[Indication for and verification of hearing aid benefit using modern methods of speech audiometry in German]. / Hörgeräteindikation und -überprüfung nach modernen Verfahren der Sprachaudiometrie im Deutschen.

The current guidelines for hearing aid supply in Germany employ the often criticised Freiburg monosyllabic speech test (FBE) in quiet. This test can be replaced with the monosyllabic rhyme test by von Wallenberg and Kollmeier (WaKo) in quiet and by the measurement of a speech reception threshold in an interfering noise at a moderate level (45 dB SPL) using either the Göttingen or the Oldenburg sentence test (criterion: 2 dB improvement in SNR, "signal-to-noise ratio"). This procedure was investigated in a group of 38 participants with a sensorineural hearing impairment (mild, moderate or severe hearing loss) and 11 volunteers with normal hearing. On average, comparable indications were achieved. Participants with a mild hearing loss and a selective problem with listening in interfering noise were assessed more fairly.

Analysis of spectral shape in the barn owl auditory system.

In a behavioral experiment, we investigated how efficiently barn owls (Tyto alba) could detect changes in the spectral profile of multi-component auditory signals with stochastic envelope patterns. Signals consisted of one or five bands of noise (bandwidth 4, 16, or 64 Hz each; center frequencies 1.02, 1.43, 2.0, 2.8, 3.92 kHz). We determined increment thresholds for the 2 kHz component for three conditions: single-band condition (only the 2 kHz component), all five noise bands with the envelope fluctuations of the bands being either correlated or uncorrelated. Noise bandwidth had no significant effect on increment detection. Increment thresholds for the different conditions, however, differed significantly. Thresholds in correlated conditions were generally the lowest of all conditions, whereas, thresholds in uncorrelated conditions mostly resulted in the highest thresholds. This can be interpreted as evidence for comodulation masking release in barn owls. If the increment in the 2 kHz component is balanced by decrementing the four flanking bands in amplitude, increment detection thresholds are not affected. The data suggest that the barn owls used information from simultaneous spectral comparison across different frequency channels to detect spectral changes in multi-component noise signals rather than sequential comparison of overall stimulus levels.