Chapter 6 140 Participants At the Amsterdam UMC, the signal detection test is routinely performed as part of the auditory fitness for job assessment. A retrospective data collection was therefore used to assess the construct validity. We retrospectively identified locomotive engineers who were referred to the Amsterdam UMC for an auditory fitness for job assessment. Eligible engineers were aged between 18 and 67, and underwent pure-tone audiometry, a speech reception test in noise, and the signal detection test. All engineers received a letter with information about the study. Because of the retrospective study design, an opt-out procedure was applied. The ethics committee at the Amsterdam UMC declared that no formal approval of the detailed protocol was needed according to the Dutch Medical Research Involving Human Subjects Act (No. 18_369 no. 18.421). A prospective power calculation was performed to determine the sample size required for the hypotheses testing. To determine the sample size required for detecting correlations of at least 0.3 with an Alpha error of 5%, a prospective power calculation was performed with G*Power software version 3.1 (Faul et al., 2007). To obtain a power of 80%, the inclusion of 67 locomotive engineers would be necessary. A total of 91 locomotive engineers fulfilled the inclusion criteria, of which eight objected to participate in the study. In total, 83 locomotive engineers were included, 81 males and two females with a mean age of 56 years (range, 33–66). Their mean number of working hours was 35 (SD, 4.1). The participants that owned hearing aids (about 20%) did not use them during the signal detection test and the speechin-noise test. Procedure Conventional hearing tests Pure-tone audiometry (ISO 8253-1 1989) was performed in a sound-isolated booth using calibrated Interacoustics Clinical Audiometers (model AC-40) and Decos audioNigma with TDH 39p headphones. Air conduction and bone conduction thresholds (with appropriate masking if necessary) were reported in dB hearing level (dBHL) at octave frequencies from 250 Hz to 8000 Hz. For each frequency, we calculated the binaural hearing impairment (BHI) by combining the thresholds of the left and right ear, with a five to one weighting favouring the better ear (American
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