[Verification of normative values for the Swiss version of the Freiburg speech intelligibility test]

Abstract

Background and objective: In the Swiss version of the Freiburg speech intelligibility test five test words from the original German recording which are rarely used in Switzerland have been exchanged. Furthermore, differences in the transfer functions between headphone and loudspeaker presentation are not taken into account during calibration. New settings for the levels of the individual test words in the recommended recording and small changes in calibration procedures led us to make a verification of the currently used normative values.

Patients and methods: Speech intelligibility was measured in 20 subjects with normal hearing using monosyllabic words and numbers via headphones and loudspeakers.

Results: On average, 50% speech intelligibility was reached at levels which were 7.5 dB lower under free-field conditions than for headphone presentation. The average difference between numbers and monosyllabic words was found to be 9.6 dB, which is considerably lower than the 14 dB of the current normative curves.

Conclusions: There is a good agreement between our measurements and the normative values for tests using monosyllabic words and headphones, but not for numbers or free-field measurements.