Speech Science Forum - Exploring the relationship between hearing acuity and operational performance in two different military environments

Speaker: Benjamin Sheffield, Walter Reed National Military Medical Center

Although hearing is known to play an essential role in military operations, relatively few studies have been conducted to directly measure the impact that a certain level of hearing impairment will have on combat effectiveness. In this talk, two studies will be highlighted that are attempting to define this relationship. In one study, Soldiers from the 101st Airborne Division at Ft. Campbell, KY, were equipped with wearable hearing loss simulators that allowed parametric adjustment of their hearing profiles between normal hearing and profound deafness. These soldiers then participated in a series of combat exercises that required three or four fire teams with different levels of hearing loss to progress through a series of waypoints in a wooded area as quickly as possible without being eliminated. A sophisticated GPS-based tracking system made it possible to track the progress of each team throughout the exercise, including information on which players were eliminated by enemy gunfire and which players were responsible for these kills. The results show that hearing impairment has a substantially negative impact on the performance of experienced soldiers in terms of survivability, lethality, and the ability to progress through the waypoints. In another study, the performance of Navy Watchstanders was tested in a simulated Combat Information Center (CIC) exercise while wearing real-time intelligibility modification systems that systematically controlled the speech intelligibility over shipboard communication channels using speech-shaped masking noise. A novel adaptive tracking procedure incorporating the modified rhyme test (MRT) was used to determine the signal-to-noise ratios (SNRs) that resulted in 80%, 60%, and 40% speech intelligibility for each individual. These SNRs were then tested along with a quiet condition in randomized blocks of the operational scenario. Participant performance was evaluated by subject matter experts in terms of the ability to respond appropriately to critical mission events. Participant comprehension of these events was also measured, and voice and eye-tracking data were recorded to evaluate behavioral changes in difficult communication settings. Results showed that as speech intelligibility decreased, participants missed more communications, lost more situational awareness, communicated less, and were less accurate when communicating. Participants also requested more repeat backs, talked louder, talked slower and diverted more visual attention away from relevant visual information sources. Taken together, these findings demonstrate just how critical the sense of hearing is in military operations and how important it is to preserve and protect hearing for the Warfighter. The results of these studies will be used to develop improved accession and retention standards for hearing impaired military personnel and to help define better requirements for the acquisition of improved hearing protection and communication systems for the military.

Time: Wednesday 15th June at 4pm

Venue: Room 118, Chandler House, 2 Wakefield Street

The Speech Science Forum (SSF) is a joint seminar series at UCL organised by the Department of Speech, Hearing and Phonetic Sciences (SHaPS) and the Institute of Cognitive Neuroscience (ICN).