PulseAudio's device-manager module is used to keep track of the names and descriptions of any and all audio devices. This module then also provides a protocol extension for other programs to query this information. At this time, device-manager will largely be used in integrating support for KDE Phonon. The device-manager module is considered experimental at this time along with its API.
The official change-log for PulseAudio 0.9.21 is available at PulseAudio.org.