I think Facebook is actually telling you that the audio may be (not may not be) copyright material, that is, material that is owned by someone else (for example, Michael Buble or his recording company).
If the audio is from Apple's supplied iLife jingles, there should be no copyright issue whatsoever. See the following User Tip by AppleMan1958 regarding copyright issues with YouTube (a similar situation will apply to the use of Apple supplied music in videos posted to Facebook).
JohnMacBook Pro (15-inch Late 2008), OS X Mountain Lion (10.8.3), Sony HDR-SR7 & DCR-TRV20E
This question comes up from time to time. YouTube and Facebook are both wrong.
There are a number of con-men who think that they can earn a quick buck from claiming that they own the copyright to Apple’s royalty-free jingles and sound effects included with the iLife applications. These are all free to use, as clearly stated in section 2.C of the iLife Software License Agreement:
“You may use the Apple and third party audio content (“Audio Content”) contained in or otherwise included with the Apple software, on a royalty-free basis, to create your own original soundtracks for your video and audio projects. You may broadcast and/or distribute your own soundtracks that were created using the Audio Content, however, individual samples, sound sets, or audio content may not be commercially or otherwise distributed on a standalone basis, nor may they be repackaged in whole or in part as audio samples, sound files, sound effects or music beds.”
You should quote this (also providing the above link) when following the dispute process with YouTube.