I don’t know if you all heard about it.
Steam released an Audio Engine which can be used for free. It can be integrated in the Unity engine and has other APIs
It also supports multiple platforms.
I didn’t have time to check it out close but here is the link if you want to give it a look
Yes, very very cool stuff 
It does look good (it’s an existing audio engine called Phonon), but remember that it is for manipulating audio in 3D scenes only. It does not play any sounds (still need OpenAL or XAudio for that). It also has the problem that it selectively supports some platforms and not others. No iOS support yet, and it looks like Android ARM 32 bit only (no x86 or ARM 64). They could have also taken this initial release to rename the libs and includes from their previous “Phonon” name.