Mw2 Sound Effects Question?

I noticed while playing Mw2 at a friends house yesterday something pretty minor but cool nonetheless. While prone and crawling along the ground on Afghan, I could hear the gravel crunching and rocks rolling down the cliff (the match was silent at this point) and other small sound effects on different maps, however, when I went home to my own house, I did not have these sounds. Crawling on gravel produces no sound effects for me. This is only minor but is sorta bugging me. I also cannot hear footsteps whatsoever, even with SitRep Pro. Is it something to do with me not having a HD TV? Because I only hear these footsteps and noises on LCDs, and never on SD TVs.