This word is pronounced deep from the bowels of ur stomach, it should sound like a old man shivering out in the cold. It has many meanings such as howling laughter and relentless chaos. It also describes the bizarre, the criminally insane, and the downright schizophrenic. UHUHUH is simply a madman's word and shouldn't be used lightly in day-to-day conversation.
huhuhihu can be used in various situations, such as when you're feeling especially happy when greeting somebody, when being filled with happiness because you're really looking forward to something great or as a meaningful way to contribute to a conversation. Derives from "huhu" and "hihi".