[Recognition function for the Freiburg monosyllabic test in noise with a signal to noise ratio (SNR) of 5 dB]

The Freiburg monosyllabic test (FBE) has been an important German speech audiometry test for years. It is nowadays also used to assess the benefit of hearing aids in noise (FBE-S). This study investigates hearing in noise using the FBE at different sound pressure levels and a signal to noise ratio of 5 dB to generate a recognition curve.

In autumn 2018, 60 normal-hearing German native speakers (age 18-31 years) participated in the study at the military hospital in Hamburg. Using one FBE test list, speech intelligibility was measured from sound pressure levels of 15 to 90 dB in 5‑dB steps with a noise level 5 dB lower in each case. Subsequently, the average of all intelligibility rates and 95% confidence intervals (CI) were determined.

Participants comprised 29 female and 31 male subjects. Average age was 24.32 years (±3.29 years). The fixed effects analysis of variance with recognition as the dependent variable demonstrated a highly significant correlation between the levels of sounds/noise and the intelligibility of speech (p < 0.0001). The average intelligibility rates with 95% CI and the frequency distributions were presented tabularly and graphically.

In comparison to the normative curve, the FBE‑S recognition curve is shifted to the right. The average values of the FBE‑S reach the saturation area at a volume of 70/65 dB with an intelligibility rate of 90% (for comparison: the point of saturation for 100% intelligibility of the FBE without noise is reached at 55 dB). Using these averaged values of the FBE‑S enables better interpretation of individual results without and with hearing aids. In the future, the benefit of hearing aids should be measured at lower noise levels than it is today.