Chapter 5 128 The large differences in predicted signal detectability between different driving situations suggest that it is important to take different driving situations into account when evaluating signal detectability inside a train cabin. Having high enough signal levels to ensure good signal detectability at maximum speed can imply that signals are too loud at lower speed rates. Warning signals that automatically adjust their level according to the background noise may therefore be warranted. Also, it is important to not only focus on detectability, but also evaluate the subjective experience of locomotive engineers. A signal with good audibility at high driving speed, may be experienced as annoying at a lower speed. Although it is likely that the results of this study reflect the real-life working situation of Dutch locomotive engineers, situations may occur in daily practice that make signal detection even harder. For example higher noise levels have been associated with passing vehicles at station platforms (Neitzel et al., 2009) and with crossing a tunnel (Dinno et al., 2011; Phan & Jones, 2017). Since the underlying physical mechanism for detecting an alarm in noise might depend on the SNR (Karunarathne et al., 2018), we need to be careful with generalizing the results to other SNR’s. Contrary to an earlier study that assessed the acoustic requirements for speech communication in Dutch train cabins (Houben et al., 2007), we found that the acoustic requirements for warning signal detectability were not always met.Thus, the fact that a workplace fulfils the acoustic conditions for speech communication, does not necessarily mean that the conditions for another hearing-critical task, detecting warning signals, are also fulfilled. This stresses the importance of evaluating the acoustical requirements for different hearing-critical jobs separately. By assessing the acoustical requirements in multiple work-settings, the work settings can be identified in which performance of the hearing-critical job is the most critical. This has the advantage that acoustical or environmental work modifications can then be undertaken to ensure safe and effective job performance in all work settings. Further, identification of the most hearing-critical work situations is useful for designing auditory fitness for job assessments. If an employee is capable of fulfilling an auditory task sufficiently in the most unfavourable acoustic environment, it is likely that the same task will also be successfully fulfilled in a less noisy environment. This method could be used to assess multiple workplaces in which hearing-critical jobs are performed, such as the workplace of police officers, firefighters, and coast guard employees.
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