I've heard that a cat has a scent organ in the roof of their mouths but I just read about the silent meow on this site.. my kitty will sit with her mouth open pretty often, I've caught her 4 or 5 times and my military husband has even seen it during the short amount of time he gets to spend with her. I assumed she was just taking in a scent but now I'm wondering if it was a silent meow? How can I tell the difference?