Performance in noise: Impact of reduced speech intelligibility on Sailor performance in a Navy command and control environment

Abstract

Noise, hearing loss, and electronic signal distortion, which are common problems in military environments, can impair speech intelligibility and thereby jeopardize mission success. The current study investigated the impact that impaired communication has on operational performance in a command and control environment by parametrically degrading speech intelligibility in a simulated shipborne Combat Information Center. Experienced U.S. Navy personnel served as the study participants and were required to monitor information from multiple sources and respond appropriately to communications initiated by investigators playing the roles of other personnel involved in a realistic Naval scenario. In each block of the scenario, an adaptive intelligibility modification system employing automatic gain control was used to adjust the signal-to-noise ratio to achieve one of four speech intelligibility levels on a Modified Rhyme Test: No Loss, 80%, 60%, or 40%. Objective and subjective measures of operational performance suggested that performance systematically degraded with decreasing speech intelligibility, with the largest drop occurring between 80% and 60%. These results confirm the importance of noise reduction, good communication design, and effective hearing conservation programs to maximize the operational effectiveness of military personnel.

The Impact of Reduced Speech Intelligibility on Reaction Time in a Naval Combat Environment

“…Sheffield et al (2016Sheffield et al ( , 2017 showed that operating with a hearing loss can significantly reduce lethality and survivability, and compromise mission success in dismounted combat. And in a precursor to the current study, Keller et al (2016) demonstrated that as speech intelligibility (SI) was reduced, Navy watch standers had difficulty responding to communications directed at them and changed behavior in several ways that could compromise the mission. The general methodology used in these studies was first introduced by Garinther and Peters (1990) to evaluate performance deficits in Army tank crew performance as a function of reduced SI and was later used by Casto et al (2012) in an aviation setting to show changes in performance for Blackhawk simulator pilots.…”

“…Task 1: Modified Rhyme Test (MRT). An MRT was completed using an adaptive procedure to establish individualized SNRs corresponding to SI levels of 80%, 65% and 50% for each participant using prerecorded stimuli from the study's two confederates (see Keller et al 2016 for details of the adaptive MRT procedure). The MRT is a closed-set speech recognition test originally developed as a more efficient way to evaluate communication systems in the military (House, et al, 1965).…”

“…The purpose of the AIMS software was to produce a communication channel that adapted in response to changes in the level of the talker's voice to maintain a constant SNR (and consequently, a constant level of SI) during each condition. See Keller et al (2016) for details of the intelligibility-modification processing.…”

“…However, it's probably far more likely that only one or two members of a unit suffer from a hearing impairment and it remains to be seen how this might impact performance of the team as a whole. Also, while Keller et al (2016) showed decreases in SA and changes in behavior as SI was reduced, it wasn't clear how this impacted the mission itself. Therefore, in this particular effort, two new questions were asked: "How does the impaired hearing of one watch stander effect their unimpaired shipmates?"…”

Management of acute acoustic trauma in mass casualty environments

“…A feasibility study exploring a new model of military hearing care suitable for use in both garrison and deployment settings is due to start imminently and will potentially allow medical officers on the ground access to super subspecialty opinions and support. For unit commanders, this is particularly important in light of recent studies showing the negative effects of temporary hearing impairment on cognition and task performance which occurs in both purely communication-based tasks and in target acquisition 1 2…”