This could be the same issue as on windows with the OpenAL drivers. Since Macs aren't as populas as a gaming platform though (and I do not as yet have one) I don't know if you will be able to find an easy fix. Check out this thread and see if you can follow the directions or look it up on google and see if there is a Mac solution somewhere on the web.
For now Vega Strike does not have any Mac developers so Privateer is stuck using the older .5 version of the binary unless you can compile from source.
Hope this helps!