If it helps at all, we have just had oak floors put down. Seems to be a cracking sound also in a particular place only (near one of the doors). Rang the fitters and they came out and said they didn't leave enough space between the boards in that area and they're coming out to fix them. I think they just have to take off the piece that is under the door and move it slightly as the door saddle covers a small gap that they left in case of expansion. Said it isn't a big job and they should be able to do it in about twenty minutes. Might be worth contacting the fitters if its a new floor.
Hope this helps.