So apparently, when using Ninja Pro, when you mantle over an object or through a window, you still make the "humph" noise. I can't imagine this was designed like this on purpose. It must of been an oversight. But then again, it also seems like an easy thing to patch, which hasn't happened. :/
Here's an idea I've been pondering about how I would modify the Ghost perk to make it less over powered. Make it so that the player shows up on radar every third or fourth radar scan. This way they are not completely invisible to radar. Also, the opposing team can put up multiple spy planes to speed up the radar scan rate.