[23] interface. This "virtual reality"-style inter- face features perspective displays of virtual rooms and spaces with figurative avatars, each of which can be associated with an audio source, corresponding to the voice of a user. A participant can rearrange the locations of avatars in virtual spaces and designate sinks, through whose ears the resulting spa- tialized soundscape is heard. Also, each participant can apply narrowcasting attributes to the avatars, altering the sound mix. Recalling the monkeys in Figure 14.4, Figure 14.9 illustrates the visual cues used for narrowcast- ing, including a hand covering the mouth of a muted avatar and hands C 2009 by Taylor & Francis Group, LLC Narrowcasting in SIP: Articulated Privacy Control View 0 View 1 View 2 View 3 View 4 View 5 View 6 View 7 Forward Center Right Backward Space Transparency Mixels Other Avatar Deafen Deafen Select Attend Azimuth Avatar 0 Avatar 0 157.5 Avita 1 Avatar 0 -10.0 -20.0 180.0 Avatar 2 -14.0 202.5 Speaker Axis: Left Right Front Back FIGURE 14.9 Narrowcasting control in virtual environment: P1 (avatar 0, right) mutes P2 (avatar 1, middle) and deafens P3 (avatar 2, left). clapped over the ears of a deafened avatar. Manipulations by participants are communicated using a CVE client/server architecture, which framework allows multimodal clients to exchange status data through the network. Clients cur- rently include sound spatializers, telepresence applications, panoramic and turnoramic browsers [10], music visualizers, motion platforms, and mobile interfaces. Besides the previously-described web- and workstation-based interfaces, we have also built a mobile narrowcasting display and control, shown in Figure 14.10, although we have not yet integrated the mobile audio stream, SO it is currently more useful as a collocated "remote control" than as a truly mobile application. Symbolic representations of narrowcasting operations were devel- oped for mobile interfaces by flattening figurative 3D avatars to 2.5D icons, as seen in the second-last row