Have the same issue... ambient sound plays everywhere.
My steps so far:
I′ve duplicated a soundobject and adjusted pitch, looping and freq-shift.
I′ve created a duplicate of a BFXobject and changed its sound to the new created.
I placed that new BFX into my cell and tested
now it is playing everywhere and everytime, but not with the adjustments I made, sound like the original one...
I removed everything from the cell - still playing
I deleted every duplication - still playing
I loaded a very old savegame - playing there as well!
I restored a BackUp-file from yesterday - and silence again -it is...

seems to be another a CK bug...
Since I don′t need that sound I rebuilt the changes I′ve made today and stay away from sound-tweaks!
Or maybe someone has a solution ...