Neither Onoki or Kurama noticed anything different aboiut the voices and Kurama sure seemed to believe Tobi was Madara, but in terms of chakra? No one's ever reacted to Tobi like this:
http://www.mangapanda.com/naruto/559/13
It's possible Kurama merely recognized the sinister nature of the vengeful Uchiha chakra since he noted Sasuke's chakra being like Madara's. Except with Tobi, the face wasn't visible and he assumed since someone with a Sharingan was controlling him like he was a lil bitch.