Background: Since 2017, the Freiburg monosyllabic speech test can be used in hearing aid evaluation with background noise in Germany. The results are used to compare the aided versus the unaided condition. However, there is currently no reference speech recognition curve for a comparison to listeners with normal hearing.
Objective: The goal is to establish a reference speech recognition curve for listeners with normal hearing and to analyze the perceptual equivalence of the test lists in continuous CCITT noise (according to Comité Consultatif International Téléphonique et Télégraphique).
Materials and methods: The measurements were conducted at two different sites with 90 participants in total. Monosyllables and CCITT noise were presented at different signal-to-noise ratios by one loudspeaker from the front (S0N0). Individual and test-list specific discrimination functions were fitted to differentiate between the sites and among test lists.
Results: The reference speech recognition curve and its region of tolerance were established. Three perceptively deviating test lists (1, 3, 20) were identified.
Conclusion: The reference speech recognition curve enables quantification of hearing difficulties with Freiburg monosyllables in noise and an estimation of the rehabilitation with hearing aids. This reference curve is only valid for frontal stimulus presentation (S0N0) and continuous CCITT noise. Perceptually deviating test lists were different to those in quiet, but partly correspond to literature data.
Keywords: Hearing aids; Hearing loss; Perceptual equivalence; Signal-to-noise ratio; Speech discrimination.