Chapter 1 38 frequencies 250Hz, 500Hz, 1000Hz, 2000Hz, 4000Hz, and 8000Hz, with adequate masking (if necessary). For a healthy, normally-hearing individual, hearing thresholds up to 25 dB HL are regarded as normal (Martin & Champlin, 2000). According to the American Academy of Otolaryngology, Binaural Hearing Impairment (BHI) was calculated from the mean of pure-tone thresholds for air conduction at 1000 Hz, 2000 Hz, and 4000 Hz and a 5:1 weighting favoring the better (American Academy of Otolaryngology, 1979). BHI provides a valid estimation of the hearing disability that a person with a degree of hearing loss would experience (Dobie, 2011). Speech audiometry was performed with the standard Dutch CVC word lists (Bosman & Smoorenburg, 1995) and was used to calculate the percentage of maximum speech recognition for the better ear. It has been recommended to transform percentages of maximum speech recognition, to enhance the normality of the data for the statistical analysis (Sherbecoe & Studebaker, 2004). Therefore, we transformed the percentages of maximum speech recognition using the rationalized arcsine formula. Speech reception threshold test Speech reception in continuous noise was assessed in a free field setting (S0N0) using everyday Dutch sentences developed by Plomp and Mimpen (1979) or the sentences developed by (Versfeld et al., 2000). These sentence materials have been shown to result in similar test outcomes (Versfeld et al., 2000). The aim of performing a speech reception test in noise is to objectify the influence of the hearing loss on functional speech understanding at the workplace. Therefore, all patients were asked if they wear hearing aids at work. If they did, the critical Signalto-Noise Ratio (SNR) was measured for aided conditions. If they did not, the SNR was measured for the unaided conditions. We have combined the SNR outcomes of patients who performed the test with and without hearing aids. We will refer to these measurements as speech in noise tests performed in patient’s daily work situation. For a healthy, normally-hearing individual, an SNR below − 4 can be expected (Versfeld et al., 2000). Survey Prior to the hospital visit, patients completed an extensive hearing survey to investigate personal and environmental factors that potentially influence NFR. This survey consisted of three questionnaires and additional questions.
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