There are adapters out there, but I cannot tell you that they work for audio processing, due to fundamental differences in transfer protocols. There seems to be debate on this out there on the web - I certainly do not know for sure one way or the other, but then again, multiple companies seem to have gone out and made these kinds of adapters.
My Google terms were: firewire usb adapter
The above returned a bunch of results, for whatever the worth,
Bob Bone