Developing a measure of auditory fitness for duty for military personnel

Abstract

The ability to listen to and understand commands in noisy environments, whilst maintaining situational awareness, is an important skill for military personnel, and can be critical for mission success. Due to the nature of their work, military personnel are regularly exposed to damaging noise exposures, which could lead to hearing loss and therefore the inability to understand commands. Accurately measuring auditory fitness for duty (AFFD) is important for ensuring that personnel have sufficient hearing ability to be effective in operational scenarios. Pure-tone audiometry (PTA) is the hearing test currently used by the UK military but it is not known whether it is able to accurately predict AFFD. The aims of this thesis were to: 1) better understand AFFD, focusing on the infantry; and 2) undertake the initial development of a credible alternative to PTA and a simulation of an AFFD task, ahead of future research to determine which test(s) best predict AFFD.

Using focus groups, followed by a questionnaire, 17 mission-critical auditory tasks (MCATs) carried out by infantry personnel were identified. Nine of these tasks were prioritised for evaluating AFFD and seven were speech communication tasks (SC-MCATs). It was anticipated that a speech-in-noise test might be a better tool than PTA for predicting performance on the SC-MCATs. Following a review of existing speech-in-noise tests, including a consultation with military subject-matter experts, the Coordinate Response Measure (CRM) was selected for this purpose, partly due to the high face validity when compared to typical infantry command structure. The CRM speech material was re-recorded in British English using NATO call-signs, was equalised in terms of intelligibility, and was implemented into an adaptive procedure with stationary speech-spectrum noise and evaluated using normal hearing civilians and hearing impaired military personnel. An AFFD task simulation of the SC-MCATs was developed. It simulated the environment of listening to commands over a military radio in a moving armoured vehicle. A final study found that while both the AFFD task simulation and the CRM were adversely affected by simulated hearing loss, only the task simulation appeared to be affected by experience of military commands. Further work is now required to determine whether PTA or the CRM, when combined with additional information such as previous military experience, best predict performance on the AFFD task simulation.

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ORCID for Daniel Rowan: orcid.org/0000-0002-7190-9997

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