Currently, the "Music & Sound Effects" wiki page mentions recordings from Edison Records as being out of copyright. According to a writing by Peter Hirtle, however, the copyright situation for the Edison Records recordings is unclear at best. (For the recordings at the UCSB Cylinder Preservation and Digitization project, aside from whether the original recordings are copyrighted, there is an issue in that the publicly available MP3 audio files are currently subject to a Creative Commons Attribution-NonCommercial 2.5 license (due to editing/acoustic cleaning/restoration) which is likely incompatible with the public domain status of LibriVox recordings.)
Peter Hirtle's US copyright chart has a section for sound recordings, in addition to copyright info for works in general.