Application of new speech intelligibility tests in silence for the assessment of acquired hearing losses

Previous studies comparing the Freiburg speech tests (FST) currently used in Germany to assess the severity of hearing loss with two modern speech intelligibility tests [the Gottingen sentence test (GoSa) and the monosyllabic rhyme test devised by von Wallenberg and Kollmeier (WaKo)] have indicated that a replacement of the old procedure would be possible. The current study investigates the consequences of the modern test procedures for the estimation of reduction in earning capacity resulting from hearing loss, and considers the optimal presentation levels for the WaKo test. The FST, GoSa, and WaKo speech intelligibility tests were performed on 29 volunteers with a hearing impairment. All tests were conducted in silence. The presentation levels for the Freiburg monosyllabic test were 60, 80, and for some participants also 100 dB SPL. The WaKo test was carried out once at 45, 65, and 85 dB SPL (a reduction of 15 dB relative to the FST) and again at 40, 60 and 80 dB SPL (reduction of 20 dB relative to the FST). A consideration across all presentation levels revealed that the best correlation match between the two monosyllabic tests was achieved at a 20-dB reduction in presentation level for the WaKo test relative to the FST. On average, the application of modern procedures and the different options for level reduction had only a minor effect on the quantitative assessment of reduction in earning capacity.