Techgage posted a tutorial on disabling NVIDIA's HDMI audio driver under Linux

For those who don't use Linux, or do use Linux but aren't aware, the audio system found within the OS is horrible. Not in quality, features or performance, but rather in configuration and execution. Since I began using Linux in 1999, and moved to it full-time in 2004, the bulk of my most frustrating troubles have had to do with audio, and a recent problem only solidifies that fact further. This time though, it's not an audio card at fault, but rather the HDMI audio chip built into NVIDIA's GeForce graphics cards.

  Disabling NVIDIA's HDMI Audio Under Linux