Fitness for Duty Assessments for Jobs with Essential Hearing-Critical Tasks (PART 2 OF 2)

By Sigfrid D. Soli, Véronique Vaillancourt, and Ross J. Roeser

This article is a part of the May/June 2019, Volume 31, Number 3,  Audiology Today issue.

The first article in this series (see “Changing the Audiological Mindset About Fitness for Duty Assessments for Jobs with Essential Hearing-Critical Tasks,” March/April 2019 Audiology Today) described a new way of characterizing real-world noise environments in terms of their potential impact on an individual’s ability to perform essential hearing-critical (HC) job tasks (Soli et al, 2018a). This second article describes how this information can be used by audiologists in the clinic to perform objective, evidence-based hearing screening of individuals seeking jobs with essential HC tasks. The steps necessary to define the screening criteria are analogous in some ways to the steps used to define pure tone threshold levels (dB HL), but use recorded speech material. The rationale and calculations that characterize real-world noise environments, like the rationale and calculations that define dB HL measures, are detailed, but in both cases the assessment process is relatively simple and straightforward.

The impact of real-world noise environments on speech communication can be expressed in terms of the likelihood of effective speech communication using different levels of vocal effort and different communication distances (Soli et al, 2018a). These likelihoods are calculated using the Extended Speech Intelligibility Index (ESII) (e.g., Rhebergen, 2006), which enables estimates of speech intelligibility in nonstationary real-world noise environments to be obtained. We assume that effective speech communication can occur during time intervals when the value of the ESII is large enough for speech to be intelligible. This value is referred to as the criterion ESII for individuals with normal functional hearing ability. The ESII is measured over four seconds, the shortest time period during which a brief two-way communication might occur. The proportion of four-second intervals in real-world noise environments with ESII values exceeding the criterion value defines the likelihood of effective speech communication for individuals with normal functional hearing ability, and provides a reference value for each noise environment, as shown for a sample of 24 noise environments in Figures 3–5 in Soli et al (2018a). The method for using these criterion ESII values for screening is described below.