As i mentioned before, if sound effects are getting delayed, particularly when speeding up, there's a high likeness that it's happening. (For me, when it happened bad, i sometimes had no sound effects at all for a minute or two, particularly when speeding up, then ALL OF THEM would play at the same time at some point after pausing and things would somewhat recover).
Still, it's good practice that whenever you visit a house or lot for some reason, to turn off their music/tv before leaving... or outright steal/break them with a klepto/technophobe/simbot or something
DISCLAIMER: Stereo/TV causing audio slowdown and general game slowliness problem is entirely unrelated to sims-getting-stuck problem.
Videocard overheating can also cause slowdowns and bugs, have you changed your video card config so it forces vsync and triple buffering for the sims 3 and each of it's expansions?, doing that greatly reduces the strain on the card, and thus, the heat it produces.