It could be a few things, John's post above explains some of them.

I would also ask HOW did you bring the wav file into RB from BiaB.
Did you 'Import' or 'Open' or (?)

Also, if RB is set to a different audio device this could easily happen.

In both programs you should be able to go to the Prefs-Audio area and make sure the audio device (drivers) and settings match between the two.

Bit rate is part of the above mentioned settings to check.

I do not work here, but the benefits are still awesome
Make your sound your own!