For auralization in room acoustics there are several problems related to the sound sources. The anechoic recordings used for auralization can give problems due the microphone position used for the recording. In the room acoustic simulation there are other problems related to the source representation. Whereas some sources may be sufficiently represented by point sources with a fixed directivity, usually defined in octave bands, this will not be a good representation for other sources like many musical instruments. Instead a multi-channel representation has been developed, which leads to a more realistic 3D sensation of the source, and at the same time it allows the directional radiation to change during the performance. Sources of extended size introduce other problems, which may be solved by a number of uncorrelated point sources.