Question: Throughout the course of the movie, why is Ian so obsessed with making money off the Chipmunks? After all, he lives in a mansion, has an outdoor pool, a nice car, and a group of house servants, and if he has enough money to afford that many extra toys for the Chipmunks when they arrive, any extra diamond or ring shouldn't be a problem for him.
Answer: Ian is a greedy "business man", no matter how much money he has he will always want more.
Question: Why is Dave so grumpy about the chipmunks being so needy to sing in front of Ian?
Answer: He knew that if he impressed Ian, he and the Chipmunks would become rich and famous. When they froze, he looked like a lunatic who thought animals could talk, making him appear foolish in front of a man who already had little respect for him.
Answer: No it isn't his voice.