Ubuntu – Regular audio corruption when listening to music

I'm running Ubuntu 13.04 (though the problem was also present under 12.04) on an HP Pavilion dv7 laptop.

Every so often, if I change the system volume while listening to music, the sound becomes corrupted – that is to say, random crackly artifacts get interspersed within the audio. If I had to describe it, it's sort of as if the music had been mixed with the sound that played when connecting to a dial-up connection back in the day – just random, data-sounding clicks and pops, interspersed with sudden (fraction-of-a-second-long) mutes. When this happens, some volume levels will mute the sound entirely and become a series of high-pitched crackles; switching volume back will restore the (still-corrupted) sound.

This happens in both Rhythmbox and Audacious, as well as with Flash e.g. when watching YouTube videos. The problem is very sporadic – sometimes it won't happen for a week, sometimes it will happen twice within the same day. The only link is changing the system volume, but there's no other common element (no particular volume threshold that always triggers it, say). One thing I have noticed is that it happens often if I change the fade slider between front and rear speakers (The laptop has a subwoofer, which for some reason is seen by Ubuntu as the front speaker – so I generally have to pan it slightly towards the rear so as not to have an overabundance of bass – the corruption when changing volume, though, happens when I am using headphones as well as when using the built-in speakers)

Closing all applications (or Firefox tabs, in the case of Flash) that are using the sound card in some way and re-opening them fixes the problem.

This could possibly be linked to the HDMI port on the laptop (I don't use it but have heard things about its less-than-great interactions between this model and Ubuntu's sound drivers), or perhaps to the issue where I have to open alsamixer and change the Speaker volume to get my headphones to work whenever they are plugged in; but beyond that I can't think of any specific cause or solution for this.

Let me know if there are any debug outputs that would help figuring out the cause of this issue (I don't know for certain what diagnostics I can run for this)

So far I've identified this happening in:

• Rhythmbox
• Audacious
• Firefox (w/Flash player)
• VidyoDesktop (conference calling software)

I'd be hesitant to say that this is affecting all sound applications, but that could well be the case – it happens so intermittently that it's difficult to test in specific programs.

Update: Even stranger, over the last couple of days it has ceased to be simply a "when changing volume" issue, and sometimes happens simply when changing tracks (though changing the volume exacerbates it once it's started). I'm starting to wonder whether it could be some strange interaction between the MP3 codecs and the sound drivers [I have a dualboot system with music in MP3 format stored on my Windows drive] – though that wouldn't go any way to explaining why it also happens with Flash, so I am utterly stumped.