Continuity mistake: When Uncle Ian is telling the chipmunks in the dressing room that they need to lip sync along to their song, there are alternating shots, and one of them is Ian and Alvin talking whilst being reflected in a large vanity mirror. However in the shot where Alvin turns around on the vanity table and tells Simon and Theodore they 'have to lip sync', Ian is not reflected in the large mirror, then in the next shot he has appeared back to where he was standing and is once again reflected in the mirror. (01:12:55)
Continuity mistake: Towards the beginning when Dave leaves the record label (after he steals the muffins), downstairs you can see a girl in a pink top, a delivery guy and a black guy in beige boots. The girl in the pink top passes Dave, then it cuts and you see her in front of Dave. Then it cuts again and you see her behind Dave and going around a corner. Also, the guy in the boots does the same thing a few times. And the delivery guy comes up close to the shot in the end, then they show him again just getting close.
Continuity mistake: In the end, when Dave is chasing Ian, we see many headlights behind him. However, once the chipmunks hop up and Dave slams his brakes, we see no lights and no cars pass him. Also, the whole time they are talking, no cars pass again. When Alvin steers the car there are all kinds of cars again flowing both directions.
Continuity mistake: The pumps of chocolate sauce in the chipmunks' coffee disappear too quickly for them to drink it all.
Continuity mistake: Dave captures the chipmunks in a pot, but right before the pot touches the counter, the chipmunks are not under the pot. They are not animated in it.
Answer: No it isn't his voice.