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Whether a speaker will be visible or not depends upon the subject and purpose of the message, and whether the spoken message belongs to the foreground or to the background. For instance, if voice output consists of just a short message initiated by the system or a short explanation given on request of the user, then the speaker need not be shown. Also in case of a description which is logically bound to the primary visual scene, e.g. a picture or diagram on the display, there is no need to show a (simulated) speaker, because it will be rather disruptive for the user. On the other hand, in cases like an "on the spot" interview; or report being part of a multimedia production, the speaker(s) will usually be visible, as the visual scene will belong to the background of the story e.g. superimposed video. Finally, in the case of a narrative or monologue, or a group discussion without abundant graphic material, presenting the different speakers is highly desirable in order for the user to follow the turn-taking behaviour of the participants, which can only partly be simulated by use of a stereo sound system.
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Copyright EMMUS 1999.
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