If you work with FireWire audio devices on a Mac Pro that you purchased after March 2009, Apple placed a little gift in Software Update for you.
Apple on Monday released Mac Pro Audio Update 1.1, which “addresses an audio anomaly that some customers may hear coming from inside their Mac Pro computer when using FireWire audio devices.”
This isn't the first time Apple has tried to squash audio bugs on the early 2009 Mac Pro. In February, Apple released Mac Pro Audio Update 1.0, which reduced CPU load when performing various audio activities such as playing or recording music.
The update is specifically targeted at early 2009 Mac Pros running Mac OS X 10.6.3.