Hi,
I had the same sound problems after upgrading my macbook air to mavericks 10.9.1 Initially I thought it was BB playing up but after much trial and error and internet surfing found out the problem was mavericks. The apple people could not guarantee an early fix so I got them to roll back to mountain lion OS X 10.8.5, The sound works OK again with no problems. ( I had to re-install everything - a lot of work!) Cheers ieh