Part III: Measuring hearing-critical job tasks 115 Introduction Inmany occupations, employees fulfil auditory tasks, such as speech communication and sound detection (Semeraro et al., 2015). This can be very challenging in some working settings, for example when high noise levels are present (Giguère et al., 2008). For locomotive engineers (train drivers), speech communication and sound detection are important for safe and effective job performance (Zoer et al., 2014). An engineer needs to communicate to the signaller, conductor, and others by answering calls, making announcements, and using communication equipment. Detection of warning signals is required to be warned in case of events that can compromise safety (Zheng et al., 2007). The signals aim to alert the driver at passing a sign and to verify whether the engineer is still alert for safe driving (Fenner, 2002; Scaccabarozzi et al., 2017). In Dutch train cabins, the Automatic Train Protection (ATP) system applies a bell-like signal combined with a warning light in the console in case of failure to stop for a stop signal, failure to reduce speed at a caution signal, or failure to comply to the local speed limit. The Driver’s Safety Device (DSD), also known as ‘the dead man’s switch,’ produces a buzzer-type auditory warning and is a failsafe in case the driver becomes incapacitated. Earlier, the appropriateness of the sound environment of Dutch locomotive cabins for speech communication was assessed, using the Speech Transmission Index (STI) (Houben et al., 2007). The STI values were 0.69 for communication using a transceiver and 0.76 for communication using a mobile phone, exceeding the value of 0.5 that is required for acceptable speech communication. It was concluded that the working environment of Dutch locomotive cabins meets the acoustic standards for speech communication. The appropriateness of the acoustic environment of Dutch locomotive cabins for warning signal detection has not yet been investigated, despite its importance for safe and effective job performance. Failure to detect the warning signals will result in decreased safety and decreased operational effectiveness (Merat et al., 2002; Semeraro et al., 2015). If the DSD or ATP signal is missed, the emergency breaking systemwill automatically reduce speed or bring the train to a full stop. To guarantee that a locomotive engineer is capable of performing the required auditory tasks, pure- tone audiometry is applied prior to employment as well as on a periodical basis (Tufts et al., 2009). In this study, normal hearing is defined as having hearing thresholds between 1000 Hz and 4000 Hz below 25 dB HL, because an engineer passes the hearing screening without being referred for additional
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