never heard of "aquiring" pops before - are you sure you dont have a short in your sound system/speakers? the only other thing I can think of is that you were playing around with adding and subtracting video and forgot to delete the sound portion of your video which has inconveniently overlaped your "good" stuff. the quick and dirty fix if you cant zoom in and find it is to cut that clip and then add the good stuff back (after you are sure you cut out the section that is giving you trouble) - hence removing the "parasite"

this can sometimes happen when you are grouping and ungrouping stuff and quickly moving it around and getting a little careless (raising my hand)

hope that helps