAC II (MAX GAIN) EB15 (HI SETTING) COMBAT ARMS (OPEN) OPEN EAR TCAPS 20 10

11 DOMINATOR QUIET PRO+ (MAX GAIN) COMTAC II (MAX GAIN) EB15 (HI SETTING) COMBAT ARMS (OPEN) OPEN EAR TCAPS 21 DOMINATOR QUIET PRO+ (MAX GAIN) COMTAC II (MAX GAIN) EB15 (HI SETTING) COMBAT ARMS (OPEN) OPEN EAR TCAPS 22 11

12 5th 6th 3rd 1st 2nd 3rd DOMINATOR QUIET PRO+ (MAX GAIN) COMTAC II (MAX GAIN) EB15 (HI SETTING) COMBAT ARMS (OPEN) OPEN EAR 23 Participant Comments EB15 +most comfortable and easy to forget they are in +wouldn t mind using for an extended period of time -wind noise was distracting -feedback/white noise was distracting Dominator +amplifies conversations well -bulky and uncomfortable -amplifies foot steps and bird sounds which was distracting -difficult to hear when windy +/-earpiece secures well in ear, but becomes uncomfortable QuietPRO+ +very comfortable +amplifies close-up sounds well -slightly bulky -background noises were distracting Combat Arms (Rocker Open) +very comfortable, no cabling -muffled signals to almost nothing -hard to communicate with experimenter -could not hear gunshot, relied on felt pop ComTac II +extremely comfortable to wear +very secure and only one cable -difficult to hear when windy -footfalls were distracting -clothing/fabric sounds were distracting 24 12

13 Conclusions -Some devices are better in terms of detection and identification of the three tested signals -TCAPS devices are not necessarily more effective than the EB15 in signal detection and localization. -Important to consider auditory threats in the design phase. -The specific needs of the user must be considered when obtaining Hearing Protection. 25 Design Guidance -Wind-noise is a consistent issue among all devices. -Due to its negative effect on detecting and identifying all three threats, Soldiers must be informed of the significant impact the Combat Arms device has on normal hearing. -The Combat Arm s level dependent setting should be modified to produce less high frequency attenuation. -No HPED/TCAPS is a panacea, therefore Soldiers need to be educated on the effects of these devices on their normal hearing

14 In-Lab Objective Test Results (USAARL) -Input-to-Output Frequency Response in continuous noise obtained -Impulse noise data obtained for each device 27 Input-to-Output Response Example 28 14

15 Thank You! Questions? 29 CAE Gen 2 & Gen 3 Generation 2 Generation 3 15

16 From CAE brochure: gives wearers a better ability to hear low-level sounds critical to mission safety-conversation, footsteps, rifle bolts. 31 -A questionable conclusion, given db attenuation from 1000 Hz to 8000 Hz. 16