I updated my Xubuntu HTPC installation yesterday. and ever since have had an issue with interference whenever audio is playing. The audio/video can still be heard (albeit very quietly), with incredibly loud interference (much like you might hear with a badly tuned analog TV) over the top of it.
I currently have my system set up with Pulseaudio, providing analog 5.1, and before yesterday, this was all working fine (apart from the front left channel. This is probably unrelated, but I thought it might be worth mentioning). There are also two (unused) audio devices, an HDA Internal Audio, and an analog TV tuner (both muted)
I have so far tried re-installing pulseaudio, muting all inputs (line, mic etc.), and generally restarting, and messing with volume levels, but to no avail.
I have tried working through various forum posts, but I have had no luck. Would someone be able to please help me firstly identify the cause, and then rectify this problem?