Sound Affecting Performance?

[dogtown]

Hi folks, new guy here. I recently got CoD via Steam and it's amazing, yet within 10 minutes of play the sound starts to get "crunchy" and lag a bit. At the same time video performance starts to do the same. When the sound gets this way it sounds like someone manually scrubbing through a sound file erratically. Chugga-chugga-chugga (I know, that's not a technical description). It's become so frustrating as I play for a little bit then have to restart until it happens again.

To try and resolve the issue I've made sure all of my drivers are up to date. I've also made sure that Steam has pushed the latest version of CoD to me. Next I started playing with settings within the game and while knocking down to lower levels of detail, resolution, etc causes faster playback, the same issue shows up after a short while. What gives?

I'm not a gamer by any stretch of the word, so I'm not entirely sure my computer is geared well for CoD - I do however do computationally intense physics work for a living, in which case this quad-core 16GB Win7 system seems fine. Perhaps I should upgrade my graphics card? Maybe I should get a proper sound card instead of the integrated one (Dell XPS)? Any ideas?