In ap revious study the authors examined intentional switching in auditory selective attention using ad ichoticlistening paradigm. In the present study this paradigm wase xtended to more natural and realistic environments by changing it to ab inaural-listening paradigm in which human performance with different methods of spatial reproduction were compared. Four reproduction methods were used: real sources in an anechoic environment, individual binaural synthesis reproduced with headphones, non-individual binaural synthesis reproduced with headphones, and non-individual binaural synthesis reproduced with twol oudspeakers and Cross-Talk-Cancellation-Filters. Speech of twospeakers waspresented simultaneously to subjects from twoout of eight different directions. Guided by avisual cue, subjects were asked to categorize the target'sspeech while ignoring the distractor's speech. Results showed greater reaction times and error rates for non-individual repro duction methods. The influences of the spatial transition of the target-speaker (switch or repetition of speaker'sd irection in space)a nd of the spatial arrangement of the twospeakers were largely identical across reproduction methods, even though it wasg enerally easier to filter out distractor'ss peech when using real sources. The findings suggest that the reproduction methods can be usefully applied to study auditory attention with only very little loss in accuracy.

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In an auditory attention-switching paradigm, participants heard two simultaneously spoken number-words, each presented to one ear, and decided whether the target number was smaller or larger than 5 by pressing a left or right key. An instructional cue in each trial indicated which feature had to be used to identify the target number (e.g., female voice). Auditory attention-switch costs were found when this feature changed compared to when it repeated in two consecutive trials. Earlier studies employing this paradigm showed mixed results when they examined whether such cued auditory attention-switches can be prepared actively during the cue-stimulus interval. This study systematically assessed which preconditions are necessary for the advance preparation of auditory attention-switches. Three experiments were conducted that controlled for cue-repetition benefits, modality switches between cue and stimuli, as well as for predictability of the switch-sequence. Only in the third experiment, in which predictability for an attention-switch was maximal due to a pre-instructed switch-sequence and predictable stimulus onsets, active switch-specific preparation was found. These results suggest that the cognitive system can prepare auditory attention-switches, and this preparation seems to be triggered primarily by the memorised switching-sequence and valid expectations about the time of target onset.

An auditory attention-switching paradigm was combined with a judgment-switching paradigm to examine the interaction of a varying auditory attention component and a varying judgment component. Participants heard two dichotically presented stimuli-one spoken by a female speaker and one spoken by a male speaker. In each trial, the stimuli were a spoken letter and a spoken number. A visual explicit cue at the beginning of each trial indicated the auditory attention criterion (speaker sex/ear) to identify the target stimulus (Experiment 1) or the judgment that had to be executed (Experiment 2). Hence, the attentional selection criterion switched independently between speaker sexes (or between ears), while the judgment alternated between letter categorization and number categorization. The data indicate that auditory attention criterion and judgment were not processed independently, regardless of whether the attention criterion or the judgment was cued. The partial repetition benefits of the explicitly cued component suggested a hierarchical organization of the auditory attention component and the judgment component within the task set. We suggest that the hierarchy arises due to the explicit cuing of one component rather than due to a "natural" hierarchy of auditory attention component and judgment component.

Binaural reproduction can be used in listening experiments under real-life conditions to achieve a high realism and good reproducibility. In recent years a clear trend to more individual reproduction can be observed as the ability to measure individual head-related-transfer-functions (HRTFs) is becoming more widespread. The question of the accuracy and reproduction methods needed for a realistic playback however has not been sufficiently answered. To evaluate an appropriate approach for binaural reproduction via headphones different head-related-transfer-functions (HRTFs) and reproduction methods were compared in this paper. In a listening test eleven explicitly trained participants were asked to localize eleven sound sources positioned in the right hemisphere using the proximal pointing method. Binaural stimuli based on individually measured HRTFs were compared to those of an artificial head in a static reproduction of stimuli and in three dynamic reproduction methods of different resolutions (5 • , 2.5 • and 1 • ). Unsigned errors in azimuth and elevation as well as front-back-confusions and in-head-localization were observed. Dynamic reproduction of any resolution applied turned out fundamental for a reduction of undesired front-back-confusions and in-head-localization. Individually measured HRTFs showed a smaller effect on localization accuracy compared to the influence of dynamic sound reproduction. They were mainly observed to reduce the front-back-confusion rate.